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Old 31-12-2015, 13:26   #1
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SSB Backstay antenna insulating cover options

I am installing an ICOM M802 and have previously installed a backstay antenna that has upper and lower Hayn Hi-MOD Insulators incorporated into the backstay assembly. The lower insulator is near the backstay chainplate close to the aft deck. See photo.
I am concerned about the safety of this and would like to somehow put an insulating cover over the antenna up to about 8 feet from the lower insulator. As I don't want to disassemble the backstay to install a slip-on sleeve, I am unsure what my other options might be to put an insulating cover over the wire.
Any suggestions?
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Old 31-12-2015, 13:47   #2
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Re: SSB Backstay antenna insulating cover options

Saw a kerf through a length of PVC pipe and slip it on the stay?

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Old 31-12-2015, 13:48   #3
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Re: SSB Backstay antenna insulating cover options

I've seen plastic sleeves on power pole guy wires, they are split so you don't have to disconnect the end of the wire.
You could even split a piece of clear vinyl hose and slip it over, I assume that would be enough insulation?


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Old 31-12-2015, 13:56   #4
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Re: SSB Backstay antenna insulating cover options

Maybe not quite aesthetically pleasing, but.....
Splicing tape or rigging tape.
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Old 31-12-2015, 13:59   #5
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Re: SSB Backstay antenna insulating cover options

For additional thickness, wrap above tape over water pipe insulation.
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Old 31-12-2015, 15:09   #6
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Re: SSB Backstay antenna insulating cover options

The danger of RF burns is WAY WAY overstated. Unless you routinely stand on the afterdeck and hold onto the backstay while someone is actually transmitting -- especially using digital modes -- don't worry about it. The likelihood of getting an RF burn is probably less than falling overboard.

NB: could have saved $300 by eliminating the lower Haydn insulator and feeding the backstay belowdecks at the chainplate. Lots of good installations work well that way.

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Old 31-12-2015, 22:04   #7
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Re: SSB Backstay antenna insulating cover options

btrayfors,
I did exactly that on my current and previous boat.
When I get howls from other HAM's I challenge them to pick a frequency and send out a CQ at full power while watching me stand on deck holding onto the stay with my bare hand at shoulder height.
They usually complain bitterly about not wanting to kill me blah blah blah...but I always insist.
After they comply I always get wide eyed looks as if to say "WTF???"
What they don't get is that an end fed antenna has max antenna CURRENT at the (bottom) feed end and maximum VOLTAGE at the top end.
The current is going through stainless wire at virually zero resistance at that point and there's not enough developed voltage in a resonant circuit to cause enough current go to through me (a much higher resistance than the wire) to do any damage or even feel what little current there might be.
OTOH, you can be sure I'm NOT going to touch the top of the antenna !!



Not once have I ever even felt a tickle.
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Old 01-01-2016, 02:09   #8
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Re: SSB Backstay antenna insulating cover options

Quote:
Originally Posted by senormechanico View Post
btrayfors,
I did exactly that on my current and previous boat.
When I get howls from other HAM's I challenge them to pick a frequency and send out a CQ at full power while watching me stand on deck holding onto the stay with my bare hand at shoulder height.
They usually complain bitterly about not wanting to kill me blah blah blah...but I always insist.
After they comply I always get wide eyed looks as if to say "WTF???"
What they don't get is that an end fed antenna has max antenna CURRENT at the (bottom) feed end and maximum VOLTAGE at the top end.
The current is going through stainless wire at virually zero resistance at that point and there's not enough developed voltage in a resonant circuit to cause enough current go to through me (a much higher resistance than the wire) to do any damage or even feel what little current there might be.
OTOH, you can be sure I'm NOT going to touch the top of the antenna !!

Not once have I ever even felt a tickle.
The end of an antenna wire is indeed a high-impedance, maximum Voltage point, but the antenna-tuner end can be anything. The other high-Voltage points will be at half-wave multiples from the endpoint. The first low-voltage current-maxima point is 1/4 wave from the end, and any others are 1/2 wave from that point.

For example: Say you have a 15-meter antenna (top of the insulated backstay to the antenna tuner terminal. Transmit on channel 12A (12.353MHz). There will be high-voltage points at the top of the antenna, and another one 12.2 meters down from that, or 2.8 meters from the tuner. That puts it about five or six feet above the deck on most boats. I wouldn't want to grab the backstay at that point!

True, on most frequencies the voltage won't be very high where you can grab the antenna, but it's worthwhile to be careful, and the low-voltage point is definitely not *always* at the tuner terminal -- that's why we need a wide-range tuner!

Re the OP question, the suggestions to use slit tubing or small-diameter PVC pipe are good ones.
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Old 01-01-2016, 05:58   #9
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Re: SSB Backstay antenna insulating cover options

UV resistant spiral wrap works well enough.

http://www.digikey.com/product-detai...-25-ND/1522503
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Old 01-01-2016, 07:34   #10
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Re: SSB Backstay antenna insulating cover options

Be careful when covering rigging wires that whatever cover you put on there can drain and breath. If stagnant (de-oxygenated) water can collect inside your cover you can cause corrosion problems. This is commonly seen on rigging fittings where people have put plastic on their shrouds to protect the sheets.

Wont happen in a week or year but long term it will cause an issue. If you put on a loose cover you can make routine to slide it up the stay and clean the wire underneath.

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Old 01-01-2016, 09:47   #11
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Re: SSB Backstay antenna insulating cover options

Spiral wrap manufactured by Panduit, Gardner Bender or Alpha Wire should be readily available from a local electrical supply house, Grainger or maybe even Home Depot.
Looks like this
PANDUIT Spiral Wrap,0.250 In.,100 ft. L,Natural - Spiral Wrap - 1LEZ3|T25F-C - Grainger Industrial Supply
I'll bet that when you think about it, you will find other places on the boat where this stuff is useful!
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Old 01-01-2016, 14:25   #12
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Re: SSB Backstay antenna insulating cover options

You need Davis Instruments Cable Covers.

Cable Covers by Davis

These are vinyl covers that have a slit in the side that tightly wraps around a piece of standing rigging. Good for several years in the sun before they get hard, and then simply replace.

Chuck Hawley
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Old 01-01-2016, 16:49   #13
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Re: SSB Backstay antenna insulating cover options

We used split electrical conduit on the shrouds and the split caused a high whistle in strong winds. Had to wrap it in insulating tape.

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Richard
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Old 02-01-2016, 14:06   #14
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Re: SSB Backstay antenna insulating cover options

Quote:
Originally Posted by muttskie View Post
I am installing an ICOM M802 and have previously installed a backstay antenna that has upper and lower Hayn Hi-MOD Insulators incorporated into the backstay assembly. The lower insulator is near the backstay chainplate close to the aft deck. See photo.
I am concerned about the safety of this and would like to somehow put an insulating cover over the antenna up to about 8 feet from the lower insulator. As I don't want to disassemble the backstay to install a slip-on sleeve, I am unsure what my other options might be to put an insulating cover over the wire.
Any suggestions?
Attachment 115968
Davis split cable cover

Cable Covers - 5/16 in. (8 mm) by Davis

and turnbuckle boot

Turnbuckle Boots with Caps, 1-1/2 in. ID x 20 in. (38 mm x 50 cm) by Davis

These are also great for backstays needed as handholds for stern boarding ladders, and unjacketed lifelines that cause raspberry injuries on shins when rubbed against when boarding or stepping off.

Ramblin Rod
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Old 02-01-2016, 23:55   #15
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Re: SSB Backstay antenna insulating cover options

Thank you all for your replies. I'm leaning toward the Davis products or using some teflon spiral wrap. It's interesting to see the opinions of low risk, by the way.
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