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Re: Radio Capacitors

From: Mike B
Remote Name:
Date: October 27, 2003


Jim, What sort of noise are you hearing? A pop or a whine? The two main sources of radio noise on your car would be the spark plug wires themselves first, and then the generator output possibility. Disconnect the generator and see if the noise is still there. If it is, and it's a "pop-pop-pop" noise at low rpm, it is probably your plug wires. You need to make sure your plug wire hangers are clean and in good condition, the wires themselves are in good condition, and that the cap is clean inside. Another old trick is to take a bare bit of silicon grease and LIGHTLY coat the contacts of the cap (NOT the rotor or you will sling the stuff all over inside the cap). This makes a slightly resistive arc point and the voltage has to build to a larger potential before it arcs and is a less noisy release. Another thing is to lift the hood when it's dark and the engine running. If you see a light show, theres your radio noise. On your generator, a coaxial style .01 microfarad on the generator output would kill any RF noise. But you might also check the generator for loose or worn brushes, field contact, dirty commutator or high mica between the commutator bars. Also, you may have a dried up elctrolytic filter capacitor in your radio, or a really noisy vibrator (the thing that makes DC into AC for stepping the DC voltage up for the tubes). Ground loops sound like alternator/generator whine, so make sure the ground braid from the back of the engine to the firewall is there, and it is a good idea to bond (fancy word for providing a ground wire) your hood to the firewall as well. The hood hinges, especially this old, are not a very good ground and the hood is a major shielding mass if properly grounded. Same goes for your fender if that is where your antenna is mounted. Last item.... your antenna shield connection at both ends must be good, otherwise the center wire can pick up all kinds of noise. Hope that's enough stuff for you to check up on. The AM radios are susceptible to any amplitude changing electrical source, so have FUN!!! Mike


Last changed: May 04, 2010