Off-Grid Radio Also Repairable Off-Grid

Low-power radios, often referred to in the amateur radio community as QRP radios, have experienced a resurgence in popularity lately. Blame it on certain parts of the hobby become more popular, like Parks on the Air (POTA) or Summits on the Air (SOTA). These are events where a radio operator operates off-grid at remote parks or mountaintops. These QRP rigs are a practical and portable way to make contacts. You would think that a five- or ten-watt rig running on batteries would be simple. Surprisingly, they can be enormously complex and expensive. That’s why [Dr. Daniel Marks] built the RFBitBanger, a QRP radio designed to not only be usable off-grid but to be built and maintained off-grid as well.

The radio accomplishes this goal by being built out of as many standard off-the-shelf components as possible. It eschews modern surface-mount components in favor of the much more accessible through-hole parts, including the ATMEGA328P at the center of the build. A PCB design is also available, but it can be built on perf board nearly as easily. The radio supports any mode a QRP operator might use, including CW, SSB, RTTY, and a new mode designed explicitly for this radio called SCAMP which is a low bandwidth, low SNR digital mode built into the Arduino-based firmware. It’s a single-band radio, but any band between 20 and 80 meters can be selected with pluggable filters.

As far as bomb-proof radios go, we can’t imagine a better way to live out an apocalypse than with a radio like this. As long as there’s a well-stocked parts drawer around, this radio could theoretically reach around the world without worrying about warranty claims, expensive parts, or even a company going out of business or not stocking parts for old radios anymore. There’s also more information about this build at the Open Research Institute for those interested. And, if you’re wondering how useful any radio could be using only five watts of transmitter power, take a look at this in-depth look at QRP radio operation.

Thanks to [Stephen Walters] for the tip.

32 thoughts on “Off-Grid Radio Also Repairable Off-Grid

  1. Off the shelf parts … from where digikey and Amazon? I haven’t seen a local electronics supplier in 15 years and I live in a town full of recording studios that need constant repair to their sometimes 30 year old gear

    1. From the Github repo:

      “This radio is designed to be assembled and maintained using the most common jellybean components that might be in a hobbyist junkpile.”

      In other words, you yourself are the source for the parts. If you’re not a tinkerer or ham radio operator already you probably don’t have these parts in bins in your workshop, but if you are then you likely do. I know I recognize nearly every part on the board from my parts bins with the exception of the Arduino.

      20 years or so ago, I built a QRP transceiver with nothing but parts from my parts bins; all discrete parts with no MCU or other “brains”, tunable with a large potentiometer. I built it on perf board and while tuning it properly took longer than building it, the result was as perfectly usable as a consumer-grade QRP rig, just not as pretty nor as expensive. Sometimes it’s more about the journey than the destination.

    1. I don’t understand your comment. “Already done”… meaning what? It shouldn’t be done again, differently, or possibly better in some respects? We shouldn’t have options, or a variety of completed designs from which features could be cherry-picked, mixed-and-matched to produce even more interesting designs?

      I find it odd that a commenter would dismiss an effort like this… and on a blog site dedicated to people who build/make stuff. Ironically, there are plenty of critics who complain that hams don’t build enough stuff and bemoan the fact that hams are largely just “appliance operators” now.

      At one point, a lot of people found circuitry like this interesting and useful. Many of us still do. I still enjoy any article written by Doug Demaw(SK) I run across.

      1. I think it’s fair enough for you to ask for clarification of what I meant by ‘already done’, but I don’t think it’s on for you to construct a load of straw-men like that! No way did I say or imply any of those things. My issue was the way the article promoted as novel some aspects that are clearly not novel, as if no one’s ever made a radio out of easily obtainable parts, that can be easily repaired, and that uses low power before, for example. The project’s fine, but the way it’s promoted in the article is a bit OTT IMO.

        1. I agree it’s great that people are designing, building and experimenting, even if it’s just a minor twist on well established deisgns like the QRP Labs, BiTx, uSDX etc. but the article and the claims made by the creator are more than a bit OTT IMO

          The “Most radios require specialized parts that would be difficult to obtain in an extreme parts shortage or in remote place” and “while not requiring any custom ICs such as SA612 or FST3253” is just nonsense when the radio uses an ATMega, HD44780 LCD, Si5351 etc. etc.

    1. You only need a sound card if you want to connect it to a computer to run software such as WSJT-X. A microphone is plugged into the jack. I would recommend a $10 headset which has a microphone and headphones combination. The audio quality is much better that pay.

      1. Not everyone is so jumpy about the whole license shaming aspect of amateur radio. Most people know if they’re looking for radios that operate on a licensed band, whether or not they are so licensed to use said band. Some of you guys are just flat out ridiculous with the constant need to interject a “license” comment with every radio post you see. Yes, we get it, you have a license that you feel somehow elevates you to a higher status of intellect or some garbage. Get over yourself.

        1. Well, it is good to warn about a license. Being a licensed Amateur is simply a requirement to (in the US) transmit on the Ham Bands, nothing more, does not confer some cachet on you as superior. If you were driving to Florida on I-95, I would alert you to needing a driver’s license, and the fact that some states do not have a reciprocal license. Get in a car to drive, get a license. Doesn’t make you any better, just makes you responsible. Besides, you go calling around on the ham bands without a license, nobody is going to talk to you anyway.

      2. You don’t need to know CW… and if you did happen to know CW you wouldn’t need to be a general 🤔 You are trying too hard to be mad lol. Any level, including extra only takes about a week of study anyhow, all the questions and answer are published, it’s all very easy tbh. Legit got my extra in a week as a joke because people like you complain about how hard it is.

  2. The last electronic parts place in my area had its inventory auctioned off around a year ago. I’m not surprised they went under. They were trying to sell things like 20 year old Fluke multimeters at full list price. Years earlier I was in there and pointed out they had a whole rack of rubber belts for turntables and tape decks that were so old they had all crumbled to dust. The owner shrugged and said, “Somebody might want them.”

  3. Not another project. HiHi. QRP is fun. I recently took my DB2040 with me to the Adirondacks. Threw a line into the trees, pulled up an end fed wire and made several contacts. Had a small speaker attached so that others would hear and made several eyeball QSOs with some hams.

    Not much can go wrong with QRP so the spare parts list will be limited. You’d be surprised how far 7 watts will go.

    I’ll have to take a deeper look into this.

    1. I made a FT8 contact from the West Coast USA to Japan on 10 watts once (over 5000 miles). It was a rarity I haven’t duplicated (I blame my dipole mounted at NVIS heights), but it was really fun. QRP is just…good times.

  4. Nope. That’s neither simple or ‘off the shelf’ by my determination. You can achieve QRP with a LOT less parts and, in particular, NO microcontroller. If you want field serviceable you want ultra simplicity and an AtMEGA isn’t ‘it’.

      1. Which parts aren’t field serviceable?
        Can you show us a simpler design that does all these same things?

        The existence of transceivers that do less with less doesn’t mean this one is complex; in the grand scheme of HF transceivers, this rig is very much on the simple end of the spectrum.

        Is it simple for a LED blinky? No.
        Is it simple for a DDS multi-mode HF transceiver? Heck yeah it is.

    1. Your determination is wrong.

      – None of those parts are hard to get, nor specialized. That’s what “off the shelf” means. Always has.
      – Can you do all the things this rig does with a lot fewer parts, or can you build an entirely different thing with fewer parts?
      – What’s not field serviceable about an AtMEGA? I mean, leaving aside how they basically never fail and cannot need adjustment…what do you need a lab for to service it?

    2. But the easiest radios to build use clock synthesizer modules for their VFOs and BFOs, and these require an I2C interface to set the frequency. They’re also much, MUCH easier to make work than any of the traditional discrete transistor VFOs. But that’s okay, you can spend however long it takes to get your first analog VFO working, and then everybody will know it’s analog by the way it drifts across the band! Also, servicing an AVR-based system is a) not that difficult, and b) not required as often.

    3. There are many components that may not qualify as “components”, but are indeed “jellybean parts”. Examples: 5V and 12V wall-wart power supplies. Audio preamps. Headphone amps. Speaker amps. USB keyboards. USB mouses. PS/2 keyboards and meese. USB/serial adapters. Lithium-ion battery chargers. Linear DC regulators. DC-DC switching regulators (boost or buck). Arduino Nano boards. An ATmega IS it. Real hackers adapt.

  5. Kudos to anyone who can put together a working and useful transceiver and this does look like it could be fun, but come on, it uses an Si5351 and Atmel ATMega, if you truly wanted this to be a radio made of scroungeable parts that can be obtained anywhere there’s E-waste then it’d be all transistor with a LC VFO and maybe spot frequencies with scrounged crystals like a 3.579MHz NTSC crystal or the various multiples.

    1. …it doesn’t say anywhere that it’s meant to be built of scroungeable parts, and the days where Arduinos were hard to find in electronics stores or makerspaces ended like a decade ago.

      You can’t do DDS and digital modem in “all transistor with a LC VFO.” The goal of this radio was not to make the simplest device that can vibrate a wire, it was to make a simple, modern QRP radio. If you want an all-analog parts-bin radio, there’s about sixty existing designs to choose from. Been done to death.

      Some of us would like to advance the hobby, not pretend like it’s 1974 forever.

  6. All these people want everything given to them. Years ago you used to have to spend years to learn and work your way up to an Extra license. Nowadays a monkey could pass the extra. It’s disgraceful. The rules have been way to relaxed. The Arrl is destroying amateur radio. It’s all a money grab. The Fcc gets $35 to renew every 10 years. Calculate that. FT8 has been encroaching on cw for years. This radio is just another nail in morse codes coffin. What about all of us that love cw? And last, China put all of the electronics shops out of business with the help of eBay and Amazon. Sad and TRUE. Thanks .-.-.

    1. You are still free to buy your parts from Digikey, Mouser, Newark, and other non-Chinese distributors. And you are still free to make all the inductors and capacitors you have the skills to make. Are LEDs too modern for you? Transistors? If so, tough.
      You are also as free to use CW as you ever were. In fact, if all of the people currently using FT8 were using CW, they’d be taking up more bandwidth than they are now.
      Does the fact that you have to spend $3.50/year on your license mean the FCC is a money grab? That seems a little harsh. (Although their treatment of the VHF and UHF broadcast TV bands was certainly a money grab.)
      Are you an ARRL member? If not, what is your standing for accusing them of destroying a hobby? They advocate for their members.
      Back when you got your first license, did everybody build their own radios? It seems to me like a whole generation of hams used nothing but WWII surplus gear, all pre-built and ready to use.

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