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MG MGA - Ignition Interference Through Radio

I just installed a modern radio in my 1600 and I hear the ignition through the speakers.
Is there anything I can do to eliminate the ignition interfence?
Any comments or suggestion are welcome.

Best regards,

Michael
Michael C.

You need those spark plug ends sold by Moss and others that have in build suppressors in them.
I just purchased some new one's and I think they were from NGK with either 45,60 or 90 degree bend.

You can also fit a suppressor in the power line of the radio, but most modern Radio's already have these.
I've also seen suppressors on the alternator too, but not exactly sure where they are wired up, possibly search the web under dynamo to alternator conversions.
Hope this helps.
Cheers <MARK>
Mark Hester

It could be that your plug leads are old. They break down over time and "leak".
Ian Pearl

Hi, Michael - literally *anything* that has a switching contact and a solid wire attached to it can make RF noise that can be heard in your radio. After all, Marconi's first radio transmission was via a tuned spark gap, so you've got to suppress that RF signal. Here's some points to install that suppression, in order of importance:

WARNING: If you've got an electronic ignition package, better talk to the manufacturer first - some of these "fixes" can cause damage or failure to these add-ons!

- 1. The spark plug wires need to be carbon core, and not solid wire style. I know that not very original, but a modern radio's not very original either. The resistive caps are a poor substitute for good carbon-core wires.

- 2. The sparking plugs themselves need to be of the radio supression type. Most auto supply houses can take the type you've got and cross to the new types (often it's the same number with an "R" or "S" added to it).

- 3. The wire feeding the ignition coil is an excellent antenna, so put a 0.5 to 1.0 microFarad (uF) capacitor (available at most every good auto store, or visit your local Radio Shack) on the 'SW' side of the coil to ground. Remember you've already got a capacitor (condensor) on the other ('CB') side of the wiring, inside the distributor. And here's a bit of trivia - the "ground" side of the high tension portion of the ignition coil doesn't ground to the case of the coil at all, but is normally connected internally to the 'CB' side of the low tension winding. Good for spark, but bad for interference.

- 4. The generator can make a 'roaring' sound (sparks off the commutator), so a larger capacitor of one to two microFarads needs to go from the large terminal to ground on the back of the dynamo. If you've got an alternator, the noise will be more like a high pitched squeal which changes pitch as you rev the engine. This requires a choke/capacitor kit. Just ask for an "Alternator Whine" kit at the counter, and they should know what you need.

Those are the big offenders, but many more items in the car can cause noise, especially in the lower AM or SW bands. The electric fuel pump is a big offender, if equipped, and a capacitor at the power supply terminal close to the pump is needed (remember to always put the cap as close to the source of the sparks as possible). The windshield wiper motor is another example, but is not always running. And, if you had one of those gawd-awful heated "voltage stabilizers" used in the gauges circuit of later cars, you'd hear clicks about every two seconds while the ignition was on.

It's all a cut-and-try solution, but some major improvements can be made. Best of Luck - - Alec

Alec Darnall

This thread was discussed between 04/05/2005 and 05/05/2005

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