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The behaviour you describe does kind of smell like a weak antenna signal that's on the borderline of okay for the tuning section when you're not driving and somehow becomes weaker when you're on the road.
o Any chance where you park and idle your car is in a better reception area, like parked out in the open or living on a hill or in a less built up area and away from power lines, while where you drive the car is in a poorer reception area, like lots of nearby buildings, in a valley, or in amongst lots of traffic?
o As others note, all connections and grounds for both the antenna and radio of course have to be solid, including a separate ground from the radio chassis just to be sure.
o You may have a ground loop. Check if the antenna base is isolated from the chassis at the mounting. It is best to have the antenna cable shielding grounded only at the radio chassis. Unplug the cable at the radio and if there's any continuity between the cable shield and chassis ground then it's not isolated. Despite what you might think and what many people say, it is actually the proper way to do shielding, as Art Benstein here once educated me.
o The antenna of course needs to be fully extended and long enough for the job. The stock position of the 544 antenna appears to be on the low front fender, beside the rounded side of the raised hood, not too far from the A-pillar. The lower 6"-8" of the mast isn't doing much good in that position. If you draw a straight line between all the high points of your car, that envelope is more or less the effective base of the antenna. The part of the antenna that extends above that envelope (as measured perpendicular to the surface of the envelope) is what's picking up the strongest signal (more of the wavelength), so the longer it is the better (within reason). The best place for an antenna is up on the roof and if it wasn't for things like garage doors, parkades and low hanging branches that's where they'd be, also out of the easy reach of vandals. Shark fin antennas on the roof are a compromise, trying to get the best signal with the least amount of antenna, using coils and signal amplifiers to try to make up for the loss of signal due to short length. Newer radios are also much better at being able to use weak signals, although with less and less people listening to AM/FM while demanding higher quality sound, more component space is needed for satellite, bluetooth and the audio section. The newer and decently rated Sony's I recently put in my 940s are not overly impressive when it comes to AM/FM reception compared to the stock radio, but of course the in-glass antenna used in the 940 wagon rear quarter panel windows doesn't at all help, but I digress....
o Any chance the shielding of the antenna cable is damaged somewhere along its run or it's near major electricals or moving mechanicals? Best not to run the antenna cable too close to things like the ignition coil, wiper motor, wiper arm linkages, fan motor, etc.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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