Matchbox Transceiver Pushes The Spy Radio Concept To Its Limits

The Altoids tin has long been the enclosure of choice for those seeking to show off their miniaturization chops. This is especially true for amateur radio homebrewers — you really have to know what you’re doing to stuff a complete radio in a tiny tin. But when you can build an entire 80-meter transceiver in a matchbox, that’s a whole other level of DIY prowess.

It’s no surprise that this one comes to us from [Helge Fykse (LA6NCA)], who has used the aforementioned Altoids tin to build an impressive range of “spy radios” in both vacuum tube and solid-state versions. He wisely chose solid-state for the matchbox version of the transceiver, using just three transistors and a dual op-amp in a DIP-8 package. There’s also an RF mixer in an SMD package; [Helge] doesn’t specify the parts, but it looks like it might be from Mini-Circuits. Everything is mounted dead bug style on tiny pieces of copper-clad board that get soldered to a board just the right size to fit in a matchbox.

A 9 volt battery, riding in a separate matchbox, powers the rig. As do the earbud and tiny Morse key. That doesn’t detract from the build at all, and neither does the fact that the half-wave dipole antenna is disguised as a roll of fishing line. [Helge]’s demo of the radio is impressive too. The antenna is set up very low to the ground to take advantage of near vertical incidence skywave (NVIS) propagation, which tends to direct signals straight up into the ionosphere and scatter them almost directly back down. This allows for medium-range contacts like [Helge]’s 239 km contact in the video below.

Banging out Morse with no sidetone was a challenge, but it’s a small price to pay for such a cool build. We’re not sure how much smaller [Helge] can go, but we’re eager to see him try.

23 thoughts on “Matchbox Transceiver Pushes The Spy Radio Concept To Its Limits

  1. Ugh, morse. An oscillator, essentially.
    Why not do AM? Crystal sets and spy bugs used to be installed in matchboxes.
    Why not make it a real walkie-talkie, thus. :D

    80m used to be a local area band, too. Like 10m and 2m.
    It was the beginner’s band, as well.
    It travels well on the ground wave, too.

    I was told there was a time (60s/70s?) when young hams built their AM transceivers in a cigar box and used a pair of headphones.

    Also, AM is not strictly forbidden here in Europe (US has AM rounds, even).
    Though in general, the recommendations says 10m is recommended for it, as far as shortwave goes.
    Because of that “oh, it uses so much bandwidth” drama.

    However, it’s okay to use AM on 80m if there’s no one around to interfere with.
    The UK band plan says so, at least:

    Other band plan recommendations like that of Germany might be more conservative/strict, of course. As usual. 🙄

    Anyway. A low-power AM walkie-talkie with a short antenna would be local, anyway, thus not hurting international shortwave.
    It would do fine for a few hundred meters, though, like any other walkie-talkie.

    These are just my thoughts, of course.
    No offense. I understand that most hams seem to have sort of a CW affection. ;)
    From time to time, it doesn’t hurt to think out of box a bit, though.

    1. CW is more powerful mode than AM or SSB. You can reach far more distance with it with very little power which was in this case.

      There is no CW “affection”. It is just powerful, easy, clean.

      Go ahead and do the same QSO with matchbox transceiver on SSB ;)

      The project is very cool. Also the kyynel-antenna was heartwarming for me as Finnish HAM :)

      1. “CW is more powerful mode than AM or SSB. You can reach far more distance with it with very little power which was in this case.”

        Thst wasn’t my point, though. My point was about making something fresh and fun, rather than another boring CW QRP transceiver + XXL antenna (long wire antenna, dipole).

        But that’s what people seem to miss these days. Ham radio is an experimental service.
        It’s not all about contests, a high score (collecting “contacts” for a diploma).

        It’s also about the human touch, about tinkering and trying out different things.

        And especially CW is a bit overrated here. Lots of glorification, but also a lot of “hot air”. Also, it’s not much work from a technical point of view.

        It’s an xtal controlled oscillator, which also acts as a reference for the receiver. Sich circuits are as old as ham radio itself.

        Don’t get me wrong, it’s cool.
        But so is making a torch light using real incandescent lamps.

        The idea about M
        Making a little AM walkie-talkie wasn’t ingeniousby any means,
        but was about having fun with your buddy within your town, rather than collecting points for DXCC.

        Some hams really forget about the social part, about the “ragchewing”.
        And about making fun little toys and miniatures, essentially.

        Otherwise, they wouldn’t compare walkie-talkies and cell phones all times, but see them as individual forms of communications.

        1. This is the kind of message that I would have responded extremely positively to… had it been attached to a project demonstrating such things.

          Barring that, it’s literally just another opinion. I’ve got too many of my own, looking to get rid of some, actually. Opinions, free to good home, maybe?

          Seriously though, there are as many “right” ideas as there are people doing them. Fun is in the eye of the enjoyer, and nobody’s paying us (that would make it work).

          (sidenote, there are plenty of projects like you described. They’re just significantly more challenging to build and debug, and require a lot more skill to fabricate. As such, they’re not so interesting on a forum not dedicated to radio topics)


          “minimal ssb transceiver” on duckduckgo or whatever is a good start… or if you’re less fond of voice, maybe “minimal bpsk transceiver” instead.

          So far, the simplest I’ve seen would be significantly more than ten times the time investment of something like this matchbox transceiver, and would require significantly more power to less reliably reach much less far, assuming that the simple cw projects actually scratch your itch.

          I’m not arguing that the simple ssb projects are not fun, just that they’re a lot more work and presume the builder has already gained the experience that would come from building the simpler ones. It’s fairly challenging to build either a phasing-type or a filter-type ssb system reliably, without access to substantial tools and skills that don’t just develop themselves. They’re good tenth projects, not first or second projects, and it seems that HaD readers tend to be looking for more basic things.

    2. “It would do fine for a few hundred meters” Well.. you answered your own question right there. People can and do make real contacts via such low power, low parts count devices using CW. With AM they would be lucky to reach all the rooms of a large house!

      With even lower bandwidth modes and the right conditions a signal can be received around the planet.

      1. The late George Burt GM0IXX worked many DXCC countries with his home brew QRP transmitters using 1watt of power or less ,as for size if transmitter gets designed and built the Oner transmitter ona one inch board ,further too that transmitter was then built with a receiver on the same board by a Radio Amateur from India ,so QRP can really communicate at greater distances than one can imagine.

      2. If you’re not inside a faraday cage or a noisy environment, even poorly-emitted low power AM can reach that kind of distance. I was messing around with using a very lossy toroidal core as a so-called magnetic amplifier, which I was actually using to AM-modulate a few milliwatts within MEDFER rules. I just wanted to see what the audio sounded like, so the only real antenna was a few inches of leads. A better result for a real device should be very easy.

    3. Well much as I love the sound of AM, CW is surely the mode of choice for a QRP transmitter like this. It will get much further, plays well in terms of bandwidth, is much more likely to get a response from other stations who are very unlikely to be using AM, and is just plain fun!

    4. “From time to time, it doesn’t hurt to think out of box a bit, though.”

      That’s an Ironic comment to make… considering the whole point of this project was to think INSIDE the box… (a matchbox, as it were!)

      “Ugh, morse. An oscillator, essentially. Why not do AM? Crystal sets and spy bugs used to be installed in matchboxes.”

      If one takes this remark to its logical conclusion, why bother building anything at all. Just use your cell phone.

      If you have to ask the attraction of Morse, you may well not appreciate the answer. But…

      (a) Morse radio equipment is comparatively simple to build, with readily-available parts (including junk parts clipped out of discarded electronics. The simplicity ends itself to interesting projects like this.

      (b) Being a narrow bandwidth mode, morse is highly efficient in terms of miles/watt. A capable operator at the receiving end can (according to an old Army study I ran across recently) engage in sustained comms with <5% error at a level 27 decibels below voice modes. If run across conditions in the HF bands many times were CW was the ONLY mode that cut cut through atmospheric and man-made noise. So, low-power CW transmitters don't have to be just cute gimmics, they can actually be usable/practical.

      (c) Morse isn't just an irritant to someone unwilling to learn it. It's a language (or dialect, if you wish) in its own right with its own traditions, history, and culture. Being fluent in a language like Dine' may not benefit your resume' as much as fluency in Chinese or Spanish, but that doesn't mean it's not a language worth learning.

    5. If you are a spy only a few hundred meters behind enemy lines, one wonders why you’d risk radio transmissions at all. Maybe you could tie a note to a rock and sling it across the DMZ? Smoke signal? Walk home in the middle of the night?

    1. Well, I bet if he really wanted to an SMA connector could be fitted on there. The rest of the wires could just be wires sticking through holes or else pigtails with some sort of sockets or plugs on the end.

  2. Reminds me of a couple of books I received from a family friend when I was a kid and was fascinated by radio transmitters. The books are part of transistor circuit series, parts 14 and 20 ‘miniature spies’ by Gunter Wahl. It involved 2 fets (BF245), a BA121 varicap diode, crystal microphone, a air cored inductor and some resistors and caps. Good times!

  3. As an electronics engineer with 40 years experience and a lifelong ham I think this project and others like it are just so amazing and wonderful for keeping our traditions alive in the age of massive solid state integration and digital applications.

  4. Let’s not argue about CW, AM or SSB. Not many hams know morse code these days. yes a beep can travel further than AM and SSB. I would be happy just to construct a good HAM radio that can do phone. I don’t care what band or if I need to get my general class. I’m planning on doing that before I even attempt to CQ someone. 73

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