Hello,
I recently installed a cobra CB radio in my 2005 F250 6.0. Power and ground are both coming from Cigarette lighter. Antenna ground is coming from negative battery terminal.
UPDATE: I did some reading and found out that running the wires directly to the battery may help. I wired the radio + straight to the battery and the ground is going to a ground point in the engine bay. No difference at all. Very loud static when vehicle is running.

Whenever the engine is running, I get lots of static. If I turn on the fans (a/c), it gets much worse. It also gets worse if I adjust the windows in any direction. (Like a whine with the window motor) Pretty much any electrical activity. When the engine is off/keys are out, it work perfect.

Also, I have a ground loop isolator from a previous project, but I couldn't figure out how to hook it up to the power. It's for audio cables so I wasn't sure how to do it. I'll include a pic that looks similar to my ground loop isolator.

I'm leaving town tomorrow and would love to have this solved! Thanks in advance!!
William

<a href="http://s66.photobucket.com/albums/h268/qwertmonkey/?action=view&current=image020.jpg" target="_blank"><img src="http://i66.photobucket.com/albums/h268/qwertmonkey/image020.jpg" border="0" alt="Photobucket"></a>

 

There is a power filter you can buy. They sell they in the radio section at walmart or radio shack or try your CB shop.

 

Thank you for the reply.

I'm assuming I need this part because the ground loop insulator will not work? The only reason I ask is because I remember buying the insulator for the same problem, but for a dvd install on another car.

Also, I was at Walmart and didn't see it. Would best buy have it?

Thanks,
William

 

something like this

http://roberts-etronics45.com/workma...se-filter.html

 

Thanks a bunch!

 

Without buying anything, try this first...run the power lead thru a piece of coax cable (same as antenna lead). Center conductor to the hot side, shield to the ground and see if that doesn't fix your problem. Doesn't matter which battery (but I'd use the one on the drivers side).

 

Ok, I will certainly give that a shot, but please excuse my inexpierence-- What do you mean by centering the conductor to the hot side, and shielding the ground lead?

Thanks

 

What do you mean by this. Antennas should be grounded at the mount to provide a good ground plane for the signal. The coax cable shield is grounded at the radio end through the coupling nut and unless it is a magnetic mount antenna the other end should be grounded at the antenna mount. (Mag mounts are grounded to the base that the magnet is in.) With the noise you are getting I would suspect something in the antenna circuit.

 

I'll put in my two cents here.
Run both leads to the battery.
Ground the chassis of the radio.
If its a crappy antenna, go buy a good one.
If its a mag mount antenna no ground is needed.
If you drilled a hole in your roof no extra grounding is needed.
Anything else ground.
If its on the roof, move antenna towards the rear of the cab.
If there isnt one, add a fuse to the power wire.
If you are running bigger power use at least 8 gauge wire.
One problem with going to the battery is remembering to shut it off.
If you are running bigger power watch out for the internal cooling fans coming on if the inside of the truck gets hot and killing your battery, most internal cooling fans cant be shut off with the power switch.

 

Inside of a coaxial cable you are going to have four parts. Starting from the inside out there is the center conductor, dielectric, shield and then insulation. What he is talking about is connecting the +12VDC to the center conductor of the coax. Connect only one end of the shield to a known good ground. Be careful to not short the shield to the center conductor though.

 

Now you have me stumped. Connecting the shield at one end only is only done in electrical control PLC type instrumentation. RF and power situations always connect the shield at both ends. First off i wouldn't use RF coax. It might help but RF 50 ohm coax is not recommended for use in power distribution. Eliminating your noise situation can and may become costly, even exhausting the expense of the radio.

Noise interference can be a compound of several different issues. One, the radio itself may have a ineffective or "cheap" built-in high pass line filter. second, the vehicle itself may have excessive noise created by it's own factors (worn or defective alternator and/or wiring as well as a inefficient battery amoung others).

Some key items: Provide a quality power lead of at least 10 or 12 awg (if a stock radio). Purchase the type that has the positive and negitive combined or you can twist the leads together using a drill which helps reduce any coupling effects or you can purchase a higher quality shielded power cable. Go direct to the battery as previously mentioned but try as short a route as possible without excess loops and trying not to cross over other electrical sources. Crossing 90 deg instead of parallel helps if unavoidable. Purchase a quality aftermarket high pass filter for the "power" line. (your audio filter is designed for a stereo system and wont work in a mono system. If it did work, chances are the noise would still be present on transmit). Ground the radio to the chassis with a large awg or braided cable as short as possible. Your alternator system may need to be addressed as well and there are filter systems for these as well. Put your stock am/fm radio on AM and compare the noise quality with that of your CB. It's a very good chance your CB could be the contributing factor. And last but not least (and you might try this first) is make sure the antenna is in good condition and is properly tuned to the radio. If the SWR (standing wave ratio) is high it can be a likely contributor. Most radio shops can do this or you can purchase one for yourself, a inexpensive one will do the job. Sorry for the long post.

 

All he is suggesting is to try it in an attempt to "filter" out interference that may be coming in on the power.

If you ground the shield of a cable in more than one spot you get ground loops which opens up a whole 'nother can of worms.

 

I had that happen once, and after screwing with it for hours... I got another CB, and tried it, and turns out. It was the CB in the first place, not the truck LOL

Try another CB...

 

It's actually ironic you mention that. I woke up this morning to a dead battery.

I left the CB off (switched off) all day yesterday so I'm not sure what drained it. I didn't even drive the thing yesterday. What do you mean by internal cooling fans. Do you mean fans inside the CB?

Also, I've tried running both - and + to the battery. I have a fuse for the + lead. I haven't mounted the antenna yet so It's grounded to a ground in the engine bay. When I get my permanent antenna, (a 102 whip) it will be mounted behind the cab.

I will also try grounding the CB itself. I think that will help because changing the lead from the cigarette lighter to the battery made no difference. I think I may be getting the interference from the box itself.

 

You have to keep this simple.
Before you even mount a CB, Get a noise filter for CBs from Radio Shack or from a ham radio shop.

Run a red +12VDC cable from the battery (temporarily run it through the window). Run a - black the same path. Install a fuse at the battery end.

Test 1: Use the noise filter on the 12 V DC power for the CB just before the +12V DC connection to the CB. You can leave the fuse on the back of the CB that comes with most CBs Connect the red and black wires appropriately.

test 2: If you have noise, temporarily use the AM/FM in-dash 12 V DC power to determine if its the CB or the power. If using the am/fm radio power still has noise, connect the noise filter. If it still has noise, its a cheap CB radio and it will never work properly in that truck.

If there is no noise with test 1, run the wires properly from the battery to the CB.

If you are concerned about draining the battery, install an ignition switched relay or a I|O switch under the dash.