[Elecraft] G5RV

[Ron D'Eau Claire]

It might look the same, but that's where the difference ends on the =
ships I
worked on. I was a civilian engineer working in the port of San =
Francisco,
but among the ships whose radio needs I took care of were fast Navy
transports like the USS Curtiss and really huge vessels like the 1200 =
foot
Hospital Ship USNS Mercy. What we had on those ships as well as =
"civilian"
ships was a "T" or top loaded vertical or an "inverted L".=20

I've strung a number of them in my day as the wire fatigued or corroded, =
and
with a single wire in the horizontal section weighing more than 100 =
pounds,
it's an exercise, let me tell you! But, in spite of the weight and size,
when it's configured as a "T", it's actually a *tiny* top-loaded =
vertical.

It looks like a lot more antenna than it is because of the differences =
in
frequency. Those antennas are designed to work as low as 450 kHz. The =
same
antenna at 40 meters would be about 1/16 the size. So if you have room =
for a
300 foot long horizontal section on a ship (200 or 250 feet is more =
common),
an equivalent 40 meter antenna would be only 19 feet long! The vertical =
wire
leading up to the horizontal is a single wire attached to the horizontal
wire might, if we're lucky, be 60 feet long. So that makes it only about =
4
feet high on 40 meters.=20

So adjusting for differences in frequency make that monster hanging on a
ship is equivalent to a very short mobile whip 4 feet high with a 19 =
foot
wire to act like a "top hat" on 40 meters. In most of the installations =
I
saw, they were configured with the feed near one end to act as an =
"inverted
L".

The antenna "feed line" became copper pipe hung on ceramic standoffs in =
the
radio room leading to a large switch (about a 8 inch to a foot in =
diameter)
for selecting which transmitter would be connected to it. True, the =
ships
did operate short waves and sometimes used these antennas, but more =
commonly
they used 20 foot self-supporting whips for those transmitters.

Indeed, for any ship following the international SOLAS (Safety of Life =
at
Sea) conventions, and that included a lot of Navy vessels who operated =
out
of civilian ports - like the Mercy and supply ships - the antenna used =
for
500 kHz could not be used for any other communications equipment. That =
was,
of course, to prevent any possible conflict between other essential
operations and monitoring the 500 kHz distress frequency. Another =
antenna
and set was dedicated to the 2182 HF distress frequency. =20

Of course, what made those *tiny* vertical antennas work was that =
absolutely
b-e-a-u-t-i-f-u-l ground plane under the ship that extended from horizon =
to
horizon!=20

Ron AC7AC


-----Original Message-----
I think if you look back in history, before G5RV invented this antenna, =
you
will find a very similar configuration on naval ships.  A multi-wire =
antenna
(4 or 5 parallel wires with a spreader at each end ) similar in =
appearance
to a hammock was stretched from the main mast to either a forward mast =
or
the forward half-mast. ...

Rich
KE0X



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