Does anyone know about an antenna for hf using the backstay un insulated and
also connecting up to the stanchions. I think it is called a ground effect
antenna, I used one years ago offshore and it worked great, I want to
install it on my current boat but am a bit fuzzy on the details.
Thanks a lot Bob

Bob Owen wrote:

Does anyone know about an antenna for hf using the backstay un insulated and
also connecting up to the stanchions. I think it is called a ground effect
antenna, I used one years ago offshore and it worked great, I want to
install it on my current boat but am a bit fuzzy on the details.
Thanks a lot Bob

Most backstays are attatched to the hull without being bonded to
ground, so additional insulators would not be required, unless
you were to put one at the mast head, which is an option. An
insulator bypass switch at the masthead, similar to HT
disconnects seen on every hydro pole at distribution transformers
could be operated with a lanyard. Such an arrangement needn't
weigh much more than a lonely insulator, and might provide some
entertainment, even sustenance, if zorching birds is your cup of
tea. If you do not use a masthead insulator, the mast and shrouds
would become part of the driven element system, increasing low
frequency efficiency in some cases, and possibly affecting
directivity on some frequencies. The mast base will normally be
grounded to the lightning ground and means that with no masthead
insulator the backstay, mast and shrouds become an inverted "V"
with 'whiskers' at about its mid point.

The shrouds may be grounded if the chainplates are connected, or
they may be left electrically unconnected at the bottom ends.
These elements, if part of the driven portion of the antenna
system, may be insulated with tubing if if makes you feel safer,
but it is unlikely thay you will be holding on to them while
transmitting, or that sufficient voltage will be there to cause
trouble, unless the 'toastee' was holding on to an uninsulated,
ungrounded, driven shroud and possibly a grounded lifeline, and
you had high power in the transmitter.

The lifelines and stanctions bonded to ground or disconnected
from the grounding system can be used as counterpoise for the
backstay with or without a masthead insulator.

Some form of tuning network could be arranged to maximise
radiation efficiency depending on configuration, frequency and
directional requirements.

I beieve that bonding metallic parts to a common grounding system
is the prime enabler for galvanic corrosion processes, and would
not permanently bond any part unless required for other purposes,
such as band switching in an antenna system for periodic use.

Every case is different. A clasically trained antenna engineer
would either explain that it would be very expensive to engineer,
might never work well and could be too difficult to understand or
master, or he would put on his ham hat and fiddle with it until
he amazed his friends. He would need to know the rig
configuration (sloop, schooner, etc) heights, angles, and spacing
of all the elements. An ARRL antenna book might help you to
appreciate some of the possibilities.

You can estimate transmission directivity by gaguing receive
sensitivity for distant stations. Changing headings while
monitering relative receive signal strength would give an
indication of directivity, as would changing angles of heel by
sheeting or easing sails. Major lobe characteristics may be used
to advantage in smart systems. Minor lobes can provide remarkable
results, but are unstable on a floating platform.

All of these considerations are in play, wether you utilise them
or try to ignore them.

Towing a ground strap or a floating dielectric insulated
radiating element might also be part of the plan.
Arranging extensive 'ground planes' inside the boat is
superfluous IMHO, as the sea provides the best 'ground' possible,
if you want to use a monopole system.

What hat are you wearing?
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Thanks guys, will take me a while to take all this in but will add to my
arsenal Cheers

Bob Owen

Bob,

Re using a sailboat's mast and all rigging as an HF antenna:

In my opinion using the entire rig, mast and all stays and shrounds as an
antenna would give one 1. a problem eliminating the ground connections of
every element while maintaining lightening protection for every element, and
2. depending on the frequencies used, it would produce a rather pretty wierd
and unoptimized set of radiation pattern "take-off angles", on the various
frequencies, especially on the higher frequencies. Also, generally the
radiation pattern on the mid to low HF frequencies, would tend to favor
medium range communications, (500-1500 nm), vs having good short range, (
500 nm), or long range communciations, ( 1500 nm).

Bob Cook K9KKY

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