Steal This Ham Radio (Technology)

Although I see a lot of wireless projects, I’m always surprised at the lack of diversity in the radio portions of them. I’m a ham radio operator (WD5GNR; I was licensed in 1977) and hams use a variety of radio techniques. If you think hams just use Morse code and voice communications, you are thinking of your grandfather’s ham radio. Modern hams have gone digital and communicate via satellites, video, and many different digital techniques that could easily have applicability to different wireless projects.

Of course, Morse code may have been one of the first digital modes. But hams have used teletype, FAX, and other digital modes for years. Now with PCs and soundcards in common use, hams have been on the forefront of devising sophisticated digital radio techniques.

The motivation for devising unique digital modes is two fold. First, hams don’t have unlimited bandwidth, especially in the high frequency (HF) bands that allow for long distance communications. Anything that takes less bandwidth is welcome. Second, HF bands have rough characteristics. Signals fade, atmospheric noise causes static and crashes, and other stations cause interference. There are other special cases too, like bouncing signals off meteors where the right digital strategy can significantly improve odds of getting messages through.

One of the first of these soundcard methods was PSK31. This mode uses a very low symbol rate and encodes data by using phase transitions. To avoid high frequency harmonics, the phase shifts occur only at zero crossings. The 31 in the name refers to the 31.25 baud rate (that’s not K baud, that’s baud; just more than 30 bits per second). To help make up for the slow baud rate, the system employs a variable length code so common letters use shorter bit patterns. Of course, the bandwidth used is also about 31Hz, so that’s one benefit.

Hams use software to decode all the signals in their receiver’s audio at once. Historically, you wanted to filter away all the signals except the one you are listening to. With PSK31, you want a wide filter and you let the DSP home in on all the signals, filtering each one digitally. For example, the picture below shows a waterfall display of several PSK31 signals coming in at one time. The waterfall is a special graph where the X axis (left to right) is frequency and the Y axis (vertical) is time. The “worms” crawling down the waterfall are signals (you can also see the snow of random noise). The PC can read data from all the signals at once easily.


Digital sound card modes have become even more sophisticated from there. One ham, [WB8NUT], has an interesting page that summarizes many modes and includes sound clips. Different modes have different purposes. For example, packet is an adaptation of X.25 over radio frequencies and can be used as a physical layer for TCP/IP. JTMS is useful for meteor scatter and JT65 for moonbounce (yes, that’s what it sounds like) and can enable slow data transfer with signals inaudible to the human ear. Many of these protocols use forward error correction and use sophisticated codes like Reed-Solomon for error detection and correction.

freedv600Even voice has gone digital. We covered that earlier and the linked YouTube video (and the picture, right) shows a voice contact (a QSO) that is difficult to understand using regular analog transmissions, but is perfectly clear using the digital techniques. Better performance and reduced bandwidth all thanks to PC-based DSP. Then again, not all solutions require DSP, but widespread adoption has been due to the ease of development and use with a common PC.

My point isn’t related to any particular mode, though (if you really want to see a demo of PSK31, check out the video below). In the non-Ham community, we see people build new computer languages, operating systems, and even CPUs. But it is pretty rare to see new radio modulation schemes. With few exceptions, hackers buy radios and take what they get with them.

If you want to experiment with little or no investment, check out WebSDR (see picture below). With the right Web browser, you can borrow someone’s radio (which is cool all by itself) and then route audio into one of the many digital mode programs (like fldigi, for example). To start, look for a radio that is in a part of the world where it is day time, tuned in the 20 meter band, and look at 14.070 for PSK31 activity. Note that in the screen shot, I was one of 147 users listening to the radio at one time and we didn’t all have to listen to the same thing.

Maybe the hacker community could take a cue from the hams. Radio experimentation has a lot of potential. Granted, it is a little easier because hams have radio frequencies where they are allowed to experiment. Yet there are digital and voice bands available to everyone and (depending on your local laws) it might be interesting to see just how much data you could ship over such an audio channel. Or you could bite the bullet and become a ham yourself (that’s a lot easier than it used to be in most countries including the United States).

Challenging? You bet. But really, no more challenging than a scanning tunneling microscope or building a custom CPU. Who’s up for it?

35 thoughts on “Steal This Ham Radio (Technology)

  1. I agree. I’ve been a ham for over 60 years now. I got into it because it gave me the opportunity to experiment with circuits. It’s at its most exciting point now, what with all of the digital modes, high speed mesh networks, digital voice, etc.etc. I’m not one who relishes chasing DX though there are those who do. Ham radio combined with microcomputers is the most fun stuff I’ve done. Keep it coming.

      1. Actually, I have seen that article. Not sure what it has to do with non ham radio operators experimenting width modulation techniques. In fact, it sort of makes my point. There is a lot of innovative work in the ham community and I don’t see much leakage of it the rest of the electronic experimentation community.

  2. I thought the name looked familiar.
    You had all those math coprocessors and other PAKs
    For basic stamps.
    Stamp project of the month.
    The call sign gave it away
    Spent some time at

      1. I think you answered an email i wrote you about my application, even, in summer of 1999!

        The good old days of micro-controllers. I was using your co-processor in a homemade fuel injection\\fuel monitoring system I made for my 50cc carb scooter!

  3. “Although I see a lot of wireless projects, I’m always surprised at the lack of diversity in the radio portions of them.”

    Maybe that’s because truly “experimenting” with RF in most countries requires a license, and the knowledge it takes to get it.

    Or Maby Not!… There are lots of off the shelf, low cost, pre-licensed/approved RF chips and/or modules available these days, and most hobbyist “Maker” types just put that stuff to work – which makes sense. And then, there IS a lot of hobbyist “Hard-RF” stuff out there too. Look at the gaggle of SDR boards available these days (almost all open-source), and all the stuff happening on the software/bitstream side like GnuRadio, etc. And isn’t amazing how far hobbyists managed to push those cheap little RTL-SDR DVB-T dongles?

    So just what was the point you were trying to make with your post??

    1. My point is in a “maker” world where we see people build custom CPUs, STMs, and lots of other exotic things, we don’t see a lot of non-ham RF novelty (mainly just people using off the shelf RF). It doesn’t have to be hard. PSK31 and many many other modulation schemes just generate audio tones into an SSB transmitter. You mention GNU Radio which is exactly to my point (I need to do a new write up on that… hmm…). Subtract out the hams doing SDR stuff and it is a very small pool. Yet things like GNU Radio (GN..R… no relation) make it really simple to do lots of exotic encoding and decoding. Maybe the data skew is simply that people who do this have ham licenses so it is a foregone conclusion.

      For years, I encouraged people to get into FPGAs. It was historically hard, but gets easier every year. We are finally seeing that go almost mainstream. I think the next frontier is RF. With SDR and easy availability of DSP that shames what would have been virtually unobtainable a few years ago you can get a lot done. You just have to get started.

      Back in 2012, the guys actually posted a link to my GNU Radio piece over at DDJ: The TV Dongles are great fun to play with.

      1. I may be wrong but I feel like if one young maker would like to improve on the current state of the art of RF communications, one might get old before she even gets it.
        Also, while SDR is great; I feel like it’s not exactly encouraging “RF diversity”.
        Unless one gets an advanced degree that has something to do with DSP (or is equivalently self-educated), one is more likely to copy or put together things that others made.
        Let generic makers be makers and RF people be RF people (except of course the RF makers :-).

      2. Most non-hams don’t even have a SSB transmitter and it’s not clear it’d be legal to use it in that way anyway, because the resulting transmission is not SSB but some other modulation that’s been upconverted in frequency by the transmitter and they’re probably not licensed to use the band for non-SSB digital modes.

        Also, to put things into perspective, one of the commonly-used wireless modules is about the size of a thumbnail, uses a protocol with 56 or so subcarriers, each of which can select from multiple modulations at an impressively high symbol rate and range of bits-per-symbol, and it costs $2. It’s called the ESP8266 and the protocol it speaks is 802.11n WiFi. Ham radio is some way away from the wireless state-of-the-art these days.

  4. Almost all countries DO require a license to experiment with RF. If you use these RF chips or modules as they are intended, you may not need a license, but many people add bigger antennas which requires a license.

  5. Excellent article!
    I hope we see more radio related articles here on HAD. The world of radio is a fascinating one with a lot of room for experimentation.
    Also, I think people tend to get way too upset over the need for licensing. Getting an amateur radio license is extremely easy and cheap in the USA, and I suspect that the process is similarly easy and cheap in most other countries.

    1. Agreed on that bit about the licensing process being easy and cheap! I got my license in the US in 2010. I studied for the Technician and General levels, got 2 wrong on the Technician test and aced the General. Haven’t done much with it except blabbering on 2-meter but I agree — it’s easy, and what an education!

    1. If you can get QtRadio going you can tune the radios that are up online – details at There is also the Hermes-Lite project to build a basic DDC/DUC (i.e Direct Digital) HF transceiver for ~$150 US. Discussion at and files on github and Amazing performance. I have 2 built here, one with a 1W driver Amplifier to which I hope to add a 20W Amplifier by K5BCQ.
      Sid — G3VBV.

        1. Hi AL, ghpsdr3 is the work of John Melton (G0ORX/N6LYT), ghpsdr3-alex is a fork of ghpsdr3 started by Alex Lee (9V1AL) with contributions from John Melton, Andrea Montefusco (IW0HDV) and others.

          ghpsdr3 supports only HPSDR whilst ghpsdr3-alex supports HPSDR, Softrock, UHFSDR, Microtelecom Perseus, SDR-iq, HiQSDR, Ettus Research USRP and rtl-sdr DVB-T dongles

  6. So yet another cry for help from the dying world of ham radio.

    I have a ham license, it’s actually going to expire in the next couple of years, and I have never put my voice on the air. I got mine because of a video transmission law I needed to comply with at the time and because my state requires it for possession of a radio (not saying the P-word) scanner outside of your residence, not that criminals would obey the law anyway… But these days I never take along a scanner anywhere anymore.

    I just put a new discone antenna and pre-amp up on my roof along with an amplified collinear ADS-B antenna. The ADS-B antenna is a lot of fun. The discone is kind of disappointing, sadly. There just isn’t much out there to listen to anymore that isn’t some sort of encrypted or spread spectrum signal. And yes, I use an SDR and a lot of different software toys to decipher some of it, but most of it is garbage.

    I have a couple of digital scanners and they work just about the same with a telescopic whip as they do with the discone and a preamp. The signal is either there and decodes or it isn’t and those systems tend to have a good saturation of signal and multicast everything, as having a small handheld and whip is what the systems are designed to handle anyway. But encryption is becoming more and more common place to protect privacy, or how ever you want to view it. I have my own opinion on that.

    I don’t care for listening to the ham bands because it always ends up being like a listening to any other boring telephone conversation, no matter the means the signal gets there, and it feels a bit creepy…

    So I guess my point is, if you are into just the RX side of the equation, like I am, there’s really no point in a ham license unless it’s to avoid some silly law.

    I just have zero interest in talking to people from afar that I can’t already do by some other means, like the internet. And I don’t think I’m alone. The novelty has wore off of RF communication and now that everything is going to digital encryption, there’s less out there for us RX guys to keep our interest as well.

    R.I.P. amateur radio…

    1. I’ve been meaning to write about this perception and why I disagree. It is true, that RX only isn’t as interesting as it used to be and scanning the shortwave bands lends credence to that. However, the rest of us are building satellites, using them, doing moon bounce, experimenting with DSP methods, and more. What’s more in parts of the world where I live, hurricanes regularly wipe out our cities and so disaster preparedness is a big thing with local hams. To keep in practice, they do public service events (like fun run crowd control) to stay in practice. Another big influx of hams have been the “preppers” who are convinced we are a few weeks away from collapse of all our infrastructure.

      Just because we don’t use horses as a primary form of transportation anymore means that no one rides horses. There are fewer farriers and saddle makers today, I’m guessing, but there are still farriers and saddle makers.

    2. While I was waiting for Al Gore to invent the Internet, I cut my teeth on some old-school radio circuitry. I still have a fondness for simple tube and transistor regenerative receivers – getting amazing reception with just one or two active stages is sort of like electronic haiku…But it seems that the “first” era of radio is sort of dying, it seems, especially analog. DXing seems almost pointless in today’s world. Would today’s kids drop their tablets long enough to make a crystal radio? What’s AM radio, Dad?

      But this article does well to remind us that amateur radio is still alive and well. How quickly we forget that hams were there long before “hackers” and “makers”. SDR is very cool, and I now have some digital RF oscillators to mess with. Just last month I finally got one of the Baofeng radios to mess with. Probably time to licence up… winter project maybe.

      So thanks for this article. I wasn’t previously aware of some of those topics, especially the new modulations on HF.

      1. Believe me, SDR is fun to the point where I describe my commercial ham gear as being here just to keep the dust off the shelves.
        I have built the old steam radios including a 23 valve (tube) superhet receiver when I first got licensed in 1965, also many transistor and IC based transceivers that I would be hard pressed to find time to put together now.

        SDR’s depending on type can be built in hours as opposed to weeks and months for some of the earlier gear which included stage by stage alignment.

        Some SDR’s can also act as Vector Network Analysers (VNA’s) to check filters and antennas.

    3. Old timers hams are falling off, but now a new generation of RF hacking & makers have given amateur radio a shot in the arm, I was the only ham in my hackerspace group now there is a few of us, we bounce off each other old hams & new RF hackers helping each other

  7. I may be wrong but I feel like if one young maker would like to improve on the current state of the art of RF communications, one might get old before she even gets it.
    Also, while SDR is great; I feel like it’s not exactly encouraging “RF diversity”.
    Unless one gets an advanced degree that has something to do with DSP (or is equivalently self-educated), one is more likely to copy or put together things that others made.
    Let generic makers be makers and RF people be RF people (except of course the RF makers :-).

    1. I am reminded of the patent office guy who wanted to close the office because everything had been invented. It is unlikely that hackers are going to invent better CPU architectures or robotic mechanisms. But they do. And even if they don’t, they still learn a lot and contribute to the overall body of knowledge. Hams have a long history of trailblazing tech. So don’t sell yourself short. Invent! ;-)

      1. Of course you are reminded; just like apples remind one of oranges :-)
        I am not (totally) contradicting you; all I’m saying is that it’s the RF makers that may/will contribute to RF not “generic” makers.
        Most other makers, even without electronics knowledge, are empowered by Arduino (like) boards and ready made RF modules to get their creativity out there.
        It is GOOD they don’t have to worry about front-ends and anything else that is just available off the shelf.
        It is GOOD different people like different parts of the creative process and I think one shouldn’t try to cover it all.

        1. I don’t understand what the term “generic” refers to in the context of RF.
          Whilst there are some ready made modules, that doesn’t mean slotting them meccano style to build a receiver or transceiver.
          In building simple Softrock SDR RX or RXTX kits one learns quite a bit about SDR hardware and Software.
          DDC/DUC SDR’s are even more complex and involves at least a knowledge of FPGA programming, also installing, setting up and using the Software.
          Soldering SMT components including those fine pitched IC’s is another challenge that extends the experience and is quite satisfying when you have done it successfully.

          Before you tell the designers of Hermes-Lite they don’t have to worry about front-ends, look at the enormous effort and challenges with circuit design and layout they face designing front-ends.

          Innovative SDR techniques such as PureSignal, WDSP and DFC (Direct Fourier Conversion) are new and involve great volumes of work. As a user of those developments they demand a certain amount of knowledge.

          Have a look at some of the kit I’ve had a lot of fun building on

          1. Generic “maker” not generic RF.
            Clearly you are an RF maker not a generic maker. That does not mean you only do RF. It means you DIG RF.
            Generic makers may benefit from your work if you make it available.
            But let’s agree to disagree :-)

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