Ralph, The symptoms you describe are those of CTCSS distortion due to limiting of excessive deviation.
If your authorized emission is 20K0F3E, the sum of voice and CTCSS deviations cannot exceed 5.0 kHz. The measurements you cited for your "test bench" HT reveal excessive deviation at 5.15 kHz. But, that's not the main issue here. Ideally, the CTCSS modulation should be in the range of 500 to 700 Hz; any more does absolutely nothing for improving detection, and it increases the chances for a buzz to be heard in the received audio. The majority of CTCSS decoders will reliably detect the tone with a CTCSS deviation as low as 200 Hz. If the CTCSS encoder in each user radio was adjusted to produce no more than 700 Hz deviation, then the microphone audio limiter can and should be set to limit voice deviation to 4.3 kHz. Unfortunately, some radios are designed so that the CTCSS modulation is mixed with the voice ahead of the limiter, and this almost guarantees that repeater talk-off will occur. Nearly all Amateur portable radios are designed this way, and there is seldom any means to separately adjust the CTCSS level. Compounding this deficiency is the tendency for economy-minded manufacturers to use far more CTCSS deviation than is necessary, just to make sure there's enough! The CTCSS modulation should be mixed with the voice modulation AFTER the limiter. If you can adjust your portable and mobile radios for the deviation levels noted above, your talk-off problems should go away. 73, Eric Lemmon WB6FLY 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 OS. 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.... 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 innumerable GE M2's I've had on the bench before... Has anyone else seen this problem? 73's and happy holidays Ralph W4XE Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/