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Amateur radio, space tech, and other nerd stuff

Can we use a Raspberry Pi model B as FreeDV modem?

I have collected a bunch of old Raspberry Pi model B's equipped with the Wolfson audio board. You may find these board lying around and collecting dust, as they have been obsoleted by an increasing number of multi-core boards. I will use these boards as simple Softrock SDR receivers, but first I want to do a little experiment. I am going try using them as a headless FreeDV modem similar to the SM1000.


Omnia SDR build status 2016.03.20

Following the successful receiver tests yesterday, I continued today with the band pass filters completing the receiver chain. I decided to build for 60/40/30/20 meters, which can provide a good all round, day and night transceiver.


First on-air tests of the Omnia SDR receiver

I mentioned in my previous update that following my noise floor measurements I tried connecting antenna to the receiver input through C27 but did not have any signals through. Today I found out that I had a bad solder at L11 and so the antenna switcher wasn't working.


Omnia SDR build status 2016.03.18

The receiver is now complete and only the band pass filters are missing. The local oscillator is working well as does the computer interface. I could measure the noise floor on all bands and check how much USB noise there is on the different bands of interest, see the screenshots below.


Omnia SDR build status 2016.03.15

Peter OZ7HVO has soldered the difficult parts for me, namely the CY8C32 PSoC, the PCM3060 audio codec and the SI570 oscillator. I consider the SI570 a bit difficult because it has 8 pads and the solder has to flow in below it, so best to let someone skilled do that.

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