[linrad] Sound card problem?

["matthieu.cabellic@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx]

Hi

I have just Linrad 01-11 installed on my computer (Mandrake 9.2).
I am using a Guillemot Fortissimo sound card (16bits, 16kSample/s) using just a rx channel. I use the default parameters for fft.  
Without any microphone connected to the sound card I have this problem:
If I increase the sound level (using the red bar) a strong spur appears on the fft display centered on the frequency of the pitch I have set. For example if I set the pitch at 600Hz and set a medium audio output level then I can see a strong spur centered on 600Hz on the fft and on the waterfall display. If I click on a frequency near the spur then the level of the spur increases but with the processing delay. 
When I set the output audio level to the minimum, the spur diseapers.
I think it's a problem of isolation between the input and the output of the sound card. Is anyone else have had such a problem?

Thanks your help and advises.

Matthieu
F4BUC



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