Working on an IDA control shelf equipped UHF GE M2 base/repeater. Normally
used to working with a lot of the
older card rack style control shelves. Never saw this happen on other GE M2
repeaters or mobiles.
Here's the situation:
I am using the repeater system looking at RUS for PL detect and CAS for COS.
Either running repeater in stock IDA repeat mode, or externally wired RC-85
controller.
Using an HT on the bench if I hit the audio hard getting close to 4.5 KHz
peaks the repeater would shut down
in PL mode (127.3 Hz FWIW). If I run in COS only mode, no issues. I had
originally thought perhaps it was something in the IDA control shelf, since
this is my first IDA equipped machine. Probing around saw that U7A 4066 in
the IDA was muting the RX audio vol/sql hi to TX audio hi path. That control
line leads to RXMUTE (amoungest other sources) which started me looking at
the PL decoder.
Used a pl deck extender card to isolate the PL deck's RXMUTE decode signal
from the IDA. Its the decoder for sure, rxmute high (pl detected) on low
level audio and rxmute drops low (no pl decode) on loud voice peaks.
This is a GE stock digital PL decoder. Swapped in another ge pl deck. Same
deal. Swapped in a TS-64MII and it also does it, but not as bad.
I even went so far as to look at R608 audio preamp pot inside the shielded
box on the audio/sql board. It adjust the VOL/SQL hi signal toward the pl
detector. Its adjusted within limits and didn't make any difference.
I swapped out the GE RX front end and audio/sql boards with known good ones
just for grins thinking distorted audio. Not the problem. Rechecked the rx
chn element freq using the F-11.2 trick on the service monitor. It's dead
zero'd.
This effect happens on several HT's on hand. Main 'test bench' HT measured
650 hz pl dev and 4.5 KHz dev voice peaks. Audio source, my highly
calibrated voice 'Ahhhhhh 1 2 3 W4XE' hihi..
Now I can fully understand a real distorted audio signal or one that's way
over deviated out of the receiver limits not being decodable. But, I can't
ever remember being able to talk off a pl decoder on innumberable GE M2's
I've had on the bench before.
The only new variable is this IDA shelf and maybe the system interface board
in the drawer. Haven't compared it to a card rack version to see if they are
different. But, not much to go wrong on that system interface board in any
case.
Thought I'd throw out an email while everyone is sitting at home dreaming
about sugar plums..
Has anyone else seen this problem?
73's and happy holidays
Ralph W4XE
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