Car Stereos: FM Reception, antenna connection, antenna cable

Question
I have a new system with a JL Class D amp. The FM reception is terrible. My installer says it is interference from the amp that is normal with Class D amps. Is this correct and what can be done to make reception better.

Answer
Hi Barry,

There's a very good possibility that the amplifier is affecting your FM reception.  This is something that does sometimes happen with Class D amps; I haven't found it to be very common, but it's certainly a known issue.  You can verify this by disconnecting the "remote" wire at the amplifier, so it doesn't power up, and test the FM reception with the amplifier off.  If you still get poor FM reception when the amp is powered down, then something else is causing the problem--there may be an antenna connection, behind the radio or elsewhere in the vehicle, that was disconnected during the installation.

If it's clear that the amplifier is interfering with the reception, though, there's really not much you can do.  You might try relocating the amplifier to another location; it's possible that placing the amp further from the vehicle's antenna or antenna cable may help.  I don't know of any filter or antenna booster that will help in this situation.  You can also try re-routing or changing the length of the speaker cables.

This problem has been rare enough that I really haven't been able to experiment with possible solutions, so if you find something that works, please let me know.  If all else fails, you can try switching to a different amplifier.

Good luck!

Brian