CB Noise

[nagal]

One of the many mini-projects I did saturday was to take a look at my noisey CB. It is a Cobra 18WXST II using a magnetic antenna base on the tire carrier. The noise is only there when the engine is running.

My first order of business was to wire the CB directly to the battery, figuring the noise was being picked up through the power wires to the CB. That did not change a thing. So I scratched my head, trying to recall knowledge long lost and disconnected the antenna. All noise gone.


At this point I am googling away trying to find some answers but I am, always open to suggestions from the crew here

[Jeri Lyn]

off the top of my head, your power wire may not be properly shielded and is picking up EM interference from the engine? I think it's called TVR wiring?

[nagal]

Its not the power wire going to the CB as removing the antenna emlinates the noise. The noise is actually being picked up by the antenna

[Old Fart]

Lots of info out there:

http://www.k2bj.com/Pages/Noise/Intro.htm

http://www.stu-offroad.com/cb/cb_install-1.htm

http://www.roity.com/rc/rfi.html

http://www.qsl.net/ka0dxm/hfnoise.html



Jeff
KG6TY

[UglyGreenJeep]

Its not the power wire going to the CB as removing the antenna emlinates the noise. The noise is actually being picked up by the antenna

Sounds like you have a bad ground. Either put it in a more permanent mount, or make sure that the tire carrier is properly grounded.

Just a thought. HTH

[TDS SD]

CB Noise

Good links Jeff. Here is a paragraph from one of them.
Your Ignition System:
Let's try some easy to answer questions first. Though your car's ignition system is not a part of your antenna system per se, it is the prime source of received RFI.

Have You Replaced Your Spark Plugs Recently?
Plugs should be replaced regularly, even on modern automobiles. In the old days the recommendation was to change your plugs every 30-50,000 miles. As automotive technology and the time span between service intervals has advanced many people don't even think to change them at all! If you are having any kind of "received-noise" related RFI, you should begin your suppression journey by replacing at least your spark plugs. It will only help to increase your vehicle's overall performance and will eliminate the prime offender from the "RFI source list."

The plug gap should be set for the minimum allowed in the vehicle's specifications. A smaller gap translates into a smaller spark, and presumably less RFI. Also, always use "resistor" spark plugs in your car. Almost universal now, there was a time where they were a luxury aftermarket item. Resistor plugs suppress RFI by including a series resistance in the spark plug body which drops the voltage at which the plug operates. In some higher-performance vehicles this has caused some reports of sluggish performance. You be the judge: I've never been able to tell any difference in performance in over twenty years of mobiling during which I've run both. If you can't tell whether you are using them or not, check with someone you trust at your auto supply or repair shop.

Are you using high-quality silicone spark plug wires?

Look at your spark plug wires: are they dirty, cracked or worn in appearance? Even if you're not a pro under the hood you can replace your old wires right in your driveway with a new set of noise-suppressing silicone spark plug wires for an investment of about $15. This quick fix goes a long way to clear up big noise problems in many cars. Your plug wires are high voltage power lines connecting the distributor and the spark plugs. The higher quality their manufacture the better the RFI suppression. Check your wires for a "silicone" reference written on the wire insulation. Generally (though not necessarily) they are white in color. Again, this is a basic upgrade you should perform, as applies, prior to moving on to other more advanced techniques for suppressing RFI which is being received via the antenna.

[TDS SD]

CB Noise

Just curious, what was the outcome of finding the problem?