Static and Signal Loss

Joined
Sep 30, 2016
Messages
3
Location
Virginia
#1
Good day everyone, I generally don't go to forums too much but I'm having a problem that maybe someone here has had an issue with.

I have 2 Motorola XPR4550s in my vehicle (VHF & UHF), no issues with it what-so-ever when I'm not running auxiliary lights. The signal is crystal clear on both radios, antennas are run to a bed rack on the back of the truck which has 2 auxiliary lights added. When I turn the AUX lights on the signal on the VHF radio either has static or cuts the signal completely.

Everything is run to a custom console inside the vehicle. The antennas are run to the same console and is an LMR-195 antenna wire. The Antenna itself is a dual band whip for VHF & UHF.

I thought it was a ground issue (the ground cable was not grounded very well) but I ran a cable to the engine bay and grounded it where the motor ground is located which also ties in the battery. This didn't solve the problem. The antenna wire and power wires are all run on opposite sides of the vehicle (Antenna run on passenger side while the power is run on the driver side).

If anyone can point me in a different direction, I would appreciate it... I don't have an issue buying new antenna cable if the LMR-195 isn't sufficient for this purpose. I also don't have a problem buying a specific type of power wire for the lighting as long as it is guaranteed to be shielded against the current setup.

I've attached a couple of pictures of the console/light rack on the bed for you to see. The light bars are in the orange/yellow rectangles and the antenna bases are circled in red.

This is not limited to this installation, I had a couple of lights on the front bumper that would cause the same interference. Power for those lights were run through the firewall into the engine bay, the antennas are run through a grommet on the back of the cab.

Any suggestions are greatly appreciated and I am willing to do whatever is needed to clear the problem up short of getting all new equipment.

That being said, this is more if a nuisance than necessity because I use the VHF mainly for listening to the weather channels and the AUX lights are not on often, but it is still annoying and I know there is a problem with it.

Thanks,
Nate
 

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Joined
Mar 15, 2010
Messages
970
#2
It's because your AUX lights are radiating noise. Every cheap LED light bar I've installed there has been a problem on VHF and AM/FM radio.

You can try some ferrite core on the DC power cables to the lights. This may help but it isn't easy to totally eliminate it.

That's why good lights go through EMI testing like Whelen, Sound Off, etc. though they're a LOT more money usually. Are these a Feniex product?
 
Joined
Sep 30, 2016
Messages
3
Location
Virginia
#3
Thanks for the reply, I'll have to look into that, I did notice that my Rigid lights don't make the VHF cut out.

They were cheap lights, I just needed something to drive in the country late at night next week where there are no street lights. Thought about keeping them, but I guess I'll look into getting a Feniex light bar for the front with a Rigid up top. The lights I got are a company called NiLight and they were $30 for the pair of 12" lights.

I did put a ferrite core on the power for just about everything but it is still happening... I even put it on the antenna wire which cleared it up very slightly.

I was thinking about the Feniex lights because some emergency vehicles use them and they don't interfere with the radios in their vehicles.
 
Joined
Mar 15, 2010
Messages
970
#4
I also forgot to add that the "noise" is RF and picked up by the antenna itself causing your radio receiver to become deaf. The noise is generated in the light itself but the DC wiring to it acts as a antenna and usually makes it worse. This is were ferrite can help.
 
Joined
Mar 30, 2005
Messages
3,062
Location
So Cali
#5
And the antennas are installed to what looks like a bracket off the light bar.
So you do not even have a correct groundplane for your antennas.
 
Joined
Mar 15, 2010
Messages
970
#6
Yeah, cmdrwill has a valid point though not really related to the interference. If you're going with L brackets a half wave no ground plane antenna on both would be your best bet giving you unity gain. Drilled in the roof would be the most superior. If you use the UHF a lot I'd put a watt meter on it and see what it's doing. Typically quarter waves don't like to not be mounted on a GP and you'll have pretty high VSWR.
 
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Messages
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#7
But the antennas are still connected to and in the interference.. the LED lights. So that IS related to the interference.
 
Joined
Mar 15, 2010
Messages
970
#8
But the antennas are still connected to and in the interference.. the LED lights. So that IS related to the interference.
What type of antenna's and how they are mounted really has nothing to do with the crap that the LED lights are emitting. It's going to wipe it out regardless how it's mounted, the lights are in very close proximity to them.

Remember, it's induced RF.
 
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Joined
Mar 7, 2002
Messages
2,528
Location
New Orleans region
#9
I would suggest putting the F cores inside the LED lights to keep the noise from using the power wire as an antenna.

ust remember that there is different type of material the cores are made of. You really need to make sure the type you have are rated for the frequency band your trying to clear up. Using a core rated for the HF frequencies won't help much at the VHF range.

Jim
 
Joined
Dec 29, 2016
Messages
51
#10
Have access to mag mount? I had issues and ended up using a mag mount until I found a spot on my truck that had no issues. Then moved my permanent antenna to that location

Sent from my SM-G950W using Tapatalk
 
Joined
Jun 30, 2006
Messages
7,191
Location
So Cal - Richardson, TX - Tewksbury, MA
#11
Yes, do this. I had a terrible problem with LED lights in my house wiping out the VHF bands and I ended up putting three #43 mix snap on cores right at the light socket. One core did nothing, two in series started to improve things and three on each light socket pushed the noise down to an acceptable level.

You can also wrap two or three turns of wire through the core and every time you double the number of turns, the inductance goes up 4 times and the RF choking also goes up. The main point here is to get the ferrite as close to the switching power supply as possible because the power leads feeding the power supply is the antenna that radiates the noise.

I would suggest putting the F cores inside the LED lights to keep the noise from using the power wire as an antenna.

ust remember that there is different type of material the cores are made of. You really need to make sure the type you have are rated for the frequency band your trying to clear up. Using a core rated for the HF frequencies won't help much at the VHF range.

Jim
 
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