SLine78

I am getting a lot of ignition interference coming through the radio on the 78. When I looked in the AIM, it showed three suppressors, one on the fan blower motor, one on the turn signal flasher and then the ignition suppressor/tach filter. Does the tach filter also serve to supress radio interference from the ignition?

Thanks,

Mike

Mike Mercury

the best way to determine how the noise is entering the radio, put it on a station that you can hear the noise easily. They pull out the antenna connection and see if it goes away.

If the noise does go away, then the noise is not entering via the 12v lead... instead it is being picked up by the antenna.
And in really strange occurances the noise can be radiating into the radio chassis itself by somethign very close to it.
Anyways, if the noise is beign radiated into the radio, then placing suppressors on the radios power lead will not solve the problem.

If the noise it doesn't go away when unplugginng the antenna, then the noise is entering via the 12v lead. You can add suppressors on just that specific power lead and take care of it.

NHvette

The tach filter doesn't (or isn't supposed to) suppress
radio noise. It suppresses spikes from getting to the tach circuit board.

ACECO

My 75 had a lot of alternator noise/whine so the addition of a filter cap on the alternator helped eliminate this. Spark plug/ignition noise "usually" is picked up via the 12V line. However I've seen it come in thru the antenna too. Follow Mike Mercurys advise to determine which is the cause in your case.

Good Luck!

SLine78

That was my understanding as well. But when I looked at the AIM, it has it in the radio section and the sheet that it appears on is titled "Radio capacitor & tachometer filter." The only part numbers listed on the sheet are the filter and the screw that holds it.

Based on the other feedback, the noise maybe induced into my amp on its power leads. The alpine radio itself has filters built into constant and switched 12V leads. The whine occurs as soon as the radio and amp are turned on and varies with engine speed.

Mike