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From: | Ian Wraith |
Subject: | Re: [Discuss-gnuradio] Source of annoying problem found |
Date: | Tue, 06 Jan 2004 08:34:11 +0000 |
Hello Rob & Group
I can only assume that you are using a frequency that is too high for the card. If the samplerate selected was, say 48kHz then your IF cannot be above 12kHz. Go do some reading on subjects like Nyquist frequency and aliasing for a better understanding.
I should be OK Nyquist wise since I am sampling what is basically a 18 KHz waveform at 44.1 KHz. I had noticed my waveform amplitude was varying before but in my last test this suddenly became much worse. I now realise this was caused by me changing motherboards between these tests. I suspect this new motherboard has a 11 KHz low pass filter where as the old motherboard (another Asus but with a different sound IC) had a low pass filter set at a much higher frequency. RegardsIan
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