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Re: [Discuss-gnuradio] saturation with multi_fft.py


From: ematlis
Subject: Re: [Discuss-gnuradio] saturation with multi_fft.py
Date: Tue, 9 Oct 2007 23:56:37 -0400 (EDT)

I don't have a chance to test your suggestion at the moment, but no, my test signal was an un-modulated 10 kHz signal.

eric

On Tue, Oct 09, 2007 at 05:11:52PM -0400, address@hidden wrote:
Thanks-

I just downloaded, compiled and installed this latest revision.  When I
test multi_scope.py in the mutli-antenna examples directory with this
release I get the same issue.  Please note, I have the LF_RX
daughterboards, so I change the daughterboard ID from BASIC to LF in the
python code.  I also eliminate the second factor of 4 decimation in the
host (sw_decim = 4) by setting it to 1.  I then run with the following
command:

multi-antenna]$ ./multi_scope.py -f0 -d250 -g0

while acquiring a 10 kHz 0.3 V p-p signal.  The max value shown in the
waveform on the gui is just over 25,000, which is way too much compared to
the standard usrp_fft.py, which by the way is no longer in the examples
directory; I used one from a previous release.  If I increase the input
voltage level to 0.4 V p-p, I get a jagged waveform with sharp
discontinuities.

So, my problem remains.  Any ideas?

What's your test signal?  Is it your 100kHz wide signal?
Can you try it with -d 400 as described below?

Eric

On Tue, 9 Oct 2007, Eric Blossom wrote:

With the halfbands, it's flat to about 70% of the passband.
decim = 320 gives 200kS/s complex baseband, a bit more than you'll
need.


Without the halfbands, I'd use about 4x the bandwidth of interest,
then filter and decimate in the host for the final channel selection.
In your case, I'd use decim = 160 giving 400kS/s.

Eric





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