XTL1500 and PM400 radio loop

[jayhawkfirearms]

Built a Xcross band repeater and had a local radio shop turn on the COS and they also recommended PL/DPL for us in the PM400. Got it back from the shop today. Hooked everything up and plugged it in, went to test it by keying up on the VHF and the video attached is the end result, only way to get it to quit is shut off the power. I have tried using both COS and PL and both do this, must have shorted something out testing before going to the shop…


Radio loop video

 

[kayn1n32008]

Built a Xcross band repeater and had a local radio shop turn on the COS and they also recommended PL/DPL for us in the PM400. Got it back from the shop today. Hooked everything up and plugged it in, went to test it by keying up on the VHF and the video attached is the end result, only way to get it to quit is shut off the power. I have tried using both COS and PL and both do this, must have shorted something out testing before going to the shop…


Radio loop video

Can you post the video somewhere I don't have to have a sign In?

 

[jayhawkfirearms]

Radio loop

 

[KevinC]

Didn’t watch the video, but that is usually caused by the TX radio RF getting back into the RX radio. But as I said, I didn’t watch the video so it could be something completely different.

 

[mmckenna]

Radio loop

I watched it.
Hard to tell for sure, but I agree with the others. Sure seems like RF getting into the receiver.

What is your antenna setup like?

And this is one of the reasons we cautioned against this on public safety frequencies. You really need to have some protections built in, and this is where having a dispatcher involved is necessary.

 

[jayhawkfirearms]

I watched it.
Hard to tell for sure, but I agree with the others. Sure seems like RF getting into the receiver.

What is your antenna setup like?

And this is one of the reasons we cautioned against this on public safety frequencies. You really need to have some protections built in, and this is where having a dispatcher involved is necessary.

That why this is 100% in test phase and not using dispatch channel only side group that rarely get used, antenna are a 1/4 wave vhf and a 800mhz phantom antenna. Our agency is trying this, but implementation is not guaranteed and just wanted to see if the system would work.

 

[mmckenna]

antenna are a 1/4 wave vhf and a 800mhz phantom antenna.

Where are the antennas in relation to the radios?
Is all the cabling well shielded and away from coax?

 

[jayhawkfirearms]

Yes, the antenna are about 15ft away. Just using normal RG58 at this time for the test

 

[mmckenna]

Yes, the antenna are about 15ft away. Just using normal RG58 at this time for the test

You may need to move the antennas farther apart, or add some filtering. Like others said above, RF getting into the radios via your audio/control cabling may be causing this.

 

[GTR8000]

Hard to tell for sure, but I agree with the others. Sure seems like RF getting into the receiver.

Like others said above, RF getting into the radios via your audio/control cabling may be causing this.

Does @KevinC have multiple personalities? He's the only one who mentioned RF getting into the other radio, no "others".

 

[mmckenna]

Does @KevinC have multiple personalities? He's the only one who mentioned RF getting into the other radio, no "others".

I do believe there is at least one other post from the OP about trying this.

 

[GTR8000]

Not a single mention of this specific RF issue in any other thread the OP posted in, but okay. I guess @KevinC's new pronouns are "them/others" 🙃

 

[mmckenna]

Not a single mention of this specific RF issue in any other thread the OP posted in, but okay. I guess @KevinC's new pronouns are "them/others" 🙃

I'm sure we'll survive.

 

[kayn1n32008]

Radio loop

What is the other radio programmed for? Simplex? Repeater? Are you using PL or DPL on the receive radio?

 

[Unitrunker2]

These are fun. Start with RF chokes on the DC power cables for both radios. The repeater builder list on groups.io can give you more detailed advice.

(Looks like an XTL2500, not '1500 in the video)

 

[nokones]

There use to be an electronics shop in Nevada that built a mini logic board I think functioned with a COR for interfacing two radios for crossbanding that would prevent them from looping. If my memory serves me right, I believe the name of the shop was Sweet Electronics.

I personally used a couple of their mini logic boards for crossbanding a couple of portable radios for an airborne repeater package a few decades ago and they worked very well.

That concept also gave me the idea for developing a vehicular repeater system (VRS) (a.k.a. Portable Radio Extenders) package for a fleet of Motorcycles that eventually GE produced.

Another thought that may be a solution is get an automatic vehicular repeater like a Pyramid In-Trunk Repeater and interface the two mobile radios with the Pyramid unit and use the logic board for the keying and passing the audios back and forth between the two mobiles.

 

[ramal121]

It looks like the PM400 is in monitor which means the PL/CSQ output is only CSQ. Either change HUB in programming or put a mic with a clip on it and plug into the radio.

 

[jeepsandradios]

This is why you do this on a bench with dummy loads first. And with a service monitor. I dont recall your bands in use but for mine they are VHF and UHF. VHF Simplex on low power. UHF Trunking again on low power. I have my PTT beep disabled so that doesnt casue issues. First thing I'd do it get it working on 2 dummy loads. It really looks like you have RF getting into the control wires. I'd also disconnect one path of cables. Make it work from 800 to VHF. Once that works and is consitent try to hook up your COR on the VHF radio and test that way. Also on trunking radio use a conventional channel first to get it working. I have it there so i can test stuffo n site also. This is a simple setup but seems you are struggling with it. May be easier to take the stuff to a shop and have them set it up correctly.