1999 RX300

I sounds like a simple case of electrical interference from the vehicle ignition. Regarding the fluctuation when under the bridge, I suspect the overall reception is reduced, but the electrical interference remains the same, giving the illusion of an increase.

Unfortunately, although I have heard of suppressors to control this, I've no direct experience with it, other that from the perspective of one having experienced the problem.

Surprisingly, there is either not much on the net related to this, or I was just inept in building the correct search.

As kids(aka teenager drivers), we simply started at the ignition leads(aka spark plug wires), and replaced every component until the interference was either tolerable or disappeared. However, in today's vehicle, I would've thought that would no longer be a problem.

Typically, a high performance type ignition lead would significantly increase this interference. Or, possibly what we thought were high performance were really just cheap unshielded junk. Is it possible that your leads had been replaced by something non-OEM?

However, I did find these:

. A reference to a Popular Electronics article of February

. A reference to a Skinned Knuckles article from January

http://64.233.167.104/search?qÊche:Y5yPYHlRUasJ:

The radio is not getting good reception or there is interference from an electrical source in or near the vehicle.

Check to make sure the antenna connections are secure and that the antennas are not damaged. I think that your RX has two antennas - the mast antenna and another one embedded in the glass in the right rear window or rear hatch class.

If the interference is related to engine RPM and you have had the spark plugs and/or spark plug wires replaced, then use OEM ignition parts as aftermarket parts sometimes cause the problem you are describing.