Re: [amsat-bb] AIDC 3733 downconverter cold weather problems

["Mark L. Hammond" <mlhammond@xxxxxxxxxxx>]

Quick thoughts, Bill:

1) when you change the voltage to your "heater resistors", do you change 
the voltage to the converter?  Or are they using separate power supplies?

2) how about using a thermistor instead of the resistor packs?

3) How cold is it getting outside? I live in NC, and we occasionally get 
some single digit temps, but not very often.  I haven't seen a temp problem 
yet.  I have one of the 37xx series units (forget which one--it's the one 
with higher gain, and the metal piece used to bolt to the BBQ dish).

73,

Mark N8MH

At 09:13 AM 1/22/2003 -0600, you wrote:
>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
>environment.
>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
>
> >
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Mark L. Hammond  [N8MH]

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