Chuck Swiger wrote:
Very interesting - of course the Y scale is a really mangified range
of only 0.04, which may or may
not be significant. There's always batteries for ultimate isolation
- I run the USRP off a 7ah 6v
sealed lead/acid battery. Also you could make your setup portable
and take it out away from
civilization. Believe me, there's nothing like explaining shortwave
or RA antennas to a park ranger
an hour after dusk, who just stopped by to check up on you. ;))
--Chuck
0.04dB may seem small to a communications engineer, but to an RA type,
it's significant.
The cycling is definitely due to my heating system warming up the LNA.
Last night, the heater
didn't come on for a couple of hours, and the baseline stayed flat to
within about 0.01dB, which is
what it's doing right now, again due to the heater not coming on for
the last 1.5 hours or so.
Two years ago, I was seeing this same effect, but on the *back-end* of
my receiver, rather than the LNA.
I had my LNA in a temperature-controlled environment, but the Sharp
BS2S-series tuner had
a nasty temperature-dependent gain property, so I ended up temperature
controlling the back end
as well.
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