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[Discuss-gnuradio] DBS_RX/USRP warmup stability
From: |
Marcus Leech |
Subject: |
[Discuss-gnuradio] DBS_RX/USRP warmup stability |
Date: |
Mon, 09 Jan 2006 17:27:23 -0500 |
User-agent: |
Mozilla Thunderbird 1.0 (X11/20041206) |
One of the things that's quite important to RA types is the stability of
the receiving equipment over longish
time periods--particularly over periods that are the same order of
magnitude as the signals they're
trying to observe.
I happened to have shut down my USRP/DBS_RX stack today to do some
enclosure upgrades, so it had
cooled down to room temperature (20C). Once I brought it back up, I
noticed the baseline drift upwards
over a period of 20 minutes, and then it stabilized. It drifted
0.275dB in those 20 minutes, and after reaching
operating temperature, seems to be stable to roughly 0.025-0.05dB,
with random excursions occurring over
periods of a few minutes.
Something that's interesting is that the system can detect when I'm
sitting at the computer, but not necessarily
typing anything. Since my feedhorn is pointed out the window, it must
be seeing a reflection of
my blackbody radiation. I confirmed that my feedhorn was able to see
me, by placing my hand
in front of the feed--sure enough a significant rise in the detected
baseline resulted. That means
that the front-end LNA and feedhorn is working properly in that
they're able to see my
blackbody radiation. Humans make good weak-signal microwave sources :-)
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