jeffsims

Factory AM radio w power antenna in my 67 442. No engine noise, but when I raise and lower the antenna, I get horrible feedback through my speakers. Any ideas? The antenna is mounted to the passenger rear fender.

Lady72nRob71

You may have a defective or missing condenser (capacitor) that helped suppress this noise. They were commonly used at the horn, blower motor, and other electromechanical parts that sparked normally internally. I know these caused a lot of problems with AM, but probably less with FM.
Also make sure V+ connections and antenna ground are secure, as well as other body grounds.

jeffsims

I have one on my coil and one on my voltage regulator. Could one or both of these be causing the problem? No engine noise though. Is there supposed to be one on or near the antenna motor?

Koda

Is the radio on or off during this?

jeffsims

Radio is on. No problem when radio is off.

Koda

Did this behavior just start? If it's always done this, perhaps the best solution is to
put the antenna up, then turn on the radio, then turn off the radio, then put the antenna down. I think what it is doing is sending crap signal to the speakers through the antenna wire when the power is on.

RandyS

There is an item called a 'ferrite choke' (a small clamshel like gizmo) that you can snap on around your antenna wire and it should block the noise on the wire. They are often used on DIY FM transmitters and such to block extraneous noise. They are available online and I believe Fry's and Radio Shack carry them.

jeffsims

Thanks for that tip. I am pretty close to a radio shack and will check on one during my next trip.

Lady72nRob71

To be effective, the condenser needs to be placed close to the device making noise.
The condenser near the coil suppresses noise from the sparking of the points.
The condenser near the regulator suppresses noise from the sparking of the regulator's contacts.
There is one right at the blower motor to suppress its noise.
The one for the horn is at the steering column connector, which is not too effective, but if the horn works, it drowns out any radio noise.
If the antenna had one it should be close to the antenna motor. Or maybe it was under the dash. However it will be connected to the motor's wiring to chassis ground. Hopefully someone with this setup can confirm if there was one originally installed. Many times parts get removed and scrapped when they are removed and their use is not easily understood, such as the watershields in the doors....

radioburningchrome

Every GM B-body car that I had with power antenna (my father bought a new 1965 J-88 with power antenna) all had some noise through the AM radio.

Noise harmonic frequencies fall within the AM band, that is why you hear it through the speakers.

Clean the ground wire connection on the antenna mast, apply dielectric grease. Check all radio and speaker grounds.

When you have a bad ground, the circuit will use the next available path to complete itself.