Re: Avantic BM611 Stereo Decoder
I have had another go at alignment using the 2022 but this time I moved the centre frequency about to cover a wider range. After the alignment I checked the demodulator output and I now get a good straight line output over +/-200kHz.
Whilst that proves the FM detection range, the other factor will be the demodulators ability to handle the high frequency multiplexed audio. In the drawing of the Foster-Seeley demodulator below there is a 40pF capacitor between the diode cathodes which I assume is RF filtering. I haven't a clue how to calculate the impact of this capacitor and don't have the test equipment to generate a 53KHz FM modulated signal on a 10.7MHz carrier to measure it.
The only solution would be to try a few values and see what impact it has on the stereo quality?
Meanwhile, I am just testing my simple J-FET buffer which will be needed to deliver the audio multiplexed signal to the decoder without losses.
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