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Re: [Discuss-gnuradio] High noise level reading GSM spectrum.

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] High noise level reading GSM spectrum.
Date: Wed, 04 Feb 2009 14:49:32 -0800
User-agent: Thunderbird (X11/20090105)

Marcus D. Leech wrote:
Matt Ettus wrote:
There is no low pass filter.  Assuming that you are setting the gain
properly, then most likely problem is that you blew out the LNA in the
front, U4.  Static or strong signals can do that.  You could try
replacing U4, which is an MGA82563.

Matt, I thought that there *was* an LPF on the I and Q channels on the
MAX2118, which is what set_bw() is all about.
  The MAX2118 has programmable lowpass filters on the I and Q outputs,
does it not?

Yes, it does have programmable lowpass filters, but he seems to have a problem on the front end. If a baseband filter had a problem he would get terrible opposite sideband rejection, which doesn't appear to be the case from the picture.


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