Maxtrac Repeater with Local Remote

RESCUE161 · Post by **RESCUE161** » Wed Mar 22, 2006 9:56 pm

I made another repeater for GMRS use with two Maxtracs (just my wife and I talking on it so no overheating issues).

Anyway, I used an ICS controller on it and it works great.

I am using a Motorola local remote in another room on the other side of the house. I hooked the local remotes TX to the TX radio and the RX to the RX radio and grounded everything.

Everything works great except that the audio on TX is split between the ICS controller and the TX radio. At first, I thought about trying a diode to block the TX audio from bleeding into the controller, but figured a relay would work better. Well, after searching, I was unable to find a voltage source that would drop to zero when the remote was keyed, but stay the same voltage if the repeater was used normally or vice versa.

Anybody have any suggestions for what I'm trying to do? The remote works AWESOME if the controller is unplugged, but the audio is very low when the controller is plugged in. Repeater functions great whether the remote is plugged in or not. The only problem I'm having is the low audio output upon transmitting with the remote. Remote also receives great even if the controller is plugged in.

Sorry to break it down Barney style, but I just wanted to make sure everyone was on the same page.

THANKS!

Post by **wavetar** » Thu Mar 23, 2006 12:12 pm

I'm sure there must be something going to ground in the handset PTT circuitry. Or perhaps you could route the "TX light" voltage in the remote into a transistor circuit to drive the relay.

Todd

RESCUE161 · Post by **RESCUE161** » Thu Mar 23, 2006 8:57 pm

If I use any of the "switching" 5 volt sources that I've found, once I hook to the relay, either the radio starts transmitting and won't stop or it stops "switching" once hooked to the relay.

I did put a diode on the PTT side which is now keeping the voltage from backfeeding into the controller, but the audio is still very low when I tx with the remote.

There's got to be something other than a relay that will make this work. Any suggextions? Thanks.

Lake Effect · Post by **Lake Effect** » Fri Mar 24, 2006 6:49 am

Have you tried a series resistor to isolate the loading of the audio? You may have to experiment with different values but maybe something around 10 K. You will have to readjust audio levels but may be able to get rid of the loading that way.
L.E.

Will · Post by **Will** » Fri Mar 24, 2006 5:00 pm

Lake Effect wrote:Have you tried a series resistor to isolate the loading of the audio? You may have to experiment with different values but maybe something around 10 K. You will have to readjust audio levels but may be able to get rid of the loading that way.
L.E.

I'll add: the series resistor goes from the controller TX Audio out to the TX radio's mic input. 4.7 k ohms works well. You may also need a series coupling cap, 2.2uf 20V, with the + side tward the radio to isolate the mic bias needed for the local mic.

RESCUE161 · Post by **RESCUE161** » Sat Mar 25, 2006 12:36 am

So like this?

[Edit] Sorry for the small size. I wasn't planning on it being that small.

RESCUE161 · Post by **RESCUE161** » Sat Mar 25, 2006 5:04 am

Thanks Lake Effect and Will. I used the above schematic and it's working like a champ now. I should have tried this to begib with instead of trying to use a relay.

Again, Thank you!