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

From: Marcus Leech
Subject: Re: [Discuss-gnuradio] A longish-term drift study of the USRP/DBS_RX combination
Date: Wed, 11 Jan 2006 09:17:21 -0500
User-agent: Mozilla Thunderbird 1.0 (X11/20041206)

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. ;))


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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