Radio heads, I have a problem

bob91yj

bob91yj

Adventurist
Founding Member
I have two communications radios mounted in my truck, one is a PCI Radio's programmed Icom 2 way radio, and the other a modified Kenwood TM-271, I run Laird antennas (purchased through PCI, same model they sell/sold to every desert race team in SoCal). My antenna's are mounted on a steel light bar across the front of the camper. I also have two HID (Chinese versions) mounted on the light bar. At one time, I had a dedicated ground wire from the light bar to the camper. I managed to remove that ground wire arrangement on a tree limb or something somewhere along the line. Lights and radio's have worked just fine since the dedicated ground wires were torn off.

My problem, and it seems to be intermittent, is that my radios do not RECEIVE transmissions when the HID's are on. They work just fine when the HID's are off, and seem to transmit with no issues. Mitch was over at my house a while back to help me look at it, and the damn thing worked perfect. Six months later, I'm trying to find Mitch in the middle of the desert and discovered that the problem was back (of course I cussed Mitch first for not answering my call outs, then remembered the light issue) turned the lights off and reception was clear again. Same trucks, same radios.

One more for you while you have your thinking hats on. I have a handheld Yaseau, and a Garmin GPS. When both of those units are plugged into my Jeep's ('05 Wrangler) 12v power ports, I get feed back through the radio.

Here's a shot of my truck, tough to see the antenna's, but they are outboard of the lights, on either side.

baja10002012039.jpg
 
How do the radios get their power? Are they connected directly to the battery with a fuse inline, or are you tapping 12v from a source inside the cab?
 
I'm no RADIO HEAD, But.......... that Kenwood puts out an impressive 60 watts of RF power and could it be interfering with reception of your other radio?
However, if the Kenwood is also having intermittent reception, disregard - it's most likely a power supply problem.
 
It sounds like a grounding problem to me. First off get a good ground from the light bar to the campershell to the truck frame or to the factory ground from the engine to the frame. Radios should not interfer with each other, I run 125watt commercial radios from Motorola and two of the antennas are close and I have no problems. Check the connections on the antenna, look to see if anything funky is going on there. Check you battery ground wires make sure they are tight and clean. Maybe the HIDS ballest has something to do with the radio problem not sure on that one. If you are going to the DVR look me up and maybe we can find the gremlin living in your rig. Also check the antenna cable to the back the radios are they tight?
DID I SAY MAKE SURE YOUR GROUNDS ARE CLEAN AND TIGHT.
 
The radio's both work great UNLESS the HID lights are on. I also have HID conversion lights for headlights/driving lights, they don't seem to affect anything.

Radio's are powered from an aux fuse block, which is wired directly to the battery (through a mega fuse). If it was a "transmit" concern I'd go with the power supply idea, seems to transmit just fine, it's receiving that I have a problem.
 
I deal with a number of different radios in different scenarios and vehicles. In my experience, most issues come down to grounding.

If I've got an issue, I try to start eliminating variables, and revert to the simplest setup I can. Then, I'll add the complications one by one until I hit the problem. In your case, I would probably completely disconnect one of the radios (both power and RF), bypass the fuse block, and go straight to the battery with the radio that's still plugged in (don't forget the inline fuse). If the problem still persists, then it's definitely an issue with the light setup (either grounding, or perhaps the HID system is just sending out a ton of RF junk that's overwhelming the receive front end of the radio).

Grounding/interference issues on radios can manifest on receive just as much as on the transmit.
 
Hid lights are driven by ballasts (high frequency transformers) so you are probably getting massive interference since they are on the same ground plane (the roof rack w/o proper grounding). Try relocating the antennas further away from the lights and grounding them to the truck frame.
 
Some reception thoughts, for what they're worth:

HIDs are noisy RF generators. A noisy RF generator next to an antenna is going to impede your ability to pick out signals from the air.*
Antenna mounts need good grounding. It helps eliminate interference - Grounding the light bar between the noisy things and the sensitive listening things may help. *
Cables and connectors wear out. When worn or poorly built, they can let in a lot of interference and cause other problems, such as poor grounding. *
Grounding the radio body can really help. There's usually a screw on the back just for that. Don't just rely on the black wire going back to the battery.*
Radios should get power directly from the battery. If they get power from a junction block, anything else on that block that causes noise, like HIDs, will cause issues - and not just on transmit)*

* 'But it worked great before.' -Cool, maybe it will work great again someday. ;)

www.k0bg.com is a deep dive and way more information than most will ever need. But if there's a question about antennas on vehicles, it's covered here.
 
Sounds like working on grounds is going to be the place to start. Thanks guys.
 
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