I am installing a VHF radio in a 1971 Venture 21. I am handy, and want to make my own antenna (mostly, so I can easily repair it whenever it gets whacked on the trailer). I have read some helpful posts (Larry and Gary) on this forum which have generated some followup questions.

Using a borrowed SWR meter, I tested the old coax and antenna, and promptly threw them in the trash. I made a 1/4 wavelength antenna, which worked so well, I am thinking about making it permanent. My questions are related to this idea.

I understand the advantages of using a 3 dB antenna on a sailboat. Is this 1/4 wave whip, giving the same donut pattern as the commercial 3 dB antennas?

Is there any advantage in making the whip the same gauge wire as the center conductor of the COAX?

I can easily make some ground radials at any angle. Would this improve the transmission pattern?

Marine antennas have gain ratings such as 3 dB, 6dB. What are these numbers based on? What would be a 0 dB marine antenna?

I understand the basic fiberglass antenna is a vertical 1/2 wavelength dipole with a 1/4 wavelength whip above and a 1/4 wavelength coaxial tube below surrounding the transmission line. I am running my transmission line up the inside of my mast, so in a sense, I already have a 25 foot coaxial element (fed from the top and grounded at the bottom) with a 18 inch whip element above. This seems like a useful configuration, but I suspect I am missing something.

Comments?

Doug