Lightbar creating noise when transmitting on mobile radio

nathanial98

Member
Oct 30, 2013
38
Wisconsin
We have 5 squads that all are having the same issue. The problem is, when the warning lights on the squad are activated and you key up the mic to transmit on your squad radio, everyone hears a loud noise like you are in a helicopter while you are transmitting.

We know it is coming from the lightbars because as soon as i disconnect those, the issue stops. I was also able to hook up a small speaker to the lightbar wires and you can hear the noise from that as well. We tried replacing several parts on the lightbar and that didn't fix it. Obviously the squad radio is picking up the interference from the lightbars. I an just not sure why now this is happening?

3 cars are using OLD ass Code 3 roof mount led lightbars and 2 are using brand new visor Federal Signal lightbars but all 5 are having the same issue. These ARE all new squad installs as well.

Any thoughts or advice would be appreciated.
 

nathanial98

Member
Oct 30, 2013
38
Wisconsin
What is the distance between your antenna and your lightbar?
The exact distance I'll have to check on, but at least 18".

I had to run my 2 radio power feeds directly to the battery (positive and negative) to get rid of RF interference and lightbar noise.
Thanks. It's just that they are hooked up the exact same as they have been for years and we are only now having an issue. I'll try it though.
 

NoLimitSquads

Member
Feb 11, 2021
330
Minnesota
The exact distance I'll have to check on, but at least 18".
That’s a strange problem then. Especially since its different lightbars. Ive run the antenna cable next to lightbar power. Ive used the same ground for the radio as the lightbar, and never had that happen. I wonder if the shield on the lightbar cable is grounded?
 

NoLimitSquads

Member
Feb 11, 2021
330
Minnesota
Thanks. I'll try a direct ground tomorrow. Maybe it has something to do with the fact that most of the body on the new Ford Interceptors is aluminum? Maybe that's why it was an issue on any old cars.
As far as radio properties, and electrical current, whether its steel or aluminum shouldn’t make a difference. The new Interceptors are still mostly steel anyways. Maybe the hood, hatch, and doors are aluminum? Idk, I haven’t drilled them, but the roof and quarters are still steel.
 

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