Re: [Discuss-gnuradio] A longish-term drift study of the USRP/DBS_RX combination

[Marcus Leech]

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.