[ARC5] Working on the FA-7989 / TRX-102

[K2GKK D C_Mac_ Macdonald]

Have you put a scope on the output of the power supply?

73 de Mac, K2GKK/5
Licensed 30 Nov 1953
Oklahoma City, OK
USAF (Retired) 61-81
FAA (Retired) 94-10

Cell: 405-642-7337
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From: arc5-bounces at mailman.qth.net <arc5-bounces at mailman.qth.net> on behalf of sbjohnston--- via ARC5 <arc5 at mailman.qth.net>
Sent: Sunday, August 27, 2023 10:51
To: arc5 at mailman.qth.net <arc5 at mailman.qth.net>
Subject: [ARC5] Working on the FA-7989 / TRX-102

I've been working on the FAA FA-8979 (aka model TRX-102) VHF AM transceiver I bought at Fair Radio a few weeks ago.   Fair Radio was kind enough to send me the manual that I forgot to pick up when I was there.

I spent a lot of time trying to understand why the internal DC voltage buss was jumping around - when I temporarily connected a SLA battery as designed it settled right down.  Seemed like it should have been OK without a battery, when running on AC, but I guess not.

The 21.4 MHz IF, demodulator, and audio seem OK with an AM signal injected from my service monitor, but the front end does not act right.  It could be my substitute signal for the local oscillator isn't correct - I don't have any crystals.

Anyone have a receive crystal from an FA-7989/TRX-102 that I could borrow for testing?  In my extensive collection I am not finding one piece of quartz in that range!

I wish I understood why I am working so hard on this piece of equipment.  I don't even really enjoy monitoring air comms.  I think it is the high-quality construction and rugged design that get me.



Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
http://af4k-crystals.com<http://af4k-crystals.com/>/
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