In article ,
"Jim Woodward" jameslwoodward at attbi dot com wrote:

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.

Looks like your "In the Groove" Steel Hull big Plus. Straight 28' whip
sidemounted on mast, plus 15' wire = 43' of wire. That makes this 1/4
wavelength at 5.6Mhz and 1/2 wavelength at 11.someting Mhz. Again this
is a good place for 1/2 wave point for an autotuner. The antenna is a
bit short for good MF Operations, but almost ideal for 4 meg Marineband
when working against a steel hull. If you get any shorter, the voltage
nodes in the autotuner, will be pushed passed the breakdown voltage of
the tuner capacitors and relay contacts that they work on, which will
cause PCB breakdown and burnt relay points when tuning at anything over
50 watts. This has always been the weak point in autotuner design since
the original Motorola Micomm HF systems of the late 70's and early 80's.
The design criteria just doesn't make for good service if the antennas
are too short, the frequency is too low, and the power is too high.
SEA tried all kinds of different ideas to correct this, including but
not limited to:
1. Double the number of relay points per step for that part of the
capacitor range.
2. Double the number of capacitor steps, in that tuning range.
3. Both of the above
4. Diddling the firmware and changing the Phase Detection circuits
for better detection in this range.
In the end, it was just cheaper, and simpler, to tell the customers and
installers to put more wire on the antenna, or not use it below 1/4
wavelength plus 50% We used to have a lot of traffic on 2003Khz,
2006Khz and 2009Khz, and you just got to have more wire to make that
work well.


Bruce in alaska
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add a 2 before @