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Re: [Discuss-gnuradio] Received signal is DANCING


From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] Received signal is DANCING
Date: Thu, 18 Nov 2010 12:17:05 -0500
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On Thu, Nov 18, 2010 at 6:34 AM, Songsong Gee <address@hidden> wrote:


What does the resulting plot look like if you remove the bandpass filter? Those discontinuities when the orig signal abruptly turns on/off is essentially high-frequency info, which when filtered out by whatever means, will result in a rx signal that is distorted from the original.

Also, why do you have a throttle? You have a USRP sink, let its Interp factor be the rate-determiner.

-Steven

    
The whole flow-graph is suggestive of deep confusion.

The bandpass filter is being told to operate at a sample rate of 7K, but in fact the samples are coming from a USRP with decimation=256,
  which gives 250KHz sample rate.  The filter bandwidth is *quite* narrow, so if it was told the correct sample rate, it would likely distort
  that signal even more.

As previously observed, the throttle blocks are quite unnecessary.  Also, why the "repeat" block?  The file source is already set to "repeat",
  so I don't understand what that repeat block is doing there.



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