I must confess to being rather puzzled by these reports. The tuner in my car (when I had an empeg installed, newish car at the moment, haven't had time to fit one, etc) didn't exhibit the behaviour you describe. I have talked to a number of people I've supplied with tuners, and they all work fine as well. There was one I got back from a guy in germany that had been having similar problems, but I was unable to duplicate the results even after much fiddling and testing.

The best explanation I have so far managed to come up with was suggested by a friend of mine who has considerable experience in the radio industry. He said it might be an issue with RDS in some way, quite possibly due to overenthusiastic auto-retuning. Apparently he had seen similar behaviour in some car radios where the receiver happened to be more or less equidistant between two FM transmitters from the same station, and kept switching between them looking for the strongest signal. If the pre-emphasis on the transmitter was slightly different on each, you would get an apparent change in high-frequency response, and sometimes bass.

He also suggested if it was rapidly switching between stereo and mono reception for similar reasons the result would be quite like that described. I'm not sure that the empeg RDS software exhibits this behaviour or not, but if it does it may be a partial explanation.

As to why some people seem to get a strongish signal in the absence of a tuned station, I really don't know. Again, possibly it's a software issue with particular types of antenna producing distorted or overloaded signals, but this only a guess. I haven't been able to produce the fault here at all. The things either work correctly or don't work at all in my experience.

Can I suggest that if you are getting this behaviour, you try unplugging the antenna completely when tuned to a local station? If it happens to be a very strong one, you should be able to receive it reasonably well with no antenna at all, or just a few inches of wire stuck into the antenna socket. If this works, it might be worth trying an inline attenuator between the car antenna and the tuner. The modules are extremely sensitive, and it's barely possible they're being overloaded by a local, very high-output transmitter.

pca