Radio Suppressor

[Deleted User]

What can be used these days in place of the old radio suppressors wired to the coil and generator to keep engine ignition noise down? Thanks

hudsonsplasher1

Be sure your plugs are the ones with built in resistor.

Marconi

Resistor wires will also work. Are you getting plug noise or generator whine? Plug noise sounds like a machine gun speeding up with the engine, the generator will sound almost like a siren getting worse as the engine speeds up.

forjack842

There are several types of engine generated noise. The typical whine varing with RPM is usually the generator/altenator. In this case you can install a noise suppression cap right at the gen/alt + output and the case. An ignition cap is sufficient to clip most all RF type frequencies. Make sure the case is ground tied to the engine and installing a short as possible ground strap to make sure is a good step.

Spark Plug Tic-Tic-Tic is usually remedied by either resistive plugs or wires.
Use of a metal sparkplug wire tube troughs also improves shielding of the wires.

Other things that should be done are:
Improve the engine to chassis ground with a heavier/newer ground strap insuring the engine and frame contacts are cleaned at the contact joint. Adding a battery terminal to frame strap removes any transfered noise across the battery lead.

Install a direct ground strap from the radio to the frame close to or at the engine strap mentioned above thereby making the radio the same potential as the engine and frame.


Install an RF filter inline with the +6 or +12 bat line to the radio. These are available at radio shack or Ebay etc. Don't skimp on cost here.

Remove the antenna and inspect the mount to metal and be sure there's a solid ground mate as this keeps the antenna coax at the antenna as close to frame ground as possible. Typically the rust reduces the effective RF ground path and this tends to float the antenna coax end.

Replace the antenna coax with newer heavier shielded coax thereby reducing ignition noise induction.

If necessary relocate the antenna to the furtherest spot on the vehicle away from the engine compartment.

Test the RF shielding capability of the hood by running a ground strap across the hood hinges insuring the hood is tied to the car frame. I've see several cases where the RF noise ground conductivity is very poor over time and a ground strap to clean connection points on the hood and frame restores the hoods RF shielding capability.

Hope this helps
Jack