XTL 2500 Pump panel speaker question

[pfd radio]

I have an XTL2500 Dashmount it is connected to a speaker in the cab of the fire engine and piggy backed on the speaker line is an amplified speaker on the pump panel.

Is that the correct way to run to the pump panel speaker.

Should the pump panel speaker be wired differently? (transformer, capacitor, etc)

I think that certain receive audio is somehow making it back to the radio and causing the radio to transmit. I know that sounds whacky, but when I got some feedback with a handheld radio it started to act in that manner. But the feedback tone had to be on the low side. If it was high pitched it had no effect. But every time I got the handheld in the right spot the radio would transmit like it was trying to be a vehicle repeater.

[thebigphish]

Are you transmitting with the portable radio when this feedback happens?

[pfd radio]

Yes - I'm using the handheld to generate the feedback

[Jim202]

Why don't you just add a remote mic off the radio and then you don't have to use a portable radio to transmit with.

Most pumpers that have the remote speaker at the pump panel also have a remote mic. Using a portable as a transmitter with another radio speaker near by is like asking for feedback. It will always happen. There are connections in the accessory connector on the radio to allow a remote mic to be connected. Do not use the connector on the rear of the control head.

To run a remote mic, you will need the mic hi connection, PTT, ground and the hangup wire if your using tone squelch on your radio system. You should use a shielded wire for at least the mic hi line. Put the standard mic connection at the pump panel so the mic can be changed out if there is a problem. As a suggestion, I would use a motorcycle mic. They are generally water proof and as such should survive longer with all the water that can find it's way around fire truck pump panels.

f you have a low powered or mid powered radio, it will use that odd shaped rectangle connector on the rear of the radio. If you have a high powered radio, there is a DB25 connector on the front of the radio near the remote control cable connector. The pin connections you need are in the service manual.

Go talk with your radio service people. They should be able to help you in this project.

Jim

[tvsjr]

Or look at a headset - if you already have a headset system in the truck, just install a weatherproof connector at the pump panel. Plug in and done. Newer systems are using Bluetooth or other RF links from controller to headset... just carry the headset with you.

[pfd radio]

The issue I have is that the radio was malfunctioning when it was connected to the amplified speaker, at the pump panel. I suspect that somehow there is audio getting back into the radio and causing the radio to act up. When I say act up I mean that at certain audio frequencies cause the radio to start to chatter in transmit.

It looks like whatever the cause the radio will start to transmit when it see the channel is busy and then then it de-keys and if the channel still has activity it starts to transmit again in a cycle of chattering on the channel.

This is the second radio to have this anomaly. I have eight other XTL2500 with no issues. Both radios did the same thing in the same fire truck. Once I disconnected the amplified speaker at the pump panel I am unable to duplicate the problem.

I guess the real question is in regards to the wiring of the amplified speaker. It gets 12 volts and ground and the audio is wired directly to the external speaker (in the vehicle cab). Should I take the audio that way? Or should I get it from somewhere else?

To clarify my first post - I just happened to be using a handheld radio to cause the channel to show activity and stumbled onto the fact that when there was a low tone of audio feedback (from the handheld radio) the XTL2500 would start to behave in that strange way. When the feedback audio was higher pitched the XTL would act as it should. This lead me to believe that the malfunction was somehow connected to the audio.

Once the pump panel speaker was disconnected I am unable to get the strange behavior - So I am guessing that the problem is related to that speaker, in some way.

Thanks for the previous posts - There is a remote mic at the pump panel that works fine (I have tried it with the mic connected and disconnected and that does not seem to have any effect on the problem). So I ruled out the external mic.

[Bill_G]

Interesting problem. Good detective work on your part to isolate, identify, and explain it. To answer you first question: does the amplified speaker hook up across the regular speaker wire? Yes, it does. Very simple set up. However, in this case obviously the long lead out to the pump panel is allowing rf to get back to the radio chassis and cause a very strange problem. The solution may be as simple as a ferrite bead near the speaker connection point. They are available from Newark. Loop the pump panel speaker wire through the ferrite once, and the problem should be solved. (fingers crossed)

Newark Ferrite Bead search page

[pfd radio]

Thanks Bill. I am not familiar with ferrite beads, is there a particular one to try?