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Re: AIDC 3733 downconverter cold weather problems


>Well I am going to try again.  I have two 3733 downconverters that exibit the
>same problem.  They do not seem to work properly when the temps drop below
>freezing.  What makes this strange is that I have a local signal source and
>can hear it.  Signal source is in the house and in a controlled temp
>One downconverter is on an offset dish the other on a 8ft prime focus dish.
>What I have done is to place a series string of resistors around the
>downconverter to act as a heater.  The downconverter is wrapped in fiberglass
>pipe insulation.  In cold weather the downconverter is over 100Khz low in
>receiving the test source.  Once I heat it up I can bring the signal back to
>a nominal 144Mhz on the receiver.  I can vary the voltage to the series string
>to control the temp.
>Now to add to the confusion, while I can hear the local signal source I can't
>copy AO-40.  I use NOVA to track the bird and I follow the times it is
>visible,  squint and MA so that I have an idea when to look for the signal
>from the bird.
>Is anyone using the 3733 downconverter now ?  Have you experienced any temp
>related problems?  Have you found a solution?  Is anyone willing to work with
>me on this type of problem?
>I have done a Google search and can't find any helpful info.
>I can go into greater detail of the tests and what I have done to try to 
>solve the problem.  If anyone is interested let me know.
>Bill K0QK
>Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
>To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
I am using the 3733 and I have noticed a minor drop in frequency,  but 
not quite as bad as yours. In temperate (15 C) weather the beacon comes 
in at about 145.360 at appogee,  but with the recent long bout of 
subfreezing (-10 C) temperatures, the beacon  has been reading about 20 
or 25 KC lower. Not enough to worry about, but it is noticeable. Signals 
from the bird are about an S-unit lower than they might otherwise(but I 
have been playing with my dish feeds as well). It has been frigid in 0 
land lately, and the cold weather could have caused thermal contraction 
to cause problems with the downconverters and so on. A strong local 
signal might be getting through, but if a stage is malfunctioning or 
there is a problem between the feed and D/C it could cause problems with 
the relatively weak signals from the bird. Just my .02 USD.

73, Bruce N3LSY

Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org