Noise Suppression (Part I)

This information was handed out at the DCART meeting. It has some good noise suppression techniques for mobile stations.

The FS-3023 Gated Noise Limiter is very effective in the reduction of noise, but this alone is not effective against all the different noises in a mobile installation.

A. BONDING: The use of 1 inch copper braid to interconnect parts of the automobile that can radiate noise such as the following:

1. Hood to firewall
2. Rear bumper to body and chassis
3. Tailpipe to body
4. Either side of muffler to body and chassis
5. Chassis to body in several places
6. Ignition coil to firewall

When braid connections are made, be sure to clean the metal "bright" and coat with grease before tightening the connection. This will prevent contact corrosion, which is the chief cause of noise.

A very good method for locating noisy fixtures is to put the FS-3023 into operation and connect a 25 foot length coaxial cable to the antenna connector on the rear of the FS-3023. The other end of the coaxial cable should hav ethe center conductor showing for about 1/2 inch. This bare end of the coax will serve as a "noise probe" to all parts of the automobile (except for the electrical system.) A large increase in noise will indicate a noisy section. This section should then be bonded and rechecked. Continue this process until a substantial reduction of noise is achieved.

REMEMBER! Ungrounded metal parts can radiate noise.

Ignition radiation suppression will be in the next post.