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Re: AIDC 3733 downconverter cold weather problems

on 1/22/03 9:13 AM, BRISCH@QWEST.NET at BRISCH@QWEST.NET wrote:

> 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?

Just got mine up and operational.  The last few days the temps have been in
the teens and low 20s.  I've had no problems with it.

My converter has not had a crystal change.  So I receive at 123 MHz.  The
beacon theoretically should be at 123.323 MHz.  When I first powered the
unit up last Saturday, the beacon came in loud and clear at 122.9 MHz or so.
Since then it has shifted down another 20 kHz to about 122.7.  It seems to
be somewhat stable there.

I leave my downconverter powered all the time.  I have the wall wart power
inserter sold by K5GNA.  It's designed to be that way.  By keeping that on
all the time, I think you nominally help to keep it warmer.

How new is your crystal?  Crystals tend to age pretty dramatically in their
first year of life.  After that the aging shift is minimized.  Also, keep in
mind that most crystals have a stability range of perhaps +/- 50 ppm (I
don't know the specs on the AIDC xtal, but I am sure they aren't that
stringent).  That's about the 50 kHz that I see in shift.  And that's over
temperature.  You may be seeing some aging drift was well as the drift over

I expect that as temperature warms, my unit will drift upward in frequency.
Not a problem if you know what to expect.

K5GNA recommends putting a pipe warmer around the converter.  You can buy
those at any hardware store.  Not a bad idea.  He says on his website that
he leaves it on all the time.  It certainly will help the stability over
temperature.  Kind of the same idea behind an ovenized oscillator.

My guess is that your downconverter is working fine.  You may hear your
local source at one point, but the beacon may be a bit lower or higher due
to any number of reasons.  Have you scanned the band over say maybe 100 or
200 kHz?

Good luck.  I hope this helps.


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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