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A Simple Modification to the GE MASTR II Station for Complete Transmitter Control
By Chuck Kelsey, WB2EDV
HTML'd for repeater-builder by Mike Morris WA6ILQ

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This modification comes in real handy when checking for desense, or most any other repeater troubleshooting. It allows you to keep the repeater transmitting continuously or to to completely disable the transmitter for testing purposes. The only part you will need is a 3-position, center-off, SPDT toggle switch (the photos show a DPDT switch because thatís what I had on hand).

I removed both of the stock slide switches that are on the front of the 10-volt regulator card and installed the new toggle switch where the intercom switch was located. I used a little acetone (nail polish remover) to remove the lettering and installed a new label. As you remove the switches leave the wires for printed circuit board pads H5, H7 and H8 attached to the circuit board. They will be reused.

Pad H5, which went to the intercom switch, now connects to one outside terminal of the new switch and when grounded disables the transmitter for as long as you keep the switch in that position.

Pad H7, which went to the remote PTT switch, now connects to the other outside terminal of the new switch and when grounded forces transmit as long as you keep the switch in that position. The TX indicator LED illuminates just like it should.

The printed circuit board pad labeled H8 is ground and connects to the center terminal of the new switch.

When the switch is in the center position it allows normal station operation.

The three photos below show the modification. Click on any photo to display it full size.
If I were to do it over again I'd swap the outer two wires on the switch so that when the the switch handle is up the transmitter is forced on, and when the switch handle is down the transmitter is forced off.


The view from the front


The view from the side


The view from the bottom


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This page originally posted on Sunday, December 7th, 2008

Photos and article text © Copyright 2008 by Chuck Kelsey, WB2EDV
Artistic layout and hand-coded HTML by Mike Morris WA6ILQ (all typos are his responsibility) and is © Copyright 2008 and date of last update by repeater-builder.com.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.