Mobile Radio interferes with Siren

[slynmitchell]

I have a mobile radio hooked directly to the battery it had a glass fuse, and I have lights and siren hooked to the battery also with a glass fuse. Neither are connected together bit when I key the mic it stops the siren and the lights turn off, turn back on, but then I can't use the controller to shut off the lights I have to unplug them. I need help because I'm not sure what I need to stop this or distribute power. At one time the lights and sirens or wired directly to the fuse but it would cause problems and come undone so I got the glass fuse and wired it directly to the battery

 

[iamhere300]

So you deleted the glass fuse? Did you use another type of fuse? What amperage fuses do you have? What size wire? Are you having any battery or starting issues?

 

[scannermanner1]

it sounds like you're siren and lights are shutting off due to insufficient voltage when you key the radio, also what type of vehicle do you have if you don't mind me asking??
another thing to recommended you could also get your battery tested ! It sounds like it might be getting a little weak !

 

[mmckenna]

Make sure all your antenna connector is properly installed an tight. Also, check your SWR. Could be stray RF getting into the controller. The fact that it does it when you transmit, seems to suggest it could be that, or something to do with a mild voltage drop when you TX.

What's the condition of your battery?
Are the power connections to the battery nice and clean, not corroded?
Where is your antenna mounted?

 

[slynmitchell]

I have a good battery. Nothing corroded. I drive a 2005 Chevy Silverado 1500. My antenna is on on my toolbox. The few that uses 30 amp, the wire is 15 gauge. The battery seems fine but I'm not sure if it needs to be replaced.

 

[ofd8001]

It could be a matter of wire size which contributes to the above mentioned voltage drop.

I suspect that as the radio transmits, it is "robbing" just enough juice and the controller for the siren/lights is sensing that and is shutting itself off.

There are many variables with your set-up. The type of siren (mechanical/electronic), the type of lights (LED, strobe or incadescent) along with the power of the radio.

I'd suggest running a separate circuit for the radio, separate circuit for the lights and separate circuit for the siren. The size of the wire for the circuit should be consistent with the power requirements as stated by the manufacturer of the radio/lights/siren. (There are charts on the internet where you can find which size of wire to use based upon the current draw).

Glass type fuses are really old school when it comes to emergency vehicle equipment. Nowadays either automotive type circuit breakers or ATC fuses are used for over-current protection.

Lastly, just to cover additional possibilities (and they could be remote). What is the condition of the car battery (does it have enough stuff to handle the emergency equipment)? Also, how about the alternator for the vehicle - is it functioning properly and putting out enough stuff?

Be sure that all your emergency equipment has good grounding. While chassis grounding will suffice typically (there are those who suggest running ground wires back to the battery itself), connections can be come loose or get dirty with time.

 

[iamhere300]

I have a good battery. Nothing corroded. I drive a 2005 Chevy Silverado 1500. My antenna is on on my toolbox. The few that uses 30 amp, the wire is 15 gauge. The battery seems fine but I'm not sure if it needs to be replaced.

15 gauge wire? Really? Houston, we have a problem.

Normal wire sizes are normally for wiring in vehicles, 8, 10, 12, 14, 16 AWG.

I would run 10AWG to the radio, another 10AWG to the siren, and finally, with a normal light load, a 10AWG to your lights and other accessories. If you are running an older rotator bar, you may want to split it out a bit more.

Using 15 feet of 14 AWG on a 12 volt system can give you enough voltage drop by itself to drop down to under 11 volts at the end of the wire, and that can be very problematic. It will cause exactly the problem you are talking about.

 

[jim202]

OK, you need to be very specific in describing your installation.

My bet is that you have a high SWR on the antenna and it's getting into the siren and light controller.

You didn't describe just what was controlling the lights. If it is just switches on the DC power feed, you have a wiring problem. As was mentioned earlier, if you don't have some heavy wiring, it could be low voltage killing you. Time to pull out the digital voltmeter and measure the voltage on the siren feed and light control feed, before you key the radio and during the time the transmitter is keyed.

The radio will pull about 10 to 15 amps in transmit for a 50 watt radio and about 22 to 25 amps for a 100 watt radio. Need to use wire size for the current your pulling. Again you didn't provide the details of what power the radio is. You also didn't provide any information on what band the radio is transmitting on. Mounting the antenna on the toolbox is an indication you have a half jackass install and didn't want to punch a hole in the roof of the truck. The toolbox is probably poorly grounded to the body of the vehicle.

What more can I say. Help us with the details so we can help you solve your problem.

 

[aschenavar]

I had a similar issue in a truck I had before..I would key the mic on my radio and it would set the siren off! I tracked it down to RF leakage from a loose antenna connection and the radio.

 

[scottyhetzel]

I have a mobile radio hooked directly to the battery it had a glass fuse, and I have lights and siren hooked to the battery also with a glass fuse. Neither are connected together bit when I key the mic it stops the siren and the lights turn off, turn back on, but then I can't use the controller to shut off the lights I have to unplug them. I need help because I'm not sure what I need to stop this or distribute power. At one time the lights and sirens or wired directly to the fuse but it would cause problems and come undone so I got the glass fuse and wired it directly to the battery

Is the vehicle motor/ alternator running when you key up ? What does the volt gauge read when you key the mic?

 

[Voyager]

I have a good battery. Nothing corroded. I drive a 2005 Chevy Silverado 1500. My antenna is on on my toolbox. The few that uses 30 amp, the wire is 15 gauge. The battery seems fine but I'm not sure if it needs to be replaced.

On an aluminum toolbox, perhaps? (AKA terrible ground plane = high SWR)