Thanks very much for the comprehensive answer. Fintry isn't a sailboat (see
http://www.mvfintry.com/pix/felev800.png ) but she does have a mast and
already has the insulator in the wheelhouse top. The 48' is the distance
between the bow and the masthead -- the masthead is about 15' above the
wheelhouse top. And the ground is easy, as the boat is steel.



--
Jim Woodward
www.mvFintry.com


..
..
"Bruce Gordon" wrote in message
...
In article ,
"Jim Woodward" jameslwoodward at attbi dot com wrote:

I hoped you'd have some thoughts here, Bruce, because you've always made
a
lot of sense in this general area.

For Fintry, for use primarily for SailMail and talking to Herb
Hilgenberg,
would you use a whip or a wire? While we could shout for help on 2182
and
everything else available, little else will happen below 4mhz.

Wire would be between jackstaff and masthead, about 48' total. see
http://www.mvfintry.com/pix/felev800.png for a profile drawing, although
the
jackstaff doesn't show. If this is your choice, where would you put the
insulators? The tuner would presumably go at the base of the mast.

For a whip, I've been looking at the Comrod AT100, which is easy to get
in
the UK. http://www.comrod.com/v2/Marine/pages/mar_1.asp

Fintry is steel, with an aluminum wheelhouse, so grounding is easy.


Thanks,


--
Jim Woodward
www.mvFintry.com

Jim,


If it was me, and I am by no means a "Sailer", but just an "Old Fud"
with 35 years in the Marine Electronics field, and I wanted the very best
MF and HF Rf Anrenna System for a wind driven vessel, I would build
the BEST Grouding System possible into the hull. this because a good
ground makes up for a lot in antenna design, and a bad ground can't
support even the absolute best antenna. For an antenna, I would side
mount a 28Ft Straight Morad whip at the top of the mast, with 18"
standoffs, and then connect that to a vertical PhosperBronze wire,
suspended by 6" insulators, straight down the mastline, keeping it at
least 12" away from any of the grounded halyards and stays that hold the
mast up. Then take the antenna from the PhospherBronze to a 6" Ceramic
ThruHouse Insulator with GTO-15, and on the inside another GTO-15
jumper to the antenna tuner. Connect the antenna tuner to my BEST RF
Ground System, with 4" wide copper foil layed against the bulkhead and
fixed in place with a coating of fiberlay resin.

Resaon for a Straight Whip over a Loaded Whip? (Morad makes both kinds)
No funny impedance bump at the loading coil frequency, for the autotuner
to figure out. Autotuners firmware really don't do well when faced with
complex impedances coming from the antenna, and they absolutly will not
tune 1/2 wave frequency of the antenna system. So pick a antenna system
design that puts the 1/2 wavelength point in a section of the band you
never want to transmit on. Back before autotuners, when all Marine Radios
were channelized and fixed tuned, a loaded whip was very nice to use, as
it provided a much better way to get a lower impedance at 2.0 Mhz and
one could be sure that the tuner wasn't tuned to a "Kinky" or False
node on the antenna, but with auto tuners this is left to the firmware,
and you can only put so much code in the tuner to account for stange and
"Kinky" antennas.

The above antenna system give you 28 Ft of whip plus 48 FT of mast plus
a few ft of GTO say 3, for a total of around 80 Ft vertical. Now that
would be just about 3.0 Mhz for a 1/4 wave and long enough to very good
at 2182.0 Khz and easily within the tuning range for most autotuners at
2.0Mhz. It also puts the 1/2 wavelength around 6.1 Mhz which is a good
place for a marine and Ham dual use antenna system to be.

Now most "Sailers" will have some problems with the above for a variety
of reasons, but I always like to say, "Do you want it to work, or do you
want it to look good, and, or, be out of the way and not a hazard to
ussuspecting guests who should never leave the cabin in the first place."
This is the Age Old Question. On BIG Ships the antenna systems for LF,
MF, and HF are always on the top of the Wheelhouse or on the next deck
aft. They are there for a reason. To keep them away from the crew
running around on deck. On a wind powered craft this just isn't possible
so the next best thing is to keep the people relativly away from the
antenna, and if they do get burned well, "That's a Sailer's Life".

I once did a SOLAS Inspection on a 100+ ft Sailing Rig that had a
complete Radio Suite installed. It had a Top Hat offset mounted at the
top of the Mainmast forward, for 500Khz, and a loaded whip offset aft
for MF. Both were feed by seperate Phos/Bronze feeds fron the Radio
Shack which was directly under the mainmast. HF antennas were just
straight wires running down like halyards from the spreader at 50 Ft.
on the mainmast. Vhf was a pair of Morad 156HD's side mounted on each
side of the Crowsnest, just under the LF and MF antennas at 80ft, and
1/2" heliax running down a milled grove in the mainmast. The operator
was an Old Seadog, who retired from Tramper Service on the China Run for
American Presidents Lines, and he used to work his buddies every day on
Cw, voice, and tty, and had the Logbooks to prove it. The inspection
went off without a hitch, and I was very inpressed with the installation
that this Old Boy had done on a replica vessel.

Bruce in alaska

--
Bruce (semiretired powderman & exFCC Field Inspector for Southeastern
Alaska)
add a 2 before @
Bruce Gordon * Debora Gordon R.N. Bruce's Trading Post
P.O. Box EXI Excursion Inlet South
Juneau, Alaska 99850 Excursion Inlet, Alaska 99850
www.btpost.net www.99850.net