counterpoise for the tuner and antenna is a twin ladder 450 ohm ladder
side of the vessel either port or starboard, cut the ladder line at
approximately 42-47 feet. This counterpoise has good RF resistance for
frequencies in the low marine bands, which also support the amateur bands.
opposite side of the vessel, again below the water line, the same 450 ohm
ladder line material, is cut to 32 feet from the start of the autotuner.
This line gives a good RF resistance and reactance to the auto tuner for the
bands below 12 MHz.
best to have the lines on the port and starboard side separated by at least
ladder line should be any length from 32 to 27 feet for the one side of the
ladder line and the second side of the ladder line is cut to 17 feet. This
side supports the higher frequencies, from above 12 MHz.
between the radio and the grounding plate
install a DC Block, which is simply a couple of one-way diodes to stop any
DC voltage looping around in the system. This dramatically reduces noise in
your radio system.
This DC Block specifically designed for marine frequencies is available
on the How to order page.