Dyneema soft shackle as antenna insulator

[Namaste II]

Trying to pinch pennies. I know that should be a non starter with standing rigging ;-) This is my idea: a dyneema soft shackle at the masthead, as a SSB backstay antenna insulator. Crazy??

Thanks
Doug
Namaste II Falmouth, ME USA

[Brion Toss]

Hi there,
I understand what you're saying, but there might be problems, like that the uninsulated portion would be too close to the mast, unless you made a 4 foot shackle. So why not an all-Spectra backstay, with a portion of wire inserted in it? I've heard good things about that. Check with Colligo.
Fair leads,
Brion Toss

[Joe Henderson]

Dear Doug,

I have had great success with full length Dyneema/Spectra backstays with integral antenna wires on all sorts of vessels.

Size the fibre correctly (see multiple threads and websites), thread the correct length of tinned electrical cable (1,84 square mm or your gauge equivalent) up the centre and away you go.

I remove about 50 mm of the copper wire from the upper end and milk the insulation over the cut end and tape lightly so you dont get a bare wire working inside the fibre.

The copper is spongy enough not to mind a bit of initial stretch.

Everyone - usually marine electricians - will tell you you need the correct sheilded cable but I have never had any trouble with this method. ( Eight Sydney Hobarts - not counting the ones we did not finish - on the boat I used to crew on, and many thousands of miles with this system on customer's boats.

It is cheap.

Regards,

Joe Henderson

[Auspicious]

The concept if very reasonable. There is a commercial product that is the same: http://www.ropeantenna.com/

Originally Posted by Joe Henderson

Everyone - usually marine electricians - will tell you you need the correct sheilded cable but I have never had any trouble with this method.

Hmm. Confusion there somewhere. The only shielded cable would be between the radio and antenna tuner. The insulated wire (usually GTO-15) from the tuner to the backstay or other antenna which is actually part of the radiating element of the antenna is only insulated to avoid arcing and possible (never seen it) RF burns.

A suitably sized wire floating in a synthetic line is dandy.

I'm not sure how ropeantenna does their feed. I'd run the wire out of the cover about a foot above the deck, use a wire nut (not a hose clamp) to connect to the GTO-15 and shrink-wrap or seize the connection.

[Joe Henderson]

Dear Auspicious,

You are quite right about the need for shielded cable, as a little thought on my part would have revealed!

The only example of RF burns from antennae and wires that I have come across was on my old boss, Harry Spencer's legs.

In the late sixties, Harry, as only Harry could, had been contacted by the Dutch support crew for the pirate radio ship, Radio Caroline.

Apparently their first try at staying the radio mast had failed due to a very narrow shroud angle. The radio mast was about 125 feet high and the old ship only about 25 feet wide at the base of the masts.

They had rolled the mast out of her in about two weeks of autumn North Sea weather.

Harry fitted a 50 foot spreader at about 1/3rd height and all was well after that.

Harry was inspecting the installation a few weeks later, via, Harwich, Rotterdam and a dodgy trawler used as a supply vessel.( another story! )

He went aloft after telling them to stop transmitting and, just to be sure, to turn off the very powerful radio transmitter.

Half way up he started to get burns off the shrouds which he was clinging to.

After much bad language from Harry and much mystification from the crew, who had turned off the trannsmitter, Harry realised that the burns were due to Radio London, which was another pirate radio station on an old trawler anchored about 2 miles away, transmitting. Her RF was "lighting up" the steel of Carolines mast!

It was not until Harry bred in the early eighties that he was convinced that he had not been made sterile after all!

But, I digress.

There are three things that I know I know nothing about; wriggly amps; anodic protection and radio comunications. There must be more, but nothing springs readily to mind.

Auspicious, I bow to your superior knowledge.

Regards,

Joe Henderson.

[Auspicious]

Originally Posted by Joe Henderson

Auspicious, I bow to your superior knowledge.

Certainly not superior, merely different. I'm always pleased when I can contribute in some small way here where I learn so much.

Thanks for the Pirate Radio story. Have you seen the movie?