Most likely, your HT is part or all of the problem.
The CTCSS is supposed to be injected after the limiter so this problem
(called "talk-off") does not happen. In some radios, the CTCSS is mixed
with the mike audio prior to the limiter, and then, "talk-off" happens.
Jeff
At 01:24 PM 12/24/2004, you wrote:
>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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>
>Yahoo! Groups Links
>
>
>
>
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