[Milsurplus] GRC-106 AME problem

[Meir Ben-Dror WF2U]

HNY all,

 

I wonder whether anyone experienced a problem with trying to transmit on AM
(actually it's AME) with the radio. My receiver/exciter is the RT-834. The
system tunes, loads up and transmits (and receives) normally in all modes,
with rated power, except when I'm attempting to transmit on AM, the
amplifier kicks off at overload. The exciter meter pegs, and the amp center
meter set on PA cathode current kicks up above the normal current
momentarily as the amp kicks off. It is immediately resettable to Tune mode,
where it works normally in all modes and the normal tuning carrier output. I
suspected the 1A5 module (transmitter IF and audio), and I got a tested one
from Fair Radio. I put it in and it does the same thing. I thought maybe the
mode switch has a problem, but visually it looks OK and after applying
contact cleaner just in case, it does the same thing.

It looks like the exciter sends a spike into the amp when pressing the PTT
only on AM (does the same on VOX as well) and that puts the amp in overload
condition.

I was even thinking that maybe the radio has a modification to prevent it
from transmitting AM, but no ham messed with it before I bought the GRC-122
shelter complete with all the installed equipment directly from a surplus
dealer's lot about 20 years ago. Everything in the shelter is still
installed as I got it, and I operate the radio in there periodically. I
never tried to use it on AM before the last few days, and I never had issues
with it in sporadic use on SSB and CW. 

 

Any input is appreciated.

 

Thanks,

 

73, Meir WF2U

Landrum, SC

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