Hello all

My new Sailing vessle (Beneteau 343) is on its way next year and it
will have twin backstays.

I like to listen to SSB and HF comms and have used active antennas
before on board with poor results always picking up more interferance
and timebase etc.

I plan to fit an insulated "wire" (using egg insulators) from the mast
head leadinng down to the transom area and use a a balun near the base
that will connect to the radio.

Can anyone suggest and pros and cons of this kind of setup and suggest
any better setups

Thanks
Franky

"Franky" wrote in
oups.com:

Can anyone suggest and pros and cons of this kind of setup and suggest
any better setups


Before you spend a dime on this project, connect just the center "hot" pin
of your receiver to the chainplate inside the boat and the radio should be
already grounded to the battery ground system just by hooking it up.

You'll be amazed at the signals on the shrouds, which aren't grounded in
most boats I've ever seen.

Our Icom M802 uses a separate receiving antenna for the GMDSS/DSC channels,
scanning them. I'm running a piece of RG-58 coax over to a convenient bolt
to the starboard handrail. The coax forms a Faraday Shield to stop the
receiver from hearing so much RF noise back at the nav station where the
noisy damned NMEA bus makes a racket. At the bolt, the shield is simply
left open, not connected to anything, while the center conductor connects
to a ring terminal on the bolt to the handrail post. The handrails on an
Amel are all welded stainless steel all the way around and all connected
together for this antenna. Works great. The handrail is not grounded to
the boat's battery negative or engine block.

Any long metal object not connected to the ground reference the receiver
uses is a good antenna.

Oh, almost forgot to suggest you get your nice receiver a lightning
arrester for any of these antennas. There's some nasty static discharges
that can destroy the receiver from St Elmo's Fire....or a direct hit, of
course.

Shh...don't tell anyone....the lightning protectors your cable TV company
use work just great for receiver protection! Don't use them on
transmitters or transceivers. If you're real nice to the cable guy, he'll
give you a few. He has thousands on his truck...(c;
Get the ones with the heavy wire terminal on the side to hook to ground.
http://www.comm-omni.com/tii/tiicoax.htm
(Ignore the 5 Mhz low end rating. They are DC connected from end to end
and have a gas tube inside that arcs when there's a surge. 5 Mhz is
cablespeak for "it'll work if you have internet broadband on your system".)

--
Larry

thanks for the info..

i have a deck stepped mast which wont be earthed I presume so will be
giving your suggestion a go for sure. I will be using a magnetic balun
which I have always had good results at home with random long wire.

Thanks

Fanky

"Franky" wrote in
oups.com:

thanks for the info..

i have a deck stepped mast which wont be earthed I presume so will be
giving your suggestion a go for sure. I will be using a magnetic balun
which I have always had good results at home with random long wire.

Thanks

Fanky



You won't need the balun. Simply run coax to the chainplate whereever you
can get to a bolt to hook it to. Leave the shield unconnected to anything
and hook the center conductor of the coax cable to the chainplate with a
big ring terminal and extra nut on the bolt.

The shield open on this end creates a cage with its reference of the
receiver chassis. Thank Michael Faraday, long dead, for his shield..

Good luck. Someone gave "Walk The Cornish Coastal Path" by John H. N.
Mason to a local thrift shop, here in Charleston. What a national treasure
your coastal path system looks like. It would be a great way to see
England in the Summer, I'm sure. I could stand to lose a few pounds...(c;

--
Larry

Larry; wuold I get the same results with a metal boat providing the
electrical system is totally isolated?
Jim

wrote in
oups.com:

Larry; wuold I get the same results with a metal boat providing the
electrical system is totally isolated?
Jim


No, because the electrical system, which would be the actual antenna in
that instance, is INSIDE the shield of the metal boat. Sorry.

What makes any receiver work is the DIFFERENCE in potential between the
part we're calling the "antenna" and the part we call "ground" or
"reference". There has to be a difference voltage the receiver can amplify
and use. If the electrical system is inside the boat, there'd be a shield
around the boat's wiring, so there wouldn't be any RF voltage induced that
was different.

So, you'll have to insulate a shroud or backstay, use a whip outside the
hull or string a wire up outside the RF in the air can induce voltage into.
There's very little RF inside a metal boat, as I'm sure you know trying to
get radios and TVs to pickup anything in there on their little antennas.
Plastic boats are as transparent as if there were no plastic at all to RF.

--
Larry