SSB Un Insulated Backstay - SailNet Community
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post #1 of 14 Old 10-09-2007 Thread Starter
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SSB Un Insulated Backstay

I have read alot about backstay isolators, Can anyone tell me if I can use my backstay as is for SSB radio use. I have read the more length you have the better as long as your ground plane is good. I have also read the reason the isolators are there are to prevent getting burned from touching the backstay durring transmission. My Islander 37MS had the tuner wire clamped to the backstay. I had the standing rigging replaced and opted not to put isolators in. Please can anyone tell me if it will work.
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post #2 of 14 Old 10-09-2007
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Backstay antenna isolators

Nope, it won't work properly. The insulators are what separates the active antenna part of the backstay from the rest of the rigging. Without the insulators the RF energy would be conducted to your entire rig. If the mast is grounded, it would short out the signal to ground. You need the insulators.

Gil
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post #3 of 14 Old 10-09-2007
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ranes,

I hear the frustration in your post. Let me try to clarify a couple of things.

Virtually anything will work. The question is, how well?

It is best to have insulators at the ends of an end-fed antenna (like a backstay). However, a fiberglass hull is a pretty good insulator for the lower end, so on most boats you can, indeed, attach the feed wire (GTO-15) from the tuner directly to the backstay. You can even do this UNDER the deck to avoid having to put a hole in the deck. HOWEVER, the usual reason for installing a lower backstay insulator is to avoid potential RF burns. When you transmit, some pretty high voltages can be present on the antenna, especially at the ends. If someone were to grab the lower end of the antenna while you were transmitting, he/she could get an RF burn. If this isn't likely or possible on your boat, then go ahead and forget the lower insulator.

An upper insulator is a good idea; otherwise, your backstay is likely electrically connected to the mast and the rest of the standing rigging. This could limit its effectiveness as a radiator.

One thing which works very well is to install a separate backstay-like antenna off to one side. I've done this on my boat, and it's worked well for 18 years now. Every bit as effective as a standard insulated backstay, and you don't have to break up the integrity of the main backstay by installing insulators.

I built mine from s/s lifeline. You can see a pic of the lower end at: http://gallery.wdsg.com/Misc-Stuff-S...y2_0130?full=1

Also, there's lots of discussion about "anternative backstay antennas" on the SSCA board and others.

Don't forget the RF ground....that's VERY important, too.

Bill
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post #4 of 14 Old 10-11-2007
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Bill,
Do you think having LifeLine wire with the plastic covering would hurt the signal at all? Would that help in crew safety if touched?

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Alan,

The insulation won't hurt the signal at all. It MAY help to quieten things a bit in precipitation. It's not likely to help much if at all with obviating the chance of RF burns.

However, the chance of RF burns is very low in most situations. You can only get one if you're grabbing the antenna in the right place when someone is actually transmitting (not listening). Further, you've got to be holding onto it for awhile. Anyone touching an antenna while transmitting is likely to feel a sharp tingle and will remove their hand quickly...long before any problem occurs.

Still, if you're going to have an antenna which is mounted anywhere within the crew's reach, then you should: (1) warn all crew not to touch the antenna; and (2) warn the crew whenever you are using the radio.

Finally, in many decades of boating and hamming I've never seen an RF burn occur or heard directly of anyone getting one. It's theoretically possible, of course, but in practice is extremely rare.

Bill
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post #6 of 14 Old 10-11-2007
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Bill- I was looking at the picture of your antenna, is it necessary to use that large of wire, would a smaller diameter work as well? I'm buying a boat with an insulated backstay and I'm not fond of the idea. Sorry to hijack the thread. John

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John,

No, any size will work OK. But, the larger diameter may help offset just a bit the fact that s/s isn't a great conductor of RF (as compared, e.g., to copper), thus more surface area (where RF travels) is good. That's more of a gut feeling than anything I've tested or proven.

Why use s/s, then? Because it's STRONG....very strong....and will last practically forever in the rough marine environment. In a rough sea it can be set up tight, and it's not gonna break and cause you to lose a halyard, lose comms, etc. And, best of all, I've never been able to discern much difference in either received or transmitted signals from s/s vs. copper antennas :-)

Bill
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post #8 of 14 Old 10-11-2007
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Antenna's vs Anchors?

http://www.gamelectronicsinc.com/

I will let you read this for yourself. This is what I prefer and if you ask about antenna's to us radio Nut's That is like asking "What is the best anchor for my boat" to a Sailing Nut . A radio,sailboat, good woman and lots of Rum, what else do I need...

Fair Winds, 73

Bill KI4GSV
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post #9 of 14 Old 10-11-2007
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Bill- thanks very much for the explanation, I've never had an SSB before so I have a lot to learn.

BillMc- looks very interesting, how long have they been used, any corrosion issues inside the coating?

John

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post #10 of 14 Old 10-11-2007 Thread Starter
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Thank you for you comments.
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