Audio Systems: Car antenna problem, car antenna, power antenna

Question
Recently bought a power antenna for my car.

After it was fitted by the supplier (Auto One)
- it would not receive any station and they replaced it with another.
Now, the replacement gets two FM stations and zip on the AM band - not even the local AM about two klicks away.

The radio works perfectly with the old non-power
job.
The new one (which goes up and down perfectly, you beaut!) is completely RS for reception.

The guy at the shop is head scratching, I'm doing somewhat similar and we are both wondering where to go. I mean it's only a lump of steel that picks
up RF, isn't it?

It's an Aerpro model AP4 BTW.

Any ideas.........Thanks Don  

Answer
HI Don.
The antenna is just a steel rod that picks up RF, or as we call it in the trade, "a twig", sticking 6 feet of cable in the RF socket of the head unit and chucking it across the roof will pick up most stations, it's that technical and a trick I suggest if the antenna is suspect as it takes the possibilty of a duff head unit out of the equation.
Common faults with "twigs" are, in-line connector under the trim undone, (3 cases this year), No earth on antenna, broken inner wire on coax. (two cases) and trim bolted or screwed down through or cutting cable.
A few things to check between head scratching.
Buy an extension cable, say 5 meters, and run it from antenna to radio outside trim/car so if that sorts it out.
Good luck , Peter