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Re: [Discuss-gnuradio] Noise floor falls ~5dB when TX is started

From: Marcus D. Leech
Subject: Re: [Discuss-gnuradio] Noise floor falls ~5dB when TX is started
Date: Wed, 04 May 2011 19:23:18 -0400
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10

> Sorry, it was accidentally posted before I was finished writing...
> ...To make sure that I receive well, I
> made myself a simple script like this:
> #!/usr/bin/
> from gnuradio import usrp
> u= usrp.sink_c()
> and run that after I've started the board.
> Does anyone have any suggestion for what might be the cause of this
> strange behavior?
> What happens when the usrp sink is initialized that would cause the
> receive noise floor to fall?
> Regards, Ruben
YOu haven't said which daughtercard you're using.

My *guess* is that you're using the WBX.  In which case, during TX, the
RX chain has one fewer layers
  of switch between the LNA and the antenna port (RX2), which will
improve the noise floor a bit.

What is your antenna configuration?

Principal Investigator
Shirleys Bay Radio Astronomy Consortium

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