Homebrew SDR Ham Radio in 9 Parts

It used to be homebrew ham gear meant something simple. A couple of active devices that could send CW. Maybe a receiver with a VFO. But only the most advanced builders could tackle a wide range SSB transceiver. Today, that goal is still not trivial, but it is way easier due to specialty ICs, ready access to high-speed digital signal processing, and advances in software-defined radio techniques. [Charlie Morris] decided to build an SSB rig that incorporated these technologies and he shared the whole process from design to operation in a series of nine videos. You can see the first one below.

The NE612 is a child of the popular NE602 chip, which contains a Gilbert-cell mixer, and an oscillator that makes building a receiver much easier than it has been in the past. The chips are set up as direct conversion receivers and feed a Teensy which does the digital signal processing on the recovered audio.

One nice thing about the Teensy is that it has an accessory audio board that makes it easy to connect audio inputs and outputs to the device. The DSP does work on the received audio and the transmit audio. There’s also a few other stock parts like an LCD, an encoder, a speaker, a microphone, and things like that. There’s also a digital clock generator (an Si5351), but again all that is common off-the-shelf stuff these days.

The first video is a bit introductory, but by video number two he jumps right into the wiring and why all the circuits work. By the third video, the receiver is actually working and it sounds pretty good. Because the receiver needs I and Q outputs, there are actually two NE612s operating out of phase with each other.

28 thoughts on “Homebrew SDR Ham Radio in 9 Parts

  1. I have always heard from sailors that marine SSB transceivers are incredibly expensive. Maybe projects like this will help bring down the cost of operating SSB on small sailboats.

    1. I’m no mariner, but given in an emergency situation your radio could easily be your only means of communication, I’d be buying the best of kit, that said I will follow this series with interest, i like SDR’s (who doesnt) and I like teensy’s (who doesnt) and I like reading about over-my-head radio voodoo.

      1. You have VHF channel 16 for that. The SSB transceiver is often used to download weather data. I think sailors also talk to each other using SSB (mainly in the Pacific) but emergencies are handled by the VHF transceiver.

          1. If you built it yourself with common through hole parts, you can always repair it if it breaks but if it’s a black box blob you got off the shelf with all encapsulated microelectronics and smd, you’re probably going to struggle to work out what broke let alone how to fix it.
            I’m my opinion, home made will always be more robust long term.

        1. In a harbor or coastal area, Ian is correct. However VHF is only useful for “line of sight” ranges; about 50 miles under ideal conditions.
          HF SSB is useful for long range communication, often thousands of miles. There are established emergency frequencies on HF bands as well. Please study “global maritime distress safety system” if interested.

          1. Yes, VHF is good for coastal sailing, and yes in principle SSB can be used for offshore distress calling. But EPIRBs are now very affordable. They send your distress signal with GPS info via satellite to International Search and Rescue Authorities. Use of marine SSB has been dying off due to high initial costs and cheap sat phones. A cheap marine SRD SSB may ignite SSB use and interest. AS a offshore sailor, I’m in.

    2. Mariner/pilot/ham/economist…
      The market is limited to companies who get a FCC and probably FAA or NOAA license or certification(not a licensed tech for either field) no do that for every country of flagging and/or home-porting.
      Small volume(how many ships worldwide from supertanker to small yacht) and competition limited by rules which keep out market entrants. Affordable and DIY SSB rigs have been around for 80+ years to the amateur radio(ham) market SDR wont change marine certified prices except perhaps again upward as these are required equipment and like medical it is regulated limiting who can afford to supply the market.
      Now there is the big GMDSS changes and satcom so SSB is fading/ has faded in importance, it might not even be on the new rules( I haven’t sailed in years now).
      As I recall it was a fight to keep VHF ch16 manned by a coastguardman along the US coast and lakes, the SSB channels I am pretty sure are officially completely unwatched for analog signals if at all.

      1. TLDR: It would be illegal to operate a DIY rig outside of ham bands and non-ham commercial SSB radios are a small regulated market limiting competition SDR wont change that.

    1. Most of the marine SSB HF radios are unable to transmit on 14.3kHz. Even ICOM’s M802 lacks the ability to transmit on that frequency. I find it a bit silly because in an emergency there’s almost a universal exception from seafaring nations that you can use any frequency, any power, any method to reach assistance.

      1. It’s probably that way because “anybody” can buy a Marine VHF…
        Sure, you need a License, but I can see the CB craze happening all over again… and the Emergency frequency getting polluted by “polluted” i.e. drunken, boat owners.
        Besides, the radio manufacturers can make a second sale by selling a separate Emergency Radio and antenna B^)

  2. When I was looking into sailing and maybe having a motor boat to live on… most everyone I spoke with (including from Tiara Yachts) noted to make sure you’re drive train is brand new at least since I was looking at free boats or cheap used ones to restore. The engine is the last piece of equipment you want to die on you out at sea. I’m thinking since the hull and rest of the boat are obvious in regards to inspection issues more-so and first to be restored.

    The radio or emergency beacon seems logical to be of high quality and new too. I’d go with a superheterodyne personally from my little experience, though I’ve read some of the SDR’s are impressive. Would be interesting to see a side by side comparison and read into this more to see if is a superheterodyne transceiver and just has a SDR interface. That seems the neatest to me. Interesting article with great info looking forward to watching.

      1. True… like market fund managers… long term performance is based on your system knowledge and maintenance skills basically. Know the history and details of the system variables (internal, boundary and external)… then maintenance skills and long term reliable data can pretty much predict the variables (less hidden or unforeseen) that can occur so you develop your standard operating procedures to be valid for reproducibility, repeatability, etc., for the specification the user requires.

  3. I am inspired by this whole video series. Being that I’ve built quite a bit of kit in my earlier days, this would be a nice new challenge. I had built a simple BFO to help in the assist of picking up Sideband reception on my AM radio. Definitely start with the small stuff and don’t rush in. :) 73 de KC8KVA

  4. HF comms at sea isn’t very reliable at the best of times and particularly bad at this low sun-activity time. If I was to sail outside VHF (A1) range I would be investing in a Satcom system (mobile will do – you can get mobile-phone-like Satcom handsets) for comms but also carry an EPIRB for emergencies.
    HF comms is a statutory requirement for merchant vessels sailing A3 and A4 category areas (Google it) – only MF comms is required for A2 areas – but a PITA for private sailors who aren’t compelled to carry or use it.

    1. Modern 406mhz digital GPS enabled EPIRB satellite beacons are the bees-knees for real emergencies, that and air band VHF HT which can talk to airliners or rescue helicopters on 121.5mhz, if you go used you can get both for easily under $500.
      The EPIRB will whoop on 121.5 too though so remember to shut off the EPIRB if you are trying to talk to the helicopter or to answer aircraft responding on guard to your beacon.
      Most EPIRBs are small enough to take hiking, boating, or out flying over water or wilderness so have a personal one, REGISTER IT!!!, and have a backup to your ELT.

  5. It disturbs me a lot that many people compare VHF to SSB. This is like comparing an apple to an archbishop.

    VHF is a frequency range (probably using FM modulation)
    SSB is a modulation, seemingly used on the HF frequency range.

    1. What about VHF SSB to work the bent pipe satellites?
      AO-10 is still rocking SSB and CW on UHF, VHF and 10m like it was 1979 even if the battery shorted for a few decades and then burned through the short, it still works on solar.

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