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Re: [Discuss-gnuradio] bandwidths< 400Khz no longer work with USRP2

From: Tom Rondeau
Subject: Re: [Discuss-gnuradio] bandwidths< 400Khz no longer work with USRP2
Date: Tue, 16 Nov 2010 20:34:26 -0800

On Tue, Nov 16, 2010 at 6:13 PM, Marcus D. Leech <address@hidden> wrote:
> On 11/14/2010 02:28 PM, Marcus D. Leech wrote:
>> I did a "git pull" for both UHD GnuRadio yesterday.  I'm on the "next"
>> branch for gnuradio, and on
>>  "master" for UHD.
>> Since doing a rebuild yesterday, bandwidths below 400KHz no longer work
>> on the USRP2.
>> I did a test with a dead-simple flowgraph:
>> UHD single source-->multi-const x 32767-->FFT
>> For bandwidths>= 400KHz, the resulting FFT, with my existing RF
>> front-end with 40dB gain feeding
>>   the BASIC_RX on my USRP2, the FFT looks just fine (showing a level
>> around -40dB).
>> But anything below 400KHz bandwidth (I tried various bandwidths between
>> 200KHz and 400KHz),
>>   produces an FFT with nothing useful in it, and a "level" around -400dB.
>> This used to work just fine below 400KHz. What happened?
> So, nobody has answered my question yet.
> Even with the "latest and freshest UHD (master) and GnuRadio (next)", Rx
> bandwidths below 400KHz don't appear to work correctly on a USRP2
>  with UHD, giving a flat-line at -410dB in the FFT display.

No answer or insight, just another data point. I've been running UHD
apps today at 200 KHz sample rates with not problem.


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