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

October 30, 2015

Previously we posted about the Raspberry Pi’s ability to modulate one of its pins to produce FM transmissions with PiFM. Now some developers have expanded on this idea, and now the Raspberry Pi is capable of modulating transmitting FM, AM, SSB, SSTV and FSQ signals.

To transmit with the Raspberry Pi all you need to do is plug in a wire antenna to Pin 12 (GPIO 18) on the GPIO port and run the PiTx software by piping in an audio file or image for SSTV. 

While the output power is very small, you should still take care as there is no filtering on the antenna output and transmissions could be causing harmonics all across spectrum, possibly inferring with critical devices.

The code for PiTX can be downloaded at https://github.com/F5OEO/rpitx. Also see the authors @F5OEOEvariste Twitter account at https://twitter.com/F5OEOEvariste for some more info about PiTX.

PiTX transmitting SSTV and received in HDSDR. From PiTX's author's Twitter @F5OEOEvaristePiTX transmitting SSTV and received in HDSDR. From PiTX’s author’s Twitter @F5OEOEvariste

Over on YouTube the author of PiTx has also uploaded a video to YouTube showing a wireless doorbell being replayed. On the video description he writes

PiTx is a software which permit to transmit HF directly through a pin of Raspberry Pi GPIO. Unlike PiFM which transmit only in FM, PiTx is able to perform multi modulation (FM,AM,SSB,SSTV,FSQ) : it has an I/Q input to be agnostic.
The demonstration here is done in several steps :
– Record an I/Q file from a doorbell transmitter on 434MHZ (first part)
– Playing it with the Raspberry Pi using Pitx on HF on same frequency
– Listen to the doorbell receiver which recognize the signal

Conclusion : Pitx is now a real TRANSMIT SDR at very low cost. Be aware that it generate lot of harmonics and never compete with USRP or HackRF.
Goal is to popularize the transmission as rtlsdr popularize the reception.

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

Source: RTL SDR

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