On 3/17/2021 12:29 PM, Donhawbaker wrote:
The receive level, i.e. mic gain, should be set to 30, not 50 or 60.
I strongly disagree with this advice when there are very strong signals present. On 6M and 160M which I most often use WSJT-X modes, I often see my neighbors decoding in the range of 30 dB, and they're probably a lot stronger than that. Let's say, for example, a station is 50 dB over S9. If I set the top of my A/D to 30 on that voltmeter (the green bar), that strong station will prevent the decoder from seeing signals weaker than 20 dB over S9. But the practical dynamic range of a 16-bit A/D is typically in the range of 85 dB or so.
The solution is to set the gain on the analog side of the A/D so that, with those strong signals present, that green bar never turns red, indicating that we've hit the top of the A/D. This can be done by reducing audio or RF gain at the radio, or at the input to the audio interface (if there is one). I use a Tascam US100, which has both front panel gain controls for analog input and analog output, and an LED that is green with signal and turns red as the signal hits digital clip. With that interface, I can run the green bar in the range of 70-80 dB WITH strongest signals present, and I use slow AGC.
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