Believe I am measuring that with these R820T receivers, best tuning resolution is 55hz.
Yes with cuSDR we can tune the chip 1hz freq, but we can only detect an audible change every 55hz.
Does this make any sense to you? Not sure why 55 hz. I thought this was only a GQRX behaviour, but tonight could measure it also on cuSDR.
Find a strong single tone birdy signal, or even CW beacon on 10m if you can hear one. I've got one from Tx that still coming in strong tonight but I've tried both.
Tune in 1hz increments until you hear the pitch change, jot down the freq, now continue in that same direction and stop when you hear the pitch change again. Difference should be around 55hz. If you now change direction back up, there seems to be about 3-6hz difference before the pitch changes back. Its a weird effect but clearly we're not getting 1hz resolution. I've never played with other SDR's, wonder if this is typical or are there ones that indeed have 1hz resolution (or better). Gotta try my hackRF board with this test case.
As you pointed out earlier regarding RTL driver, this may be something with the RTL code, or our downsampling code. This might explain why I'm still seeing some offsets and cannot zero it out with the freq_offset. The resolution is 55 hz which may be enough to push me over/under 100hz skew.
Believe I am measuring that with these R820T receivers, best tuning resolution is 55hz.
Yes with cuSDR we can tune the chip 1hz freq, but we can only detect an audible change every 55hz.
Does this make any sense to you? Not sure why 55 hz. I thought this was only a GQRX behaviour, but tonight could measure it also on cuSDR.
Find a strong single tone birdy signal, or even CW beacon on 10m if you can hear one. I've got one from Tx that still coming in strong tonight but I've tried both.
Tune in 1hz increments until you hear the pitch change, jot down the freq, now continue in that same direction and stop when you hear the pitch change again. Difference should be around 55hz. If you now change direction back up, there seems to be about 3-6hz difference before the pitch changes back. Its a weird effect but clearly we're not getting 1hz resolution. I've never played with other SDR's, wonder if this is typical or are there ones that indeed have 1hz resolution (or better). Gotta try my hackRF board with this test case.
As you pointed out earlier regarding RTL driver, this may be something with the RTL code, or our downsampling code. This might explain why I'm still seeing some offsets and cannot zero it out with the freq_offset. The resolution is 55 hz which may be enough to push me over/under 100hz skew.
-dt-