Radio Interference

I have seen your page and found it informative, but i have one question, i am running a cobra 29 LTD classic cb radio in my 1991 ford taurus, i have real bad rf from my fuel pump. i have a filter on the power line that is connected directly to the battery. and i also have a rf filter on the + line of the fuel filter. i have bought a new antenna, but it does take care of some of the noise. i also have the noise blanker on full. but i still cannot recieve distant stations that i could when i have the engine off. so if u have any ideas please let me know.
thanks for your time.

Hi There:
I don't have a lot of experience in this area. I have done some reading on the subject however.
"Radio Frequency Interference: How to Find it and Fix It" A book published by the American Radio Relay League, Newington, CT, says that most fuel pumps are in the fuel tank and powered by long wires nowadays. The book also has diagrams of recommended filters for use on fuel pumps (page 13-4).
If the electrical portion of the pump is external to the tank, you could try covering or shielding it with a grounded metal box along with filtering the power leads.
If the pump is in the tank you could try locating the antenna as far from the tank as possible. For example an antenna mounted in the middle of the roof(?Mag mount???) might pick up less pump noise than an antenna on the back of the car.
Make sure the fuel tank has continuity with or is grounded to the chasis or frame of the car (assuming the tank is metal).
There are special QRN or noise filters available on the Ham Radio market that receive the noise through a sensing antenna and mix the phase inverted noise signal with the desired RF. These do a great job of eliminating interference generated locally similar to what you are getting.
JPS Communications model ANC-4 Antenna Noise Canceller is carried by Amateur Electronic Supply (phone 1-800 558-0411). They claim it reduces local noise by typically 50 dB and it runs on 12 VDC.
That's about the best info I can think of right now.
Sincerely, John K. Browne

Click on the picture for RFI filter construction.

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