Talbot Andrew wrote:
> Would be possible to include 100Hz bandwidth option as well?
Yes, but SAQrx uses a complex FIR filter for the main
selectivity so it will take some CPU power if you want:
1. narrow passband width AND...
2. small ripple in the passband AND...
3. steep skirts AND...
4. large stopband attenuation
i.e. a "brickwall" response.
A complex FIR with, for example:
Passband width = 100 Hz
Passband ripple <= 0.1 dB
Stopband width = 150 Hz
Stopband attenuation = 80 dB (either side of +/-75 Hz)
designed with Parks-McClellan requires 2 * 1526 = 3052 taps.
The main filter in SAQrx is run at Fs = 11025 Hz.
I think ~3000 taps would work OK on a fast machine although
I haven't checked it. The existing 1000Hz filter has 2*206 taps.
You will have to choose a passband shift frequency (CW pitch).
Maybe 700 Hz is OK?