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From: | Matt Ettus |
Subject: | Re: [Discuss-gnuradio] 8 bit samples have an odd spectrum |
Date: | Fri, 11 Jul 2008 10:36:09 -0700 |
User-agent: | Thunderbird 2.0.0.14 (X11/20080501) |
Chris Stankevitz wrote:
Johnathan Corgan wrote:You *may* be seeing an artifact of the truncation of the ADC samples.Johnathan, others:I believe this is not the case. When I download 16 bit samples from the USRP and remove the 4LSBs myself, the spectrum looks normal. When I ask the USRP for 8 bit samples, the spectrum shows a 1MHz wide sinc lobe. Since it turns out the bottleneck for me is writing to the hard drive, I'm happy removing the LSBs on the PC for now, but I'd love to hear your ideas!
Look at the samples in the scope sink. Do you see a pattern of A A B B C C D D...., meaning instead of unique samples, is every one repeated? If so, it means that the halfband decimator is probably not being bypassed properly.
Matt
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