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Re: [Discuss-gnuradio] QPSK phase noise

From: Johnathan Corgan
Subject: Re: [Discuss-gnuradio] QPSK phase noise
Date: Tue, 7 Apr 2009 12:02:09 -0700

On Tue, Apr 7, 2009 at 11:49 AM, Paco Garcia <address@hidden> wrote:

> you usually get a much sharper constellation, don't u?

That depends on your overall SNR.  I'd suggest trying lowering your
transmit power, as the amplitude you are using is driving the RFX into
non-linearity, and with the raised cosine filter you are using, the
modulation is no longer constant envelope, so you are generating
unnecessary distortion.  The RFX boards typically remain linear up to
an output amplitude of about 2000.

Similarly, on receive, it looks like you are using the default
mid-point gain of the RFX, which likely too high for a path loss of
only 40dB.  I'd suggest experimenting with lower receive gains to see
if things improve.


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