Just How Simple Can A Transceiver Be?

We’ve frequently talked about amateur radio on these pages, both in terms of the breadth of the hobby and the surprisingly low barrier to entry. It’s certainly the case that amateur radio does not have to mean endlessly calling CQ on SSB with an eye-wateringly expensive rig, and [Bill Meara N2CQR] is on hand with a description of a transceiver that’s so simple it only uses one transistor.

It’s a 40 meter (7 MHz) QRP or low power transceiver in which the transmitter is a simple crystal oscillator and the receiver is an equally simple regenerative design. What makes it so simple is the addition of a three-way switch to transfer the single transistor — a J310 FET — between the two halves of the circuit. It’s no slouch as QRP radios go, having clocked up real-world contacts.

This circuit shows us how a little can go a long way in the world of amateur radio, and we can’t help liking it for that. It’s worth saying though that it’s not without flaws, as a key click filter and another transistor would make for a much higher quality transmitted signal. But then it would no longer be a single-transistor rig, and thus would miss the point, wouldn’t it.

20 thoughts on “Just How Simple Can A Transceiver Be?

  1. Hmm, fascinating a great UK Heath Robinson type construction that functions, well done and straightforward write up, thanks :-)
    Wonder if someone with more time and focus than I could compress this into a SMT board to hang it off any CPU to generate 4.5KHz FSK for all sorts of short range signalling and data logging whilst monitoring the channel with a cheap pocsag pager…

    1. -cough – LoRa – cough- ;-)

      But yeah – agreed that it’s nice to be reminded of the elegance of a simple radio design. I’ve been a devotee of regenerative HF receivers for decades.

      1. LoL
        I’m such a minimalist at heart, eg saving/testing power walking around middle of night no mains lights just headlight torch for 30 days to illustrate issues ;-) Lucky no neighbours in sight on my spread – phew.
        Less is more (thought) in my book or rather the current chapter whilst assessing change of many patterns.
        On topic – all the Lora stuff I’ve seen so far too big too messy, prefer newer CPU/RF combo chips at the least though better for me and tolerable would be a cpu tsop20-24 & same footprint smd RF board on top, coin cell underneath – some odd dataloging on way in fundamental physics, Newton may suffer an onslaught on angular momentum – Nobel anyone, Cheers

        1. I’ve been messing with the TTGO ESP32-LoRa boards on 915 MHz – pretty compact, tested range of up to 750m so far without a case, built-in Li battery management, they can interface on wifi or bluetooth to nearby devices -eg phone.

          There are other, smaller radio modules available of course, even down to those tiny raw 433MHz receiver & transmitter sets you can get for $1 to $2. Or adapting a QRP design…

          Have (more) fun!

          1. Tah, will widen my scope, seems I need to get back on the product research path. It does seem to me there are many potential paths of rationalisation and augmentation in IOT comms converging on some ideal product path, with enough players in the market it should be possible to achieve good integration.
            FWIW On the CPU path I understand there are 8pin CPU’s with 32 bit processing appearing offering all sorts of new opportunities in even smaller packages. Fascinating times indeed, cheers

  2. For some reason electronics gets a more magical feel with so little components achieving a feat such as transmission through the ether. That feeling gets lost when you buy a box off the shelf that does the same thing.

    1. Unfortunately the off the shelf thing seems to apply to a lot of ham clubs as well now. Seeming to be less amateur extra licensed who’ve built and continue to build their own radios in favor of techs and older folk with retirement money to blow on high-end icom. I’d say it’s even starting to wind it’s away into antenna building as well. As much as products like the DX Commander allows for a great setup on a small footprint for it’s price, a lot of hams are forgetting that it not just about making those contacts and contesting, but learning, building and teaching what you know as well.
      And don’t even get me started on so called ‘network radios’ over wifi or cell towers.

      1. The RF and electronics understanding (and satisfaction!) that comes from building and refining your own gear is important, but the ‘network radio’ stuff is the leading edge, and where amateur radio needs to extend into, if we are not going to surrender the control of those advanced technologies to the commercial world. Voice on HF is not going to be efficient in the face of communications emergencies like Hurricane Maria’s devastation of Puerto Rico.

        1. But some things are by definition !imited to a few. Moonbounce won’t be common, even if more people were interested, too.much equipment and skill. Though by now enough big stations are in place to allow more to do it with smaller antennas.

          But I think of repeaters, that drove 2M FM. For those involved it was a “new” thing and they got deep into it, building repeaters and different controllers, and even networking. For them it was cutting edge at tge time, but for most it just made it easier to use a walkie talkie.

          Packet radio went the same way. Small groups working on it, then the masses buying TNCs to just use the mode.

          And so on.

          Just building even simple equipment may not be cutting edge, but it elevates more people even a bit. I never pursued radio or electronics professionally, but I was interested in building and it is a foundation of the rest of my life. In a world with way more electronics than when I was a kid, we have an illusion of technical competence because so many people use tge internet and cellphones, but that doesn’t mean they know much abkut the inner workings.

      2. Yeah, but amateur extra ops get old, lose eyesight, finger dexterity, and deserve to retire to a nice shack and be the simple part of the station. I earned my spurs on Heathkit, radio courses, MARS, FD, and homebrew antennas. KY1E

        1. Except, all those oldtimers came in the same way. They probably were quite young, and got old being hams. I think the experience is different now, and even different if you come into the hobby at a later age.

          I’ve been licensed since I was twelve, fairly common back then. I am now technically a seniir citizen, turning 60 last month. It’s been a long time since I coukd have joined the QCWA.

      3. I so agree. Upon returning to amateur radio, after being away for several decades, I was surprised by the lack of hardware building and experimenting. I joined a local ham club, and chose one with older folks in the majority. The members knew almost nothing about hardware. The members decided to have classes in hardware building, which I thought was a great idea. Well, it was revealing, since one of the first classes covered soldering. Almost every member in attendance, and the were about 40-50 people there that night, participated, since they didn’t know anything about how to solder. The closing half hour covered how to buy a small soldering set of tools. Pathetic! 50, 60, and 70 year old hams that didn’t have any soldering skills. They relied on buying pre made cables, etc. Very few had ever built an antenna, or soldered a connector. One class was on CW, and how much fun it COULD be. It inspired only one person to learn the code, and the majority didn’t know the code. We even had a couple people that had used cw years ago, but had actually had forgotten Morse code! All these people talked about was contacts, contests, and swap meets. I often tried to get radio design discussions going, but my attempts were typically followed with silence, until someone talked about the transceiver raffle, the setup in the local park to participate a contest…

  3. Technically, it’s not simple, it uses an Arduino nano and a complex, pre-assemble circuit board, but for low cost, ease of assembly, and versatility it is hard to beat the µBITX from India. “Build the µBITX transceiver in an evening. A general coverage, 10 watts HF SSB/CW transceiver kit with features you NEED for operating ease, convenience and versatility. It works from 3 MHz to 30 MHz, with up to 10 watts on SSB and CW, with a very sensitive receiver. It features digital tuning, dual VFOs, RIT, CW Keyer and more.” And all for $129.


    SSB also gets you access to the growing number of digital modes.

    1. The economics of scale are amazing. Look at what you get for a $129 kit, which no doubt is neat, but you can get a Bafong dual band, VHF/UHF transceiver that is assembles and ready to go for a bit over $100 less.

      It would be cool if someone came out with an HF radio in that price range, kit or ready to go.

      1. An HF band shortwave transceiver is infinitely better than a VHF FM walkie talkie. One problem with ham radiator these days is that entry level now.means local communication via FM. So there’s a disconnect. Even when I was licensed in 1972 I operated on 6M, but AM. kind of DX. That’s closer to HF operation than 2M FM.

        2M FM is less of a stepping stone.

        $129 is a great price.for an HF transceiver. And they aren’t made in nearly tye same quantity as a Baofeng.

        And yes, by using transistors may not “simplify” but the circuit is more followable.

        1. I would argue that is is all about what you want to do. They are not mutually exclusive. I have not been on the air in many years, but when I was, most of my time was on HF. I had a 2 meter rig in the car. The thing is they can sell the sub $30 radios because they sell a lot of them. I think the same economy of scale could be put into a little HF rig.

          1. The Baofengs are bought and used by ANYONE, and I’m guessing that unlicenced commercial use is the default reason people buy them in most of the world. Hence a much greater market.

            HF would be a much smaller market. Plus – it’s relatively cheap to make single-board sophisticated VHF and UHF transceivers because of dedicated ICs and everything is smaller. AT HF, most reactive components are bigger and more expensive.

            So, about the best we can hope for in HF are offerings like the (very cool) uBITX

  4. But switching the transistor is an ilusion of simplicity. It actually compllicates things.

    In the thirties many a VHF transceiver were made with a tube switched between a superregen receiver and a modulated oscillator. It made sense, tubes were expensive (especially when money was scarce in the depression )and big. Even license free walkie talkies did it, with a multipole switch in the sixties.

    But transistors are cheap, and tiny. The switch if bought new is likely way more than a transistor. It’s inconvenient, the switch has to be close to the circuit. Switching RF circuits will add lead length, not good at RF, at least adding instability. Switching DC is so much easier.

    Design for absolute simplicity maybe novel, but in reality adding components often simplifies the overall design.

    1. Agreed. Switches are also much more prone to eventual failure. But this radio is more of a “what if…?” and a testbench for ideas than a design for a reproducible everyday unit.

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