Joe:

Please take this OK -- there are parts of boating in which I consider
myself expert -- but this isn't one of them. I flunked out of the EE
school at Cornell a long time ago, so I'm really trying to learn here,
not be argumentative.

I have two questions about what you wrote below:
First, am I correct that as far as choice of antenna is concerned,
receiving and transmitting are the same problem -- an antenna that
receives well will transmit well, and vice versa? If so, I don't
understand why you start off with, "...we are talking about a simple
RECEIVE antenna here." If you're trying to pick a weak signal out of
the noise, I should think you'd want as good an antenna as possible.

Which brings me to the second question, or perhaps I should say
"objection" to your comment. My experience with receiving weatherfax
is considerable -- in several oceans, from many different stations, on
a daily basis. It was all in 1995-98, which, IIRC was a low sunspot
year. We had both an insulated backstay on an 82' mast and a 23' whip
and a lot of well bonded copper screen for the ground under a Furuno
1502. The weatherfax stations were never as loud as medium frequency
broadcast stations and were often much more difficult to copy
successfully.

Now, I can't speak directly to how good our installation was -- a
professional did it, but that might be good and might be bad, so all I
can say is that we did talk to people all over the Pacific with no
problem.

Now for a question on which I am soliciting opionions as widely as I
can. We're going to have SSB on Fintry (as well as Inmarsat C and,
probably, one of the low orbit services -- Iridium or one of its
cousins.) The usual choice would be a tall whip hung top of the
wheelhouse about six feet from the mast. We could also do a long wire
from the jackstaff on the bow to the top of the mast -- 44 feet at
about a 20 degree angle from horizontal. Which would you chose and
why?

Thanks,


Jim Woodward
www.mvfintry.com


"JAD" wrote in message ...
Jim, in answer to question #1...we are talking a simple RECEIVE antenna
here. Insulated backstays and whips are used with HF-SSB TRANSCEIVERS. In
another vein, there are a whole slew of boaters here (mostly hams for
recreational use) that "load up" the ENTIRE standing rigging (on fiberglass
sailboats) against a good ground for a really fine antenna. No good for
offshore where salt water may ground the rig at the chainplates....or where
someone my grab something during TX.....but it does work and it works well
(again, for RECREATIONAL HF use.) Shoot...there was a thread here not long
ago about guys loading the entire standing rigging against the lifelines and
toe rail......and THAT supposedly works, too. Building a good capacitive
ground can be difficult on some boats.....but sure is the best choice. Any
boat doing serious offshore cruising should have a properly insulated
backstay or large whip for an HF antenna.

As far a question #2 is concerned....see Meindert's post above. The ARRL
handbook presents some antenna designs....but not ALL of them...and not all
of the GOOD ones....... I can tell you, as in my original post...connecting
a receiver to my old boat GROUNDED (to keel bolts....lead
keel....encapsulated somewhat,) standing rigging, produced one of the
quietest, best performing receive antennas I have ever played with. I did
not ground the rig on purpose for this arrangement....is just the way it
was. In the marina...where stray currents and noise abound....the receiver
worked like a champ on ALL HF bands.

And...to the guy who says receiving broadcast stations and HF telefax is
different......I say..NUTZ! If you have a good antenna, the signal is
there....AND there is good signal / noise ratio...you should receive
quality faxes. Simple as that. Knowing the wefax broadcast schedule and
location / frequencies of the stations would help........

Fair winds....'73
Joe
"Jim Woodward" wrote in message
om...
OK. I know just enough to be dangerous here. In an effort to learn
enough to be even more dangerous, I ask two questions:

1) If this arrangement yields a satisfactory signal and a better SNR,
then why does virtually every crusing boat use an insulated backstay
or a whip? Remember that we're talking about weatherfax, which is
often difficult to receive.

2) I note that the ARRL Antenna Handbook devotes a full chapter to
loops. All are carefully isolated from ground at all corners -- the
ground comes after the matching network. Am I missing something?

Jim Woodward
www.mvfintry.com

"Meindert Sprang" wrote in message
...

In this configuration, the mast and standing rigging work as a magnetic
loop
antenna, which *should* have something you would call a short-circuit to
ground in order to close the loop. A loop antenna picks up the magnetic
component of a radio signal and is far less suscebtible to noise than a
whip
antenna (single isolated backstay too).

Meindert