I am going to be installing a 23' whip antenna for a new SSB radio
installation on my boat. My vessel is all-aluminum construction with a
center pilot house. How would you suggest mounting this antenna on this
vessel? I understand that it is important to keep the whip from coming
too close to any metal. This is an obvious problem, since this boat is
all aluminum. Any suggestions or references would be appreciated.
bradleyj

Ho Boy! Lots of feedback again, here. I would try to keep in mind that
the lower frequencies are what will be useful in attracting USCG and
commercial vessels in the 100 mile range. Not too familiar with East Coast
HF traffic, but here 4125KHZ would be useful. On these lower frequencies the
17' whip isn't likely to perform any thing like the 23' whip you mentioned
earlier. Some auto tuners will be jumping in and out of tune as you transmit
with either the 17' or 23' as your craft rolls and pitches in a stormy sea.
I'd opt for the 23'er for 4125 any day.
Look closely at the lower swivel mount you intend to use..... I'm not
sure there are any stainless swivel mounts on the market that will allow
free movement in more than one plane. If you use non-metallic line (I guess
we're talking synthetic braided rope here) for guy wire/line support,
there's GOING to be movement judging from the size and shape of the vessel
in the picture you posted. REAL MOVEMENT! It will surely make short work of
that lower mount.
As a practical matter, when the seas get snotty, and your engines are
swamped out, you don't need a downed antenna thrashing around the gunnels
after the bottom end of the antenna has suffered a failed mount, or one of
the guys has parted.......... now is when the radio is supposed to earn it's
keep. More than one of my old customers can tell you all about why the SSB
using a well anchored emergency battery is worth all the fish you've got in
the box.
I still think the best compromise, by far, is the old hat system of a
two-piece mount on a vertical surface, metallic or not. You may lose a
percent or two of efficiency, but at least you'll have an antenna. If you
absolutely must use guys, (perish the thought), use good stainless steel
aircraft type cable, available at most larger general hardware stores, and
insulators at the lower end of the cable. "Egg" or "aircraft" in-line
insulators work ok, and they prevent the guy wire/cable from being part of
the ground system. From the looks of your picture, the guys are not going to
be long enough to be any substantial part of a wavelength on the lower HF
bands, so a single insulator at the end nearest the pilothouse overhang
would do it. The "egg" or "aircraft" type insulator, if you are not
familiar, is designed so if the insulator cracks, breaks or disappears, the
two cable or wire ends find themselves looped together and the guy only
gains about an inch or so in length.
Another thought, The Shakespeares (smashed by heavy seas) that I've
seen, have the radiating wires, four, usually, imbedded in the fiberglass
shell fairly near the surface. If you drop a plate over the fiberglass to
attach guys, try to provide something to keep the plate from working around
and wearing through to the radiators not far under the gelcoat.

That's my story, and I'm sticking to it......
Old Chief Lynn