marine stereo radio reception

[bigdude2468]

I get really crappy reception on two different boat stereos. They are good quality, one Clarion one Jensen. Both have external antennas not the crappy piece of wire that comes with them. Here is the thing I cannot figure out. If I touch either antenna, the reception gets much better, as soon as I let go it goes south. If I take a crappy $39 battery operated radio out it works fine. Almost seems like the radios are not grounded other than there is no ground on a boat, just the battery negative which obviously is connected or the radio would not work at all. Any ideas?

[YoEddy]

Propagation over water tends to polarize RF signal into the vertical component. Not sure what kind of antennas the 'good' ones are, but i bet they're more directional, and horizontally oriented, than the more omni shape of the 'crappy' one. Try an easy experiment - turn the good antennas 90 degrees vertically and see what happens.

The best solution will be to put an omni whip as high on the boat as possible (to help mitigate additional Fresnel Zone interference).

edit: of course this assumes you're having issues out on the water, or that the signal is crossing the water to get to you. If not, then it's most likely ... sunspots

[bigdude2468]

My fishing boat is aluminum and when I went to turn the antenna the FM reception got better when the connetion to the metal was broken. AM even for a local station still sucks. Why does the AM on the battery operated radio work just fine? Would a car type windshield mount antenna work or do I just need height?