Audio volume slowly pulsing with NR on

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Audio volume slowly pulsing with NR on

Postby AussieSusan » Wed Aug 16, 2017 7:19 am

(New user - searched for a previous topic but nothing found: apologies and pointers if I've missed something)

- Windows 10 Home Edition, 32-bit - running in Parallels VM on a iMac (Sierra, 10.12.6) all fully patched
- RSP2, Input A (connected to QFH)
- SDRuno (Rel 1.3)
- 4MHz sampling, Decimation 1, Single VRx, Gain reduction mid-range
- VFO A - Freq 137.62MHz, (LO:137.204MHz), FM/MFM, 38K filter, NBOFF, AGC Off, De-emphasis off

I'm trying to get the NOAA satellite signals (hence the frequency) and the above setup works well but there is quite a bit of a background hiss.

When I turn on the Noise Reduction (NR) option, the noise drops off nicely but then starts pulsing on an (approx) 7 second cycle. The sound disappears and then comes in strongly before gradually fading away for a few seconds, increases slightly and then fades to nothing. Then the cycle repeats.

Turn off the NR option and it returns tot the steady hiss.

I have the SDRUno output going to the (VM's) speakers. I don't think it has anything to do with this issue, but I also have a virtual audio cable installed so that I can pipe the audio to the 'APTDecoder' software. Using Audacity to sample the output of the virtual cable,I can get the exact same issue when I turn on the NR option in SDRUno, so I don't think it is an issue with the other software.

It may well be a 'rookie error' on my part, but I would appreciate some assistance in finding a way for the NR option to be used but with a steady signal.


Last edited by AussieSusan on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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