Jim, first off, no argument intended! Just discussion! Perhaps my use of
caps????

Anyway, my original post was to answer the guy's question about a simple
receiving antenna for his weatherfax on a small sailboat...thus my comments
on my experience with receive ONLY antennas.

YES....receive only antennas and antennas that are required to transmit AND
receive are different. More on this in a moment...

As to the fact that broadcast stations were easier to copy then weatherfax
stations at THAT given time, location, propagation, and goodness knows other
factors....there is no surprise to me....BECAUSE of so many factors
involved. I'll be willing to say that the transmitter power of those fax
stations was FAR less than the comparable broadcast stations....but that
would only be ONE factor describing your reception at that time, location,
propagation etc... See where I am going? Impossible to predict
everything, or explain everything in long-distance radio.

By the way, FINTRY is one gorgeous boat! I had a look at her on your site
to see where (I) would put an HF antenna. Here's what (little) I know as a
sailor: First....your boat looks like a trawler...a general description of
this style boat, that has become VERY popular with serious motor-cruisers as
of late. You are going to find many other folks with HF stations on this
style boat...and I would sure get in touch with some of these people to find
out what THEY are using. I'll bet most use a WHIP antenna.....but the true
rule-of-thumb for an HF antenna is to go as LONG as possible to get the best
performance! MY GUESS would be to go with the (insulated) WIRE for the
reason of LENGTH alone.....but this wire at 20 degrees off of the horizon
might not give you all of the "local" (50-200 mile) performance you might
desire, due to polarity being mostly horizontal, and MOST other marine HF
stations antennas out there being polarized somewhat vertical. Someone
(hopefully from EXPERIENCE) may comment on NVIS and other factors to support
/ poo-poo my thoughts here....PLEASE DO! That is why I titled the post that
way....hopefully other "trawler" style boaters will contribute something.

The BEST signal I have ever heard coming from a boat (given the distance and
propagation conditions at the time,) was from a STEEL sailboat with a 33ft
!!!??? whip off of the transom, according to the operator. 33ft whip? Who
makes such a beast....I've never seen or found them advertised. BUT...a BIG
doggone whip well supported up on that wheelhouse might be the ticket! NOT
the little 23ft whips commonly available....

It seems that you know something about a proper capacitive ground, and it's
ABSOLUTE NECESSITY for a good TRANSMIT signal....she's a WOODEN boat, eh?
Build the most elaborate ground you can, with AS MUCH area below the
waterline (and bond the engine, tanks, metal through-hulls ad nauseum) as
you can. Whatever long antenna you choose, the ground will be the MOST
IMPORTANT factor in signal output besides the transmitter and antenna tuner.
Take the ground stud of the radio itself to some point in the ground with a
wide copper foil (as well as the tuner,).....the tuner should be as close to
the FEED POINT of the antenna as possible. Bring AS MUCH of the ground
complex to the ground of the tuner as possible, using multiple legs of
copper if need be....with the tuner as the "apex." Steel yachties have it
easy....and often have the best signals on the water....a near perfect
ground with the whole damn hull for signal to "push against."

LEARN TO USE the antenna tuner properly. MOST of them will bypass the
"tune" function in some way....most common is to cut the power to the tuner
and then turn it back "on". (THIS circuit breaker goes separately right next
to the radio operation position, if the electrical panel is elsewhere!)
Puts the tuner into a "bypass" mode in which the transceiver is connected
directly to the antenna. Try this for reception when tuning across
different bands looking for something. That way, you are not tuned to only
the last frequency in use....to the detriment of others (sometimes, to the
detriment of others in the same band!) If your "tune" button on the
transceiver works (hopefully with very low TX power) on all
frequencies....in theory...if the tuner tunes to resonance...it should
RECEIVE better while tuned....but is easier to find a broadcasting station
in the bypass mode FIRST. I am by no means suggesting that you should
transmit (even for a second or two, even at low power) on frequencies that
you are not licensed on. THAT'S what the "bypass" feature is for!

Hope this helps just a little bit, as I'm no "expert" either, Jim! There
are quite a few guys on this group that will contribute more direct answers
to your good questions, and if I've scared them up from the deep...I have
done OK!

Good luck with that wonderful boat!

Joe


"Jim Woodward" wrote in message
m...
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