http://www.walcottcb.com/product_inf...roducts_id=920

Best $39 you'll spend on radios. You don't know what the condition of the
transmitter or antenna really is. This little meter will tell you what
it's putting out and whether it's going out the antenna or just coming back
from that rotten connection at the base of the mast.

Self powered. Simple to use. Instructions are in the box.

Most problems in a boat are antennas. Of course, antennas can zap the
transmitter on a cheap radio. Cheap radios don't have protection circuitry
in them.