Noise through speakers when electric aerial extends

[uncle]

My 1988 VL Calais has an annoying problem when the electric aerial extends. There is a very loud hash/electrical static noise through the speakers which is interference coming from the aerial motor. I can lower the volume of it by using the volume control on the radio (original). This happens 98% of the time - there have been few odd occasions when the aerial has extended without the noise. I suspect that there is a faulty capacitor or suppressor either in the radio or near the aerial motor. Can someone point me in the right direction?

[simon.w]

Hi uncle - few questions.

did the problem occur over a period of time?
did it happen when you fitted a new antenna?

There are a few things you can try, however the problem is that noise is probably feeding straight into the back of your head unit through the coax cable. This may happen due to warn brushes in the electric motor... If this is the case, a new antenna is the fix.

If it has occured over a period of time, there is a possibility that the antenna earth has degraded due to corrosion building up around the mounting hole. Powered antennas can get their -ve through the bracket that mounts under the guard - so if this has gone rusty, you will have problems. First thing I'd try is removing the antenna and cleaning away any rust, and spraying it with WD40.

If it's still there, I'd try a power filter on the main power feed into the head unit. There are a couple of different types available at Jaycar: Jaycar Electronics

You could try running the antenna power feed through one of these too.

This probably won't help if warn brushes are causing the problem.

[uncle]

Thanks simon.w, you are a great help.
I'll look at the earth first, shouldn't be worn brushes. I bought the car 2 years ago, had only travelled 50,000k and had been sitting in the garage for 16 years after the previous owner died. The noise problem was there when I bought it.