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Old 04-13-2007
btrayfors btrayfors is offline
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Andre,

OK. With the additional info you provided (boat size, it's YOUR boat, the M700 and tuner, your interest is in the marine bands, not ham, etc.), here are some options:

(1) Most versatile. Install either a Gam antenna (I can't believe I'm saying this) or, better, an "alternate backstay" antenna consisting of a length of insulated s/s lifeline at least 23' long. This can be hoisted with a spare halyard, and the lower end tied off to one side of the pushpit. With either option, locate the tuner under the deck as close to the base of the antenna as possible. With both options you need a good RF ground. Easiest of all, but not very efficient: run a wide copper strap from the tuner to the nearest bronze thru-hull. To increase efficiency, add radials under the deck (insulated wire, any size, the more the better). A couple of 1/4 wave radials (length in feet = 234/Freq in mHz) for each desired band would be sufficient.

(2) Most efficient for long-distance communications -- one or two vertical dipole antennas, constructed according to data referenced in the links I provided above. This is an extremely effective long-distance antenna. A vertical dipole is best rigged forward of the mast, about halfway between the mast and the forestay, tied off to a toerail. This placement works well when at anchor, in a marina, or when under power. When sailing, it's only necessary to undo the lower end of the dipole and pull it back into the shrouds. It will work fine there, but with a bit less efficiency. The coax feedline should be run off at a right angle, or as close to that as can be easily done. Usually, this means running it back to the mast high above the deck, then down the mast to the rig. On my boat, I've fitted a little custom-built "black box" attached just below the gooseneck, which contains connections for the coax and which is permanent. You may find it easier to feed the coax thru a deck ventilator, or a hatch or a s/s coax deck fitting or anything handy.

The dipole is a single-band only antenna. When tuned, it does not require a separate tuner...attaches direct to the radio. While it is possible with a tuner to transmit on additional bands, this is not a good idea and is very inefficient.

If I were making the trip you contemplate, I'd choose both: a versatile backstay antenna with tuner and good RF ground system which could be used on any frequency, and vertical dipoles for 14mHz (MM net) and 21mHz (Pacific Maritime Net) ham bands for really efficient long-distance communication. If you are not a ham or there's no ham aboard you can listen to these nets which have a wealth of information and, in an emergency, you could use them to seek help. For the trip you're about to take, ham radio is much more useful than marine SSB, IMHO.

Re: verticals, they can be very effective. However, for a very long ocean voyage I wouldn't want a 23' vertical (or even a 16' vertical) whipping around back there in a seaway. Not a good idea, IMO. They do make good emergency antennas, though, in case you lose your mast. I have a Hustler mobile antenna mounted on my pushpit and wired to an antenna switch near the rig. I carry the mast and resonators for several bands below, ready to deploy in an emergency.

Bill
WA6CCA

Last edited by btrayfors; 04-13-2007 at 10:13 AM.
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