CB Interference Issues

vicsryd · 08-15-2005, 10:11 AM

What are the most common causes for signal interference on CB's using the Winnebago pre-wired setup/antennae?

My specific problem is the CB works fine in ACC mode. But if I turn the ignition on/start the motor the signal strength on all channels pegs high with noise and by the time I squelch the out there's nothing left to receive. Also, my transmissions are garbage even by somone 100 feet away.

vicsryd · 08-15-2005, 10:11 AM

What are the most common causes for signal interference on CB's using the Winnebago pre-wired setup/antennae?

My specific problem is the CB works fine in ACC mode. But if I turn the ignition on/start the motor the signal strength on all channels pegs high with noise and by the time I squelch the out there's nothing left to receive. Also, my transmissions are garbage even by somone 100 feet away.

John_Canfield · 08-15-2005, 02:41 PM

Jon,

It sounds like you are getting some electrical noise coming into the radio via the 12v supply. If this is a cheap CB radio then they probably have not designed much noise supression or power supply conditioning into the electronics. Easiest thing to do is to go to Rat Shack and tell the salesperson that you have a noisy radio and you need some filters for the 12 volt supply. (This could be capacitors, an inductor, and/or a torroid)

Solve one problem at a time. Get the 12v supply cleaned up and then see what happens.

--John (wb5tht - extra class ham of 30 years)

vicsryd · 08-16-2005, 08:34 PM

It's a Texas Ranger so it's no slouch.

I'll try powering it from a isolated, non-coach 12v source and see if that makes any difference.

Thanks.

kenbt · 08-17-2005, 08:32 AM

I was having problems with my 2005 Vectra with the factory C/B. It was feeding back thru the surround speakers when ever I keyed the mic to talk. The factory tech went in and isolated the antenna wire from the other wires running down the left column of the windsheild by wrapping it with foil to help sheild it better...that worked in my situation

JamesOne · 08-17-2005, 12:42 PM

I am going to install a CB this weekend. I did a search here and read a zillion posts regarding CBs. My manual said my coach was prewired for a CB. So I looked and found the plastic bag under the dash. I called customer service and asked how it was terminated on or near the roof. I was told there was an antenna on the roof. The only time I have ever been up there was during my PDI. I climbed the rear ladder, looked at the roof and said it looks good to me. I never saw a CB antenna. So yesterday I climbed up there and lo and behold laid back under the air horns was a CB antenna.

Now to my questions, if I get feedback in the surround sound system, what kind of foil would be most effective to cover the antenna lead? Would regular ole household aluminum foil suffice?

For those of you with a CB in a fairly recent Journey, where in the cockpit is it mounted?

wagonmaster2 · 08-17-2005, 05:42 PM

My main problem with the Winnebago CB antenna is I haven't been able to get the SWR reading down low enough to use the radio. Other than grounding the radio case has anyone had any problems with this and how did you handle it?
Wgonmaster2
2004 Meridian 36G

dirko · 08-18-2005, 08:04 AM

Hi Ho: A high VSWR means that the antenna doesn't look like 50 ohms to the radio. Most people use an SWR meter to tune the antenna for lowest reflected power. You should have a tuning instruction manual with the antenna, or go to the web and get the required info. Good luck.

John_Canfield · 08-18-2005, 08:54 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JamesOne:
Now to my questions, if I get feedback in the surround sound system, what kind of foil would be most effective to cover the antenna lead? Would regular ole household aluminum foil suffice? </div></BLOCKQUOTE>With a properly tuned antenna, a radio that is grounded, SWR of less than 1:5 to 1, and only running 5 watts input (the legal limit for CBs), you should have NO RFI (radio frequency interference) problems.

I am an extra-class ham and years ago when I was running high power (we are restricted to 1,000 watts max depending on frequency) my neighbor complained about interference in his stereo. A little detective work was necessary, but I easily solved the problem. It was NOT my problem - I ran a clean station, but I felt it was my job to make sure I had a happy neighbor.

There is an easier way other than shielding the wiring. IF you find that you have RFI , isolate exactly what is affected. If you are getting RFI into the sound system, first test is to disconnect the speaker wiring from the amplifier. If you still have RFI, then the speaker wires are acting as an antenna. Get a few .01 mfd disk capacitors at Rat Shack and solder them across EACH speaker terminal AT the speaker lugs.

If you have no RFI with speakers disconnected, then you are somehow getting RFI coming in to the amplifier. I would try 12V filters for the amp.

However it is difficult for me to believe that only 5 watts input power (probably only about 3 watts out the antenna if it is tuned) would cause RFI.

On my coach I have sucessfully tuned the Winney factory CB antenna (and factory Cobra CB radio) to a low of about 1:3 to a max of about 1:5 to 1 using my ham test equipment.

Hope this helps..

--John