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I have fitted an internal RTL dongle for LeanDVB/WB FM listening etc when out portable, and I used the RPI audio out jack which works on WBFM RX.
I have searched around but can't find reference to the audio route from MT to Longmynd on a RPI to the outside world. Does it route through the 'selected' RPi output?
You need to use the "OMX Player" button to get audio out of the LongMynd receiver on Portsdown. You can then select between the RPi audio jack and an external USB dongle using one of the buttons on the Receiver "Config" menu. The default is the RPi audio jack.
I've a lot of ex-early car-phone kit Electret mics in nice little plastic cases with 'sun visor' clips on the back.
How should I use an electret with the easycap input, currently wired direct to a front panel phono socket.
I'm thinking add 5 volts via a 10K resistor the the plug centre and a DC blocking capacitor (?100nF) between it and the Easycap input?
Not sure that the audio level from your proposed arrangement would be high enough to drive an EasyCap properly.
I suggest that you purchase one (or 2) of these cheap little USB Audio dongles on eBay. They are designed for the job (with power on the ring and signal on the tip), and the Portsdown is designed for them.
I bought 2 a few weeks ago from a UK seller and they arrived within a few days.
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I subsequently discovered a 5.6GHz (non atv) use. It is an ideal circuit to generate enough audio to drive the FPV transmitters with enough audio to have decent voice qsos
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Had a look inside the mic assembly and found a lovely PCB with what I think is a low power single rail opamp 33171 https://docs.rs-online.com/a748/0900766b815744ea.pdf. The PCB has the motorola logo on the back so I'm assuming its exactly that, an amp, possibly with a bit of AGC in the circuitry. There are only two wires to it though, so I'm wondering how power and audio can go up/down the 'live' wire. Unless its like an electret, where the voltage drop via the feeder resistor IS the audio signal? So a bit like DC up the coax, only at audio. How to do THAT??
Be nice to use as-is. Worst case I suppose would be to change the feed wire to 3 core and add a specific 3.5 stereo jack suitable repurposed. The large electrolytic is 16V rated.