Any done this - 1 Mic & 5 Radios (Using Pre-Amps)

[mrtor]

Hi Group from Sunny Melbourne, Australia
I have just come back from Le Tour DeFrance after doing some recon. work for a big bike race here in Australia. Got to look at and talk to the radio techs there and have come up with my own wacky version of something they paid mega bucks to get made up.

We use 8 different radio channels, 6 UHF 2 VHF. In the radio van there is also 4 repeaters & 2 cross banders.

I want to make up a unit where I have 1 mic, and through a series of push buttons be able to select where I route the mic audio & PTT signal to.

I propose 1 mic via a preamp then switched 5 ways to 5 seperate radios 3 GM300's and 2 GM950's to go into the mic sockets via a small 5k pot, 1K resistor and 2.2uf Electrolytic (similar to NAND's old repeater circuit which has done the rounds here for years).

PTT keying will be via a seperate set of relay contacts per radio and selectable from my proposed interface box

Anyone done this or see any potential problems before I start blowing things up

Thanks in advance
Mike

[Bruce1807]

There are plenty of cheap consoles around but if you want to do it yourself go ahead. You can even cheat and take the preamp out of a MOT microphone.
Sunny Melbourne?
It probably pouring.
It winter!

I'm an x-Melbournite so I know
Car'n the pies!

[kc7gr]

<snippety>

I want to make up a unit where I have 1 mic, and through a series of push buttons be able to select where I route the mic audio & PTT signal to.

<snippety-two>

Suggestion: Do what I did, and adapt an aircraft audio panel to your task. You may have to 'hack' some extra channel positions into it for more than three or four transceivers, but I've had pretty good results with mine.

There's also a company that makes a commercial version of the device you describe. I don't recall who they are, but they advertise in QST and MRT. I believe you can get a six-channel version for around USD $350.

Happy hunting.

[mrtor]

<snippety>

I want to make up a unit where I have 1 mic, and through a series of push buttons be able to select where I route the mic audio & PTT signal to.

<snippety-two>

Suggestion: Do what I did, and adapt an aircraft audio panel to your task. You may have to 'hack' some extra channel positions into it for more than three or four transceivers, but I've had pretty good results with mine.

There's also a company that makes a commercial version of the device you describe. I don't recall who they are, but they advertise in QST and MRT. I believe you can get a six-channel version for around USD $350.

Happy hunting.

I'll do some investigating, I have my prototype working well with one small problem that maybe someone here can help me with

The audio routing & PTT routing works a treat.

As I have 5 radios on panel, I planned to take the PL/DPL decode signal from the GM300's to drive a LED to indicate which radio was receiving the signal. Now on a GM300 that is cool, set PIN 8 to ACTIVE HIGH and away we go. I am stuck using 1 M120 2 channel job that you can't alter the settings on PIN 8 which is ACTIVE LOW, so my LED works arse about !

I think you could fix that with a transistor or 2, I am perfectly competent building a circuit from schematics, overlays etc, however I am not flash on building a new one from scratch.

Anyone know an easy way to fix this, I don't have the space to put 5 relays in the box as well, so I need something small(ish)

Thanks in advance
Mike

[resqguy911]

http://www.ncsradio.com/commercial/products.shtml

[mrtor]

http://www.ncsradio.com/commercial/products.shtml

Cool unit, I want one ! That's exactly what I need.

Mine doesn't look that swish but the simple audio routing & ptt routing functions are basically the same which is what I wanted to achieve.

Still need to fix this problem getting the PL/DPL led to function the right way around on an M120 from PIN 8.

Anyone ?