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Re: [Discuss-gnuradio] Works with GR 3.6, breaks with 3.7

From: Luke Berndt
Subject: Re: [Discuss-gnuradio] Works with GR 3.6, breaks with 3.7
Date: Mon, 3 Nov 2014 22:13:45 -0500

Thanks Andy! Good catch - I made the changes you suggested. I was just doing a 
simple back of the envelope calculation to come up with channel size. It does 
look like cleans things up and adding the waterfall graphs does make it easier 
to see. Unfortunately, it does seem to change the decoding. I am still getting 
the same amount of CRC errors.

Did the overall signal look right, like something that should be decodable? 

Anything else I should try?

 - Luke

> Hi Luke,
> I have not built the SmartNet blocks yet, but:
> Your low pass filter looks way too wide and you'll get aliases when you
> decimate by 185.  2 Msps / 185 = 10.81 ksps, so the Nyquist frequency is
> 5.405 kHz.  I winged this is as a low pass filter and things looked
> better:
> firdes.low_pass_2(1, samp_rate, 4500, 1000, 60, firdes.WIN_HANN, 6.76)
> The 60 dB down may be overkill, you can make it smaller for a filter
> with less delay.
> I found an offset slider value of -15k made things look about centered
> manually.
> You might want to put a waterfall sink before and after the FLL
> Band-Edge filter to observe how it is making the spectrum wobble around
> a little. If you change your offset slider, you can see the FLL
> band-edge filter centering things back up; so that looks like it is
> working.
> Regards,
> Andy

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