Topic: problem with ignition noise on CB radio

[SuperSlideStyle]

Ok, haven't tested my cb radio since I installed other than hear the local traffic, but I'm getting a lot of high pitched ignition noise that mimicks the engines RPM's.  I routed the wires away from other electrical wire except for the ones for the driver side brake lights near the rear.  Since the cb is mounted in the center console, I thought maybe the antenna wire might be too close to the restraint system ECU mounted under the center console also.  I have an antenna cable 90 deg angle connector that might help with that interferance.  Any ideas what it could be from?

[Ghost65]

Irwin...you will need to install a resistor in your power line I believe to cancel this out.

PaulXyZ would be the authority here for sure.

[SuperSlideStyle]

What size resistor do I need?  Also, the internal speaker doesn't seem audible, even with the RF at max and the squelch to the minimum.  Do I have to add an external speaker?  Seems like I won't be able to hear it as is on the trail.  The cb radio is brand new.

[knightrider]

An external speaker is almost a requirement when mounting the radio in the center console.  I got a 20w uniden bearcat speaker and never turn it up past halfway.

[Ghost65]

What size resistor do I need?  Also, the internal speaker doesn't seem audible, even with the RF at max and the squelch to the minimum.  Do I have to add an external speaker?  Seems like I won't be able to hear it as is on the trail.  The cb radio is brand new.

Irwin...I'm just not sure.  Give Radio Shack or Ham Radio Outlet in San Diego a call and they should be able to point you in the right direction.

[knightrider]

First you need to find out if the noise is coming from the power or antenna cable.  Try unplugging the antenna to see if the source of the interference is the antenna.  If the noise is the same then its the power source.  Try running power directly from the battery temporarily to see if that fixes the issue. If its coming from the antenna, you need to reroute it.  If you still have noise you can install a rf choke to block interference on the power leads

[Bobby B.]

For the most part on these trucks, the primary source of this noise is interference from the fuel pump and a crappy ground/mount for the antenna.  I completely eliminated all noise from my CB by doing the following:

-- run clean power to your internal accessories and do not tap into an existing power line, like the cig lighter

-- removing the antenna and mount from the stock roof rack or thereabouts as it doesn't ground for crap.  The minute I bolted it to the steel of the rear swingaway it eliminated the last if not all of the noise

-- wrap some ferrite chokes around the power wires for the fuel pump, accessible by removing the little steel access plate under the seat

-- add a little inline box called a "noise chopper" in the coax

I think it was the external ground that did the most.  Even running ground straps from the doors to the body to the frame like with ham radios can help if you have to leave the antenna up top.

[SuperSlideStyle]

Thanks guys.  Found the problem.  Turns out the K-40 coax cable I bought, the removable head on the radio side wasn't threaded in enough.  Took it to VIKING CB Radios in Truck Town in Fontana off of Cherry Ave. and they calibrated the whole thing for me.  Great guys.  Turns out my SWR was near 2.0 on the lower channels so I had to change the 1/4 x 20 screw on the FireStik antenna to one that was 1.5" longer.  Brought my SWR down to 1.4 max on the lower channels.  Works great now.  Thanks again.

[npgtech]

Thanks guys.  Found the problem.  Turns out the K-40 coax cable I bought, the removable head on the radio side wasn't threaded in enough.  Took it to VIKING CB Radios in Truck Town in Fontana off of Cherry Ave. and they calibrated the whole thing for me.  Great guys.  Turns out my SWR was near 2.0 on the lower channels so I had to change the 1/4 x 20 screw on the FireStik antenna to one that was 1.5" longer.  Brought my SWR down to 1.4 max on the lower channels.  Works great now.  Thanks again.

May have to stop by those guys this weekend or next.  They are open on the weekends right Irwin?

[Ghost65]

Thanks guys.  Found the problem.  Turns out the K-40 coax cable I bought, the removable head on the radio side wasn't threaded in enough.  Took it to VIKING CB Radios in Truck Town in Fontana off of Cherry Ave. and they calibrated the whole thing for me.  Great guys.  Turns out my SWR was near 2.0 on the lower channels so I had to change the 1/4 x 20 screw on the FireStik antenna to one that was 1.5" longer.  Brought my SWR down to 1.4 max on the lower channels.  Works great now.  Thanks again.

Glad you got it fixed.  CB's can be finicky little suckers...or I should say antennas and their connections/grounds can be finicky little suckers.

[SuperSlideStyle]

Not sure if they are open or not.

[Paul]

There are two main RFI (radio frequency interference) problems with trucks - ignition noise and alternator whine.

Ignition noise is a crackling - a popping noise - that is tied to the spark plugs. New vehicles rarely have this as they're pretty well built to prevent their own ignitions from interfering with all the electronics. We use to fix those with a coaxal cap that was grounded to the engine and the other line ran to the distributor cap ... which we ain't got! Could also be the ground on the coax cable feeding the receiver or the lug on the antenna side not making clean contact.

Alternator whine is a high pitch whirling caused by a wee bit of AC coming from the alternator rather than pure DC. Sometimes this is a ground problem - clean up the paint under the screw grounding the power. If that doesn't clean it up you'll need an alternator filter which is a big coil of wire and sometimes they'll throw a cap or two in there for a pi type filter action. Make sure you get a filter rated at least as large as the fuse on the CB so you don't smoke it.

The K40 is a nice antenna. I bought one last month. Not the same quality as 35 years ago but good enough. The coils are about 50% smaller and much lighter. The whip is much thinner too. Even the magnet isn't as big as back in the late 1970's.

[SuperSlideStyle]

Update.  Sounds like a bit of alternator whine.  Also, sound is inconsistent.  I turn on the unit, sometimes i get reception, sometimes I don't.  Seems to be coaxial cable.