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Re: Reverse-engineering the AIDC-3733 VCO



Bob,
I have been reading with interest your comments about movement in the
TranSystem LO.  I am modifying a Cal Amp MMDS converter so I checked its LO
with a frequency counter and saw movement.  It appeared to jump around a few
kHz.

Today at work I put the converter output on an HP8560E spectrum analyzer
with a 2401 MHz input signal.  The output at 145 MHz was very stable.  The
analyzer was set to 1 kHz span, 300 Hz resolution bandwidth, 300 Hz video
bandwidth, and video averaging off.  I also measured LO phase noise at 10
kHz offset as being -86 dBc/Hz.  There was no evidence of the frequency
jitter that the frequency counter indicated.

This does not explain the frequency counter measurements, but it does agree
with your observations of not hearing drift in the received beat note.

73,
Ward - WC0Y


----- Original Message -----
From: <BobsImsai8800@aol.com>
To: <mahlonhaunschild@home.com>
Cc: <amsat-bb@AMSAT.Org>
Sent: Thursday, April 05, 2001 5:42 PM
Subject: Re: [amsat-bb] Reverse-engineering the AIDC-3733 VCO


> Art,
>
> I started to draw the schematic on the VCO, I ended up just doing the 8
MHZ
> oscillator.  But, I have been in contact with the TSI factory people on
the
> matter of a schematic.  The original comments were "don't expect any
answers
> back from the Engineers at TSI in Taiwan for 6 weeks."  I have asked for
more
> information on the oscillator and now with what appears to be movement in
the
> LO, I am reformulating my information so I can ask them to address the
> problem.
>
> I hope they will give us some insight into what is happening.  I still
have
> the question on why I don't hear the frequency changes in the beat note?
>
> Anyhow, my Jan crystal prototype crystal cut for 60 degrees C (PTC
> thermistor) will be here in week, we can see if it makes any difference.
>
> Bob
> K5GNA,
> k5gna@aol.com
>
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