On 02/01/2018 00:31, Steven Franke wrote:
I think that jt65sim is working properly in r8391. The fac vs rms thing was taking
care of a hidden feature, whereby the simulator generates a noiseless signal
whenever the requested SNR exceeds 90 dB. That wasn’t working properly with
nonzero Doppler spread, even in the original version, because the peak amplitude
is random - so I made some changes that will cause a noiseless (SNR>90 dB)
signal to be scaled so that the (random) peak magnitude is 32767.
I also changed the hardwired Nyquist frequency from 6000.0 to (fsample/2) so
that the noise should be scaled properly for either sampling rate.
With the new option for an arbitrary “gain offset", I decided that it would
also be worthwhile to print a warning if the simulated data is clipped in the wav
file. The user should probably re-run with a smaller gain value if clipping is
detected.
Steve k9an
Hi Steve,
thanks for looking at that. It all makes sense now. Sorry for passing a
half baked job over to you but I ran out of free time and now am back at
the salt mine. I think we have a good tool now for comparison with WSJT
so that better estimates of relative performance can be done. I will
have a look at the jt4 simulator at some point and check if similar
enhancements can be made.
73
Bill
G4WJS.
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