ID-O-Matic 4 Linking Help

Alright, things have started to settle down here after Hurricane Matthew (at least in my area) and I am getting back to a project I had. I have a repeater that I am testing around with. Its not much really, its just a CDM750 for VHF RX and a Maxtrac for VHF TX (Low Power) all being done through a ID-O-Matic 4 Repeater Controller. It has been working nicely on the third floor of my home. So here is the question... I dug out my Motorola GM300 UHF and programmed it up along with a UHF Maxtrac I have. My Idea is to link the radios (Like a linked repeater) and have the VHF and UHF transmit and the VHF and UHF receive. (2 ways into the repeater, 2 ways out) I know, you probably all know how a repeater works.

So I ordered a second ID-O-Matic and took the wires form it and connected it to the 1st one. (plus having a second will be a nice backup if i need one)
I connected it all together (Except the UHF Power IN) and...well... The TX works great on VHF and UHF, Crystal Clear!
But the Receive is a different situation... The UHF seems to be very static-y you can barely make a voice out. and the VHF is pure static. But when you turn off one of the two receivers, POOF! Crystal clear audio through the repeater, and TX works great on both VHF/UHF!

So my question is, can/how can I make it work for both VHF/UHF RX?

The Manual for the ID-O-Matic 4 Can be found easily if you Google it. But I can post the link if need be.

any help would be appreciated! thanks!

That's weird. So with both TX going, it sounds good with either RX but not both?

How are you disabling the RX?

Have you tried removing the input to one of the RX while both are active?

Could RF be mixing in the RX front ends and affecting each other band?

Could the VHF IF and UHF IF be leaking between each radio?





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RFI-EMI-GUY said:

That's weird. So with both TX going, it sounds good with either RX but not both?

How are you disabling the RX?

Have you tried removing the input to one of the RX while both are active?

Could RF be mixing in the RX front ends and affecting each other band?

Could the VHF IF and UHF IF be leaking between each radio?





Sent from my SM-T350 using Tapatalk

Click to expand...

This is correct, only one of the receivers is audible one at a time.

I am disabling the RX by simply turning off one of the receive radios and after doing that, the static starts to fade off and then the other RX is clear.

I messed around with it earlier and since I have 2 ID-O-MATIC boards, I left one with just VHF input and VHF/UHF output and then added the 2nd board to output UHF audio to the input of the first board. Now the VHF RX is crystal clear with 2 receivers running and the UHF RX is 1/2 static 1/2 audio you can make out.

I am not sure about this effecting the other radios but I am not sure, Its weird, especially now with 2 boards hooked up and one RX being clear and the other being 1/2 static.

marksroberson said:

This is correct, only one of the receivers is audible one at a time.

I am disabling the RX by simply turning off one of the receive radios and after doing that, the static starts to fade off and then the other RX is clear.

I messed around with it earlier and since I have 2 ID-O-MATIC boards, I left one with just VHF input and VHF/UHF output and then added the 2nd board to output UHF audio to the input of the first board. Now the VHF RX is crystal clear with 2 receivers running and the UHF RX is 1/2 static 1/2 audio you can make out.

I am not sure about this effecting the other radios but I am not sure, Its weird, especially now with 2 boards hooked up and one RX being clear and the other being 1/2 static.

Click to expand...

Have you checked this by turning off the transmitters and listening to the receivers alone? In other words do both receivers work properly when both are on and the TX radios are off?

If so:

1) The IF Leakage from one radio to another is sufficient to desensitize the other.
or

2) The Local Oscillators of each radio are harmonically related to the RX frequency or an Image frequency of the other. The LO frequency is usually derived by subtracting the IF frequency from the operating frequency of the receiver. This is low side injection. If the radio uses high side injection the LO frequency is the operating frequency plus the IF frequency.

marksroberson said:

This is correct, only one of the receivers is audible one at a time.

I am disabling the RX by simply turning off one of the receive radios and after doing that, the static starts to fade off and then the other RX is clear.

I messed around with it earlier and since I have 2 ID-O-MATIC boards, I left one with just VHF input and VHF/UHF output and then added the 2nd board to output UHF audio to the input of the first board. Now the VHF RX is crystal clear with 2 receivers running and the UHF RX is 1/2 static 1/2 audio you can make out.

I am not sure about this effecting the other radios but I am not sure, Its weird, especially now with 2 boards hooked up and one RX being clear and the other being 1/2 static.

Click to expand...

Are you using a discriminator tap from each radio as input to the ID-O-MATIC boards or the speaker output from the radios?

A schematic would be helpful.

You might have better luck summing the output of the ID-O-MATIC boards and feeding the sum to both TX's.


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You need to use the Filtered receiver audio output.

cmdrwill said:

You need to use the Filtered receiver audio output.

Click to expand...

Thank You! That fixed it!!
I tried moving around the RX units and the TX units, But it didn't help.
But I read the code plug from the CDM for VHF RX and it was programmed for Flat Audio, I changed it, programmed it up, and it works great!! thanks!!