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Author Topic: antenna for really big sailing ship  (Read 432 times)
KK7WN
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Posts: 54




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« on: November 15, 2005, 07:14:50 PM »

Spring 2006 I will sign on as a temporary crewman on a square rigged sailing ship out of northern Europe. The ship is a three masted Barque with masts about 180' high. I can operate marine mobile and I was wondering if any of you have some words of wisdom about an antenna type. The ship does have a steel hull.I could use some form of dipole or a vertical. I would operate HF from 40 to 15 meters.Power would be about 20 to 100 watts.I am quite familiar with most antenna types but I have never had the experience of rigging an antenna  for shipboard use.
My great grandfather was a Norwegain deep water sailor and died when his ship hit ice in 1885. I thought it would be interesting to have such a sailing experience, minus the ice, of course!
 
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K7AAT
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« Reply #1 on: November 15, 2005, 08:10:09 PM »


   I have no marine experience, but I'd think, with that metal hull, that either a verticle run up a mast, or an Inverted V antenna would work well.  But I must ask,  do you think the Captain will let you run wire up there, in either case?
   If not, then perhaps a smaller vertical, with perhaps a nice SGC Tuner, would work well for you.


    Ed   K7AAT
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KC8VWM
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Posts: 3119




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« Reply #2 on: November 15, 2005, 08:51:57 PM »

Well you could go stealth by trailing a longwire behind the ship. The leader line at the end of the antenna would be about 6 - 12 feet long and be non-conductive string etc.

Tie a lead weight on the end of the leader line that connects to the trailing wire to keep it straight.

Use something buoyant in the water to make sure the antenna remains above the water and doesn't become submerged under water.

Can you make a 135 foot fishing line antenna? Alligator clips can be used to connect the make shift fishing rod antenna to the antenna tuner. The fact that the antenna is located away from the ship would probably mean less HF noise and interference.

Ok..., it's only an idea. I guess I am thinking like a ham again. Bon voyage!

 Smiley
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KC8VWM
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« Reply #3 on: November 15, 2005, 09:02:07 PM »

You might even "catch" some good DX...
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W6HB
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Posts: 38




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« Reply #4 on: November 15, 2005, 09:08:38 PM »

....to keep it simple and effective, I would suggest a 30' vertical with an auto tuner such as one of the SGC products. With the steel hull as the ground and minimal interference from the rigging and masts, it will be quite efficient on 40 through 10 and will function surprisingly well even on 75.
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K0BG
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« Reply #5 on: November 16, 2005, 05:56:54 AM »

Even though you are over sea water, it is necessary to have at least a modicum of ground plane. Keel plates help, but I suspect there isn't any side rail guards to add to the mix.

The suggestion of using an SGC auto coupler is a good one, but you should use as long a wire as possible. The ground side needs to connect to the keel plate with as short of connection as possible; inches, not feet.

If there isn't a keel plate, then a V antenna may be necessary. In this case, both wires need to be of he same length. Thirty feet maybe okay for 40, but 50 or 60 would help a lot.

The only problem you're going to have is keeping the wire out of the rigging. And on such a large sailing vessel, there's a heck of a lot of it.

Alan, KØBG
www.k0bg.com
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N3JBH
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« Reply #6 on: November 16, 2005, 06:21:39 AM »

what is the mast made of? maybe you can simply shunt feed the mast? this be about as stealth as you can get. and i think it make one heck of a antenna aswell.
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WW5AA
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« Reply #7 on: November 16, 2005, 08:55:02 AM »

"what is the mast made of? maybe you can simply shunt feed the mast? this be about as stealth as you can get. and i think it make one heck of a antenna aswell."

And one heck of a surprize for the rigger when your transmitting.  LOL

de Lindy
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AA4PB
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« Reply #8 on: November 16, 2005, 10:36:25 AM »

I'd use that steel hull as the ground for the antenna system. Feed the antenna with a tuner. Make the antenna as long as practical and as vertical as practical (so it won't be directional).

The Navy often uses a 30-foot vertical that, when necessary, can be lowered to 45 degrees or even horizontal over the water to get it out of the way.
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WB6BYU
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Posts: 13252




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« Reply #9 on: November 16, 2005, 02:15:55 PM »

The first thing to do is to talk to the Captain and find
out where you can run wires without getting them in the
way of the rigging.  You may be able to use a spare sheet
to hang an antenna while the ship is at anchor, but have
to take it down when the sails are hoisted.  Most important,
be flexible, since you won't know what type of antennas
you can use until you actually get on board.

Some various thoughts:

1)  I would NOT recommend an antenna that uses the steel
hull as a ground plane.  You can't guarantee getting a
good connection to it from near your antenna/operating
position.  If you do go this route, bring some extra wire
to make counterpoises for all bands as a backup.

2)  Closed loops are a good approach - they don't require
any ground connection and can be installed in a number of
shapes.  Install for vertical polarization if near the
deck; try both polarizations if near the top of the mast.

3) A simple vertical dipole requires only one support
(such as a yard-arm, or down the ratlines)

4) My general suggestion would be to take a length of
coax with a dipole center insulator on the end and
wing nuts for the antenna wires.  Then cut half wave
dipoles for each band (using color-coded wires if
possible) that can be attached in whatever combination
circumstances suggest.  Also take a large spool of
extra wire in case you get a chance to put up a special
antenna - like a 2-element quad for 80m, vertically
polarized over salt water, and rotatable (by turning
the ship.)

5) Make sure all connections are stainless steel/bronze
etc., to reduce problems with salt water corrosion.
Use grease liberally on the fittings.
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W8JI
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« Reply #10 on: November 17, 2005, 01:19:00 AM »

Over seawater and especially with a steel hull you almost certainly would want to run a vertical or near vertical antenna.

The steel hull would be a very good ground IF the connection to it was both very short and solid. You could probably get that from a deck rail post or something else big and solidly mounted to the hull and deck.

A 30 foot wire or mast with a tuner right at the base would be OK for 40 meters and up, but you can get into trouble on lower bands with autotuners. If you want to work 160 and 80 you might want to use a 100 foot wire. With auto tuners, you would want to avoid antennas less than 1/8th wave long or even multiples of 1/4 wave. It's extremely easy to blow a tuner up when you work against a even multiple of 1/4 wave in a lossless system or have a thin wire less than 1/8th wave long. Also most ham tuners or auto tuners won't handle saltwater spray long.

You might consider a tall fiberglass fishing pole with a wire run up the side for the antenna. That way you wouldn't kill someone or ruin equipment that doesn't belong to you. It's always a good idea to not put anyone or anything at risk, including boats, by stringing or trialing floating wires all around.

73 Tom
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RobertKoernerExAE7G
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Posts: 1435




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« Reply #11 on: November 17, 2005, 09:28:38 AM »

A few months back, we had a non ham asking how to set up a maritime transceiver with auto tuner at his house.  I scanned the Icom site to find out about his gear.  It seemed as if the transceiver and auto tuner could be used on HF ham bands.

May be all you need to do is bring your key.

Bob
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VA7CPC
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Posts: 2386




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« Reply #12 on: November 17, 2005, 08:05:26 PM »

I _do_ operate from a sailboat.

Use the steel hull as the ground -- you can´t do better.  Use an SGC SG-230 autotuner mounted just below the deck (if the deck is wood) or just above the deck (if the deck is steel).  You´ll need some weather protection if using above-deck mounting.

Get permission to run a wire from the tuner up toward a masthead.   Try to keep it away from other rigging, and terminate it in an insulator _at least_ a few feet away from the mast.   One good location would be from the stern quarter to the top of the aft mast.

Note that you only need 1/4 wavelength of wire at your lowest operating frequency.  So you needn´t go all the way to the masthead.

This would be a good installation, with minimal changes to the ship´s current rig.

Some alternatives:

Many sailors have ben happy using an insulated triatic )masthead-to-masthead) stay, using a mast as a ground.   This requires a balun at the masthead, where the triatic is fed.

You could run a dipole _somewhere_, but it wouldn´t beat a vertical with a steel-hull ground.

There´s lots of information on the SGC website -- check out the manual for the SG-230 tuner for some ideas.

Good luck, and good sailing!

 
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