Hackszine.com: HOWTO - DIY radio modem

HOWTO - DIY radio modem

Eric Seifert sent in some information on creating a home brew radio modem using a standard PC sound card, an iPod FM transmitter, and an FM radio. He has his current revision working at 9600 BAUD for distances in the neighborhood of hundreds of feet.

The sending side outputs an amplitude encoded data stream to the sound card, which is connected to the FM transmitter. On the receiving end, an FM radio receives the transmission, and outputs it to the receiving soundcard's line-in, where it is then decoded. The hardware set up is extremely simple. It's the software for reliably encoding and decoding the data (and handling error conditions) that's the tricky part.

Eric released some example encoding/decoding software on his site, so you can start with that and take a swing at improving its error handling ability. You'll need a Linux box with the ALSA and SDL libraries to compile it.

Radio Modem - Link

Posted by Jason Striegel | Dec 16, 2007 09:22 PM
Electronics, Linux, Wireless | Permalink | Comments (3)

Comments

Newest comments listed first.

Posted by: Max on December 17, 2007 at 4:04 AM

Hmm, re-inventing the wheel sadly. checkout soundmodem

http://www.baycom.org/~tom/ham/soundmodem/

-Max

Posted by: Jason Striegel on December 17, 2007 at 3:35 PM

Thanks for the tip, Max. That's no-doubt a better software stack for the radio modem.

Do you have any recommendations on a cheaper or more simple solution for the hardware side of things?

Posted by: Max on December 17, 2007 at 11:47 PM

hardware wise I'd use an isolating interface between the radio and the computer. Unless you're a HAM you could use some walkie talkies, and this http://www.sparetimegizmos.com/Hardware/SoundBuddy.htm

Why not become a radio HAM, and get to play with this stuff with some real radios. google for 'd-star' it's a system allowing digital voice and data over HAM radio. On the 1.2Ghz band you can have a mobile 128k connection. Although sadly it uses a proprietry codec.

-Cheers Max