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Re: GM900 TX tuning, lacking GTF180

 

¿ªÔÆÌåÓý

First of all, do you have, or have access to, a calibrated service monitor?

Next, do the radios individually meet specifications for transmit and receive?

If so, don¡¯t mess with the tuning. ?Very easy to screw up an existing radio that is functional by trying to tweak it ¡°just a little bit better¡±.


Interface box. Needs separate, radio specific cable to connect to radio. Motorola had one similar to this for servicing?


Milt
N3LTQ

On Mar 3, 2025, at 14:41, Patrick TK5EP via groups.io <pegloff@...> wrote:

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Hi all,
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I'm currently working on a pair of Motorola GM900 to replace the TX/RX in one of our UHF repeaters.

I could program them with a RIB on the right frequency and they both work, the repeater is working OK.
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Now I want to align them as precisely as possible with the "tuning procedure" as found in the service manual.
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Unfortunately, this procedure needs a GTF180 test box which I don't have.
Nowhere is the GTF180 described and where the different signals have to be fed into the radio.
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The transmit deviation balance says a 80 Hz and a 1000Hz is to be injected into the test box.
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Does someone know WHERE these signals are to be fed or has a GTF180 diagram and manual ?
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Thanks for any help,
73 Patrick

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