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Re: AIDC 3733 downconverter cold weather problems

on 1/22/03 11:13 PM, Wayne Estes W9AE at w9ae@earthlink.net wrote:

> I have a 3733 downconverter on my roof.  I used it last night when the
> temperature was about 5F.  It drifted for a few minutes after I applied the
> power, but then was fairly stable.  I have the stock crystal which gives a
> 123 MHz IF.  Soldered to the crystal is a 60C PTC thermistor that is powered
> by 13.8V.  That keeps the crystal and the surrounding components very near
> 60C all the time, no matter what the weather is.  This time of year it would
> be more stable if I wrapped the downconverter in pipe insulation.  The drift
> is barely noticeable 5 minutes after I switch on the power, and after that
> it gradually drifts another 1 kHz over the next 20 minutes.

Wayne and others,

I leave my unit power up all the time, but I don't have the thermistor on
it.  The frequency of the beacon is relatively in the same spot, but there
is some movement in the signal.

The question is if that frequency shift from Doppler or is it a combination
of both the Doppler and temp drift from the crystal.  I have assumed that
with the downconverter powered 24/7 that at a given temperature (or in a
small range), you won't see a lot of drift.  Over larger temperature ranges,
yes, I would expect to see a drift.

Am I incorrect in my assumptions?



Jon Ogden
NA9D (ex: KE9NA)

Citizen of the People's Democratic Republik of Illinois

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

http://www.qsl.net/na9d   <- Updated on 1/12/03!!!

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