Radio GTX connections

Has anyone have any documentation for connecting a URI to a 900 GTX radio? I’ve looked in the documentation here and found nothing.
I know that the accessory pins can not be program like the Gm300 and Maxtrac radios can. Therefore I made a COR circuit for it, before I make the final connections I wanted to see if there was someone who had already had a working GTX on Allstar.
Thanks Mike

Are you wanting to use it as a simplex node? IIRC, according to documentation on repeater-builder.com and batlabs.com (http://www.batlabs.com/gtx.html) the connections are the same 3 PTT 5 flat tx 7 gnd 11 flat rx.

Note that the gtxs are deaf for receiving much below 925 MHz, so, if you are looking to use this as a simplex node to get into a repeater, it will probably work.

If you’re looking for a more useable 900 band radio, I suggest you look at the Spectra series; the GTX were the ‘ecocnomy’ radios of the batwing line back in the day.

I haven’t done a GTX to Allstar as a permanent thing though a few years back I did experiment with it. Audio and PTT aside (those are easy) COS is the problem. You can program a pin to switch when a valid COS/PL come in, but I could not get it to reset. So…I looked at the speaker lines. When a valid signal comes in the Audio chip turns on. And there is DC on the speaker lines which is why you cant have a grounded speaker. But what I used was a resistor isolated input to the URI for COS. I may have made is a voltage divider, don’t remember.

FWIW, re the other note about RX bandwidth, the reason I was playing with it was to see if a GTX could be used as a repeater receiver. Well with the normal preselector no way, but I dropped in a pair of Toyo filters for the right range. That did work but had to fiddle with the VCO

Hope this helps
GeorgeC W2DB 2360, 28599

Thanks George I may just go ahead and use a Maxtrac they seem to work better for I’m trying to do.

Mike

···

From: George Csahanin via AllStarLink Discussion Groups [mailto:noreply@community.allstarlink.org]
Sent: Saturday, November 14, 2020 11:41 AM
To: mzfb@aol.com
Subject: [AllStarLink Discussion Groups] [Allmon] Radio GTX connections







George_Csahanin
November 14

I haven’t done a GTX to Allstar as a permanent thing though a few years back I did experiment with it. Audio and PTT aside (those are easy) COS is the problem. You can program a pin to switch when a valid COS/PL come in, but I could not get it to reset. So…I looked at the speaker lines. When a valid signal comes in the Audio chip turns on. And there is DC on the speaker lines which is why you cant have a grounded speaker. But what I used was a resistor isolated input to the URI for COS. I may have made is a voltage divider, don’t remember.

FWIW, re the other note about RX bandwidth, the reason I was playing with it was to see if a GTX could be used as a repeater receiver. Well with the normal preselector no way, but I dropped in a pair of Toyo filters for the right range. That did work but had to fiddle with the VCO

Hope this helps
GeorgeC W2DB 2360, 28599


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