WSPR Transmitter Shows True Value Of Raspberry Pi For Hacking


Don’t get us wrong, we love our Raspberry Pi. But if you’re merely running a Linux image without adding a hardware hack into the mix you’re missing out on part of the power for which the platform was developed. This project is a great example of how to embrace the Raspberry Pi’s ability to deliver both low-level hardware access, and solid embedded Linux performance. [Dan Ankers] and [Threeme3] have developed a program which turns the RPi in to a WSPR transmitter. The GitHub readme shares many of the details on how it was done. But you’ll also want to dig through the .c file to see how they’re making use of the GPIO header pins.

[William Meara] sent in the tip for this. He’s been featured on Hackaday previously for his work with WSPR (Weak Signal Propagation Report). It’s an amateur radio protocol which lets you communicate over very long distances using relatively weak transmitters. The trick is to use computing power to find the signal hidden in all the noise. Be warned that you do need a HAM license to try this out, but otherwise all you need to connect to the board is a low-pass filter and an antennae.

[via SolderSmoke]

[Photo credit: WSPR hompage]

33 thoughts on “WSPR Transmitter Shows True Value Of Raspberry Pi For Hacking

    1. To clarify, you need a license to use the RasPi in such a fashion (the only use of the hardware hack is to transmit). You don’t need a license to use their website, view their updated maps, etc…

    1. Take it seriously, bro. Don’t ruin it for those that worked hard to get their license. Don’t risk the fines. One of these days I’m going to get my license, in the meantime I just enjoy listening to various bands when I get the chance.

      1. That and it’s truly not hard to get a license. A technician license which has full privileges on all ham bands from 50MHz on up is pretty much at the same level as the A+ certification in computers. If you have a pulse and have an interest in the topic you probably know and/or can guess your way to a license. If you find you like it, a general license that gets you in to the rest of the bands is a bit of studying beyond that. I missed general by two points my first try when I only intended to go for technician (if you pass one you can take the next for free) and hadn’t studied for anything.

        1. The Technician license is wayyyyyyyyy easier then the A+ certification. I have both and I only studied part time for a little over a week for the Technician license.

    1. With the narrow band mandate used scanning radios that cover 868Mhz should be relatively inexpensive used & new. An outdoor antenna, and a preamp mounted at the antenna if needed. Assuming the signals you want to hear are FM, and the public safety agencies in the area went with digital technology to comply.

  1. Bill,

    I haven’t looked at this specific code, but it is basic GPIO bit banging. The question becomes one of discovering how fast your CPU can toggle the pin while still leaving enough CPU time left for performing the work of the program and other overhead. A few years ago, I did some tests on a C2000 Piccolo USB stick to determine how fast I could make it go, but only got the GPIO up to 3 MHz or so with all the CPU spent. That board’s probably not a candidate for this project.

    Try writing a simple bit toggling program and scope it or use a counter. I would feel confident if I got a frequency of at least 5 to 10x the frequency I need to work at. As a bonus, look at the waveform on a scope and you’ll see why you need a filter! :)

    US hams don’t have 136 kHz or 470 kHz allocations, so if the ‘Duino doesn’t work on 160M, it’s a no go. (But, I have a Beaglebone for another project and it will likely do the 70 cm band (430 MHz) :) )

    73 and GL,

  2. Just a warning that you need to have an amateur license to do this. Whilst the risk of getting caught is small it is still there and the fines the FCC issue are five figure.

    Getting an amateur license isn’t all that hard or expensive to do and opens up a whole new world to investigate and play with. Amateur radio is about learning and experimenting with radio and there’s a whole host of really interesting stuff to do including communicating by bouncing signals off aircraft, rain clouds, meteors and even the moon itself. A lifetime isn’t enough to do everything possible in amateur radio.

    1. There was a group at a Make Fair a while back using a plotter/cutter to make peel and stick fractal antennas. They were using a 4′ wide roll of adhesive metal foil like the kind they use in sign and graphic shops. Some were in sheets others were applied to PVC pipes. I know very little about antenna theory but they claimed to be able to shape the fractal to “tune” any antenna to any application.

  3. I wish they’d include what they consider a suitable low-pass filter. It must be simple, and it’s something of an oversight to omit it. Perhaps they expect any qualified ham to be adept at adding that last step (selecting suitable component values), but that’s definitely not going to be the case. This project is easy enough for beginners, but they need that detail.

    1. This is a question I’d like to ask as well. Will a standard 1.8-30MHz TVI low-pass filter be sufficient, or does this really require individual band-pass filters for each band a user intends on transmitting on?

  4. does any one know how to call and run in the c file in raspberry pi websever. i have web interface for pifm transmitter and i have pifm.c code how to link it

  5. I don’t know in USA, but 10 mW in Italy are considered a “radio toy”, so there’s no need of any HAM license at all. Am I wrong? It’s 10 mW, not 50W or similar. If I’m wrong please correct me. 73 de IW9HGS

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