from Hacker News

Transmitting FM, AM, SSB, SSTV and FSQ with Just a Raspberry Pi

by irfan on 10/31/15, 7:04 AM with 23 comments

  • by pi-rat on 10/31/15, 1:03 PM

    Very cool, but please don't do this without a proper filter, you're spewing garbage all over the spectrum.

  • by radiof on 10/31/15, 4:48 PM

    Build yourself a low pass filter before transmitting:

    http://www.ebay.com/itm/LFCN-HFCN-FV1206-Filter-Design-Kit-M...

  • by mschuster91 on 10/31/15, 11:14 AM

    Awesome. Now, the critical question is: how to implement a proper filter and a HF afterburner? And can it do live streaming - i.e. use an USB/Pi-Shield soundcard with a Line-In or Mic input?

    I could imagine this being a cheap platform for crisis regions where radio transmission channels are run by government (or not existing at all).

  • by makomk on 10/31/15, 11:19 AM

    I hope the spurious emissions aren't as bad as they look in the waterfall, because they're basically stomping all over the band and all the neighbouring bands and they're closely spaced enough that I'm not sure it'd be realistic to filter them all out. Is this even legal to use?

  • by Animats on 10/31/15, 7:33 PM

    In working with RF, the test gear you need to see what's going on costs far more than the radio gear itself. The prices go way up as you get into the GHz range.

    There's a lot of filter adjustment, antenna tuning, and shielding placement as you look at a spectrum analyzer and see spikes that shouldn't be there. This is why there are little RF modules in cans for many applications. Someone already did that work for you. Some vendors: [1][2]

    [1] http://www.rfdigital.com/ [2] https://www.linxtechnologies.com/en/products/modules

  • by wyldfire on 10/31/15, 1:19 PM

    Wow, bit banging radio? Neat idea. But there's gotta be USB SDR kits on the cheap, too, right?

  • by frik on 10/31/15, 4:47 PM

    Interesting.

    The DAB iniatives doesn't seem to work out (eg Canada) though the lobbyists are still strong. Analog radio works even with bad signal quality (https://en.wikipedia.org/wiki/Digital_Audio_Broadcasting )

  • by callesgg on 10/31/15, 1:34 PM

    I am slightly confused by the screen-shot of an ubuntu OS with a windows XP desktop. :)

  • by bajsejohannes on 10/31/15, 5:44 PM

    > all you need to do is plug in a wire antenna

    Just to make sure I get this right, a "wire antenna" is just a wire, right?