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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