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Raspberry Pi pirate radio?
7 March 2014 | by Over at Make, they’ve posted an interesting project showing you how to convert your $35 Raspberry Pi into a wide coverage FM transmitter.
This simple hack turns your Raspberry Pi into a powerful FM transmitter! It has enough range to cover your home, DIY drive-in movie, a high school ball game, or even a bike parade (depending on the stragglers).
The hack, called PiFM, uses hardware meant to generate spread spectrum clock signals and outputs them as RF energy on the Raspberry Pi’s GPIO (general purpose input/output) pins. The original creators report getting a range of 50m through heavy walls and multiple rooms.
Luckily, they include this helpful warning:
The Raspberry Pi’s broadcast frequency can range between 1Mhz and 250Mhz, which may interfere with government bands. We advise that you limit your transmissions to the standard FM band of 87.5MHz–108.0MHz (see Step 3) and always choose a frequency that’s not already in use, to avoid interference with licensed broadcasters.
Good advice, don’t you think? :-/
5 Responses to “Raspberry Pi pirate radio?”
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Some back-of-the-envelope math shows that the PEP would be about 27mW (given the GPIOs 3.3V levels and assuming a 50 ohm load). That’s a bit more than the rule-of-thumb 10mW limit for Part 15 FM broadcast band transmitters, but the actual transmitted power is likely far less when using the antenna given in their instructions. There’s probably all kinds of nasty harmonics though.
Still, I have to wonder how well this would work as an APRS transmitter when used with a proper filter.
Looks like a nice way to make a cheap fox hunt beacon…configure it for 146 Mhz and create a MP3 of a fox beacon…set it to loop…and your ready to go…all for 25 bucks
73,
Brian K9WIS
https://groups.yahoo.com/neo/groups/Raspberry_Pi_4-Ham_RADIO/files/pifox.zip
Narrowband autofox
Updated!
Try my foxhunt script for pi based on nbfm which is based on pifm
Most up to date will be at
https://groups.yahoo.com/neo/groups/Raspberry_Pi_4-Ham_RADIO/files/pifox.zip
Non yahoo link v113
https://www.sendspace.com/file/wpvvm2
Pifox raspberry pi fox hunt transmitter is now a github project
https://github.com/km4efp/pifox