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Help With Injecting Audio into a GM300 for a DMR Repeater

Posted: Sat Jan 27, 2018 12:24 pm
by kb8qdx
Greetings all,
I've been trying to find info on where to inject the TX audio on a GM300 to use for a DMR repeater to get the required 9600 baud for the transmitter. I have the HLE8300B RF board and all the info that shows where to inject the TX audio are for the HLD8029 board, Shown Here. The resistors and cap (R222, R223 & C228) that are referenced in the HLD8029 schematics are not the same as on the HLE8900B. Does anyone have any ideas on where I can obtain this information for the HLE8900B? I'm pulling my hair out over this and one would think it would be simple to figure out, but without a proper schematic, I'm shooting in the dark!! This is my first attempt at building a DMR repeater and I would like to get it up and running sometime in the near future!!

This is from batlabs referencing the HLD8029 RF board 9600 baud packet modification:

"The GM300 Series are 9600 baud packet capable. They do need a minor modification though. For RX, its no big deal, just take RX audio from PIN 11 of the Accessory Connector and swing JU551 to the (A) position (Flat RX Unmuted).

For TX audio, you will have to run a jumper to the junction of R223, C228, R222 on the RF board to inject the data (if applicable you may need to set the deviation pot in the radio to maximum). You might want to put a pot on your TX line somewhat like the setup Motorola uses (voltage divider) to adjust the deviation.

Again, this info assumes you have the HLD8029 board, which I do not!!

Thank you in advance for anyone that can help me with this..
Ernie
KB8QDX

Re: Help With Injecting Audio into a GM300 for a DMR Repeater

Posted: Mon Jan 29, 2018 12:05 pm
by ve3nsv
Have you tried injecting the audio on pin 5?

Re: Help With Injecting Audio into a GM300 for a DMR Repeater

Posted: Mon Jan 29, 2018 12:18 pm
by kb8qdx
Yes I have.. That's what I've been reading, but also I've heard that the tx audio has to be injected in the VCO.. If you look at the link that I posted, it shows the place between R222 & R223 & C228, so I guess that's what I need to do, but I have a different board as said in my initial post.. Thank you for your quick response..

Re: Help With Injecting Audio into a GM300 for a DMR Repeater

Posted: Mon Jan 29, 2018 4:19 pm
by jackhackett
You can get the GM300 manual from the repeater builder site. It comes in 5 sections, you want to look at part C. Find the HLE8300 board layout, and on the component side look at the top right section, you should find those resistors and cap there. They have the A version board, hopefully the B version is similar.