Radio problems

[dammstrate]

So I re-installed the refurbished original radio in my 65 sport fury this weekend. Tested it, all seemed good. Went for a drive in the car and turned on the radio, clearly there is some kind of electrical interference related to the ignition causing static. You can hear the high frequency bap-bap-bap. Pulled over, try with just the accessory ignition on, no problems. Seems like some kind of shielding problem? Do I need a better ground? Works fine until the engine is running. What to check/fix?

 

[Xenon]

Especially in older cars ignition and alternator noise can be heard thru the radio....
The use of a good radio suppressor usually works....

 

[Big_John]

There's a few things that can cause this, particularly on the AM band. You didn't specify if it was AM, but I'm going to assume that.

Spark plug wires can be a problem, especially if they are solid core wires. There should be a suppressor on the coil too, most times those are missing. Looks like this..

There are other things too... Bad ground for the radio and sometimes a bad antenna connection can make it worse too.

 

[Yatzee]

So I re-installed the refurbished original radio in my 65 sport fury this weekend. Tested it, all seemed good. Went for a drive in the car and turned on the radio, clearly there is some kind of electrical interference related to the ignition causing static. You can hear the high frequency bap-bap-bap. Pulled over, try with just the accessory ignition on, no problems. Seems like some kind of shielding problem? Do I need a better ground? Works fine until the engine is running. What to check/fix?

What you need is a transformer rated 12v in and 12v out. Use to be able to buy them at Radio Shack and some auto sound retailer/installers. The way they work is the primary 12v windings are separate from the secondary 12v windings out so noise from the electrical system can't transfer across the windings. They're pretty small transformers and will mount just about anywhere. Haven't sourced one lately but they're out there for sure.
You also need to look at ignition condensers and poor grounds especially where the antenna connects to the sheet metal of the fender, and fender to body. RFI noises can be suppressed with antenna filters especially if your radio was converted from AM only to AM/FM which is very sensitive to RFI noise. Here's one solution for power induced noise:
IBP NC SHIPPING 10 Amp Audio CB/Radio Noise Filter Suppressor Stereo NF-102

and here's one for RFI antenna induced noise:
usa seller. CAR AM FM RADIO ANTENNA NOISE FILTER WHINE HUM SUPPRESSOR ELIMINTOR | eBay

 

[Yatzee]

So I re-installed the refurbished original radio in my 65 sport fury this weekend. Tested it, all seemed good. Went for a drive in the car and turned on the radio, clearly there is some kind of electrical interference related to the ignition causing static. You can hear the high frequency bap-bap-bap. Pulled over, try with just the accessory ignition on, no problems. Seems like some kind of shielding problem? Do I need a better ground? Works fine until the engine is running. What to check/fix?

There was one item I forgot to mention and that was the type of ignition wires you have. Best they be the type with "Noise Suppression" printed on them to ensure their resistance is sufficient to stop RFI.

 

[CBODY67]

If the noise is from something under the hood, it should get louder with the hood open and quieter when the hood is closed. Otherwise, there is something in the power feed line, somewhere.

Plug wires are important, too, but if it's them, that noise decreases significantly when the hood is closed. Carbon-core type wires should only have a faint noise with the hood open and silent with the hood closed. Magnetic suppression wires generally have a slight bit more, but not much. Adding resistor spark plugs should be used with "wire" wire, but can be used anyway.

A whine might be related to the only part of the charging system that turns with the engine speed, the alternator. Might try grounding the case to the engine (using a valve cover or similar bolt). Then ground the engine to the body, ala GM, with a braided ground strap.

What about clicks from the brake light switch or similar, when they are operated? Might need to try grounding the case of the radio to the body, too, which an existing "back brace" would do.

Please advise of your progress.

CBODY67

 

[dammstrate]

Ordered both items recommended by Yatzee, many thanks. Will advise of conclusion when they get here!

 

[dammstrate]

Well, the antennae part did nothing. On to the suppressor.

 

[MoparJim]

A blast from the past. I can remember dealing with this same problem back in the mid-1970s when installing a new Pioneer 8 track/AM/FM in my 1967 Chevelle (dad wouldn't let me get a Road Runner, afraid I would kill myself). The coil suppressor always seemed to be missing and always seemed to solve the problem, at least as I recall.