Quote:
Originally Posted by Larry Acklin
Yes, Galaxy 25, the IA-5 international. The transponders that seemed to be off were the weaker ones, and I suspect the LNB drift (cold/unpowered until I aligned the dish) and the receiver drift were causing the poor quality numbers. I had lock, else I would not have had picture at all.
I had severe breakup on channels I can usually get in well, even on a smaller dish. The BUD with Ku seems to be the best bet for DXing, and I just set up the 80cm so I can surf channels on G25 without repointing the big un. (normally on NASA C band feed)
I did some testing for industrial electronics in the later 70's and we had a -40 to +70 spec. We had to do some major tweeking and design work to get (close) to there.
And a chamber with a forced air heater and CO2 spray to chill.
Larry |
I guess your -40 to 70 was centigrade, which corresponds to -40 to 158 F . I think that's pretty similar to what we were
aiming at, which I think was mil spec 810e or something like that. I had remembered 120, because I think that's as high as we went in the particular chamber I worked with, but we had another chamber that we took higher. The other chamber just did temperature and
solar, but my chamber did humidity as well. It was a pretty neat chamber, that was about 5'x5'x8' inside, and was hermetically sealed, because we tested nerve gas detectors. We could program the thing to go through all sorts of preprogrammed cycles of temperature/humidity. I can't remember how it cooled, I think just via regular freon refrigeration.
Before that job, I used to work at a place where I had a gas chromatograph that used CO2 spray for subambient cooling. One night I was working late, and ran out of CO2, so I emptied about 8 CO2 fire extinguishers to finish the job. Next day I kind of got in trouble with the company's safety guy, who was upset because he had to fill out fire reports or something whenever an extinguisher was used.
Re consumer stuff handling temperature changes, I had an LNB once that went into oscillation whenever the temperature hit 15 deg outside, and I'd completely lose reception. I'd have to turn the thing off and back on to get it working again. I eventually had to hook up an X10 switch to turn it off, since the receiver it was on kept power to the LNB even when switched off. Also, I have one of the cheapest lnbfs that
Sadoun sold, and it drifts about 5 MHz when it gets cold. My big dish lnbs only drift about 1 MHz.