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Re: [Discuss-gnuradio] minimizing interference with usrp


From: Matt Ettus
Subject: Re: [Discuss-gnuradio] minimizing interference with usrp
Date: Mon, 11 Feb 2008 15:38:31 -0800
User-agent: Thunderbird 2.0.0.9 (X11/20071115)

Juha Vierinen wrote:
Hi,

I have been doing some radio astronomy experiments with USRP using a
30 MHz dipole antenna (actually it is more of a riometer experiment).
I am running into various interference issues. E.g., at one point I
noticed that if my laptop power supply is too close to my USRP I get
switching power supply harmonics in my signal. At other times I have
been pretty sure that the inteference comes through my antenna.


I have found huge differences between laptop power supplies from the manufacturer of the laptop (like Lenovo, HP, etc.), and cheap replacement supplies made to look like the originals. Once I was testing something on the USRP while the computer was attached to one of these supplies and I saw a huge mess on the spectrum analyzer. I spent an hour trying to figure out what was happening, only to find that it was there even if there was no USRP hooked up at all -- it was all radiating from the power supply.

If you really need low noise, run the laptop off of its internal battery only.

Matt





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