[TMC] GPE Questions

[Roy Morgan]

At 12:43 PM 11/5/2007, telegrapher at att.net wrote:

>The 1 meg 20W linear taper modulation control on my GPE is highly erratic. 
>...an on-off switch on the back of it,

Larry,

So you mean two watts?  I suspect so. Any one meg or 500 k pot with switch 
will do.  The original is likely an Allen Bradlely type J.  (If you can get 
a new one from some supplier, it will cost you well over $50.)  So just 
drill a hole in the side and squirt in some Caig MCL.   Problem solved.


>... when i turn on the GPE exciter, ... i can hear the carrier or Osc 
>running in the background on my receiver.

I think the GPT 750 operates the same way in CW mode, at least.  The 
oscillator is quite well shileded in that one, however, and may not cause 
trouble.  I suggest you open every chassis compartment, clean all  mating 
metal surfaces, make suer there's a good tube shield in place and that sort 
of thing.

>Now to determine if it's a buffer tube that is not cut off

To do that, pull the buffer tube out.

>Suppose this was a hidden problem with the TMC gear and not noticeable 
>because of either split frequency or split site operations?

Quite possible. Many of their transmitters saw duty 24/7 so it did not matter.


>Another item of concern is that they do not specify what kind of level to 
>input audio on the back of the unit at the 600 ohm line inputs.

Line level. You may discover that the thing reaches 100 percent modulation 
with half or less of that. Line level is one milliwatt in 600ohms - 0.7.. 
volts rms.  If it's measured in VU, then 0 VU is often 4 dB above one 
milliwatt.  Trly half a volt RMS and see what you get.

>   ...What level of line input audio do you use into a BC transmitter?

Generally 0 dBm or 0 VU.

Roy



- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
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