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(Roger) wrote in
om:

I am installing an Icom 802 ssb with a 140 tuner. I am looking for
advice/experience on the difference in performance between
Shakespeare's 17'6" whip vs. the 23' whip.

In any HF radio installation, the closer the antenna is to resonance (1/4
wavelength long or 1/2 wavelength long) at the desired operating frequency,
and the further it is located in the clear from CONDUCTIVE surfaces, the
better it operates. 1/4 wavelength, in feet, is 234/frequency in
megahertz. 234/8 Mhz = 29.25 ft. So, the 23' antenna at 8 Mhz requires
less loading coil than the shorter one. quarter wavelength, or shorter,
radiators require a good ground system to operate properly as that creates
an "image antenna", in a boat underwater, to make a half wave dipole.

Marine radio HF uses 2, 4, 6, 8, 12 and 18 Mhz, mostly the 4-8 Mhz
frequency bands at night and 8 to 12 Mhz bands in the daytime is best.
It's easy to get either whip to radiate on 12 or 18 Mhz. As of this
particular period, you'll find few signals on 18 Mhz. Our ham 21 Mhz band
has been dead, really dead, for weeks.

So, the longer the whip, the better on these lower bands.

I have a sloop with a split backstay and probably will go with a
whip.I only have about 3' between the antenna base and the mounting
clamp on the transom. Insulating the backstay and running the feed
wire along the split (through the bimini) is my second choice.

"Lionheart" has a 50+ ft long insulated backstay length to the insulator
near the mainmast. She had a very nasty problem as the boom's lifting was
a stainless steel cable, grounded to the mast, which just sucked away the
RF signal any time the boom was anywhere near centerlined. Replacing the
steel cable with nylon eliminated this problem and still holds up the boom
quite nicely. At 50 ft long, the resonant 1/4 wave freq of the backstay is
around 4.6 Mhz, making her have great signals from that frequency up and a
very respectible signal even in the 2 Mhz band when she has lots of loading
coil inline (the tuner). This length of antenna is near 1/2 wavelength on
the 8 Mhz band. A 1/2 wavelength antenna, end fed at the bottom by a good
tuner, requires no ground at all to "get out" well. (The Metz VHF antenna,
for instance, is an end-fed 1/2 wave on 156 Mhz Marine VHF. It requires no
ground at all.) I sat at E-dock at Ashley Marina in Charleston, SC, and
talked to Hawaii, Australia, Japan and New Zealand on the 14 Mhz ham band.

Is the backstay grounded at the bottom end where it attaches to the
fiberglass? Most aren't. So, you only need one insulator, about 2' from
the top of the backstay to form the antenna. To feed the split
configuration, which is fantastic for a wideband antenna, put the tuner
between the two splits at the bottom, and run two, equal-length wires from
the tuner's high voltage output antenna terminal to the bottom end of both
port and starboard mountings. A good grounding strap to the battery
negative terminal the shortest path possible, completes the installation.
The longer backstay will easily outperform the short whips on the lower
frequency bands. Another great improvement when you are cruising is to
keep 100' of small cable attached to the ground terminal of the tuner.
Throw this cable off the stern with a small drag on its open end to make it
lay out in the sea behind the boat. This makes an AMAZING RF ground! Just
don't forget to coil the cable back up before entering any port and backing
into it under power. 100' of 1/4" or smaller stainless wire or
"copperweld" antenna wire that won't corrode is great. Tie the wire to any
handy handrail post or other tie point then run a slack wire to the ground
terminal on the tuner. Retune every time you change from trailing wire
ground to no-trailing-wire-ground condition as the impedance of the antenna
system changes a lot with changes in grounding condition. It's always a
good idea to push the tune button, even if the Icom is a happy camper....

Larry W4CSC
S/V "Lionheart"
Amel 41 ketch
WDB6254
MMSI 366920680

PS - you only get TWO chances to put the MMSI into the Icom. Follow the
instructions in the manual very carefully....
Call us on DSC HF...We'll do lunch!...(c;