Stumbled upon this write-up- SSTV from the Raspberry Pi camera, with direct RF synthesis, i.e. no outboard radio required, complete with motion detection and callsign overlay. Neat!
Low pass filter mandatory.
Nothing stopping this being adapted for HF SSB, in fact it would probably work better.
I have a lovely Wouxun KG-UV950PL 6/4/2/70 mobile radio, but a hands free kit doesn’t seem to be available. So I set about working out the connections required to build one. Here they are:
Using a standard RJ45 Ethernet cable:
- Orange+white / pin 1: RX audio – NC for this application
- Orange / pin 2: +5V on receive (unverified) – NC for this application
- Green+white / pin 3: PTT – wire to one side of switch
- Blue / pin 4: unknown, probably buttons – NC for this application
- Blue+white / pin 5: unknown, probably buttons – NC for this application
- Green / pin 6: +8V constant – wire to 2.2k resistor, then to positive side of mic
- Brown+white / pin 7: ground – wire to ground side of mic and to other side of PTT switch
- Brown / pin 8: – TX audio – wire to negative side of 100μF capacitor, then positive side of the cap to positive side of mic
Looking forward to building a version for the car and seeing how it is for road noise etc.
According to this, increase resistor size to increase mic output level (sounds counter-intuitive, but hey).
Update: that 2.2k resistor should be a 47k. That seems to produce clean audio and keeps the current through the mic element down. I’ve ordered a MAX9812 module to see whether a pre-amp brings the punchiness of the audio up a bit, since it’s a bit quiet as-is.