unknown
1970-01-01 00:00:00 UTC
* plot the RF signal FFT and the FFT of a WBFM demodulator
block as found in GNURadio (always same settings: 30 dB IF
gain and 30 dB RF gain)
Hmmm, Dongles are different. I suggest that you compare themblock as found in GNURadio (always same settings: 30 dB IF
gain and 30 dB RF gain)
at maximum gain which is different for different dongles.
on the list can comment: what are the gain ranges for the various
front ends ? I have not been able to identify neither in the source
code of osmosdr & rtl-sdr nor on the datasheets what the RF and IF
gain ranges are. Are they different for the E4K, FC0013 and R820T ?
If so indeed, I'll have to adjust the emitted power to observe a constant
received power.
* assess the receiver quality by the signal to noise ratio of the FM
output. This is a very good method - but it is necessary to place the
frequency right. I can see from your graphs that the signal is at
the passband centre where you have a spur and 1/F noise.
this also explains what I observed when I was trying to reproduce the measuementsoutput. This is a very good method - but it is necessary to place the
frequency right. I can see from your graphs that the signal is at
the passband centre where you have a spur and 1/F noise.
with AM: the signal would be lost if locking exactly on the carrier frequency due
to the band pass filter after the mixer in the zero-IF scheme. I was not
able to identify the reproducible setting condition you mention below
for the experiement: I will do so.
Repeat and place the FM modulated signal signal halfway between the
passband center and the passband edge. Your current results are not
valid because of the center spur which is within your passband.
Thank you for these informations. I am away from the lab next week but willpassband center and the passband edge. Your current results are not
valid because of the center spur which is within your passband.
update the measurement results asap.
JM