Callsigns: VK7TW – previously held – VK5ZJV, VK7ZTW, VK7KTW.

Name: Justin Giles-Clark

Biographical details and other information:

An amateur radio operator for 39 years, I have an interest in: AR training and assessment, SDR, DATV, SOTA, magnetic loops, microwaves, satellites and anything else that makes RF behave. Since 2004 I’ve served as President, Vice-President and Secretary of my local club, and co-convened the last two Tassie Ham-E-Cons, VK’s premier ham radio conference. Nationally, I served as WIA Director and President (2017–18), continue as a WIA Foundation Director, and are WIA Regulatory Counsel and chair of the WIA’s Spectrum Strategy Committee. I’m also an ACMA Specialist Assessor.

Formally, I hold a Bachelor of Science (Geology & Geochemistry), a Graduate Certificate in Public Sector Management, a Graduate Diploma of Public Policy and Management and a Certificate IV in Training and Assessment. Professionally, I’ve spent four decades across private and public sector ICT, policy, HR, IR, major projects, and business transformation, including the rollout of statewide systems and the introduction of new Tasmanian government employment legislation.

I bring a blend of technical depth, regulatory experience, and government know-how that I believe remains highly valuable to the WIA. My strengths in inter-government relations, process redesign, project, change and business management along with legislative interpretation, position me to contribute meaningfully to the Institute’s future.

Saturday & Sunday November 1st and 2nd 2025 was the running of the inaurgural QTech Conference run by the Brisbane VHF Group. A huge thank you to Kevin VK4UH, Scott VK4CZ, Peter VK4EA and the conference team for the great weekend.

https://qtechbrisbanevhfgroup.wordpress.com/

Held at the Kendron-Wavell RSL in Chermside a historic suburb of Brisbane, the theme of the conference was “Attention/Retention – The future of amateur radio is in your hands”.

The program was an interesting one with a broad range of topics and interest areas.

Starting with Youth On The Air (YOTA) and a couple of University of Queensland engineering students talking about their projects and how that was their bridge into amateur radio. Next was an update by WIA President Scott Williams VK3KJ. A panel / open forum discussion was then held with the following questions posed to the audience: What bought you to amateur radio and is it still relevant?

Marty VK4KC gave us an update on POTA, Grant VK5GR did a remote presentation on the Changes to the Band Plans and Rex VK7MO presented on Optical Communications. David VK5KK presented an update on the 241GHz radar chip based transceiver.

Trevor VK4AFL did a presentation on Deep Space reception using amateur radio and our last presentation for Saturday was remotely by Bo OZ2M on the future of VHF and microwave beacons, PI4 Project and the European 6m project.

Saturday night after dinner was an ARISS contact with Kedron-Wavell High School students.

Sunday’s first presentation was by Andrew VK3FS and was an introduction to microwaves then Rex VK7MO was back with a presentation on Lightning Scatter propagation. Graeme VK2QJ gave a presentation on the expansion of the IC-905 and the final presentation was by Richard VK7ZBX on his 10GHz EME adventure. VK7 punching way above it weight!

Thanks to the organisers for a great conference.

A huge thank you also to Dave VK5DG and XYL Catriona who suggested a SOTA activation in the mountains behind Brisbane. Dave found a drive up activation – VK4/SE-117, Tennison Woods Mtn – at 770m and a 6 pointer. We both made 8 contacts and I added another association to my list and thanks to all who contacted us.

We drove back to Brisbane via Samford and had a wonderful dinner at the Samford pub – a great end to the weekend. Thanks to Dave and Catriona for an great afternoon and I got to see some of the landscape around Brisbane.

73, Justin, VK7TW

The new 60-meter frequencies approved by the FCC in December will become available to amateurs as of February 13, 2026, along with new power restrictions on those frequencies. It’s a bit confusing, as different rules apply to different segments of the band. The changes result from the FCC’s action to approve a worldwide 60-meter amateur allocation made by the World Radiocommunication Conference...

Robert W. “Bob” Jones, VE7RWJ, a former top official of the International Telecommunication Union (ITU) and Canadian telecommunications regulator, passed away on January 7, 2026, at age 82. His early fascination with amateur radio led to a career in telecommunications and engineering, according to his obituary.

Jones was Director General of the Canadian Radiocommunications and Broadcasting Regul...

At the urging of ARRL The National Association for Amateur Radio®, the Federal Communications Commission (FCC) is expected to exempt radio amateurs from foreign adversary reporting requirements. These rules would have applied to citizens of the listed countries (see below), including those living in the United States, who hold or are applying for an FCC license.

On January 8, 2026, the FCC relea...

With a special tip of the cap to the no code, no electronics knowledge, 8 days to an Extra Class license ham, someone has finally explained what a ham operator is. Cuddle your Baofeng UV5R and just Enjoy!

Or “The One-Transistor Regen That Turned Into A Two-Transistor Regen” with thanks to G3XBM and N0WVA.

(Note – if reading this post on a computer, you can click on any of the images for a slightly larger version.)

About 10 years ago, Doug N0WVA told me about an impressive little regen he had built with a very minimal number of parts, that received CW and SSB surprisingly well. A few years later, in 2019. Bill N2CQR built it, and said that it had completely changed his opinion of regens. Here’s another post from Bill, with some videos of his little one-transistor regen, in which you can hear how good it sounds. Amazing stuff from one little FET.

Recently, Bill reminded me of his build of the N0WVA one-FET regen. Doug’s one-FET marvel has been at the back of my mind for the last 10 years as a receiver I wanted to have a stab at some day. Bill’s message came at the right time, and I realized I needed to build this thing. Not only does it only have one transistor, it also has a vario-coupler to control the regeneration. Not a variable capacitor or a potentiometer, but a genuine throwback to the 1920’s and 30’s in the form of a vario-coupler. I needed to build it, and it all began by making my own vario-coupler. Bill, as well as Will KI4POV who, like Bill, built two of these receivers, both made their vario-couplers from pill bottles, as did Doug. I made mine from a schedule 40 PVC coupler which, with an outside diameter of just 1 1/8″, was smaller than the pill bottle formers used by Doug, Bill, and Will. In addition to it’s smaller diameter, the coupler I used was made of thick PVC, which limited the diameter of the inner tickler coil further still. I used the plastic bobbin from a package of dental floss for the tickler former –

The shaft was made from the plastic barrel of a veterinarian transfer dropper –

A short length of heat shrink tubing over one end allowed the knob to fit snugly, while small holes were poked through the other end, on each side of the shaft, for the wires from the tickler coil to pass into the inside of the barrel, so they could emerge from the end. At the time of taking these pictures, the tickler coil hadn’t been wound, but it was wound with 38 AWG magnet wire –

And it turned out like this. Vinyl grommets served to hold the shaft in place –

To cut a long story short, I didn’t have the success I was hoping for with Doug’s regen. In retrospect, I think it had a lot to do with this vario-coupler. I had to wind 4 turns onto it in order to get the circuit to oscillate. Doug only needed one turn on his. Discouraged, I disassembled my build in favor of a different design, that used a throttle capacitor to control the regeneration instead of a vario-coupler. Doug later observed that the spaced-out windings on my main coil might have been the reason. I think he was right. Also, my former was a little smaller in diameter than his (1 1/8″ as opposed to 1 1/4″). In addition, because my former was much thicker than his pill bottle former, this further limited the diameter of the tickler winding. As cute as my little homemade vario-coupler was, I had to admit that it wasn’t ideal for the purpose.

While this was going on, I mocked up a different one-transistor regen circuit on an old Radio Shack breadboard. This was a design by Roger G3XBM. The coil was wound on a toroid and it used a variable capacitor to control the detector feedback. Even though this initial mock-up was a bit of a rat’s nest, it worked on initial power-up and before I knew it, I was listening to Ken WB0IRU and shortly afterwards, Jack WW5R, both in the 40M CW sub-band. It was something of a revelation to be able to copy CW signals from this –

Because I was so thrilled at being able to hear anyone at all on this motley collection of parts stuffed into a breadboard, I emailed Ken WB0IRU, the first station I heard, to let him know. Well, you meet the darndest people through this hobby of ours, because it turns out that Ken is a builder too. About a year ago, he completed Greg Latta AA8V’s 6×2 receiver. Ken writes,

“My fixation toward tubes comes from my high school days, when I used to go to the library and look through old hardback versions of the ARRL handbooks and see the absolutely beautiful home brew equipment that the ARRL staff had created and described.  My dream over the years was to construct similar equipment I could use.  It took about 60 years to realize my dream”

It can be the dreams we’ve had the longest, that are the most satisfying when we finally realize them – and Ken certainly did that. Just look at his home-constructed 6×2 superhet receiver. Wow, look at that thick front panel! Sourcing all the parts for this beautiful receiver must have taken a fair bit of time and effort –

It’s no slouch under the hood either! –

In retrospect, I gave up on Doug’s regen too early, but sometimes in the fog of war, you lose your head and some of your spirit. I needed a success, and Roger’s design promised it. I made 3 changes to his circuit. He placed a piezo earpiece between the top of the choke and ground. I wanted to use one of my high impedance vintage headsets, so I removed the 2.2K resistor in the +ve supply lead and replaced it with the headset. Coincidentally, the DC resistance of the Western Electric 509-W headset is also 2200 ohms, with a reported impedance of ~20K. N0WVA found that the parallel capacitor and resistor combination that is often used in the source lead of an oscillating detector can be replaced with a green LED to effectively set the bias, with slightly increased audio output. I applied this change to Roger’s circuit, which yielded 3 benefits –

1. Reduced parts count
2. Slightly increased audio and
3. A little green light!

The third change I made came as a result of noticing that every time I connected an antenna, the oscillator became unstable, and listening to the note on a nearby receiver revealed that it went from a steady pure tone to a rough, unstable one. I installed a 1K RF attenuation pot in the antenna lead but found that by the time I had reduced the incoming RF signal enough to stabilize the oscillator, the receiver was very deaf. Reluctantly, I gave up on the dream of a very minimal one-transistor receiver, and added a unity gain RF buffer amp (lifted directly from one of Charles Kitchin’s high performance regen designs), to provide greater isolation between the antenna and the oscillating detector. It worked a treat. The end result was a still quite minimal parts count regen that behaved itself and worked well. I would later change the schematic slightly, but this was the version I was working with at this point, with thanks to G3XBM, N0WVA, and N1TEV. I named it after my blind cat Jingles aka Jingy who is now, sadly, SK –

When winding toroids, the convention is that one pass of the wire through the toroid counts as one turn. For the antenna link winding, which is one turn, the wire doesn’t wrap around the core – it simply passes through the center of the core; this constitutes one turn.

Construction began with an offcut from the piece of mahogany that I had used for the baseboard of my build of Jim W4LF’s Hobbydyne Crystal Radio Kit. A NOS (new old stock) Hammarlund MC-20-S 20pF variable capacitor had been sitting in it’s original box on my shelf for a few years. Together, these two parts gave me great hope for the future of this project and represented, in my mind, an excellent and inspired start. This variable capacitor has cadmium-plated brass vanes and ceramic insulators. Fix yer peepers on those two very thick washers behind the shaft nut. Such great quality!

Front and rear panels were cut from FR-4, and drilled, then received several thin coats of matt black Krylon Fusion spray paint. It dries with a slightly textured finish that I think is rather attractive. In this shot, the light is catching it so you so can see the texture. In most situations though, it looks much darker, and only the texture is visible (as in the shot at the beginning of this post) –

The copper sides were scrubbed with a pot scrubber, then coated with several thin coats of clear lacquer from a spray can –

At this point, the main circuit had been constructed, though I hadn’t yet decided to add the unity gain RF amp. The main tuning cap increases in capacitance as the shaft is rotated clockwise, in direct opposition to more modern convention. To correct this, it was mounted backwards. In this shot, the knob has been placed on the long shaft temporarily, to tune it while testing. The lengths of thick magnet wire used for some of the ground connections are 18 gauge –

Roger used a T50-2 core for his coil. I used a T68-6, for the slightly greater mass and slightly lower temperature coefficient. How much they helped I don’t know, but I have not noticed any appreciable long-term drift in use, after an initial warm-up period (note that I said “not noticed” as opposed to “not measured”). Not that it matters, but I quite like the way the green wire looks with the yellow core. With 22 gauge wire, the toroid is self-supporting. The tap helps a lot in that regard –

I really don’t love working with these terminal strips, bought from a well-known company that specializes in parts for vintage radios and tube amps. Even with scraping and/or flux, they don’t take solder well, and need such a lot of it. By comparison with soldering on PCB’s and the Manhattan pads from QRPMe, they devoured my thin 0.02″ solder by the bucketload and still didn’t give very satisfying joints. If making this again, I think I’d use a small piece of copper clad, and build it Manhattan-style –

I used a James Millen part for the throttle capacitor. A Millen 19075, the specs quote a capacitance range of 5.5-75pF. I measured 6.5-80pF on mine, which turned out to be far more than needed. I placed an 18pF NPO in series with it, which reduced the effective capacitance range from 6.5-85pF to about 5-15pF. I still only ever use about 10-15% of the maximum rotation though. As I understand it, a high LC ratio in the tank is better for circuit Q, leading to more gain in the oscillating detector. With this receiver, I’d be curious to try a few more turns on the toroid, and a reduction in value of the 220pF parallel NPO cap. The higher the Q, the less throttle capacitance is needed to tip the circuit into oscillation. I’m thinking that the fact that I am already using very little throttle capacitance bodes well for this circuit. In retrospect, a 15 or 20pF cap in this position would probably have been enough, and a quality part would carry the benefit of an even lower minimum capacitance. At this point though, the mounting holes had been drilled in the baseplate, so I stayed with this part. Like the main tuning cap, it was NOS, with the terminals never having been soldered to before. It’s not bright and shiny like the main tuning cap, but it rotates very smoothly indeed, which is a big plus. The headset binding posts were made with #8 hardware. The knurled thumbnuts and machine screws are brass, and the washers regular zinc –

One more thought about the regeneration control while we’re on the subject. With a previous regen build, I posted a video of it in action. A fellow ham asked why I wasn’t constantly adjusting the regeneration control as I tuned. At the time, I didn’t know how to answer that. The feller in question must have seen videos, or perhaps had direct experience, of regens that cover a wider range of frequencies. With such sets, the regeneration control (reaction, if you’re in the UK) needs to be adjusted more frequently as one tunes. The reason for this near-constant adjustment lies in the fact that, as the LC ratio, and therefore the Q, changes, so does the amount of feedback that is required to maintain oscillation (or to keep the set just below the point of oscillation if you’re receiving AM). In a regen that covers a narrow range of frequencies, such as a CW sub-band for instance, the LC ratio changes very little. Therefore, the regeneration/reaction control needs little, if any, adjustment as one tunes around.

The National MCN Midget Calibration Dial is quite a looker. It was another NOS part. When removing these parts from their original boxes and using them for the first time, I feel a sense of responsibility to use them carefully and well. They have waited many decades for this moment! Notice how well the spray can finish of the Krylon Fusion paint goes with the finish on the old National dial plate –

In the next shot, note the thick wire passing through the center of the toroid. It is the antenna link “winding”. That is all that is needed to couple the antenna to the tank.

Frequency coverage was set with the trimcap for approximately 6990 – 7195KHz. This covers the entire US CW sub-band, as well as the more interesting DX window of the SSB portion. If you’re in ITU regions 1 or 2, then the values given in the schematic should cover the entire 40M band – or very close. If you want more, or less, coverage, adjust tank values accordingly.

I’m thinking about constructing a little transmitter, also on a wooden baseboard, to use with this regen. In the meantime though, I paired it with the GM3OXX “OXO” transmitter on 7030. Many thanks to Gene KD7BCF in Turner, OR for returning my CQ. We exchanged 529 reports for the first QSO with this FB regen and 300mW from the OXO TX, a distance of 480 miles. Not bad for a first QSO. On the second night, I powered the combo from a little 5AH sealed lead acid battery on charge, with a voltage of 13.9V, which upped the transmit power to a whopping 450mW of RF out. A QSO with David KI7NRI resulted (688 miles away), with reports of 559 both ways –

If you have never operated homebrew separates like this before, one question you may have, is, “What about the sidetone?” Well, I don’t think you really need one. The DPDT switch in the transmitter, as well as switching the antenna between transmitter and receiver, also switches a 50 ohm dummy load, comprised of 2 x 100 ohm 1 watt resistors in parallel, between the transmitter and the receiver antenna inputs. On receive, the transmitter is protected if you accidentally hit the key. On transmit, having a 50 ohm resistance across the antenna terminals helps to make it just a little deaf. You still won’t hear a sidetone; the transmitter is too close, and regens are easily overloaded. However, if you’re lucky, your regen won’t completely freak out, and you’ll hear something that will be useful. With this setup, when sending, I hear a slight buzz in the headset, accompanied by soft key-clicks. It’s all I need in order to keep track of what I’m sending. With one hand on the key, the other hand on the transmit/receive switch, a 100 year-old headset clamped to my ears, and the sound of buzzing and clicking in my ears, as N2CQR might say, I feel a connection to our tribal radio elders. I almost feel like a telegraph operator!

G3XBM’s original schematic used a crystal earpiece. For some reason, I haven’t had much luck using them with crystal sets. They work but, compared to the sensitive high impedance headsets I like to use, they’re not very loud. I imagine the fact that a headset has an earpiece over each ear helps a lot. I was curious to see what this regen was like with a crystal earpiece, so I connected one up and was pleasantly surprised; it was quite loud – possibly louder than my headset. It’s possible that the natural resonant audio frequency of the earpiece contributed to this on CW. Encouraged, I decided to include a 3.5mm jack for plugging in a crystal earpiece as an extra option. I also added an RF decoupling capacitor at the top of the 100µH choke. I had noticed that touching that point changed the operating frequency slightly. In light of the fact that adding a crystal earpiece jack on the back panel would entail running a long-ish wire from the top of the choke to the back panel, I decided to decouple that point. After installing it, touching that brass binding post made no difference to the frequency of the oscillating detector. Objective achieved! When using a crystal earpiece, a resistor needs to be connected in place of the high impedance headset. A value of somewhere between 1K and 6.8K will work. I run my set on 12.5 – 13V from a gel cell. The resistor value is not critical, but 2.2K works fine for me. As the value gets higher, the audio level in the earpiece goes down slightly. Here’s the revised schematic, representing the final one for my build –

Some more pictures of the final version. It looks a bit messy, but it’s electrically solid and it works –

The rear panel with the jack for a crystal earpiece installed –

The copper on both front and rear panels was grounded. The ground wire and solder lug for the front panel is clearly visible in some of these shots –

The new 0.01µF decoupling capacitor can be seen connected between the right-hand binding post and the frame of the throttle capacitor. You’ll also notice that the capacitor in series with the throttle cap has been changed. Originally it was an 18pF NPO part. I changed it to two 4.7pF C0G caps in parallel = 9.4pF. They are the two little blue capacitors –

Four stick-on felt feet from the local hardware store were attached to the base –

Regen enthusiasts are often so keen to spread the word about this technology, that we’ll be tempted to oversell the benefits of regens, while underplaying the drawbacks. After listening to this set for a few days, here are my observations –

1. The oscillator occasionally wanders slightly around the center frequency. I don’t always notice this on CW, especially if I tune the receiver for a higher-pitched note, but it is hard to ignore on SSB. I don’t think this is due to slight movements of the antenna and feeder affecting the oscillator, but probably related to the differing temperature coefficients of the tank components. A regen receiver is, after all, basically a VFO. Further supporting this theory is that it seems to happen less after the receiver has been powered on for a while. You wouldn’t notice this drift at all on AM – it is only of the order of a few tens of Hz. It doesn’t affect copyability of a CW signal, but it’s a bit disconcerting on SSB. If I ever experiment with this, my first move would be to try a different trimmer for the band setting capacitor, to see if that is the culprit.
2. The RF attenuation control reduces the input signal smoothly; it works well. I quite often need to back it down a bit to prevent strong signals from overloading the detector.
3. Even strong signals don’t sound loud in the headset. There is a limit to how much volume you can get with no audio amplification after the detector. I find it difficult to give good signal reports as, although I can hear quite weak signals, it can be difficult to distinguish between, say, a 539 and a 599.
4. As a follow-up to #3, I am surprised that if a signal is marginal on my main rig, a K2, I can often hear it on this regen. It is a little less sensitive than the K2 (no surprise there) but not as much as I would have expected. However, filtering and single-signal reception of the K2 are big advantages with very weak signals and in packed bands (such as during contests). I’m definitely not trying to suggest that this 2-transistor regen is as good as a more sophisticated receiver; I’m not that far gone!
5. A general comment here. After a few days of listening, I find it a very enjoyable receiver to listen to. Regens can be a bit frustrating at first, until you get used to them. Then, the extra operator input required can be quite engaging. Having a throttle capacitor that is very smooth in it’s physical operation is a benefit. Sometimes, I like to coax the receiver slowly from oscillation, to the threshold between the two states, and then to just below the point of oscillation. While doing so, you hear the CW tones gradually change into a rushing sound, then all you hear is the sound of the carrier switching on and off. It is still possible to copy the signal at this point and, as I listen on a 100 year-old headset, I think to myself, “This must be what it was like in the old days!”

As with nearly all simple circuits I build, I go through two stages. At first, I am completely bowled over that it works at all, and am amazed that so few parts can work so well. After using it for a while, the initial novelty wears off, and I start noticing the shortcomings. It’s at that point I have to remind myself how simple the circuit is. I mean, this receiver has only 14 parts – 15 if you count the headset – and that includes all 3 capacitors in the main tank (a variable, a trimmer, and a fixed cap).

Few homebrew projects are ever really finished. If I revisit this regen one day, I’d like to remove the terminal strips (I don’t particularly like them) and rebuild the circuit on a piece of copper clad, Manhattan style – or just use smaller terminal strips that are more suited for modern solid state components.

This is a fun receiver for listening. Powering it from a battery is very practical, due to the low current draw of 5mA. I power mine either from a 5AH 12V gel cell, or a pack of 10 x 1.2V Eneloop NiMH cells (about 2AH). I am open to the potential for improvements. This is the thing about such simple receivers – they keep me coming back, lured by the promise of greater performance with just one modification or tweak!

Thank you Roger G3XBM, and Doug N0WVA. It’s because of designers like you that people like me get to build things.

And here’s Jingles the blind kitty aka Jing aka Jingy. She left us a while back, so it’s high time she had a radio named after her –

No new construction projects here, I’m afraid, and none planned for the foreseeable future, though I have made some exciting and worthy acquisitions. A couple of years ago, I was looking for a vintage high impedance headset to use with crystal sets. For regular use, I found a set of Baldwins (the famed “Baldies”) and a Western Electric 509-W headset. I also came across a set of Baldwins in never-used condition in their original box, with the instruction leaflet. They had never even been assembled! The spring metal clips that grip the earpieces are so strong that it would have been difficult to assemble them without leaving some telltale small scrapes or abrasions on the bakelite earpieces. In addition, the bakelite on the earpieces was so shiny and new-looking, that I felt confident in concluding that these had spent their entire life up to when they reached me, in the original box, most likely only being taken out for the eBay seller to photograph them for the listing. He had bought them at an estate sale a few decades earlier, and stored them away until it was time to pass them along to someone else. That particular set of Baldwins are a sight to behold – a piece of radio history. Museum grade, for sure –

This is my NIB (new in box), unassembled and unused Baldwin Type C headset. Absolutely beautiful. When I am firmly in old codger territory in about 15-20 years, I’ll be looking eagerly for a radio museum (or similar) who can display them, or an individual collector who will treat them with the care they deserve –

At this point, I had a set of Baldies and Western Electric 509-W’s for daily use, and a set of Baldies in beautiful display condition. I rarely use the Baldies, as the Western Electric headset produces a louder signal. Although not known for being loud, due to the balanced armature construction, the Baldwins are thought by some (though, I must add, not all) folk to be more sensitive to extremely weak signals. I am not a crystal set DX’er, so the Western Electric is the set that gets all the use here. Shame really, as the Baldies are more comfortable for extended wear.

These are my everyday use Western Electric 509-W’s. They are sensitive, and ruggedly built. With a DC resistance of 2200 ohms across the terminals and a stated impedance at audio frequencies of around 22K ohms, they are the ideal headset for use with crystal sets –

At this point, I thought I had bought all the vintage headsets I was going to. Then recently, I saw a set of 509-W’s on eBay in really excellent condition – with their original box! To be accurate, it was a 1002-C headset, which used the 509-W earpieces. The headband is a little different from the one that would come with the more common headset that used the 509-W earpieces. I am not an expert on these matters, but I don’t think it’s very common to see the original box for this headset. The box, as well as the excellent condition of the entire headset, was making it hard to get these out of my head. I rarely purchase anything on impulse. I tend to give wants (as opposed to needs) some time to sit in my head. If, after a while, I still want them, I go ahead and make the purchase. The more expensive the purchase, the longer I wait, to avoid the onset of buyers’ remorse. After a day or two of deliberation, I realized this was a headset I really wanted to own.

About a week later, a box arrived at the AA7EE radio ranch –

It was well-packed. Seeing this put my mind at rest. I had been hoping that the original box would not suffer any damage in transit, and I needn’t have worried –

Underneath the layers of bubble wrap, the box itself was wrapped in paper towels. Oh – and that box! I had been confused by the fact that the box is for a 1002-C headset. However, Scott Balderston, on his very informative vintage headphone site, says of the 509-W’s, that “The box these were sold in was marked 1002-C, though it contained 509-W headphones.” My guess is that although we commonly use the term 509-W to refer to the headset, it was actually the product number of the earpieces. Just look at that box, all of 100 years old! How many of these do we see these days? –

Inside the box, with the earpieces loosely wrapped with paper towels, was the headset –

Interestingly, this particular headset has a different headband from the one that more commonly seems to come with the 509-W’s. On most of the sets I have seen, there are metal pieces at each end of the two lengths of headband fabric (four endpieces in all). They neaten up the ends of the fabric, as well as serving to prevent fraying. This set doesn’t have those endpieces. When viewing the eBay listing I almost didn’t buy them, for this reason. However, closer inspection convinced me that the metal endpieces weren’t missing. This appears to have been a design that didn’t have any to begin with. This headset isn’t mint, but it’s in great condition, and looks to only have seen light use. Just look at them. 100 years old! –

The metal on the earpieces has some light scuffing – perhaps from use, and/or from polishing –

Just look at those shiny black bakelite earpiece caps! –

The next two pictures show one end of the headband fabric. It’s slightly frayed. I’m guessing this is why the more popular (later?) design included metal endpieces to cap off the fabric –

Another detail that really drew me in was the paper label around the cord; another factor that served to suggest this headset had seen very little use –

The cord is in such fantastic condition. It looks close to new –

There is not a spot of corrosion or rust on any of the metal. It’s all very clean –

I do tend to take quite a lot of pictures of things that interest me, so pardon me if this is oversharing, but just look at these beauties!

At the risk of repeating myself, 100 years old. Wow!

They are, incidentally, fully functional –

As if that wasn’t enough, a few days later, I came across an original instruction leaflet, which I am guessing would have come in the box with this headset. I thought about it for a day or two, though it was almost a foregone conclusion from the moment I saw it; I needed this to include with the 1002-C headset and box. It arrived flat-packed between two pieces of corrugated cardboard and placed inside a protective plastic sleeve –

I probably paid a little too much for it but, like the original box, I don’t think you see these in good condition too often. Here are scans of both sides of the tri-fold, for (slightly) easier reading –

If you’re really interested, I can furnish you with files of the front and back in high resolution, either for printing out, or for viewing on a computer. They are a lot easier to read than the images on this site – and it’ll save you paying what I had to in order to get this leaflet in my collection! My email address is good on QRZ. The problem with owning nice examples like this is that I feel a responsibility not only to preserve their condition while they are in my possession, but also to ensure they go to a good home when it is time to let them go. Historical pieces like these need to be preserved. I certainly hope that future generations will have the interest to do so. There is a slightly more technical sheet on this headset, named the Instruction Bulletin #103, about 1/2 to 2/3 of the way down this page over at Scott’s Headphone Museum Gallery. I would love to find an original physical version of this sheet or, failing that, a higher resolution scan than is available on Scott’s site.

My other recent exciting radio-related acquisition was something that has been on my mind for a few years now. A fan of the regen receiver, I have long been curious about Bruce Vaughan NR5Q’s book “Surviving Technology”. Bruce built many regens (all tube-based), gradually refining the art, and culminating in a design that he dubbed “The Ultimate Regen”. In the book, he notes that it is not necessarily the best regen, but it is the best one that he has built. “Best” is a subjective description, so Bruce was probably wise to qualify his comment. The design of his Ultimate Regen doesn’t consist of just a schematic, but also a thorough description of the physical construction. This is the mark of a serious regen builder – the detailed attention paid to the physical layout. For a regen in particular, it is as important as the circuitry involved.

Before I continue extolling the virtues of this book, I must point out that it is not primarily a book about building regens. It is the story of Bruce’s lifelong love affair with radio, starting as a young boy growing up in small town Arkansas in the 20’s and 30’s. It begins with his earliest memories of radio, when constructing your own gear was a virtual necessity, unless you were wealthy. Even then, some of the equipment simply couldn’t be purchased, at any price. The book continues with a recounting of his years with the military during WW2, and then as a radio repairmen afterwards. As well as running a radio repair business, he also owned a camera store, laundromats, and sold television sets. He builds a lot of ham gear along the way, eventually deciding that he needs to start building regens – and boy does he ever, having built 59 regens before deciding on the design of his ultimate best performer, which was presumably the 60th. That is just the number of regens he built, and doesn’t include all the other gear he constructed along the way, such as superhet receivers, CW and AM transmitters, and linear amplifiers. Pictures of some of these projects are shown in the book. Beginning in the mid 1920’s, Bruce’s memories and experience with radio occurred during some of it’s most exciting times, from it’s early adoption by select members of the public, and continuing through it’s rapid expansion, and transformation into the dominant method of mass communication that it became. Heady times indeed! An easy and engaging read, the last few chapters are devoted to the serious task of building Bruce’s Ultimate Regen. Although I purchased it for the regen content, I am really enjoying it for the firsthand recounting of the life of a radio enthusiast lived during the Golden Age of radio. Bruce’s storytelling is engaging, and peppered with lively anecdotes, including one of a particularly brave (one might even say foolhardy) prank that was undertaken very close to the end of the war. As he said, if he and his pal had been caught, they would have been in a whole lot of trouble. I’ll let you, dear reader, discover that risky escapade for yourself! It is clear that Bruce was a confident young man, though some of the descriptions of his abilities are quite self-effacing. He seems to have possessed the perfect combination of confidence and ability to learn; self-assuredness got him through the initial tough spots, but his intelligence and learning skills saved the day and propelled him to success.

Oh, and in the chapters where he’s telling the story of his years as a self-employed radio repairman, look out for the anecdote of the RCA 6-T table radio. It’s a good ‘un!

In the later parts of the book, a whole chapter is devoted to building the power supply and output stage of his “Ultimate Regen”, which he makes a good case for doing so on a separate chassis –

The hallowed 6L6 has a chapter all to itself, in tribute to this vital part of many a home-constructed amateur rig of the era –

Building the “Ultimate” receiver –

Many pictures of Bruce’s various homebrew projects. Vintage homebrew heaven! –

You can purchase Surviving Technology by Bruce Vaughan NR5Q from the Electric Radio Magazine website. After Bruce passed, it went out of print, and the original files were thought lost. Thankfully, they were eventually located, and this wonderful publication is back in print, on a heavyweight, quality grade of paper. A recommended read, and well worth owning for any vintage ham radio enthusiast. A big thank you to Ray N0DMS, the editor and published of Electric Radio Magazine, for making this wonderful book available again.

Recently, I built a simple little TRF receiver for the AM broadcast band using a TA7642, a modern equivalent for a chip that was quite popular with electronics homebrewers in the 70’s and 80’s. The ZN414 was a device made by the British semiconductor company Ferranti. Housed in a metal TO-18 can with three leads, it looked like a transistor, yet contained a whopping 10 transistors. Just think of it – 10 transistors on a single chip! This IC offered 4 stages of RF amplification (all at signal frequency), a detector, and AGC. Building this little receiver was an exercise in nostalgia for the radio I built in a matchbox in 1975, using an honest-to-goodness ZN414.

This recent project is working quite well, but some comments that Australian lover of vintage technology John Hunter made on his page about the ZN414, got me to wondering if a genuine ZN414 would have worked better in this circuit. I don’t remember any details of the performance of my original ZN414 matchbox radio. I was only 11 or 12 and frankly, was just over the moon that it received a few big signals, from the national BBC radio stations. I did comment in the blog-post that I was interested in locating a genuine ZN414, and two very helpful people came to the rescue – Don ND6T and Rob N7REP, who both had examples of this IC in their parts drawers. Not wanting to be a parts hoarder, I accepted Don’s offer, but am very grateful to Rob as well.

The US Postal Service ain’t quite what it used to be. It took a while but 11 days (7 business days) later, an envelope turned up, having traveled the 204 miles as the crow flies, from Don’s QTH to mine. Inside was something I never thought I’d see again, a genuine Ferranti ZN414 in the TO-18 can –

It was pretty dang exciting seeing one of these little fellers again, after nearly 50 years. I got to work almost immediately, and breadboarded a few different circuits, keen to compare the performance with the TRF receiver I had just built with a TA7642. For the next day or two, I breadboarded several different circuits. Firstly, there are two main methods of feedback, as detailed in my previous post, as well as in John Hunter’s page previously linked. The first method, and still the most popularly used and quoted, is a 100K fixed resistor between the output of the IC and the cold side of the tank circuit. The other method, which I found to be superior (as John said it is on his page) involves the two outer terminals of a 10-100K potentiometer wired between the output of the IC and ground, with the wiper being connected to a 100K fixed resistor, the other side of which goes to the cold side of the tank circuit. Schematics for both methods are in my previous post, as well as on John’s page. In addition to that, I tried slight variations of both circuits, to accommodate various different types of transducer – a piezo/ceramic earpiece (commonly referred to as a crystal earpiece), a high impedance magnetic headset (my 100 year-old Western Electric 509-W), and a set of modern low impedance earbuds. As well as trying each circuit with the ZN414, I also tried them with a TA7642, for comparison.

That was a lot of circuits and frankly, it was a bit of a rabbit hole. I took fairly detailed notes and, in the first draft of this post, began typing them out, with diagrams. Trouble is, I was beginning to confuse myself. If I was confused, I knew I didn’t stand much chance of clearly stating my findings to you! To make things a bit more complicated, the performance of my breadboarded circuits were all slightly inferior to the finished TRF that I built. I think it was due to the longer leads and breadboard connections, giving greater opportunity for feedback loops to develop around the fairly high gain IC (72dB in that little package).

After building multiple circuits with the ZN414 and attempting to evaluate the performance of each, I eventually came to the following conclusion – while we don’t know what differences (if any) exist between the internal circuits of the ZN414/ZN414Z and it’s modern counterparts, there is little significant difference in performance between them – in my experience at least. If anyone reading this has experimented with both the original ZN414/ZN414 chips and the modern equivalents, I’d be very interested to know what you found. I’m just not hearing much difference. For the record, I also have some YS414’s that I got from Mike’s Electronics, and they gave the same good results. Mike’s sell several different types of ZN414 equivalent IC, and they are apparently all the same, except for the KM484 (not the MK484, which they also have), which has slightly higher gain.

So – don’t worry about it. Buy any of the modern equivalent IC’s and build yourself a little radio receiver! If you want a portable receiver with very low current draw, and are happy with using earbuds instead of a speaker, this circuit is the one I used in my previous post. It consumes just 1mA at 1.4V. The parts count is mind-bogglingly low, and yet it works. Quite frankly, it’s astounding –

Many thanks to Don ND6T and Rob N7REP for offering their ZN414’s to me for experimentation. Nostalgia is a powerful force. We remember the radios we owned and built when young very fondly, and I think those memories often cloud our judgement. The matchbox receiver I built with a ZN414 at the age of 12 was quite an achievement for the young me. I was the brave pioneer in the story of my own life (aren’t we all!) I was hoping to discover that an original ZN414 would perform better than the modern equivalents. It doesn’t seem to and really, this is good news. It means that you can get good results from most any of the modern equivalents available in abundance nowadays. The only two I can vouch for are the TA7642 from Dan’s Small Parts and Kits, and the YS414 from Mike’s Electronics, but I wouldn’t mind betting that the other ZN414 equivalent IC’s from Mike’s, and probably many other suppliers too, are just as good.

In the previous post, I described my recent build of a very simple little TRF receiver for the AM broadcast band. It happened as the result of a month or two spent with much more complex projects, namely a scratch-build of the receiver section of a Norcal 2N2/20, and a kit build of a complete Norcal 2N2/20. After that, I wanted to get back to simple circuits, so made a slightly improved version of the AM receiver that I built in a matchbox as an 11 year-old kid. It had a mere 9 parts, including the earbuds and the battery. 9 parts total! You can’t get much simpler than that.

Or can you? How about a complete receiver that uses only 4 parts, including the headphones? I won’t say including the headphones and the battery, as it’s a crystal set and there is no battery. Maybe I’m overdoing this recent drive towards extreme simplicity, but there is a magic about tuning in a radio signal with a coil and a variable capacitor. The receiver I built with a TA7642 got me very close to that magic, but I wanted to get even closer. That’s how I ended up building a crystal set which, after all, is not much more than a coil and a variable capacitor!

I’m about to show you the circuit of what I built but, before I do, allow me to emphasize that this circuit works better than I had hoped. I can sit down and comfortably listen to one of around 10 or 12 stations with this circuit, with no external antenna. It has no long antenna wire, and no ground connection. Here it is, drawn on the back of a chocolate wrapper –

This is the basic circuit of a crystal set that is often seen in articles and books that contain simple crystal sets for beginners, with two exceptions – the circuits shown in beginners’ books usually also include a long wire antenna connected to the top of the coil and a ground connection at the bottom of the coil. Obviously, a long piece of wire hung outside the house and a good ground connection are both essential if your crystal set is to stand a chance of working properly, right? That is what I thought. It is the common wisdom that is drilled into most of us from an early age; that in order for a crystal set to work, you have to have a long piece wire high up and in the clear, and a good ground connection.

Back in 2013, I constructed a tunable loop frame antenna for the AM broadcast band. It gets used occasionally but, like a lot of the projects that are built here, spends most of it’s time sitting up on a shelf. Recently, with the revival of my focused interest in the subject of coils and capacitors, and just how dang fantastic it is that you can put a coil and capacitor in parallel with each other, and pick a signal off the top of the tank, I looked up at this loop antenna and realized that if I added a diode and a high impedance headset, I had a crystal set. I live in a densely populated urban area with a lot of strong AM signals. I thought it was hoping for a lot, but figured I might stand a chance of at least hearing something faintly. Boy was I wrong; it worked a lot better than I had hoped. A lot better.

Here’s a small update to the previous circuit, to show that the coil in the crystal set is a frame antenna, also drawn on the back of a chocolate wrapper (same type of chocolate though; just a different bar) –

The very simple circuits in books for beginners usually have very broad tuning. The reason this set doesn’t have that problem, is because there is no long wire antenna attached to the top of the coil to dramatically reduce the Q of the circuit. The coil is the antenna. A very simple circuit, and good performance. Genius!

Here are a couple of pictures of the tunable frame antenna, taken from the blog-post describing it, as it looked when I constructed it in late 2013 –

And here it is now, 4 brass binding posts, a diode, and a good high impedance headset later. It was so simple to turn this frame antenna into a crystal set, there was really no reason not to –

The 4 binding posts were all made with parts purchased from the local Ace hardware store. Two posts hold the diode, so that different diodes can be tried out. The other two attach to the headset. The diode in the photo is a 1N5711 Schottky diode. I also tried a 1N5817 schottky diode and a selection of 1N34A and similar germanium point contact diodes. It may not be apparent in this picture, but the binding posts for the diode are #6 size, while to adequately grip the headset terminals, the greater size of #8 hardware works well. Note the strain relief on this headset cord. It’s a useful feature found on many vintage headsets (a good reason to use binding posts for the headset, and not Fahnestock clips) –

The wiring from the frame of the variable capacitor, which is connected to the rotor (the movable vanes), runs underneath, while the rest of the wiring between the binding posts in this extremely complex circuit is on the top –

Binding posts are a handy way to make connections in a simple circuit like this, and make it easy to change out diodes or insert other parts (capacitors, resistors etc.) to experiment. They’re also a good way to connect to the terminal ends on vintage headsets. When implemented with brass hardware, I think they look nicer than Fahnestock clips. All the parts to make them are available at my local hardware store too, which is a plus. Each binding post is made from a 1″ brass machine screw, a knurled head brass thumb-nut, a regular nut, and 5 stainless steel washers. In the following two pictures, all parts are brass, except for the washers. Brass washers are available too though, if you want to use those. Looking from right to left, after the screw head comes three washers. I use two washers on the underside of the panel if there is going to be wiring to that post underneath the panel. Otherwise, only one washer is needed underneath the panel, and one on the other side, between the panel and the nut –

As mentioned before, the two headset binding posts are made of #8 hardware, while the two that hold the diode are #6.

The first diode that I used for the maiden run was a 1N34A purchased (I think) from Dan’s Small Parts and Kits. I was hoping for something, but wasn’t expecting much. Imagine my surprise on finding that from my home in the SF Bay Area, I could hear the following 10 stations, most at very comfortable listening volume, and most with no bleed-over from adjacent stations –

610 KEAR, 740 KCBS, 810 KSFO, 910 KKSF, 960 KNEW, 1050 KTCT, 1100 KFAX, 1400 KVTO, 1510 KSFN, 1640 KDIA.

Things got even better on installing a 1N5711 Schottky diode. The volume went down just a little, but the selectivity increased noticeably, eliminating the bleed-over between adjacent stations, and allowing these 6 stations to also be received. Most of these extra stations weren’t at what you’d call a comfortable listening volume, but all were identifiable –

680 KNBR, 860 KTRB, 1010 KIQI, 1170 KLOK, 1310 KMKY, and 1550 KGMZ.

As well as the 1N34A from Dan’s, and the 1N5711, I tried out a variety of germanium diodes as well as another Schottky diode, a 1N5817. Here are the diodes I tested –

1N34A types from Dan’s
1N34A types from Scott Balderston
1N34A’s from Lance WB5REX (Borden Radio)
1N34A’s from George K9TRQ (very kindly offered in a FB crystal set group)
A selection of Russian germanium diodes, namely D9B, D9D, D9E, D9K, and D9V

The 1N5817 was nowhere near as good as the 1N5711 so, of the two Schottky’s I tried, the 1N5711 wins. The set wasn’t as selective with any of the germanium diodes as it was with the 1N5711, though it was a bit louder and the audio was a bit more pleasant to listen to. It was hard to discern the differences between all the germanium diodes; some of the differences were either minimal or simply didn’t exist (other than perhaps in my head!) However, there were some standouts among the germaniums –

The ones from Scott of Scott’s Crystal Radios and Antique Headphones, and George K9TRQ were among the best for both loudness and selectivity. The ones from Dan’s were loud, but were the least selective of all the germaniums. The Russian diodes were all fine (somewhere in the middle, in other words). As a result of this test, I am earmarking two diodes for using with this set – a 1N5711 for most listening then, if I want to listen to one of the stronger stations for an extended period, one of the better germaniums, for the more pleasant audio.

The headset in use was a Western Electric 509-W. If you want a sensitive and robust high impedance headset, this model is well worth having. They are not hi-fi quality – not even close but then, no headsets from that era were. The 509-W was patented in 1918 and manufactured until the mid 1920’s, so they are around 100 years old. I have not had extensive experience with a wide variety of crystal receiver headsets but, based on everything I have read from people far more experienced than me, I have concluded that the only high impedance headsets that are more sensitive than 509-W’s are Baldwins, or a pair of RCA sound-powered headphones (the ones known as deck talkers, or “big cans”). They are unlikely to be louder than 509-W’s, due to the physical limitations placed on the armature movement, but may allow you to hear weaker stations. In my humble opinion, Baldies and/or RCA sound-powered headsets are only worth investing in if the rest of your entire setup is optimized for DX reception – and that’s definitely not the case with this basic set. Long story short – get a pair of Western Electric 509-W’s. They are great for general as well as much DX crystal set listening.

The Western Electric 509-W has a DC resistance of about 1100 ohms per transducer. They are wired in series, for a total DC resistance of about 2200 ohms, meaning the AC impedance is several times that. This is a great headset for crystal radio listening!

Oh, the cheap crystal/piezo earpieces that come with a lot of lower-priced crystal set kits? They do work, but you’ll hear more with a good, sensitive headset. The common wisdom when using crystal/piezo/ceramic transducers with a set like this, is that you need a high value resistor of 47K-470K across the headphone terminals, otherwise it won’t work. Using a crystal earpiece with this set, I heard no difference either with or without the resistor. Also, many circuits show the use of an RF bypass capacitor of somewhere between 220pF and 1nF across the headphones, to get rid of any last traces of RF. I didn’t find this part necessary either. My guess as to why, is that the large amount of very thin wire in the high impedance windings of the headset probably has enough self-capacitance to scrub any traces of leftover RF from the audio signal. Likewise with the ceramic earpiece, which probably has enough capacitance to act as an RF bypass without the need for an extra capacitor.

When walking around with this set while taking the pictures for this post, I had the headset on and was listening to the local 50KW clear channel news station KCBS on 740 AM. It occurred to me that, while by no means pocket-sized, it’s actually quite portable. The frame antenna is 17″ on the sides, which is a nice compromise between portability and signal capture area. I am so taken by the performance of this simple crystal receiver that I can’t help wondering how a set with a larger frame would perform. These things do get unwieldy quite swiftly as the size goes up though.

If you’re sitting on the fence about building a crystal set, or have built one in the past and been disappointed in it’s performance, I hope this post will persuade you to have another go. Not that it has anything to do with crystal sets, but here’s one of the chocolate wrappers I drew the schematics on the back of. It’s good stuff –

PS – another reason to build a good crystal set that just occurred to me, is as an emergency radio. Many American households have radios for emergency use, either with an extra supply of batteries, or with built-in hand cranks or solar panels. Crystal sets don’t need any power at all, other than the power from the transmitter. As long as there is AM service in your area, this must make them a worthy part of any household’s emergency planning.

My last project, a Norcal 2N2/20 kit build, which also involved a partial scratch-build of the same circuit, rather took it out of me. As a result, I’ve been revisiting some of the circuits I built in my pre-teen years. Giving myself permission to play around with simple circuits is really fun, as well as a reminder that, for me at least, this is what it’s all about.

In the 1970’s in the UK, there was a BBC television show called Tomorrow’s World, which showcased the latest technologies. In November 1972, one of the marvels mentioned was a new integrated circuit. Housed in a metal TO-18 can and looking for all the world like a regular transistor, it contained a whopping 10 transistors, as well as a few resistors and capacitors. Made by British company Ferranti, it was known as the ZN414, and enabled a radio receiver to be built for the AM broadcast band with as few as 7 external components including the battery – 8 if you include the earpiece. Performance of this little TRF radio receiver chip peaked at around 1MHz, though it was usable from 100KHz up to 3MHz – and with diminished performance up to 5 or even 6MHz. It’s best performance was in the 531-1602KHz UK AM broadcast band.

The first ever published article describing a receiver built with this IC was in the January 1973 edition of Practical Wireless. Dubbed “The Mighty Midget”, the circuit was shockingly simple –

The little receiver was built into a small plastic snuff box. The 3.5mm earpiece socket was modified so that insertion of the crystal earpiece plug into the jack would switch the circuit on. This saved space in what was a very small radio. Further details are in the article, which you can download from the previous link.

My first awareness of the ZN414 was in 1975, when the September edition of the UK publication Everyday Electronics contained an article titled “Matchbox Receiver”. It described the construction of a simple receiver for the AM broadcast band, also using the ZN414, in an England’s Glory matchbox. British matchboxes, in the pre safety match era, were larger than their US equivalents. The England’s Glory matchbox was about 2″ length x 1 3/8″ width x 5/8″ height, which equates to approximately 50mm x 35m x 16mm – still small, but big enough for an 11 year-old to build a radio receiver in! You can download the entire issue here. As with all the links in this post, it opens in a new window. The article begins on page 484. For convenience, here is the schematic –

Like the earlier circuit in Practical Wireless, it used a modified 3.5mm jack socket to act as an on/off switch for the receiver, to save space. Unlike that circuit, it added a transistor to provide extra audio amplification, as well as a variable resistance in the +ve supply line to the ZN414 so that the gain of the chip could be reduced to prevent overload in the presence of strong signals.

The 11 year-old me was captivated by this circuit. It was simple enough for me to contemplate building, yet promised very usable performance. I remember putting it together in the kitchen at home. I used a crystal earpiece with it, though don’t remember what I did about the variable resistance. A regular pot would have been too big to fit in the the matchbox. For the matchbox, I used the England’s Glory brand, as in the article.

On finishing the wiring, it worked right off the bat. We lived just a few miles from the BBC Droitwich transmitting station, so signal strength wasn’t a problem. The matchbox radio received several BBC stations at good signal strength. I was so proud of it that I just had to take it to school. Unable to contain my excitement at the novelty of this miniscule receiver, I sat in class listening to the cricket scores and passing them out on little bits of paper to my classmates. It wasn’t long before the teacher got wise to our little scheme, and I found myself in the office of the deputy head, Mr. Lane, who confiscated my prized homebrew project. This was a time when corporate punishment was still very much a thing in British schools and, for my transgression, I received a few swipes of the cane. In our school, there were two ways in which the cane was administered. The first was the good old time-honored method of having the boy bend over and receive a caning on the rear end. For lesser offences, the punishment was administered on the hand. This was the way I received my penalty, and I do remember that it didn’t hurt a bit. The deputy head was fascinated with my little radio. He asked me several questions about it, and was obviously quite impressed. He seemed reluctant to confiscate it. I remember him communicating to me that it was something he had to do, and I got the distinct impression he was merely doing what was required. Same thing with the caning; I don’t think his heart was in it. It didn’t even sting. In my odd schoolboy way, I was quite proud of the fact that I’d received the cane. I was a good student, and generally reasonably well-behaved. A caning allowed me to, in my mind at least, perhaps keep some credibility with the less well-behaved students, while the reason I had received it kept me firmly in “electronics geek” territory. I was a rebel, but of the best kind, thanks to a ZN414 integrated circuit and a BC107 transistor!

Probably the best and most comprehensive overview of the ZN414, the various circuits in which it is used, their pros and cons, and the subsequent clones of this IC since it’s demise, is on this page by Australian electronics enthusiast John Hunter aka cool386. If you’re interested in this IC, I strongly recommend that you read this informative page.

Ferranti, the company that manufactured the ZN414, went out of business in the early 1990’s, and with it went the ZN414. In the years since, various near-equivalent IC’s have become available, such as the MK484, KM484, YS414, and the most recent TA7642. Of these, the TA7642 is currently the most commonly available.

I decided to breadboard a few different circuits in order to help decide which was the best one for this project. The ZN414, and all of it’s successors, has just 3 leads. One would think that you’d need a minimum of 4 leads, for input, output, +ve supply line, and ground. However, this chip combines the output and +VCC in one connection – it’s rather clever. Here’s the very first circuit using the chip, that was published in the January 1973 edition of Practical Wireless. I have omitted the switched earphone jack, to make it easier to see what is going on with this circuit –

The +ve supply terminal of the IC doubles as the audio output. There is a small variation in current in the positive supply line that varies in sympathy with the detected audio. In the above circuit, that audio appears as a slightly varying voltage across the 1K resistor, which is enough to drive a crystal/piezo earpiece. This circuit also has what appears to be a 100K feedback resistor between the output and the input. I am not entirely sure whether this resistor exists to feed detected audio back into the input, or to apply a DC bias to the input – or both. I suspect it’s a bit of both. I’m not sure whether anyone has the definitive answer on this as, to my knowledge, Ferranti never released the internal circuit of the ZN414, and I have not seen it anywhere online. Because the original circuit is not publicly available, it does not appear to be known whether any of the subsequent successors to this IC are exact clones, or just near-equivalents.

I built the above circuit with a TA7642 (purchased from Dan’s Small Parts and Kits), and found that it worked quite well. Current consumption was a miserly 0.25mA at 1.35V from a rechargeable NiMH cell. Volume was listenable in a quiet room, though audio from the crystal/piezo earpiece was tinny sounding. I live in the densely populated San Francisco East Bay, with some strong signals on the AM band, and found that some signals overloaded the circuit, driving the sound into distortion. Alternative versions of this circuit employ a variable resistor in series with the +ve supply line, to reduce the supply voltage to the chip, and therefore also the gain. See the Everyday Electronics circuit above for an example of this. It didn’t work very well when I tried it with a TA7642. Instead of investigating further, I moved on to a method of gain control which John Hunter aka cool386, on his ZN414 web page, says is superior, giving better control over the amount of feedback and gain than other methods. It was first implemented by an Australian kit company called Technicraft. The next circuit illustrates this method. Instead of the 100K resistor being connected between the “cold” side of the tank circuit and the output of the ZN414, it is now connected between the cold side of the tank, and the wiper of a pot that is connected between the chip output and ground, allowing the amount of output signal (both audio and DC bias) that is fed back to the input to be adjusted continuously from the full amount down to zero –

Note also, that instead of a very high impedance crystal/piezo earpiece being connected across a resistor that is inline with the +ve supply line, the supply current now flows through a pair of low impedance earbuds that are connected in series. I was pleasantly surprised to discover that this results in a good listening volume, as well as much better audio quality than the tinny sound from the crystal earpiece. There is another benefit too. If a 3.5mm jack is fitted for the earbuds, no type of on/off switching is required, as unplugging the earbuds automatically breaks the circuit and cuts off the supply voltage to the chip. Very simple and elegant!

John aka cool386, says that this method of feedback, developed by Technicraft to work with the ZN414, doesn’t work at all well with the TA7642. It does, he says, work with the YS414 and MK484, which can be regarded as direct equivalents. This statement has really piqued my curiosity, because I’ve been using a TA7642 (from Dan’s Small Parts and Kits) and it works quite well. I tried a YS414 (from Mike’s Electronics) in the same circuit, with exactly the same results. The performance was no better, as John’s page suggested it would be. This leads me to the conclusion that not all TA7642’s, YS414’s – and probably MK484’s, KM484s’ etc are the same. Most of these parts are not branded with the insignia of a major manufacturer, so we have no clue as to their pedigree. Even if they do have a logo on them, we cannot be sure of it’s authenticity. In other words, it’s a zoo out there in semiconductor land. I’m thinking of purchasing some MK484’s and KM484’s from Mike’s Electronics, to compare. They have 3 different types of 7642 as well – the TA7642, UTC7642, and a CD7642. Are these from 3 different manufacturers, or were they all made in the same factory with the same dies, and are just branded differently?

I would really like to find an original ZN414, in the metal TO-18 can, to try out in this Technicraft circuit. I did find an eBay seller who is offering the ZN416E. As well as producing the ZN414, Ferranti also made the ZN415E and ZN416E chips. They were in an 8 pin DIP package, and were simply a ZN414 with an extra audio amplifier stage. The ZN415E offered an extra 6dB of gain, and the ZN416E an extra 18dB. The price for this ZN416E gave me pause at $25. He assured me that the chips he was selling were genuine, so I took a chance and ordered one. Does this look genuine? It says GPS, which I assume stands for GEC/Plessey. (In the late 80’s, GEC acquired Ferranti and soon after, took over Plessey) –

Although the internal circuit of the ZN414 is not available online, the internal layout of the ZN416E is, in the datasheet. I have redrawn the circuit of the ZN416E, showing how I wired it up in a way that I could still use the Technicraft feedback/biasing method –

This was my first chance since childhood to use what I thought was a ZN414, and compare it’s performance with my TA7642 from Dan’s Small Parts and Kits. With the circuit wired as shown, the audio was quite distorted. A resistance in series with the earbuds, of around 150-220 ohms cleaned up the audio, though it did reduce the volume somewhat. At this point, performance was roughly on par with the TA7642 version, though the setting of the feedback pot was more critical in the “ZN414” circuit. I put the ZN414 in quotes, as I am not sure whether it is a genuine GEC/Plessey part. Current consumption was ~1mA at 1.35V with a pair of C Crane earbuds. You can cut the current consumption to a stunning 0.25mA by inserting a 1K resistor in place of the earbuds, and connecting a crystal/piece earpiece between the output of the ZN414/TA7642 or equivalent and ground. Volume in the piezo earpiece is lower than with the low impedance earbuds, and the audio not as full-sounding, but if a very low current draw is your goal, this is the way to go. A AAA alkaline battery has a capacity of 850-1000mAH. Assuming a capacity of 1,000mAH, with a piezo earpiece, one of these radios would run continuously for over 5 months! Alternatively, if fitting it into a very small enclosure is the desire, you could power it from a small button battery and still achieve a very respectable runtime. For instance, a P675 1.45V hearing aid battery has a capacity of around 600mAH, and would still run this radio on a piezo earpiece for over 3 months. If you wanted the greater volume and fuller audio of a low impedance set of earbuds, you’d still get a continuous runtime of just under a month.

I did also try using the 18dB buffer stage in the ZN416E, but it provided too much volume. I could have fitted an AF gain control, but seeing that I wanted to fit this radio into a small enclosure, and that I was getting enough gain without the extra amplification, I decided to keep it simple. An extra bonus was the current consumption of 1mA (with the lo-z earbuds) as opposed to 3mA using both stages of the ZN416E. I liked the idea of a very simple circuit and 1mA of current draw, so decided to stick with this circuit –

While deciding which circuit to build, I breadboarded the different variations –

That trimcap is actually a 365pF part, believe it or not. I’ve had a few of them for years, and am hoping to find a use for them one day –

On the left-hand side in the next shot is a circuit using the ZN416E, in the 8 pin DIP package. On the right, I used a 100pF fixed cap in parallel with the ferrite rod antenna. By sliding the ferrite bar in and out of the coil, I was able to tune the entire AM broadcast band. I did consider implementing a PTO in the final build, but eventually ditched the idea in favor of the traditional variable cap and coil approach. I’ve never been able to fully get on board with PTO’s –

For the final build, I was very tempted to recreate my original ZN414 radio, and construct it in an England’s Glory matchbox. I won’t bore you with the several reasons I decided against that, but eventually decided to put it in a small plastic project enclosure. The ferrite rod antenna and matching polyvaricon from an old Sony SRF-39 pocket radio were a perfect fit in the small case. These radios, part of the SRF-39, SRF-49, and SRF-59 model group, were some of the first receivers adopted by the Ultralight DXing folk. All 3 models share the same internal circuitry – it’s the same board in each one. The polyvaricon is smaller than your standard polyvaricon, as is the diminutive ferrite rod antenna. The variable cap measures just 16mm square, and the ferrite rod antenna is about 45mm long. Their small size was an advantage. In addition, I didn’t need to concern myself with whether the coil and cap combination would tune the entire band, as they had already been matched up in that regard –

The ferrite rod antenna was easy to remove with soldering wick, as the connections to the board were made on 2 small pieces of PCB material mounted to the coil. This made the part easy to insert into a new build, as I didn’t have to fiddle with unsoldering and resoldering the litz wire. Connections are made directly to the PC board pads –

Just to be sure, I mocked up the circuit using the very same coil and cap that were going to be in the final build –

The polyvaricon didn’t have any mounting holes, so I glued it to the interior of the plastic enclosure with JB Weld. You can see that I used little pieces of foam to friction-fit the rod antenna and the AAA battery holder into the plastic case. The foam holds everything firmly enough that it wasn’t necessary to use screws or any more glue to hold things in place. The stiff wires connecting the antenna to the variable cap helped as well –

You can see what looks like 2 separate coils on this ferrite rod. They are wired as one coil with a center tap. It is possible to vary the inductance of the coil by scraping off the wax that secures the smaller winding to the rod, and sliding it along the rod. Moving it further away from the main coil reduces the total inductance. This is how, in the Sony SRF-39 from whence it came, it is adjusted so that it tracks with the oscillator. I slid the smaller coil to the end of the ferrite rod and was able to cover the entire AM broadcast band –

The value of the feedback/biasing pot isn’t critical. If you’re particularly concerned with keeping the current draw as low as possible, it’s worth noting that the difference in total current consumption between using a 10K pot and a 100K pot is about 0.12mA. This is tiny, but if you’re using a piezo earpiece, for a total consumption of ~0.25mA, the use of a 100K pot can lengthen the already very long battery life by almost an extra 50%. The smallest pots in my parts drawers were Alpha brand, purchased from Tayda. The biggest value I had was 50K, so I used that. The pot is wired backwards i.e. turning it clockwise reduces the gain. It was done this way to simplify the wiring and keep the relevant wires short, but I have to think twice before adjusting it!

It probably seems a bit of an over-reach naming this simple little receiver, especially as the design is very simple and isn’t even mine. That’s why I didn’t include the name in the title of this post. Also, as The Sproutie and The Sproutie MKII are regen receivers, it only feels right that a receiver named The Little Sproutie should be a tiny regen receiver. Maybe I’ll call it “The Little Sproutie TRF”, so as to leave room for a Little Sproutie Regen in the future. I do like naming things after my cats though so, for the time being, the Little Sproutie it is –

This little marvel measures 71mm x 41mm x 23mm –

As a TRF receiver with just one tuned circuit, it’s not the most selective design by a long shot. Nevertheless, I am able to receive the following 15 stations from home, all with good separation from nearby stations – one more with great care and some bleed-over from nearby stations – KDIA 1640, KGMZ 1550, KSFN 1510, KVTO 1400, KMKY 1310, KSFB 1260, KLOK 1170 (just), KFAX 1100, KNBR 1050, KIQI 1010, KNEW 960, KKSF 910, KSFO 810, KCBS 740, KNBR 680, and KEAR 610. I wonder how this little receiver would perform with a tuned loop antenna placed next to it? (UPDATE as of 6/11/2025 – I just tried it, with good results. Scroll down for a little more info.)

I am curious to see if a genuine original ZN414 would work better with this Technicraft feedback arrangement. If you have a Ferranti ZN414 in the TO-18 metal can that you’re willing to part with, I’m very interested in purchasing it. If you have an old homebrew project with a ZN414 inside, I’ll buy it from you. Just leave a a comment underneath this post or, if you have access to QRZ.com, you can email me. I’ll be very grateful – and I promise that I’ll treat the ZN414 with great care!

I still think I should have built it into an England’s Glory matchbox though, for the ultimate nostalgic reminder of my youth.

6/11/2025 UPDATE

I just did a quick test with a tunable frame antenna that I built a few years ago, and initial results are very good. After a 5 minute test, signal strengths on all stations were much improved. Based on this, I hope to be able to receive one or two stations that were previously inaudible without the tuned loop antenna. Presumably because this TRF receiver has a fairly broad front end, it is possible to use the tuning control on the loop antenna alone to tune in a lot of stations at many different locations on the band, with the receiver remaining tuned to one frequency –

The diode underneath the variable cap was part of an experiment in turning the loop antenna into a crystal set. With a Western Electric 509-W high impedance headset, several stations were easily audible with no external antenna. It is tempting to install some Fahenstock clips on the frame, so it can do double duty as both a tuned loop antenna and a crystal set* –

These are all very encouraging results!

*Shortly after finishing this little set, I did just that. I turned this tuned loop antenna into a very serviceable crystal set.

Note – this is a rather long and wordy post, with a lot of pictures. Perhaps surprisingly, after 16 years, there are still some unbuilt Norcal 2N2/XX kits floating around in the wild. If you have one, or are hoping to aqcuire one, and are interested in suggested and recommended minor mods and parts substitutions, I mention them in the description of my build, as they come up. They are also listed in one place near the end of this post, under the heading “Mods and Parts Substitutions”. Some of these changes could also be relevant to a 2N2 scratch-build.

Images in this post can be clicked on for a slightly larger version. Not as big as I’d like, but I can only expect so much from a free format.

An astonishing 16 years ago, I assembled a Norcal 2N2/40 QRP CW transceiver kit, and became very much beguiled by it. At the time, an FT817 was my main station rig. I put the 817 away, and placed the 2N2/40 on the desk in pride of place. It remained on 24/7, connected to a pair of earbuds and a loaded vertical on my apartment balcony. Whenever I wanted to operate, all I had to do was sit down, put the earbuds in, and start tuning around. The antenna was already tuned for 40M, so transmitting was as simple as tapping the key. Limiting myself to CW on one HF band, thus simplifying the mechanics of operating, was a wonderful way to experience an amateur band. Combined with the lack of AGC in the receiver, operating this rig was a little like driving an old British sports car through the country roads; I really felt as if I was in direct contact with the band.

I’ve long had a special regard for Jim K8IQY’s series of 2N2 rigs. The original dictate of the contest which the design won, was for a transceiver that used 2N2222A transistors as the only active device, and no more than 22 of them. Once the contest was over, the circuit was modified, and some of the 2N2222A’s replaced by other NPN bipolar transistors in order to improve performance. Jim kept the circuit to an all-discrete component one though retaining, in my opinion, the integrity of the design. (Bill N2CQR of Soldersmoke fame would be proud!) This final 2N2/XX design was issued as a kit by the Norcal QRP Club, in versions for 40, 30, and 20M. There are certain designs and circuit architectures that I become particularly enamored with, and just have to build. This was one of them and little did I know, when assembling my 2N2/40 kit in late 2009, that I wasn’t done with it yet.

Recently, the 2N2 series of rigs came back into my head, and I began thinking how great it would be to have another 2N2 rig, but on 20M. A quick Google search led me to an ad on a ham trading site that had been placed by a gentleman who had not one, not two, but three unbuilt Norcal 2N2/XX kits – one for each band. Occasionally, the laws of supply and demand come into sharp focus, and a feller feels compelled to seize the moment. Despite the fact that I already had a Norcal 2N2/40, and wasn’t terribly bothered about 30M, a week later, a US Priority Mail flat rate box arrived at the AA7EE radio ranch with 2N2/40, 2N2/30, and 2N2/20 kits inside, all unbuilt, and all in their original sealed states, as they had been delivered to the seller about 16 or 17 years earlier. What a wonderful classic QRP kit time capsule! Around the same time, I also bought an unbuilt 2N2/40 kit from a different gent, and I’m still trying to rationalize why I now have so many, and what I intend to do with all of them. I’m wondering whether I should feel guilty for having quite a few, whether this bestows upon me a particular responsibility to preserve and archive, build them with extreme care and keep them completely stock, or whether I am thinking too much about all of this. I will say though, that I have a real regard for this design and, at least for the time being, am not interested in selling any of them to anyone else. If, however, I still have them when I’m in my 80’s, feel free to email me (I’m currently in my early 60’s).

As illogical as it sounds, there was some kind of method to the seeming madness of suddenly acquiring so many unbuilt kits, even though I already had a fully functional 2N2/40. At least, there was some logic to it in my head. I had never been fully happy with the fact that, in order to fit my 2N2/40 with a digital frequency display, I had drilled 4 small extra holes in the front panel, as well as a fifth hole for the function button of the KD1JV Digital Dial. Initially, I was happy with it but over the years, became slightly bothered by a feeling that I had disturbed the clean aesthetic of the original front panel. Here are before and after pictures of my 2N2/40, and I think you’ll see what I mean.

Recently, I attempted to make the drilled front panel look a little more pleasing, by substituting white nylon screws for the metal ones that were previously used. It helps a little, I think. Unfortunately, the screws were slightly translucent, and the paint I used to cover the visible metal in the countersunk holes was a slightly different shade of white. I did my best –

Further upsetting the front panel aesthetic, in my judgement, is that my addition of the rectangular cutout for the frequency display makes the “The NORCAL 2N2/XX” graphic look out of place. It was good for the original panel layout, but ideally, with the rectangular cutout, should be placed more to the left.

Contributing to this feeling of mild dissatisfaction with the front panel was the fact that for a kit, it is a particularly sturdy, quality enclosure. Only a total of 500 were ever made available, so the enclosure for my 2N2/40 represented one less that was in original condition. Purchasing a few unbuilt kits was my way of somehow “preserving” a piece of what I consider to be classic QRP kit history. On the other hand, maybe it’s just a hoarder’s mentality – something which, I hasten to add, I am not!

The 3 kits arrived well packed, and in the same condition that the seller would have received them from the Norcal QRP Club all those years ago –

It was really exciting seeing these kits, in pristine “just been packed” condition –

This particular one is the 2N2/20, which is the one I was intending to build first. Honestly, it’s almost a shame to build it, thereby erasing it’s “unbuilt kit” status. Documenting this in pictures is my way of allowing myself to unpack the kit and progress –

I put the smaller parts in mint tins when building, to keep them from getting lost. In this shot, I had already deployed the hardware tin. You can’t see it in this next shot, but the lid has a Dymo label on it, saying “Hardware”. Other tins were labeled “Semiconductors”, “Resistors”, “Caps”, “Inductors”, and “Trimcaps” –

Parts were transferred from their sealed plastic bags to labeled mint tins –

The pair of rounded pliers that I use to get the rounded leads of vertically mounted components. The black band on one of the jaws is a Sharpie mark. Each end denotes where I place the lead to achieve a different radius of bend. The majority of parts (mostly the resistors) required the smaller radius, while the molded chokes the larger one. Markings like this ensure that the radii are all roughly equal, for a uniform look. The Sharpie band had a habit of wearing off, so I later replaced it with a piece of insulating tape wrapped around the jaw –

Following are the 4 envelopes containing replacement and missing parts, as well as the envelope with 8 crystals, for the filters and local oscillators. The crystals are marked in such a way that the builder can tell which ones to use for each application. However, these markings might not be immediately obvious. If you are lucky enough to have a 2N2/XX kit, I strongly recommend that you join the norcal 2N2 group on groups.io/, download the archive of messages from the old (and now defunct) Norcal 2N2 group on Yahoo Groups, and spend all the time you need to read all the posts before embarking on your build. It’s useful reading, and you will almost certainly learn a few things of interest and significance. All the other necessary documentation is in the files section too. If you really want to gain an understanding of this design and it’s history (and in my opinion, you should), you’ll find this page on Jim K8IQY’s site to be very informative. Start at the bottom with the original 2N2/40 and work your way up. If you want to scratch-build a 2N2 rig, then Jim’s site is even more of a must-read.

It is a dense board – not for beginners. As pointed out in the manual, this is not a beginner’s kit. It is also not really a kit for anyone who wants to be told exactly what to do, in full detail, and wants that information spoon-fed to them. The same schematic is used for all 3 band versions of the rig. The assembly instructions will tell you which parts to install and at what point, but they will refer to parts by their component designation without mentioning the value. For instance, you might be told to “install capacitors C59, C60 and C61”, but you won’t be told that they are 0.1uF parts. To find that information, you will need to refer to the schematic and/or the BOM (bill of materials). This approach serves two purposes –

1. It streamlines the process of writing the manual, allowing one set of instructions to cover the assembly of all 3 band versions and
2. It forces the builder to consult the schematic and/or BOM, in the hope that a more in-depth knowledge and understanding of the design will ensue. Jim would later comment, in a presentation given at Ozarkcon in 2009, that this approach didn’t seem to help newer builders learn, as much as was hoped it would.

Despite #2, I still think it doesn’t hurt to slow builders down, and require them to check and double-check each individual part before installing. My personal view is that if you don’t have plenty of time to dedicate to a project like this, you might be better off with a more straightforward kit.

The first step is to install the 8 threaded stand-offs that allow the builder to sit the board on the bench either way up while building, without causing any of the installed parts to contact the workbench. It’s a detail that helps assembly go more smoothly. It’s a handsome board, for sure –

The rig is built stage by stage, with tests being performed on each stage after completion. This way, a builder can verify that a stage is working before continuing. I much prefer this way of building to merely stuffing boards with parts until the board is fully populated. That approach to kit assembly, instead of building a stage at a time, often concentrates on installing all the capacitors in one fell swoop, then all the resistors, then all the semiconductors, etc etc. It may be more efficient, but it doesn’t help to give one a sense of the general circuit architecture, and how each stage relates to the others. I’ve said this several times before when describing other projects, but building a receiver backwards, beginning with the audio amp, is a great way to build. The builder hears the way that the sound of the audio from the speaker changes, as the signal is processed by a gradually increasing number of stages, all the way back to the beginning of it’s journey as an RF signal at the antenna socket.

The first two stages to be assembled are the power conditioner and the final AF amp. On completing the AF amp, you can touch the input with a piece of wire or screwdriver and hear 60 cycle hum, and possibly also loud local AM stations –

The next stages to be built are the receive/transmit keying (near the bottom left, just below and to the right of the rather portly polarity protection diode), and the receive mute circuit (to the left of the volume pot). D2 and D3 are back to back 1N4418 diodes, to provide some protection against loud and sudden spikes in the audio. K8IQY suggests that if you want a bit more protection, you can use Schottky or germanium diodes instead. I had fully intended to install two 1N5711’s in these positions but for some reason, forgot, and used the 1N4418’s that came with the kit. Another time perhaps –

Then comes the audio preamp (to the left of the receive mute circuit and the final AF amp), and the RxLO, the receive local oscillator (just below the final AF amp) –

The next part is where things start to really pick up, and get quite exciting. The next stage to be installed is the product detector. It doesn’t take long to install, consisting of just a resistor, a couple of capacitors, a molded choke, and a little double-balanced diode ring mixer package. However, it transforms the circuit from an audio amplifier into something that can receive atmospheric noise. That’s the magic of this little diode ring mixer package!

Earlier scratch-built versions of the 2N2 series employed diode ring mixers that were constructed by the builder, from 4 diodes and toroidal transformers. This little commercial package, the ADE-1, takes up much less space, and simplifies the assembly somewhat. I love these little mixers –

Connecting some kind of antenna to the input of the mixer, such as a length of wire, or even a metal screwwdriver held in the hand, results in static being heard in the speaker. This is always the first magical moment for me. The radio frequency signal from the RxLO is being mixed with the atmospheric energy picked up by the antenna. The band of frequencies that are a few KHz either side of the frequncy of the local oscillator are converted to an audible signal that you hear as static in the speaker. To put it simply, radio frequencies are being converted to sound. You are listening to the ether!

In retrospect, I rather wish I had installed a slightly higher grade trimcap in the receive local oscillator, as I ended up doing in the the TxLO. The lttle brown trimcaps that are used throughout the rig, with the exception of the VFO, are Sprague Goodman’s “economy grade”. In my experience, they are fine for tuning bandpass filters, but not ideal for oscillators. More on that later.

The next stage to be constructed, the post IF amplifier crystal filter, is almost as straightforward, consisting of just a couple of crystals, a few capacitors, and a resistor. Progress is encouraging at this point, because simple stages make quite noticeable differences to the sound in the speaker. After constructing this stage and touching the input of the crystal filter with an antenna, the same atmospheric noise is heard, but is more restricted in bandwidth, due to the effect of the filter. It really feels as if the receiver is gradually coming together!

The IF amplifier adds about another 35-40dBdB of gain to the receiver. There was an issue with the MPSH10 transistors supplied with the original kit, as they had lower gain than the Motorola devices used for the prototype. This kit (and hopefully yours too) had the little brown envelope with two substitute higher gain Motorola MPSH10 transistors –

This fledgling receiver was beginning to get serious, with the addition of the main 4 pole crystal filter. It’s just 4 (matched) crystals and a few NP0 capacitors, but narrows the bandwidth of the received atmospheric static significantly. Looking at circuits has a definite gratuitous aspect for me, as odd as it may sound. Just look at those 4 stout crystals, valiantly narrowing the bandwidth of our received signal. Beautiful!

This was the point in the build where I began to have some slight misgivings about how it was going, though my concerns later turned out to be unfounded. At every point up to here, each stage seemed to be producing the kind of noise from the speaker, as well as the levels, that I expected. On touching the output of the main crystal filter (i.e. the input of the IF amplifier) with a small metal jewelers screwdriver, loud static and AM stations were heard in the speaker, as expected. On touching the input of the main crystal filter, the sound from the speaker was more restricted in bandwidth but greatly reduced in volume. As a comparison, I tried the same tests on my fully functional 2N2/40, and found that the volume from the speaker when touching the input of the crystal filter was a lot louder than with the 20M version. A lot louder, and much more lively. I checked every single solder joint in the crystal filter as well as performing close visual inspections on each NP0/C0G capacitor. Nothing looked amiss. At that point, out of ideas, I decided to continue. Maybe things would be OK?

Below and to the right of the 4 pole crystal filter, are the two toroidal transformers and the PN2222A transistor that comprise the receive post-mixer IF amplifier –

Now for the VFO. Now we are talking! After building my 2N2/40, I discovered that, when operating on battery power, there was a slight chirp in the transmitted signal. The 2N2 rigs were intended to be operated from a well-regulated bench supply and for this, the 6.2V zener diode in the VFO circuit lends adequate stability for that usage, while staying within the original contest dictate that the only active devices be 2N2222A’s. I did want the option of running the rig from a battery though, and implemented a mod suggested by Bob WB2SRF in the old Norcal 2N2 Yahoo Group. He substituted an LM431 shunt regulator for the zener diode, resulting in better regulation of the voltage supply to the VFO. The mod is detailed here. This circuit alteration shatters the purity of the design, in that it introduces a non-discrete component. If that concerns you, stick with the zener. A linear regulator IC, such as a 78L06, would probably offer even better regulation, though you’d need to modify the board a little. The advantage of the LM431 being a shunt regulator, is that the circuit, consisting of the little IC and the 2 voltage-setting resistors, are a drop-in replacement for D9, the 6.2V zener diode. Here’s the circuit for the new regulator. I measured 6.26V across mine which, with the voltage drop across D8, a 1N4007, provides 7V to the VFO –

Initially, I used a tantalum capacitor for the 10uF part, and mounted it below the board. I later changed it to a slightly larger electrolytic, necessitating relocating it above the board. Here’s the assembly during construction, with one of the two voltage-setting resistors soldered in place –

With both resistors –

The first implementation employed a small tantalum capacitor mounted below the board. Heat-shrink tubing was used for insulation –

The leads of the capacitor were allowed to protrude through the top of the board, so that the rest of the assembly could be soldered to it –

The main assembly was soldered to these leads –

I had misgivings about the age and reliability of the tantalum capacitor, so later substituted an electroytic instead. It was larger and, as a result, was mounted above the board. You can see it at the back of the next picture. As it turned out, the PCB enclosure that I fabricated for this rig allowed me to use slightly higher stand-offs, so there would have been room for the electrolytic. I didn’t know that at the time though –

Here’s the board with the VFO completed and the 10-turn tuning pot temporarily connected. Although it wouldn’t be possible to get a final take on the VFO stability until it was mounted in an enclosure, it seemed quite good at this point, and definitely usable –

To the left of the tuning pot, at the edge of the board, is the LM431 shunt regulator. If you’re building your 2N2 stock, the zener diode D9 will be there. To the left of it is Q9, the VFO transistor. Above and to the left of that, close to the polystyrene capacitors, is not another transistor, but D10, the MV1662 varacter diode for the main tuning –

After installation of the VFO buffer and VFO driver (the mixer package requires a +7dBm drive level, which is about 5mW) –

The next stages to be installed were the receive main mixer, the RF amplifier (not required on 40M), and the input bandpass filter –

On the receive side, the RF gain circuitry, as well as the RF mute and RIT circuits still needed to be constructed. However, at this stage, it was possible to test the receiver out. RF gain is nearly always at maximum anyway, and the other two circuits are only needed in transceive. This was the point at which I really began to have concerns about the receiver. It seemed quite insensitive. It was receiving and, as far as I could tell, would receive pretty any signal my main station rig (a K2) could receive. However, the volume from the speaker was very low. In addition, there was the occasional “squirrely” noise in the speaker that sounded like a spurious unstable oscillation. Based on my earlier observation, about the main crystal filter appearing to attenuate the signal to a much greater degree than I had expected, I wondered if any of the crystals were defective. A very kind gentleman ham sent me a fresh set of closely matched 11MHz crystals for both filters, which I duly installed, only to experience the same result.

I wasn’t convinced that comparing results with my 2N2/40 was the ideal test. The 2N2/40 has a 4.9152MHz IF, as opposed to the 11MHz IF of the 20M version. At the lower frequency, it’s possible that the restricted bandwidth imposed by the crystal filter would cut out a lot more extraneous static and broadcast stations at 4.9152MHz than at 11MHz, as there tends to be more noise and static at lower frequencies. This could explain the much greater reduced volume of general noise in the speaker of the 2N2/20 than the 2N2/40.

This was not a very encouraging result. I decided to attempt a scratch-build of the 2N2/20. That way, I would have another 20M version to hopefully help with troubleshooting. The plan was to have the scratch-build occupy the same footprint as the kit version, and make a PCB enclosure of roughly the same size as the kit enclosure. I knew that my Manhattan scratch-build wouldn’t achieve the same density as the Norcal PCB, so the idea was to stack 2 boards. Holes drilled in the top board would allow access to trimcaps on the lower board for alignment and adjustments.

While building the scratch version, I observed the same thing with the main crystal filter as I did with the kit version – a huge reduction in the general noise and static level, on top of the expected more restricted bandwidth, when touching the input of the filter with a small metal screwdriver, as opposed to the output; a test suggested in the assembly manual. Perhaps this was normal? This was quite encouraging. On completing the receiver portion of my 2N2/20 scratch-build, unfortunately, it was even more deaf than the kit version. I won’t concentrate much more on the scratch-build, as it’s still possible it may be the subject of a future post if I return to it and am able to get it working. In the meantime, here are a few pictures –

Space was getting tight around this mixer, so I mounted some resistors on top of it, in order to fit them in –

This next one illustrates how dense Manhattan builds can get quite messy when viewed close up –

I temporarily shelved the scratch-build and decided to complete the kit version, by building the transmitter section.

Back to the kit version. In this picture, I finished off the receiver by installing the circuitry for the RF gain and RF mute, and RIT. When assembling the RF gain control and circuitry, I incorporated a couple of mods and substutions that had been suggested by Jim in the original Yahoo Group, and used successfully in my 2N2/40. They were –

1. Replacing R75 (4.7K) with a 2.2K resistor and Q20 (2N4124) with a 2N3904. A number of builders, myself included, noticed that our transmitters emitted spurii, as well as having a slightly rough sidetone. Making these parts substitutions cured that. There is no harm in making these substitutions, regardless of whether or not you have experienced this issue, per Jim, so it makes sense to implement them during the initial build.
2. The transition from full RF gain to quite a large degree of attenuation happens quite swiftly. Changing R77 (1K audio taper) to a 1K linear pot, R76 (1.5K) to 1K, and placing a 220 ohm resistor between the wiper and the side of the pot that connects to C20, makes the transition just a little smoother, though it is still fairly abrupt. However, having said that, the dynamic range of the receiver seems good, and the RF gain control will be on full nearly all of the time. The only time you’ll need it, you’ll actually want a lot of attenuation so, in practice, the way this control operates is not an issue. You could also keep the log pot and reverse the connections to the end terminals, if you don’t mind that the control will now work in reverse. In that case, you wouldn’t need to change the value of R76, or add the 220 ohm resistor.
3. Although not a suggested or recommended modification, I wanted to limit the amount of frequency excursion that the RIT control allows. As built, I was getting about ±3KHz. Due to the fact that the RIT pot is a center detent type, there is a small amount of frequency excursion either side of center, that is impossible to set. This is due to the tendency for the pot to want to “click” the control back to the center. As a result of this center detent, if the other station is within about 100Hz of you, give or take, it is not possible to “zero” him in, to exactly match the pitch of both yours and his transmitted signals. Reducing the maximum amount of frequency deviation that the pot will accomodate helps to lessen this effect. I changed R51 and R50 from 1.5K to 1K. This gave me ~±1.2KHz of RIT, which is all I need. It’s even enough for working most DXpeditions. Besides, transmitting just 1 up puts me (hopefully) at the edge of the pack and makes me more noticeable!

I then constructed the transmit local oscillator (TxLO), transmit main mixer, and transmit cascode amplifier. I would later replace trimcap TC10 in the TxLO with a higher quality part, but more on that later –

Then, in short order, the TX driver amp, and the TX final amp and LPF. The board was now complete. The 2SC5739 PA transistor was temporarily soldered at this stage, as I wanted to test some different transistors in it’s place –

At this point, although I had been testing the stages as they were being built, I was keen to plug it in and see whether the whole circuit worked as a transceiver. Initially, it was disappointing, as the receiver was still quite deaf. I also noticed the occasional “burbling” sound in the speaker. However, on hitting the key and transmitting a fairly brief carrier, suddenly, the receiver sprang to life. Background band noise increased significantly in volume, and the sporadic burbling sound disappeared. The receiver was working normally, and the transmitter was putting out close to 4W with R87, the drive trimpot, set to maximum, at a supply voltage of 12.8V. I can live with 4 watts. With a 13.8V supply voltage, I’m thinking it would output close to the full QRP gallon.

With the board on the bench, the VFO seemed quite stable, so I went ahead and tried some QSO’s with it. For the very first QSO, I couldn’t even wait to tack solder a key jack to the board, using both ends of a breadboard patch wire as a makeshift “key”. With that arrangement, the very first QSO was with K8LX in Michigan. Soldering a key jack to the board, I went on to QSO with Alberta, Hawaii, Colorado, Quebec, then VP2VI in the British Virgin Islands (the first DX), Washington State, Montana, etc etc…….it was working!

Now to put it in a case. There were two additions I wanted to make – a KD1JV Digital Dial and a CW keyer. Both of these would require cutting and drilling extra holes in the enclosure. I really didn’t want to do that to the stock enclosure that came with the kit, so decided to fabricate an enclosure from black FR4 copperclad. I’ve been getting my copperclad board from the eBay seller abcfab since 2011, and like his board very much. The sizing is accurate, and all the corners are square, which is very helpful when you’re making enclosures.

Incidentally, I assume you will want to use the stock enclosure, which is very nicely made. If you want to have a good idea where you are on the band, but don’t want to put extra holes and cut-outs in it, another way to go would be to use a nice, large turns counter, like Jim did with the earlier 2N2 rigs. This one from Mouser has two options for mounting. One involves drilling a small hole in the front panel, that will be hidden by the turns counter. The other option requires no holes at all to be drilled, This Bourns turns counter is Mouser #652-H-46-6A and Bourns #H-46-6A. DigiKey have it also –

I learned how to make enclosures with PCB material from Ken LoCasale WA4MNT, from this article. If you have never attempted to make one, definitely read his write-up first. My first ever PCB enclosure was this one, and it turned out really well. I’ve built a few over the years for some of my other projects, but then began to veer away from them, due to the work involved. Using a ready-made enclosure is so much easier. There’s something about an enclosure you make yourself though, that makes a home-built project feel even more personal. It must be all the extra work that goes into it.

First, the main pieces were cut out, the front and rear panels drilled and the cutout for the digital dial made (a lot of work to get it right), and all copper surfaces scrubbed with a steel wool pot scrubber, then dried and coated with a few thin layers of lacquer spray –

After drilling the front and rear panels, they had some minor surface scratches, so received a few light coats of Krylon Fusion satin black spray paint. This paint dries with an attractive fine stipple finish –

This was another point in the project that was very encouraging – having the enclosure continue to turn out well, so that I can easily visualize the finished item. At many points during the building and assembling of something like this, there is often the fear at the back of my head that something might not work out; the possibility that a mishap or run of bad luck could derail the whole thing. So far though, that hadn’t happened –

A top cover was fabricated, and controls and connectors fitted. The 4 holes on the back panel were for securing the internal keyer board with black nylon 2-56 screws (from McMaster Carr) –

For installation in the enclosure, all the temporary connections to the controls were removed. Flux and solder wick were used to reopen and clean up all the pads and holes for the controls and connectors. You’ll notice that I have changed TC10, the transmit oscillator trimcap. It was originally a brown part, and is now a yellow trimcap. All the trimcaps that were supplied with the kit, with the exception of TC7 in the VFO were the little brown Sprague Goodman economy grade trimcaps. These are fine for the adjustment of bandpass filters but for more critical adjustments, such as in oscillators, the variation of capacitance with rotation can be erratic. I must have been particularly unlucky with the specific one I used in the transmit local oscillator, as adjustment in that circuit was particularly difficult. TC10 is used to adjust the transmit frequency so it is the same as the receive frequency. It’s an operation that should take 20 or 30 seconds normally, but with this rather unpredictable component, adjustment was a game of chance, taking several minutes to get right. I had some yellow 45pF Murata trimcaps purchased from Dan’s Small and Kits. They operate much more smoothly, and made the act of adjusting the transmit frequency a quick and easy task. The same type of brown trimcap was used for TC9, the receive local oscillator. Adjustment of this frequency wasn’t as easy as it should have been though, in my case, not as hard as with the transmit local oscillator. If I were doing this again, I would have swapped out both trimcaps, in both local oscillators. If I build another 2N2 rig, I plan to do that –

It’s a pretty good-looking board. If only this WordPress blog site would display the pictures in greater size and resolution, you could see how nice it is. Clicking on any of the images here will take you to a slightly larger version, though not as high resolution as I would like –

Back when Dale N0XAS used to run HamGadgets, I bought several programmed chips from his PK-Plus Keyer. One of them was incorporated into my scratch-build of the SST-20. I used another one in this rig, building the board Manhattan-style. The schematic is very simple. Please note that what I have labeled as a piezo “buzzer” is actually a piezo transducer. Alternatively, pin 2 of the chip can be coupled into the AF amp of the rig –

The command/control button was relocated to the rear panel, as it is rarely used. Doing this helps to keep a cleaner front panel appearance. It’s the white pushbutton on the back –

The wiring to and around the the keyer board got a little messy but, as is said, “it is what it is” –

There are two separate key jacks. The lower one is for a paddle, and the upper one for a straight key. I like my rigs to be very usable. I have always much preferrred a speed pot instead of having to control the speed via a menu and/or the paddle. When operating, it makes adjusting speed on the fly much easier. I wonder why folk who write software for keyers often omit this feature. It’s either because they haven’t spent a lot of time operating CW and don’t appreciate the value of a speed pot, or it’s because they’re very adept at changing speed during a QSO via the menu/paddle process. It’s a mystery to me. While on the subject, I’d love to find some firmware for a keyer that has a speed pot and uses an ATTiny chip. All the code I have seen for ATTiny keyers implements speed change via a menu option. Perhaps there is a hardware limitation that prevents this?

Wow, that keyer board looks messy. Oh well. It works. Also, I’d have preferred to have routed both RG-213 cables underneath the board, but practical concerns made it inadvisable. The input to the KD1JV Digital Dial is taken from the top of R40, the side that connects to T5, via a 4.7pF cap that is enclosed in heat-shrink tubing –

All in all, it doesn’t look too bad under the hood and frankly, at some point I need to accept my own limitations and be happy with what I’ve done –

Looking quite presentable, I hope you’ll agree –

I arranged the controls so that the ones I’d need most often and in more of a hurry, were easier to access. On the left-hand side the AF gain is at the top and the RIT at the bottom. The RF gain is in the middle, making it a little less immediately intuitive to access. It is rarely used, so this is not a problem. The speed control is on the far right at the bottom – a quick and easy position to find when needing to swiftly adjust sending speed while operating –

The “DISP” button has only two functions – to switch the display off, and to shift the digits over two positions to the left, so that the first two numerals in the frequency can be read. For example. if on 14.030 MHz, the display normally reads 030.0. Briefly pushing the button changes the display so that it reads 14.03. Being a monobander, we already know what band the rig is on, so this function is never used.

A longer push, of about one second, switches the display off. There are two main reasons (I can think of) that one might want to do this. Firstly, to reduce current consumption if under battery operation. The other reason is tthat the KD1JV Digital Dial introduces a small amount of digital noise into the power line that can be heard in the receiver on a fairly quiet band when the AF gain is up. Earlier versions of the circuit used 1K current limiting resistors to individual elements of the LED display, and the digital noise was more noticeable. Connecting a 100 ohm resistor in line with the 12V supply to the readout and a ~100uF capacitor across the +ve and -ve terminals of the supply at the display board eliminated this noise. The current version of the Digital Dial uses 2.2K resistors. This reduces the noise significantly, though it doesn’t eliminate it altogether. After taking these pictures, I implemented the same supply line filter, which completely eradicated the noise. As a result, I never need to use the “DISP” button. Putting it on the rear panel makes it accessible “just in case”, but helps to clean up the front panel and rid it of uneccessary items.

I added jacks for both a paddle and a straight key. I like to have both plugged in at the same time, so that I can use either at a moment’s notice. I nearly always use a paddle but if I hear an SKCC op, for example, it’s nice to be able to quickly call them back with the minimum of fuss –

I had success with this rig just with the bare board operating on the bench, as noted earlier. It was fun to work the British Virgin Islands with the board and the connectors and pots temporarily soldered in place. As soon as I installed the board and all pots and connectors in the enclosure, wired it all up, and switched it on, I heard TX9A on Tubai Island in French Polynesia – and worked them! It really happened that quickly, and felt like a good omen. Although not true split, the RIT is useful for working DXpeditions. You just have to remember to use it in reverse i.e. if the station is listening up (as is the convention), you turn your RIT anti-clockwise and tune so that you can hear the DX op’s signal. Then, when you transmit, you will be on a higher frequency.

I didn’t measure the 3dB bandwidth of the rig, but the specifications on the Norcal QRP site say that the 6 poles of filtering give a bandwidth of 500Hz, which sounds about right. This is a comfortable width for general operating, though it’s a bit wide when the band is packed full of signals during a major contest. If I were of the mind to investigate further modifications, I’d possibly look into either making the existing 4-pole filter variable, or replacing it with the 3-pole variable bandwidth filter that was used in earlier versions of the 2N2 design. It would be really handy to be able to dial down the bandwidth when needed.

One question that might be on a readers’ mind is that of the eventual fate of the enclosure that came with the kit. I have been wondering that too! If I ever get around to finishing my 2N2/20 scratch-build, I’m thinking I might put it in the PCB enclosure that you see in this post, along with the KD1JV Digital Dial and internal keyer. The 2N2 kit board could then be rehoused in the stock kit enclosure with either no keyer, or a simple keyer that requires no extra holes to be drilled. A turns counter, such as the Bourns H-46-6A could be used for frequency indication, along with a logging scale.

A fantastic rig, and a very worthy project.

VFO Drift Test

The rig was switched on from cold, and VFO drift tracked over a 24 hour period. This was done by listening to the note produced by an Si5351-based VFO in the 2N2/20 receiver, adjusting the Si5351 VFO for zero beat against the 700hz sidetone in the main station rig (a K2), and noting the change in frequency over time. The Si5351 VFO used an Etherkit si5351 board with a TCXO for greater stability. This VFO could be tuned in 1Hz steps, so I think that the drift measurements are quite accurate.

For the first hour, measurements were taken every minute, then every 30 minutes thereafter. I finally decided to take my life back at the 32 1/2 hour point! If automatic logging was available here, it would be interesting to take more detailed measurements, to see how the different temperature-sensitive parts of the VFO interact to produce the observed drift. Faced with so much data, it is tempting to describe it in detail, but that will hinder the purpose of this test, which was to get an idea of how stable the rig will be in everyday use.

The initial drift from a cold switch-on is interesting, though not that instructive, as most amateurs of our vintage(!) are used to turning our rigs on for a good 15-30 minutes before serious use. My 2N2/20 drifted upwards about 500Hz in the first 5 minutes, and another 500Hz (approx figures) in the 15 minutes after that, for a total of about 1KHz upwards drift in the first 20 minutes. You probably don’t want to start a long ragchew in the first 20 minutes after switching on! After that, drift slowed considerably. At the 1 hour mark, it really settled down, with typical drift being about 20Hz/hr, often much less. Very occasionally, it drifted up to 30Hz in one hour, though that was the most in a 1 hour period. Some hours it didn’t shift more than a few Hz, for several hours in a row. In practice, you are unlikely to notice much drift after the first 20-30 minutes.

Mods and Parts Substitutions

As promised, here is the list of parts substitutions and minor mods that I made or, in the case of #1, fully intended to make, but forgot. I am not suggesting you do all of these, but #3 seems worthwhile for all builders.

1. For D2 and D3, which are both 1N4448 diodes, substituted Schottky or germanium diodes. This provides slightly greater protection against sudden spikes in the audio – a useful feature in a receiver that doesn’t have AGC. I intended to do this but, in the heat of construction, forgot. I would have used 1N5711’s. If I pull the board from the enclosure again, I will make this substitution.
2. Substituted an LM431 shunt regulator for the 6.2V zener diode D9. See text for details. For even better VFO voltage regulation, the more ambitious builder can use a linear regulator, such as the 78L06.
3. Replaced R75 (4.7K) with a 2.2K resistor and Q20 (2N4124) with a 2N3904. A number of builders, myself included, noticed that our transmitters emiited spurii, as well as having a slightly rough sidetone. Making these parts substitutions cured that. There is no harm in making these substitutions, regardless of whether or not you have experienced this issue, per Jim, so it makes sense to implement them during the initial build.
4. Changed R77 to a 1K linear pot, R76 to 1K, and placed a 220 ohm resistor between the wiper and the side of the pot that connects to C20, for slightly smoother control over RF gain. As part of this mod, changed R76 from 1.5K to 1K, to provide a bit more current, per K8IQY.
5. Changed R50 and R51 to 1K, to limit the scope of the RIT control. I had a specific reason for doing this, and most builders won’t feel the same. See text.
6. Changed TC10 to a higher quality trimcap, for easier adjustment of transmit local oscillator. If I ever pull the board out of the enclosure, or build another 2N2 rig, I will do the same for TC9 as well.

Thank you to Jim K8IQY for an interesting and engaging design, and The Norcal QRP Club for a great kit.

Noise la la la la la hinders if I were a rich man effective a noise annoys an oyster communication but a noisy noise annoys an oyster more.

Or said differently, when you're trying to communicate, something that the hobby of amateur radio does in spades, you'll need to deal with a phenomenon called noise.

This noise comes in different forms, but the effect is the erection of barriers to successful communication. We refer to the impact of noise as a signal to noise ratio or SNR, the signal being the desired information, the noise the undesired interference. Expressed in decibels so you can deal with a massive range using a small number, an SNR greater than 0 dB means that the signal is stronger than the noise.

Building a shack requires that you consider noise in many forms. If you've been a radio amateur for a few moments, your mind is likely to head straight for the hiss, crackle and pop you might hear whilst attempting to communicate on HF, but there's a few other things to discuss.

There's all sorts of electronic noise received by your radio. In addition, there's audio noise picked up by your ears, and often your microphone. Then there's the noise that you produce, either from your transmitter into the rest of the building, or from your mouth or speakers into the ears of the people you share the space with.

Starting with audio, having a space that you can close the door on is a good way to limit the noise coming into and leaving your shack. An alternative is to wear headphones and generate text to speech, or prerecord your voice, ready for a contact, potentially ideal for contesting, not so much for free form discussion. Another consideration is audio from other radios, including those tuned to a local broadcaster, or aviation frequencies. In other words, if you're transmitting with a microphone, make sure that there's no other audio coming through. In some cases it's even illegal to transmit that audio, but in all cases it's noise that makes communication more difficult.

This kind of audio noise mitigation is pretty straightforward.

In stark contrast, achieving the same with electronic noise is pretty much a balancing act between budget and effectiveness.

The impact of noise is inversely proportional to distance. Essentially, the closer it is, the more impact it has. With that in mind, when you start dealing with noise, start nearby and work your way out. As you eliminate the nearby noise, other sources will become apparent.

Without turning this into a noise mitigation class, the process is essentially one of elimination. First locate the noise source, then eliminate it. That's easier said than done.

For example, if the noise source is a power supply sitting on your bench, you can turn it off, except if that power supply is the one powering your radio, so perhaps I should say: "attempt to eliminate it" instead.

There's plenty of ways to have a go at this and volumetric kilotons of content published on the subject, some of it even useful.

In many, but not all cases, noise is an electrical phenomenon that enters via any means possible and you'll need to attempt noise mitigation at multiple points of entry. Obvious sources are the power supply, coax and the antenna connection, the speaker cable, the microphone lead, and if you're using a computer, the USB, serial or Ethernet cable and within the computer itself. Each requiring different approaches.

The obvious one is to disable the noise, that is, turn off the offending device. As I said, that might not be an option, but you can replace noisy gear, or place it further away.

There's isolation, using tools like ferrites and chokes to stop the noise from reaching your radio. Often in the form of a clip-on blob, you'll find these on things like monitor and USB cables. Place the ferrite as close as possible to the input of your radio. If it's loose on the cable, wind it through the ferrite, the tighter the better.

There's software solutions with varying levels of effectiveness. You'll find DSP or Digital Signal Processing knobs and buttons on many radios. They're generally helpful for narrowband repeating noises, like the hum of an electric motor or power supply.

There's tools that attempt to impose a noise on your signal that cancels out the noise, anti-noise, if you like, by receiving the noise, inverting it and adding it to your signal, thus, at least theoretically, eliminating it, noise minus noise is silence. This can take the form of a device for noise coming in from the antenna, but it also applies to things like noise cancelling speakers. In audio this is called active noise cancelling.

There's also a new crop of noise cancelling software, using A.I. or Assumed Intelligence, that captures your signal, attempts to figure out what's noise and what's not, removes the noise and then feeds it back to you. Your Mileage May Vary and if you break it, you get to keep both parts. Consider your privacy and security implications of sending your audio out the door to be processed.

That's not to say that, at least theoretically, effective local Machine Learning models could be created to help with this. I have yet to see one.

At some point you'll hopefully reach a place where the noise inside your shack is no longer an issue. Then you'll discover your noisy neighbours, with solar panel inverters, pool pumps, plasma televisions, broadband modems, kids toys and pretty much anything electronic, purchased with no consideration whatsoever in relation to your hobby.

I'm mentioning this, because more often than not, you'll have little or no control of those devices. You could cultivate your relationship with your neighbours and discuss your situation, but don't expect compliant hardware to magically solve all your issues.

Antenna orientation, horizontal versus vertical might assist, as might placement or distance from the noise source. It's why I suggest that you start this journey with simple antennas, with plenty of room for evaluation and modification to suit the conditions.

All this to point out that once you have the perfect shack, your work is only just beginning, but then I suspect that you've already realised this.

Like antennas, I will note that noise and its elimination is an integral part of this hobby. It's easy to forget that, whilst you're in the middle of a frustrating hunt for a noise source, and if you like you can think of it as ripples or waves on the pond whilst you're casting a fly.

When you discuss this with other amateurs, you'll likely come across terms like QRM and QRN, the last letter describing either Man-made or Natural noise. I'm not sure how helpful the distinction is, but it's there if you need it.

One resource worth mentioning is a website called qrm.guru. It has documented processes and tools to discover where noise is coming from and how to go about dealing with it.

I'm Onno VK6FLAB

Here is a selection of the latest QSL cards received direct for VK5MAZ and VK5PAS.

Here is a selection of the latest QSL cards received in the mail for VI8POL.

An opportunity presented to activate both a SOTA summit and and IOTA island thanks to Murray VK7ZMS over the Australia Day Long Weekend. Son Reuben VK7FREU and myself activated.

Although only one point summit (~400m elevation) for SOTA the opportunity to activate for the Islands On The Air (IOTA) program (OC-233) had some appeal. I have never activated an Island for IOTA before and so I contacted Grant Willis VK5GR who knows the IOTA program well having activated quite a few Islands through DXPeditions.

Timing:

To give some idea of how long things took the following timings were recorded:

0500 – At the boat ramp / wharf at Triabunna.

0650 – Dropped at Crocketts Bay beach on Schouten Island.

0710 – Found the start of the Mt Story track.

1000 – Reached the summit of Mount Story operated over the UTC day changeover.

1230 – Left summit of Mount Story for walk back to Cocketts Bay beach.

1500 – Picked up from Crocketts Bay beach for trip back to Triabunna.

1640 – Dropped at Triabunna boat ramp / wharf

SPECIFIC TRACK NOTES:

Crocketts Bay to Mount Story:

After being dropped on Crocketts Bay beach we spent 20m looking for the start of the track!

All the notes about this track we found online said it was a taped track that started on the headland between Crocketts Bay and Morey’s Beach and we eventually found the start of the track next to the new composting toilet block. Walk past the front of the toilet block and the track start can be found weaving its way through the Sheoaks.

The track is no longer taped but there are remnants of tape you find along the way. The track is well worn where it traces through the lightly wooded forest and is easy to follow.

Before the final climb up Mount Story there is a plateau and from there the track is marked with rock cairns where the track goes across the larger granite boulders. Keep your eye on the next cairn. On the plateau we watched a Wedge Tailed Eagle circling on the thermals.

Near the summit the track runs behind (South) of the summit and as you summit you see the pine post that has been embedded into a stone cairn. The post is intriguing and I think it is an endemic Oyster Bay Pine tree trunk with regularly spaced holes bored it.

Allow 3 hours for the walk up to Mount Story and about 2.5 hours to walk back down. We originally estimated a 2 hour walk in and out but underestimated the walk in. This meant compressed operating time on summit. Fortunately our boat ride (Murray VK7ZMS) was watching the weather reports and extended the pickup time to 3pm which gave us more time on summit.

Operating Notes:

Given this was a IOTA activation and there was some international interest in making contacts we decided to take my Yaesu FT-897 (4kg) and an 18Ah LiFePo battery (3kg) with us to provide a little more power for DX contacts. This was a good move!

I took my normal SOTA antenna – 9m Squid Pole and 8 band linked dipole and I also took my ICOM T-90A triband hand held for local 2m contacts and liaison with Murray VK7ZMS on the boat.

We setup on summit and we knew propagation was going to be a challenge as the sun had recently been creating some unfavourable conditions!

We started with 2m for a couple of local contacts then moved to 40m and made 21 contacts with VK1, 2, 3, 4, 5 & 7 including a local CW contact. We then moved to 15m and made 12 contacts with VK1 & 2 and ZL3. On 20m I made contact with 15 contacts with VK1, 2 & 3 and ZL1, 2, 3 & 4. Whilst on 20m someone commented that 10m sporadic-e propagation was happening and so we finished on 10m and made 10 contacts with BX8, N1, K4, NW7, JF2 and VK5.

We estimated that had about a 2.5hours walk back out so we packed up and left the summit at 1230 to be on Cocketts Bay beach around 3pm. The walkout was uneventful apart from seeing a well fed Blue Tongue lizard and a White-lipped Snake.

A huge thank you to Murray VK7ZMS and Mark for the boat ride to/from Schouten Island. Thanks also to all who made contact with us and we ended up with a total of 60 contacts between Reuben and myself.

Logs are being uploaded to ClubLog and QSL cards for the IOTA activation have been created and will be distributed.

73, Justin, VK7TW

SOTA double points day 2024/25. The UTC year changeover offers VK an advantage where our UTC year changeover happens at 11am on New Years Day offering an opportunity to activate the summit prior to 11am and then again after 11am for double points!

I have done these two summits previously but not in 2024 so these were chosen. Both mountains are part of the Wellington Range and were accessed via the Myrtle Forest Track, Collins Cap and East-West Fire trails.

Timing:

To give some idea of how long things took the following timings were recorded:

0540 – Start from Myrtle Forest carpark accessed via Collinsvale.

0641 – Reached Collins Cap Fire Trail.

0700 – Reached the E-W Fire Trail junction.

0734 – Reached the Ringwood Trail junction.

0739 – Reached start of Mt Marian Track (Mountain name misspelt on sign – Mt Marion).

0830 – Reached top of Mt Marian and operated before and after UTC year changeover.

1135 – Left top of Mt Marian.

1226 – Reached start of Trestle Mountain track.

1305 – Reached top of Trestle Mountain.

1430 – Left top of Trestle Mountain.

1450 – Reached bottom of Trestle Mountain and junction with East-West Track.

1509 – Reached Collins Cap and East-West Fire Trail Junction.

1529 – Start of Collins Bonnet to Myrtle Forest Track.

1606 – Myrtle Forest track junction.

1636 – Back at Myrtle Forest carpark.

SPECIFIC TRACK NOTES:

Myrtle Forest to Mt Marian:

The Myrtle Forest track starts at the carpark and follows a road up to the picnic area and toilets taking about 10m. The Forest track starts at the foot bridge and is a well marked and well used track that follows the Myrtle Forest creek and crosses the creek twice and after about 35 minutes of continuously rising you reach the junction with the Collins Bonnet track. At this point the track rises more steeply up until you reach the Collins Cap Fire Trail.

Turn Left down the Collins Cap Fire Trail for about 20m until you reach the junction with the East-West Fire trail and turn right down the E-W Trail. This is about a 40m walk to the start of the Mt Marian track and you get glimpses of Mt Marian in the distance.

The Mt Marian track is well marked with a sign that is misspelt (Mt Marion) and this track has medium steepness with some pushing through the scrub so long sleeves, pants and gators are recommended. The track steepens up closer to the summit and the mountain is flat topped with many areas to operate from. I nearly stepped on a small White-Lipped snake on the track that was about 300mm long!

Propagation over the New Year period was not good with significant activity from the sun depressing HF propagation. It was a struggle to get the 15 contacts before 11am and 9 contacts after 11am mostly on 40m.

Mt Marian to Trestle Mountain:

The walk out from Mt Marian was uneventful until I got to junction with the E-W Fire Trail. I put my pack down to take off my rain coat and placed it onto a convenient rock. I was about to unzip my pack and realised there was a Tiger Snake coiled up behind the rock! Suffice it to say I gingerly picked up my pack and moved further down the track to take off my coat!

About half way down the track between Mt Marian and Trestle Mountain I watched a Wedge Tailed Eagle being harassed by three Currawongs. It settle in a tree near the track and I was able to take some great photos and video.

The track up to Trestle Mountain is a steep rocky track and you are rock hopping on various parts of the track. You reach the top of Trestle Mountain after about a 30m slog! Trestle Mountain gets it’s name from the Trestle.

There are many areas you can operate from on summit and there are great views into the Derwent Valley on one side and the Huon Valley on the other side.

Trestle Mountain forms part of Sleeping Beauty along with Collins Bonnet.

Trestle Mountain to Myrtle Forest:

You need to be very careful coming down the track from Trestle Mountain as it is steep and rocky in parts and if you have a heavy pack on your back then you need to watch your equilibrium as you come down. It takes about 20m to reach the E-W Fire Trail.

If you head back toward Mt Marian along the E-W Fire Trail there is a short-cut track off to your right about 3-4 minutes up the track that cuts off some walking time – it was muddy and quite wet even on New Years day.

You reach the junction of the E-W and Collins Fire Trails in about 20m and this is where the slog starts up the E-W Fire Trail toward Collins Bonnet. This is a long slow slog until you reach the level at the base of Collins Bonnet. At this point I was contemplating whether I would activate Collins Bonnet but the weather closed in and it started to rain quite hard just as I reached the junction of the E-W Fire Trail and the track down to Myrtle Forest via the Collins Bonnet Trail. This is a recently cleared and well formed track unlike when Reuben and I did this track back in 2014 and had to push through scrub.

The track takes just over an hour to get back to the car park via the Myrtle Forest track.

Thanks to all who made contact with me and I ended up with 32 contacts across the two summits and 24 activator points even though propagation was challenging.

73, Justin, VK7TW

I found myself again in the NW of VK7 accompanying my XYL who was attending a Harp gathering that was being held in the historic town of Sheffield.

Whilst Helen was at her Harp day I planned to activate Mt Claude (VK7/NC-005) and Mt VanDyke (VK7/NC-028). I had missed Mt Claude in previous trips and this one I was not going to miss this time. These mountains make up what is called the Fossey Mountains.

I started my journey by doing a Google Map elevation plan which showed me that it would be a steep start at the Round Mountain lookout end however you are already just below 700m ASL and therefore it would be a steep start but quick ascent to the Mt Claude Plateau. You then take the Mt Claude Traverse track, drop down about 300m elevation into the Junction Track gully and steeply back up onto the Mt Vandyke plateau for about 350m elevation . From there it is a long relatively flat walk to Mt VanDyke then down to Reggies Creek junction with the Mt Roland track and 1.5 hour gradual 700m elevation descent and walk out to the O’Neills Creek Road Carpark. Sounds simple Huh!

I used for the first time the APRS.fi IOS application on my phone to beacon out my position regularly and it worked a treat. Unfortunately, I only switched it on around Mt Claude but from then on it provided some SOTA watchers some entertainment! Note for app users you need to remember to allow access to location services all the time so the app beacons regularly. If you don’t it will only beacon when you open app.

Even though the elevation plot say 16 kms total this does not take into account the twists and turns of the track and the actual length walked was just over 24km according to my Garmin watch.

Timing –

I took note of the time at each milestone to assist planning for anyone future planning this activation:

0800 – Left Round Mountain Lookout carpark

1000 – At Mt Claude and 10m setup and 20m of activation time and 10m pack-up

1215 – At Junction Track – lunch & rest – 15m

1400 – At Mt Vandyke and 10m setup and 30m of activation time and 10m pack-up

1530 – At Reggies Creek Track Junction with Mt Roland Track

1620 – At Junction track intersection with O’Neill’s Creek track

1635 – At O’Neill’s Creek track carpark.

SPECIFIC TRACK NOTES:

Mt Claude Track –

You start at the quarry opposite the Round Mountain Lookout which is accessed along Claude Rd (C136) then turn onto Olivers Rd (C138) and wind your way up for about 5 minutes until the Round Mountain Lookout.

The walking track follows the telecommunications facility vehicle access track. There are seven sections of concrete poured on this track indicating how steep this track is – definitely a 4WD low ratio slog! You climb about 300m in 2.5km of track.

The track levels out from the Telecommunications facility and is a gentle rise to a junction indicating a lookout (120m) where there is also a single antenna mast. This is not Mt Claude however it is within the activation zone of 25 vertical meters and this is where the author operated from. Operation was in thick cloud. Mt Claude is slightly further on and can be accessed through a cave and climbing rope. The author chose not to try and do this and continued on the Mt Claude Traverse Track.

The track condition was good although quite wet following heavy rain over the last few days. As you descend to the Junction Track intersection the scrub increases in height to about head height and in some places you are pushing through scrub. Long sleeves and long pants are essential! There is a gentle slope dropping about 200m over about 1500m down to the Junction Track intersection. At this point you can walk out the Junction Track which joins to the O’Neill’s Creek Track or continue up via the Mt Vandyke track.

Mt Vandyke Track –

From the Junction Track intersection there is a steep rising track of about 300m elevation over less than 1000m and many sections are climbing over boulders of conglomerate. Once you are on the plateau there are a few sections where you drop down then climb back out but these are not steep. You follow the plateau to the pile of boulders that is labelled Mt Vandyke.

I operated from the middle of these boulders after finding a relatively flat boulder. From Mt Vandyke it is a gentle descent to the Reggie Creek track intersection with the Mt Roland Track and then down the track following Reggie Creek to the fire trail. The fire trail is a gentle decent all the way to the O’Neill’s Creek track car park.

Thanks to all who made contact with me and I ended up with 11 contacts (40 & 20m) on Mt Claude and 15 contacts (40m) on Mt Vandyke.

73, Justin, VK7TW

Hayden VK7HH asked me if I would like to accompany him for his first SOTA activation to Collins Cap and I jumped at the chance. The weather was forecast to be 30 degrees C so, we started early!

It was great to see the further regrowth of the blue gums, fagus and other vegetation in the burnt out areas that were quite obvious on the last activations in 2014 & 2015.

We walked up the Myrtle Forest track and across the fire trail and then up to Collins Cap.

Hayden started on 2m handheld with local amateurs and the author started on 40m and quickly got seven contacts.

Hayden then moved to HF and after a slow start made many HF contacts including a Summit to Summit with VK2VRO.

This was the first outing for the author’s IC-705 in it’s new 3D printed case and it performed well and was comfortable with it being put into the backpack and not worrying about damage to the knobs and touch screen.

Hayden VK7HH runs a very successful YouTube Channel – Ham Radio DX and his video of the activation can be found at: Ham Radio DX First SOTA Activation

Thanks to all who contacted Hayden and myself for a successful maiden SOTA activation for Hayden.

I found myself accompanying my XYL Helen to another Harp Gathering – this time in Launceston at the replica Swiss village Grindelwald over the long weekend celebrating 8 Hour Day. I contacted the repeater team through Tony VK7YBG from the Northern Tasmania Amateur Radio Club (NTARC) of which I am a member and they were planning a trip up to the repeater site at Mt Arthur. I offered to help them carry equipment, etc up to mountain in return for a SOTA activation!

Tony VK7YBG and the author set off with car packed and picked up Andre VK7ZAB along the way and visited David VK7JD to pickup some heliax and equipment needed. Off along the Lilydale road until the turnoff to the Mountain Road and we picked up Colin VK7ZCF and Peter VK7ZPE who met us at the turnoff.

Heading up Mountain Road and given the 4WD we were in we could drive to the end of the track to a small corrugated tin hut that has information about Mt Arthur.

We headed up each with a roll of heliax around us, a new wind generator, test equipment and antenna pole. You head through fagus forest, there are a few areas where you need to clamber up rock shelves as you ascend about 600m from the carpark.

Mt Arthur is host to many many repeater and radio station sites all over the plateau. The first you get to is the NTARC site, you then continue to the old fire spotting tower and on to the cairn at the highest point going past many other repeater sites and radio station sites.

The weather was spectacular with blue skies and no wind! In fact we couldn’t test the new wind generator as there was no wind! According to the NTARC crew it is usually blowing a gale on Mt Arthur!

Whilst the NTARC crew did their maintenance the author setup his SOTA station and made 13 QSOs. Thanks to all who contacted me.

With the maintenance completed we made our way back down with much less equipment and coax!

A huge thank you to the NTARC crew for chaperoning me up Mt Arthur and for all the amateurs who contacted me.

Whilst in the Launceston area I made a trip out to the Tamar Island reserve and came across stump jump plough embedded in an old Oak tree on the highest point of Tamar Island. The tree has grown around the plough and therefore has obviously been there for many years. I find this fascinating and if anyone has any information or a story about the plough the author would be very interested.

I found myself in the NW of VK7 accompanying my XYL who was attending a Harp gathering that was being held at the Claude Road Memorial Hall at the base of Mt Roland. Claude Road is C136.

Whilst Helen was at her Harp day I planned to activate Mt Roland, Mt VanDyke and Mt Claude – more on that ambitious plan later! These mountains make up what is called the Fossey Mountains.

I decided to start at the Kings Road track up to Mt Roland then across to Mt VanDyke past the O’Neills Creek Road tracks and end up at Olivers Road after activating Mt Claude. Best laid plans!! It was a cloudy day with a high of about 19 degrees and there was cloud visible across the top of the Fossey Mountains.

I signed the book at the start of the track at 8:30am and proceeded to walk up the hill. It is a steep track starting at 400m and rising another 700m (to 1100m) along about a 2.5km track to a plateau. There are very steep segments, boulder hopping and boulder clambering along the way. From the plateau you slowly rise up to 1234m over about another 2km with some boulder hopping in the middle before seeing the rocky outcrop with the Mt Roland trig point on it. It took me just under 3 hours to get to Mt Roland via the Kings Road track.

I setup and operated just below the rocky summit outcrop and well within the 25m activation zone – this got me vaguely out of the wind. I quickly made six contacts on 40m and then packed up and moved on. The track leads on down the plateau past some block fields – track can be challenging as there are muddy patches and lots of rock hopping over the conglomerate that makes up the Fossey Mountains.

A kilometre or so before the O’Neills Creek track there are duckboards and a lookout looking South Westish. The O’Neills track junction is very well marked with platform and signs 1.5 hours to Mt Roland and one hour to Mt VanDyke. I kept going on to Mt VanDyke and the track is a much easier walk mainly on dirt with few conglomerate boulders to navigate.

The Track gently rises to Mt VanDyke which is a rocky outcrop you see for most of the walk. For some of this walk you are pushing though low alpine shrubbery which when there is low cloud it is also wet!

It was very windy and I managed to setup on the leeward side of Mt VanDyke in the gap between to outcrops and quickly made seven contacts on 40m. The low cloud very quickly wets any surface so, I was not sticking around. I packed up and headed back to the O’Neills Creek track junction. It was 3pm when I started back to the track junction.

Considering there was another 3km from Mt VanDyke to Mt Claude and then another 1.5km from Mt Claude to the the Olivers Road pickup point I decided to abort that stage and plan it for another day. I did not know the condition of the track and if it was like the Mt Roland track then it would be 3km of rock hopping which my legs were starting to let me know they were not enjoying!

Around 4pm I let my XYL Helen know I would not be meeting her at Olivers Road but at O’Neills Creek Road as there was good mobile coverage across the top of the Fossey Mountain Range. The longer O’Neill’s Creek road track is well maintained – only steep in some parts and most of it from the carpark is a gently rising firetrail that follows the contours! Luxury after the Kings Road track!

I got the carpark just after 5pm for pickup.

My Fitbit told me I had walked just under 20km and my legs were telling me that was pretty accurate!

Thanks to all who made contact with me and apologies I could not stay longer at each contact site.

I am planning Mt Claude which has a telecommunications facility on it with an access track to it so, this should not be anything like Mt Roland or Mt VanDyke!

73, Justin, VK7TW

I found myself in North East VK7 with WICEN Tas (Sth) helping with radio communications for a Equine Endurance ride from 9-10 October and planned to stay another night to activate Mt Saddleback on the way back to Hobart.

Mt Saddleback is accessed off the Mathinna Plains Road (C423) 4.5km south from the intersection with Mount Albert Road or 16.6km North from Mathinna. It is well sign posted. Head up about 200m to the marked track. If you have a 4WD then you can drive up the track about 1.8km to a small carpark where the track starts.

The track is well marked with tape and cairns all the way to the top. The path is steep for the first two thirds of the track as you rise up through some impressive dolerite pillars. It takes about 1.5 hours up and about an hour down.

Once you rise past the pillars there is a series of plateaux that rise in a Southern direction until you see the stone cairn at the highest point.

It was a brilliant day with sun and little wind on summit. I setup the squid pole, linked dipole and IC-705 and started calling CQ on 40m. I had sketchy mobile coverage with Telstra on summit and therefore I could not spot using the Parks and Peaks App. Thanks to those who spotted me when I contacted them.

Looking NE I could see the mountain summits on Cape Barren and Flinders Island in the misty distance.

At 1256m you have fantastic views – this panorama from left (west) to right (east) shows Ben Lomond, Ben Nevis, Mt Barrow, Mt Arthur, Mt Cameron, Mt Victoria and Mt Albert.

Thanks to all who contacted me during the activation.

Well on Monday 31st August I received my ICOM IC-705. I think the first to arrive in VK7!

Given the delays in its arrival in VK the author had time to read up the manuals and watch the plethora of YouTube videos and come to grips with the rig before its arrival.

This resulted in a presentation to the local club – Radio and Electronics Association of Southern Tasmania Inc. on Wednesday 2nd September 2020 and the YouTube videos of the presentation can be seen here:

Whilst the weather was reasonable the author did a quick trip up to Mt Wellington (VK7/SC-001) to tests the ICOM IC-705 on Saturday 5 September 2020 in a SOTA situation.

When the rig was first switched on there was absolutely no noise and I thought I had a broken wire in the antenna! Then it was realised that all the Noise Reduction, Noise Blanking and narrow Notch Filter settings were on. Switch these off and things came to life. Trap for young (and not so young) players in a very low noise environment!

I operated mainly on 40m and all my SOTA contacts where made on this band I also listened and heard DX stations on 20 and 15m but didn’t make contact with them.

It was great to make a couple of IC-705 to IC-705 contacts with Perrin VK3PT/ and Peter VK3GV. It was also good to make some Summit to Summit contacts and also good to get some great comments about the voice quality from the Bluetooth VS-3 headset.

The 10 watts is certainly an advantage over my usual SOTA rig the FT-817 and the ease of operation and Bluetooth headset does make things easier when juggling a log, etc.

A YouTube of the activation can be found on the Author’s YouTube Channel at:

The IC-705 is certainly a nice rig for SOTA operations and will be my rig of choice for future SOTA activations. Thanks to all who made contact with me during the activation.

73, Justin, VK7TW

Reuben VK7FREU and I decide to activate Collins Bonnet VK7/SC-002 for the UTC year changeover from 2019-2020.

Instead of the usual track from Myrtle Gully we decided to take the Mt Connection track and started out at around 8:00am. This track starts about two kilometers along the Big Bend track. The Big Bend Track is accessed off the Pinnacle Road just next to the Lost World Track.

About a kilometre in on the Big Bend track I lost my footing and landed heavily on my right knee! After about 10m of rest we decide to continue and take it easy with a note to self about putting some pain-killers in the first aid kit! The Mt Connection track is well marked with a signpost and heads down and across the swamp area that forms the source water the Mountain River. The track in the swamp area is all duck boarded.

You then head up and around Mt Connection with some great views to the North East and Mt Dromedary and towards Collins Cap and Bonnet.

Looking towards Collins Bonnet on top of Mt Connection

The Mt Connection track eventually links with the East-West Trail and about two kilometres further on is well signposted track up Collins Bonnet. This is a rock hopping excercise for most of the distance with the track marked with long snow poles.

We summited around 10:30am (UTC 23:30) and setup the linked dipole and FT-817. There was plenty of activity however the power level on the FT-817 was down and we were struggling to be heard. We both managed three contacts before the UTC year changeover so, unfortunately did not activate for 2019.

The wind was strong and overcast clouds started rolling in. We made UTC 2020 contacts on 40m and local 2m to activate Collins Bonnet for 2020. Thanks to all those who contacted us. After the antenna collapsed due to wind and we put it back up I noticed that power level had increased on the in-build power meter. So there is definitely something that needs investigation including the possibility of a small power amplifier to boost our QRP power level given we are rock bottom of the sunspot cycle.

On summit selfie

Panorama South to North looking West – mid picture is the Huon Valley

Panorama from North to South looking East – with Mt Wellington next to trig point

Impressive ravine next to Trig Point operating position

At around noon local (01:00 UTC) we started back down and stopped for lunch before heading back up the Mt Connection track.

Looking toward the North facing side of Mt Connection on the East-West Trail

It was about a 15km round trip using this track and was a picturesque walk on a part of Wellington range we hadn’t walked before. We got back to the car around 3:00pm.

Thanks to all who made contact with us during this UTC Year Change-Over event.

I attended Gippstech 2019 over the weekend of 12-14 July 2019 along with five other VK7s which is a record number of VK7s for the event. Thanks to Hayden who passed on the group photo.

L2R: Rex VK7MO, Justin VK7TW, Richard VK7ZBX, Murray VK7ZMS, Larry VK7WLH and Hayden VK7HH.

The weekend was cold and wet but the presentations were inspiring as usual!

Starting with David VK5KK, Iain VK5ZD and Tim VK5ZT and their 5800km Epic Microwave DXPedition. This was a humorous presentation of the trip up through Victoria, NSW, Queensland and South Australia over 12 days. They took every microwave band up to 122GHz and made many contacts with the locals in the area and set a few records along the way.

Then the Doug McArthur VK3UM (SK) award for last year’s best presentation went to Jim VK1AT and Alan VK3XPD’s Microwave Enthusiasts Award went to Stefan VK4CSD.

Coffee break and some nice goodies from Brian VK3YNG – thanks Brian.

David Smith VK3HZ then gave us a presentation on his experiments on an Azimuth finder. This uses the Real Time Kinematics (RTK) – Carrier Phase tracking feature available in some GPS modules and communicates between the modules using the 900MHz ISM band. It uses the NEO-M8P – C94-M8P02 evaluation kits and with a 3-4m baseline it gives 0.2 degrees accuracy and better than 0.1m with a baseline greater than 5m. This was used in ZL by Rex VK7MO for extending the 10GHz EME world record.

Mark Spooner VK5AVQ gave a wonderful presentation on Non-Ionising / RF Radiation Safety. Mark’s presentation simplified the elements of the ARPANSA RPS3 standards and how to interpret and apply these standards in amateur radio scenarios. The comment was this would normally be a 5 days course that was condensed into 45m! Great work Mark.

Peter Schrader VK4EA – a first time presenter gave a fascinating talk on the way that VK4RBB derives its frequencies for all the microwave beacons up to 10GHz by some interesting mixing of base GPS locked frequencies and mixing them all the way up to 10GHz.

We then enjoyed a yummy lunch.

The first presentation after lunch was Dale Hughes VK1DSH with an automatic satellite ground station for satellite telemetry reception. Dale has been experimenting with the Fox and Funcube satellites and how to use their respective data capture, logging and upload applications. Dale has also built a nifty azimuth controller for his yagi which is fixed at 45 degrees. This system uses an Arduino, magnetometer and some control circuitry. Dale has also build a nice user interface using NatSemi’s LabView development environment.

Yours truly then presented the next instalment of his 10GHz Microwave adventure covering the updating of the White Box transverter to a GPS Locked ZLPLL, low noise preamp and 3watt Power Amplifier.

Peter Pokorny VK2EMR then gave a most humorous outline of how we end up with the Leap Second and the Status of UTC. This started as a very serious expose of what leap seconds were and why they are needed and then a bureaucratic nightmare of Utopian size developed with more and more organisations becoming involved until Peter put the following slide up….

Peter then referred to his book of acronynms to decode and display some of the key relationships from the diagram. A most entertaining presentation.

A coffee break with more raffle tickets and goodies!

Rex Moncur VK7MO then presented how he and the ZL team extended the 10 GHz EME World Record from ZL to the United Kingdom. The talk covered how Rex managed to get a 1.13m dish from Australia to ZL in suitcase!

Roger Harrison VK2ZRH took the audience through an interesting presentation on the mechanisms of sunspots and the conveyor belt that powers the sun and creates and presents sunspots. The important question was pondered – namely “Are We There, Yet?” with a bottomed out sunspot cycle and the scientists are still unsure and much of the current thinking was presented.

We wrapped up the day and retired to a nice dinner at the Morwell Club.

On Sunday the first presentation was given by another first timer at Gippstech – George McLucas VK4AMG entitled – GPS Disciplined Frequency Reference – traps for Young and Not- So-Young Players. George took the audience through some thought provoking aspects of building a GPS Disciplined Oscillator and many of the things you need to take into account. This included the errors when generating a frequency, overcoming those errors and some other factors that need to be addressed. George then took the audience through his development of his frequency generators for a range of rigs and how they can be GPS Disciplined.

Our last coffee break and last chance for raffle tickets, goodies and books from Pages of Cobram, thanks to Peter VK3FPSR.

Tim VK5ZT then gave a quick talk on the 3.4GHz panel documentation that he has created which runs to over 60 pages about the panels and their modification and this is available of the EARC.org.au website.

Glen English VK1XX then presented the issues with the ICOM IC-9700 (in)stability and showed his work on developing an oscillator that can be GPS Disciplined for the IC-9700 to improve the stability of the rig for narrow band weak signal work on the microwave bands.

Another Gippstech first timer presenter Wayne Pearson VK5APN gave an entertaining presentation on Grid squares which then lead into his experiments with an independent location finder that gives a range of data including Maidenhead to 10 digits.

Yours truly finished up the presentations with a K3NG based AZ/EL GPS rotator for 10 GHz EME. This showed the applications and the equipment along with the easy of configuring. Pictures showed the Arduino based controller including GPS module that can be used to determine your location and the CCTV AZ/EL based mount to track the sun and moon.

We then retired to the common room for the raffle draw before enjoying pizza and heading in many different direction following another enjoyable Gippstech.

73, Justin, VK7TW

I’m a long time Heil Headset user. I love the fit of the BM-17 dual side headset and it has served me well for many, many years. But that model was discontinued last year and a replacement is not yet available. I’ve gotten countless requests on what is a good substitute for the BM-17, and after careful review and selection, I’ve come up with this: Koss SB40 Communications Headset.

In this week’s video I take a look at the Koss SB 40 communications headset, use it on the air, and determine if this is a good choice for portable ham radio operation. Watch I test the Koss SB40 Headset – Why I’m Using It for Every POTA Activation https://youtu.be/eN4AO21BvvU

Links/Resources

Koss SB40 Communications Headset: https://amzn.to/4aITokJ

Koss Electronics: https://koss.com/products/sb40

Heil AD-1-YM 8-pin modular adapter (Amazon): https://amzn.to/3N8b0N9

Heil AD-1-YM 8-pin modular adapter (DX Engineering): https://dxengineering.pxf.io/EELM1n

RJ45 Extension Cable 1 foot: https://amzn.to/3N8ZgtS

Build a hand switch for your headset: https://youtu.be/b5Wu8BlrSF0

What about Icom Users

Most amateur radio transceivers use a dynamic element for their microphone, so matching a microphone or headset to the radio is relative easy. As long as the impedance is somewhat similar (I’m looking at you Astatic Silver Eagles), it will operate with minimal fuss.

Icom, on the other hand, is different. They use an electret condenser microphone element. Electret microphones are great in that they are quite sensitive and can delivery beautiful audio. But they also require power to function. Plugging a dynamic mic into an Icom transceiver often results in a myriad of problems, most notably very poor audio.

Heil solved the Icom issue by building microphones and headsets with a specific Icom element. The electret elements in their I series microphones are great and an excellent solution.

Other Icom users have gone another route, using an adapter cable with an integrated capacitor to block the phantom power needed for the electret condenser element. One such solution can be found here: https://www.ebay.com/itm/157028823624

But when you use a dynamic mic on an Icom transceiver, you will most likely have to increase both your mic gain and compression to compensate. There’s no one value to set the mic gain to, you will have to experiment. Everyone’s voice is different and watching the ALC meter while making adjustments is the only way to get a good audio match.

In reading the feedback from this video, many Icom users have said the Koss SB45 headset works great with Icom transceivers. They say that model, which is slightly cheaper and smaller than the SB40, has an electret microphone. I haven’t tested this, but it may be an option, and the price is right, so go and give it a shot.

Another option, and one that will deliver better results is to use a preamp with your headset or dymanic microphone. Matt, K0LWC, has a video that tells you how to get superior audio with a dynamic microphone out of your Icom transceiver.

Since I am not an Icom user (I sold my IC-718 many years ago when I upgraded to a newer transceiver), I don’t have any specific recommendations on settings for using this headset with your Icom. You’ll have to experiment and do a little sleuthing. There is a wealth of information out there, so a quick google search will get you on the right track.

Finishing Up

Our January thaw came a little early. This week brings us temperatures in the 30s with rain and freezing rain. That is one thing I can do without. I’ve got most of the ice chipped away, ready for the next round.

The melting snow may be a bit of a godsend, though. Hopefully our snow pack will go down enough so I can get into a couple of my favorite wildlife areas. Those spots often aren’t plowed out, but with a bit of melting the windrow at the edge of the drive will be low enough to get my Outback into. Yeah, I also carry a shovel with me, just in case.

Well see what happens this Friday.

I hope to catch you on the air soon.

Michael
KB9VBR

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To many, this will be just another Si5351 VFO project, with nothing to distinguish it from the others. In fact, that’s exactly what it is. The “how to” of connecting an Arduino board to an Si5351 board, wiring up a display, and loading the firmware, is straightforward, and well established. To me though, it was a complete mystery. I have been very adept, my whole life, at studiously avoiding anything to do with digital electronics, computing, coding, and the like. When my friends in school were getting excited over Sinclair ZX81’s, BBC Micros, and Commodore 64’s, I was building a one-tube regen, an 80M DSB transceiver, listening to my British military R107 shortwave receiver, and talking to hams on the local repeater on my converted Pye tube VHF base station. I remember wandering into a Tandy store (what us Brits called Radio Shack) in the city of Worcester at some point in the late 70’s, and being greeted by the sight of a Tandy computer – probably a TRS-80 or something similar.

“What does it do?” I asked the salesperson.

“What do you want it to do?” he replied.

This seemed like a strangely non-committal response. Maybe he didn’t know what it did, and was merely throwing the responsibility for finding out back on me? I don’t remember anything about him now, but perhaps he was some gangly teenager who knew little about the stuff he sold, and whose main thought was getting off work so he could go to the pub with his friends? That’s it! He was just trying to appear knowledgeable by giving me a non-answer! This suspicious reaction was quite representative of the way I thought about computers back then. Just as it’s hard, if not impossible, to get the measure of a person if they willfully refuse to reveal anything of themselves to others, so it seemed with computers. These expensive boxes just sat there, doing nothing, except waiting for instructions. Such a disappointing lack of character! How is one supposed to respect a person or an object that sits quietly in a corner, waiting to be told what do? How feckless! Dedicated hardware, however, was different. When you bought a radio receiver, you knew that, on twiddling a few knobs and flicking a few switches, it would receive radio signals. A burglar alarm would alert you to the presence of burglars (well in theory, anyway), and those remote control cars that RS sold by the gazillion were guaranteed to quietly drive your family nuts in the days after Christmas before work, and school, resumed. Computers, on the other hand, promised everything but actually did nothing, until you told them what to do – and even then, there were a myriad of ways in which they could obstinately refuse to comply with your wishes. Not for me!

And so it was that, throughout my adult years, I deprived myself of exposure to things digital. I am not proud of my incurious nature about many things – though, when I am interested in something, I exhaust myself with the sheer intensity of focus. It’s an odd type of blinkered approach to the world that leaves others confused. I can’t say I blame them. The projects I built ran off anything from a few volts, up to 15-20V or even more. 9V batteries worked fine (we called ’em PP3’s), as did the old 12V lead acid battery that would no longer power the family lawn mower, but did a sterling job of powering the radio gear in my bedroom. My circuits weren’t picky about voltage, but these new-fangled digital chips just wanted to see 5V. Really? What kind of a voltage was that? They came with a surfeit of incomprehensible nomenclature too. Words that sounded like something John Lennon would have made up for a song post-1965. Words like NAND. You know, it wasn’t so much that this stuff wasn’t interesting – it was simply that I was really into building little radio receivers, and didn’t see how this digital stuff could help me (I wasn’t very imaginative). I had a small stash of ferrite rods, variable capacitors, resistors, and transistors, and some 9V battery snaps and with that, I had all that I needed. These were the days when loading a program onto a computer meant playing an audio cassette into the “line in” jack of your computer. I just didn’t see how any of that world full of DOS, NAND gates, tiny amounts of RAM, and the like, as well as really weird voltages like 5V, could possibly apply to me. Yes – I was that closed-minded. It’s not hard to see how a few years later, when we all graduated from University, my colleagues went on to successful careers with big technology companies, designing integrated circuits, and building the backbone of the internet, while I moved to Los Angeles and promptly became a DJ

A few years ago, a friend generously gifted me a Bare Bones Arduino board. I didn’t know what it was. It had header pins sticking out of it but, at that point, I didn’t really know what header pins were, or how to connect to them. I looked at it, and wondered what to do with it. What did it do? How did it do it? What was I supposed to connect to it? I placed it carefully in a box along with some other electronic things that confused my simplistic analog mind, and carried on with my life. Every now and again, I’d take it out of the box, blink at it a few times, and put it back. I knew that Arduino was the new big thing, and something that was going to play a big part in ham radio homebrewing in the coming years but I guess that, with my toroids and air-spaced variable capacitors, I wasn’t ready for it yet. Not that my experience level in this arena was completely non-existent. I had taken part in the beta tests of the Etherkit CC-20 and later, the planned CC1 series of QRP transceivers. These experiences had taught me that I could solder SMT devices, and even replace an SMT ATMega328P with nothing more than a soldering iron, soldering wick, flux, and a sharp blade. It was a small revelation to learn that I could do this stuff. Jason NT7S very patiently walked me through the process of flashing the firmware onto the ATMega328 via the ICSP header mounted on the board. This was a first for me, and quite exciting to gain a new skill, which proved handy when I built the SPT “Sproutie” Beacon, and needed to flash firmware onto the ATtiny13 in that little transmitter.

Then, recently, I took the Bare Bones Arduino board out of the box which had been it’s home for a few years and, this time, something clicked. “Goshdarnit” I thought, “I’m going to make an LED blink. If others can do it, so can I!

I spent a few days and nights with the LED blinking and pulsating at various rates, as I loaded different sketches, and adjusted the parameters. As fun as flashing lights are to a simple lad like me, it wasn’t the reason I wanted to resurrect this little Arduino board from it’s relaxing life in storage. I had an Etherkit Si5351 Breakout Board that needed to have life breathed into it. I wanted to generate RF, by golly!

This next stage was where things started to come into focus, and it began to dawn on me that using one of these little breakout boards to generate a stable RF signal wasn’t all that hard at all – well, from the point of view of the end user, at least. Once I did a bit of reading up on how to control the Si5351, I was just a little gobsmacked. You mean all it needs in terms of data input is 2 connections? SDA (serial data) and SCL (serial clock)? That’s it? I made those 2 connections between the Arduino and Si5351 board, uploaded the Etherkit Si5351 example sketch, and almost fell off my chair when the Si5351 began emitting RF on the frequency I had entered into the sketch just before uploading it. It was a moment of realization – that this little board actually was a programmable oscillator. How incredibly neat! No more custom-cut crystals – for ~$10, you can get a board like this, and program it to the frequency of your desire (within it’s specified limits), and it replaces both the crystal and the oscillator. For a single frequency, once you have programmed it, it doesn’t even need a micro-controller connected to it.  Fantastic!

I suppose that was the moment at which my mind, which moves at the speed of molasses, “got” that a VFO with this board is really a micro-controller which, with the help of a rotary encoder, is re-programming the Si5351 “in real time” as the encoder knob is turned. Every single click of the encoder sends a new instruction to the Si5351, to step up or down, in an increment which the firmware has already specified. I was hot to trot, so began looking around for a basic Si5351 sketch. The word “sketch” reminds me of the Etch-A-Sketch which I never came close to mastering as a child. I must admit that I think this association slightly trivializes Arduino programs (which are written in a type of C) in my mind, but that is what they are called, so that is what I will call them.

What I was looking for was a sketch that would allow me to vary the frequency of the Etherkit Breakout Board continuously in the HF region, from at least 3 – 30MHz. I was only concerned with one of the 3 clock outputs. At this point, I simply wanted to use it as an HF signal generator for testing purposes, or to control a general coverage direct conversion receiver. Perhaps at some point, I’ll begin fiddling around with code, and learning how to modify it for my own purposes, but at this point, I wanted a sketch that I could upload to the programmer, and immediately be in business. I also wanted to use one of those tiny little OLED displays, due to the enclosure I was considering.  This was the point at which I found Thomas LA3PNA’s sketch entitled, “A simple VFO for the Si5351 for either LCD or OLED.” Perfect!

This was also the point at which I discovered that the ATMega168 in my little Arduino clone board didn’t have enough memory to hold Thomas’ VFO sketch. I considered purchasing a newer Arduino board or clone, but most of the ones I saw had more stuff on them than I needed or wanted, in terms of inputs/outputs and programming ability. All I wanted was the ATMega328P, and a 6-pin ICSP header to program it with. Then I remembered back to my time working on the Etherkit CC-20 beta, and how I had expertly fried the micro-controller. Jason sent me a replacement and, wisely, included a few extras, in case my prowess at destroying delicate chips were to reassert itself. I still had those little SMT ATMega328P’s lying around, as well as a supply of breakout boards to mount them on. Problem solved! Building something from parts on hand is so much more satisfying than purchasing a ready-made solution – at least, for the first time, it is.

I sat down to scribble out a schematic, and it was during this process that the realization hit, as to what an Arduino board is. What makes Arduino, well, Arduino, is not the board, but the software platform that supports it. Apologies for stating what is well known fact to many readers, but this had all been previously unknown to me. The board itself is really just a micro-controller, with the power supply and input/output options either suited to the tasks at hand or, in the case of a larger and more general purpose board, such as the Uno, many different such options, to make it as versatile as possible. Ths was fantastic, because what it meant was that all I needed to control the Si5351, was a micro-controller (ATMega328P), a 16MHz crystal with the two associated capacitors, a 5V power supply, and some 0.1uF capacitors for bypassing. Oh – and a 6-pin header for programming. The schematic for the VFO is simple because, as far as the hardware goes, everything happens inside the micro-controller and the the Si5351 (which are both internally complex). The rest of it happens in the firmware. As far as hardware goes, we’re simply tasked with the 21st century equivalent of assembling a crystal set.

Here’s what I came up with. There are an awful lot of unused pins but, for this purpose, there are a lot of pins we don’t need. Without thinking, I was about to connect the AREF pin to +5V, because that’s what I was seeing in the various schematics I was using as references, until it occurred to me what AREF stands for. It’s an Analog REFerence pin. This application uses only digital inputs and outputs, so figuring that I didn’t need an analog reference, I didn’t connect it –

While planning this little VFO, a number of questions were presenting themselves to me. The main one concerned the issue of both the Si5351 Breakout Board and the OLED display being connected to exactly the same SDA and SCL connections. The I2C protocol does allow for multiple devices on the same line, but my understanding was that if more than one device is employed, then the firmware needs to include the unique address of each device. Would Thomas’ sketch work from the get-go, I wondered? As it happened, it did and, as of writing this, I don’t know if this is because

a) the address of the OLED was included in the library definition for this little display, or

b) with a setup like this that only has 2 devices connected, the instructions for the OLED are ignored by the Si5351, and vice-versa.

I’d like to be able to describe the exact steps I took when setting up the sketch, but I have, lamentably, forgotten them. I do remember installing the UG8lib library in the Arduino IDE, which supports the commonly available OLED displays. I also remember, at some point, uncommenting a line that specifically refers to devices that have an SSD1306 driver chip. If you purchase a cheap monochrome 128 x 64 OLED, this is probably the driver chip your display will have. These little displays are available for <$3 including shipping. Deal!

Here’s the ATMega328P mounted on the breakout board –

The controller part of the circuit constructed, with it’s supporting components. No power supply yet, as during initial testing, it will be powered through the ICSP header –

And with the Etherkit Si5351 Breakout Board fitted. The I2C control lines and 5V supply line are connected underneath the Etherkit board –

It took a while to figure out how to mount the OLED to the front panel. The 4 mounting holes are sized for #2 screws. I thought of running 4 #2 screws from the front panel, straight through to the OLED, and spacing the display away from the panel with 4 #2 nuts. The nuts were so close to the glass covering the display though, that they could have cracked it while being tightened. In retrospect, stacked #2 washers might have worked, though long before thinking of that, I came up with this rather more complex solution. It involved a small piece of PCB material, drilled and cut to size. #2 shakeproof washers and 3/16″ x 3/16″ nylon spacers were also employed. Their use should be apparent in subsequent photos –

I seriously considered fabricating a PCB enclosure for this little VFO, even getting as far as cutting some of the main pieces. The primary reason for wanting to use a custom enclosure was that the other case I was considering (which I ended up using) was a little too high. As a result, the front panel had, in my opinion, too much empty space. A PCB enclosure, about 4″ x 4″ x 1.5″ high would have looked mighty spiffy. However, I didn’t have the mettle to go through with it. I just couldn’t get quite inspired enough to put all that extra work into making a custom enclosure, and fell back on my favorite ready-made enclosure, the 143 from LMB Heeger. It is 4″ x 4″ x 2″ high, and available in plain aluminum finish, smooth light grey paint, or a sort of wrinkled black finish. They are also available with either an undrilled cover, or a perforated cover. The encoder was connected using header. The main reason for this was that I wasn’t sure if the cheap Chinese encoder ($1.68 each, inc shipping) was up to the task, so wanted to facilitate easy replacement –

A close-up, showing a little more detail of the mounting of the OLED to the front panel. Like the encoder, the display was also connected using header, making installation, and any dismantling for repair or upgrade purposes, easier –

Amazingly, it worked!

With the perforated cover you could, if you wanted, add some internal LED’s, for a splash of light to brighten up the shack, and add some flair. Being frugal energy-wise, I left the LED’s out for the time being. As it stands, the VFO already consumes 86mA at ~12V, which is not an insignificant amount –

Although the hardware side of this little project is finished (or very close to it), I am still very much fiddling with the firmware. As well as using Thomas’ code, I have been trying out sketches from other folk too. I began by trying to find a sketch that would do exactly what I wanted it to do, and fast discovered that, at the very least, an ability to modify code was required. That lesson led to a desire to actually develop a more complete understanding of C, so that I can at least do intelligent re-writes, if not write my own from scratch. This is all a bit overwhelming, and I vacillate from having fun, to being very grumpy, and back again

Thank you Thomas LA3PNA for the sketch – and also to the many others whose code I have been borrowing, and will no doubt butcher. I view this little VFO very much as a learning platform, from a programming point of view. Also, a big thank you to Jason NT7S for the Etherkit Si5351 Breakout Board, and the very useful libraries, which are seeing much use from homebrewing hams.

PS – I just started reading “Beginning C For Arduino” by Jack Purdum. Great stuff.

UPDATE (Jan 30th 2021) – I made a few small changes to the sketch, to improve the display a little. I found a font to display the frequency, that is a little larger. It is in the U8G library, and is known as helvB18. I also removed the word “step” from in front of the step size, as I felt it was self-explanatory. The text needed to be moved around on the display a little to fit it in, and this was adjusted in the sketch.

Since building this little clock generator, I noticed that, although the sketch set the Si5351 to start up on 7030KHz, it would nearly always start up 100Hz higher. Unsure whether this is a software or hardware issue, I did the clumsy workaround of altering the sketch to start up on 7029.9KHz. As a result, it now starts up on 7030KHz. I’d like to find the reason for this discrepancy, and fix it at the source.

I also added a 5mm red LED inside the case, with a 1K resistor in series with the +ve lead, connected to the 12V DC power connector on the back. The LED lights up the whole inside of the case, though this is not so obvious in the daylight shot below – 

However, when used indoors, the red light is visible through all the perforations in the case, and looks great. It’s almost reminiscent of the old tube days. The red light effect actually looks a bit better in real life than in the photo. This Si5351 VFO/signal generator draws 105mA, of which 10mA is the LED –  

Although I’ve had quite a few thoughts about using it as a stable signal source for other projects, it’s very handy to have around the shack, just as it is. Calibrating receivers is a lot easier with this accurate signal source. I didn’t run the calibration sketch but, through a process of trial and error found a correction integer to place in the sketch, that places the VFO to within a few Hz, as verified by beating the output against WWV. (EDIT – I finally figured out how to use Jason NT7S’ calibration sketch, and used that to calibrate the VFO.)

Aug 2025 Update – In the years since building this VFO, I have been pleasantly surprised by how often I use it. A constant companion when shortwave listening with my regen receivers, it is a simple procedure to beat the signal of the VFO against an incoming station, to determine what 5 KHz channel it is broadcasting on. In conjunction with online databases, such as the very useful one at short-wave.info, identification of heard stations is usually straightforward. It is also useful as a stable oscillator in conjunction with a regen, for enhanced SSB reception. No need for a direct connection to the receiver, as a very short length of wire in the output socket of the VFO provides enough signal level to be heard on a nearby receiver – both for frequency determination and enhanced SSB reception. It could also be used to receive SSB and CW on a crystal set, though I haven’t tried that yet.

This has proved to be a very worthy project.

Jan 2026 Update – as a follow-up to last year’s update, I realized recently that, although I built this envisaging that it would be used as a VFO for various homebrew projects – a building block, that has not been it’s main use. It has been very useful as a signal generator. Unlike more expensive pieces of lab gear, it doesn’t offer selectable waveforms or calibrated output levels. What it does offer though, is an accurate and repeatable frequency source. It allows me to know where my homebrew receivers are in the band and, by beating the signal against the one under test, I can perform drift tests on VFO’s and VXO’s. I wonder how I ever managed without it!

With eleven Boat Anchors now gone, I found a trove of homebrew radios that have been stashed away. Today was no exception.

Preparation:

This was another “fill-in” activation after dropping my wife off at her Physio rehab centre. A week earlier, I had tried to activate Haspelmoor, made one contact and then the radio failed on me, first with high VSWR on speech peaks and then with a “COMMUNICATION LOST” error between the head unit and body of the radio, even though they are bolted together, and no firmware upgrade has been performed on one half and not the other.

On getting home, the radio worked perfectly, and I was unable to recreate the issues. This activation, therefore, was to see if I could find the fault under EXACTLY the same circumstances (I packed a second radio as backup in case the problems reoccurred).

I had several hours for the activation and a chance to get lunch at the only open restaurant in the area (Tuesday’s most restaurants are closed). As it turned out, I had plenty of time to also activate the “4-fer” that I had activated in December, as it was on the route back to my wife’s physical rehabilitation centre. We have just come out of 2 weeks of sub-zero temperatures, but the ground is still frozen and partially ice-covered, so this meant that the activations would again be “PLOTA” activations from within the car, only stepping out to attach or adjust the HF-PRO2 antenna.

As usual, all radio gear was put ready in the car the day before, for this PLOTA.

The Activations

POTA DE-1136 Haspelmoor Flora and Fauna reserve

After dropping my wife off, having driven the route the previous week, it was a clear run down to the same parking spot next to a strange metal (artistic sculpture?) construction as last time in the forested Haspelmoor.

I started on 20 metres, catching one P2P contact into Wales where the activator was in a 3-fer POTA location. Following this a spot in POTA and calling CQ brought in 7 strong calls but thene the well known military digital QRM (OTHR) started wiping out the top of the band. Trying to find a clear frequency on 20m to QSY to was impossible as there was a contest on (normally contests are only allowed on weekends and this was a Wednesday). It turned out later that the increased contest activity were participants in the WWA “World Wide Award” which was running every day in January. It seems that by calling it an “award” rather than a contest, the organisers decided they could run it on weekdays aswell. It certainly has increased activity on the HF bands, but of course, for low-power portable stations, this is very bad news.

So to get away from both of these types of interference, I decided to move to 40 metres. Up to this point, the radio had operated perfectly, so I was starting to think the testing purpose of the activation might come to nothing. Conditions on 40 metres were not good; in this case, the atmospheric noise was high, and it took over ten minutes to just get 2 contacts. However, at this point, I started to see the High SWR on speech peaks problem again and had an idea. I changed the setting on the loading coil on the antenna just a little, to move it away from my calibrated position and then, while the base SWR after running the AATU sat a little higher, I no longer got the sudden high SWR peaks that I had been seeing.

I decided to switch back to 20 metres to get a few more contacts before driving to the restaurant for lunch. Dour more contacts followed in the next 10 minutes before I went QRT.

Regarding the high SWR on 40 metres, at the time, I wasn’t sure why this was happening. Perhaps the antenna’s adjustable coil was wearing out (I have had the antenna at least 8 years) – Perhaps the 3-magnet base?? At least I had a temporary fix for the time being. Later, at home, I think I may have the answer … The calibrations that I made with the antenna were with it on top of our Peugeot car. In the meantime, we have changed to a similarly sized Citroen car, and the actual “ground plane area” and type of steel, the magnetic mount is sat on, could easily give a different ground plane to the antenna. On the higher bands, the ground plane has a lesser effect than on the lower bands, such as 40 metres. It could be that I just need to recalibrate the antenna scale settings on the new car’s roof!

POTA DE-0466 Augsburg Statswald/DE-0942 Via Julia NHT/DE-0968 Romantische strasse/DE-1056 Lechauen

After lunch at a really old-fashioned German restaurant, I saw that I still had nearly three hours of free time before I would need to pick up my wife, so I decided to activate this convenient “4-fer” location on my way back in the direction of the Reha.

This activation took place early afternoon, not usually a good time for 20 metres contacts but I managed quite a few with the contact of the day being with VA1SEA in Nova scotia, Canada. Apart from that, all contacts were around Europe. The biggest problem with this location was that, being directly on a main road, the ignition and engine controller interference from passing cars and trucks on the wet road was horrendous, but as you’ll see from the map extract below, this “had” to be the location to get all 4 parks in one:

After 14 contacts on 20 metres, I switched to 40 metres, remembering to offset the setting on the loading coil. However, the QRM on 40 metres was even worse than on 20 metres, and I managed only three more contacts, all German stations. The main thing was that my quick fix of off-tuning the antenna worked again.

Once the QRM got too much, I decided to pack up and even had time to do some food shopping before picking up my wife and driving home.

Photos:

DE-1136

DE-0466, 0942, 0968, 1056

Equipment taken:

• Xiegu G-90 radio.
• Xiegu X6200 radio (not used)
• Komunica Power HF-PRO2-PLUS-T loaded vertical antenna.
• 3-magnet car roof mount and single magnet mount (single not used).
• 8 Ah LifePO4 battery.
• 2 x 4Ah Eremit LifePO4 batteries (not used).
• Lightweight headphones.
• Smartphone for spotting.

Log:

DE-1136

POTA DE-0466/DE-0942/DE-0968/DE-1056

Conclusions:

Overall, these two activations went well, and if I have indeed now found the reason for the earlier problems, it was worth doing the activations. That contact into Canada out of nowhere was the “icing on the cake” and VA1SEA must have a fantastic station set-up!

73 ’til the next activation!

Building on the recent test of an analog RF attenuator, this post flips the narrative and asks the question, will the Mini-Circuits ZFAS-15 component function as a RF mixer? Recall that the ZFAS-2000 (currently available similar component) had a schematic that looked the pretty much the same as a double-balanced RF mixer (using SBL-1X as an example mixer). Are these essentially the same when operated as a mixer?

The thought is to setup a simple mixer test setup and see how both devices (ZFAS-15 and SBL-1X) behave when mixing a CW signal with a fixed 100 MHz local oscillator.

Below is the setup using a 100 MHz crystal oscillator at +8 dBm for the local oscillator and the Pluto SDR TX and RX ports as either RF or IF of the "mixer". A test signal at 80 MHz will be mixed up to 180 MHz and the signal level captured at that frequency.

Interchanging the RF and IF ports did not make any difference for the simple tests performed today.

Test Notes: Setup to use device as a RF mixer. 100 MHz LO at ~ +8 dBm, 80 MHz @ -5.9 dBm test signal, 180 output at -17 dBm. Pluto TX to Out, Pluto RX to In. No change when in/out swapped. A screen capture of SATSAGEN is below showing the received signal at 180 MHz at -17 dBm.

The test result is YES, the ZFAS-15 performs as a RF mixer as expected. Let's see how it compares to a real RF mixer (SBL-1X). Below is the adjusted test setup.

Test Notes: Swapped in SBL-1X mixer. LO to LO, TX to IF, RX to RF. Same reading of -17 dBm at 180 MHz. SATSAGEN screen capture below confirms no difference in mixed output signal level between these two devices.

The conclusion from this activity is that there appears to be no significant difference between the ZFAS-15 analog RF attenuator when operated as a RF mixer, and a conventional SBL-1X RF mixer device (as tested).

Summary: Use what you have for either of the two applications (attenuator or mixer). While there may be some subtle differences, today's test showed essentially the same mixer performance between the two devices. YMMV!

All author photos taken with an iPhone 16e.

Today I want to cover my Ham Radio plans for this year. When I worked for a living, I often reflected on the saying: If you fail to plan, then you plan to fail.