Position of backstay isolaters


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jgbailey (Past OCC Member)
jgbailey
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Can anybody assist? The current position of my back-stay insolater is at above head height which means that I need to keep the SSB cable away from the stay by the use of plastic tubes. I understand the burns risk when transmitting.
However would it not be easier to have the insolater at the bottom of the stay attached to the hydraulic ram, with a tube on the stay above the insolater for burn protection?
Better opportunity for maintenance, less joints in the rigging, less cost.
Any experiences or thoughts.
Alex Blackwell
Alex Blackwell
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I am not a radio expert, but I have spent a lot of time looking at the isolaters and the antenna wire running up to them. They always are located about 4-6 feet above the deck, and no there does not really seem to be much sense in this, particularly when you consider that the antenna wire is in fact part of the antenna and not as some think a lead to the antenna. However, I am not sure how good it would be for the hydraulic ram to be subjected to 5kV, particularly since it is also presumably connected to your hydraulic pump etc.

As to the burns risk, I am sure you could add a tube to the antenna wire leading to your back stay. However, our experience is that when we use our SSB we are both there listening intently - the evening 's entertainment.

What is very important are the spacer tubes you mention. the antenna wire must be kept well away (4 inches) from any parallel metal (back stay).

Bottom line, changing from what you have would be costly, so why do it?
jgbailey (Past OCC Member)
jgbailey
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Alex, the cost is not the issue. The main reason for considering the change was to make things easier to maintain and the back stay a bit more bullet proof. I currently use Norsman terminals but can reduce the number of these joints by 2 making the changes. The hydraulic tensioner would not get any electrical power through it as the ariel cable would be attached above the isolater as is the existing arrangement.
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I asked the guys in the dockyard this question and they said two things: First, the specs on the isolaters and attachment hardware are better than the backstay itself (might not be true in every installation but those things are pretty strong - have never heard of one giving way). Second, you CAN do what is suggested but then you have to warn people to let go of the backstay every time you transmit which might be a pain.

For me, I tend to grab the backstays all the time to steady myself. I would not want a tube that rolled when grabbed.
jgbailey (Past OCC Member)
jgbailey
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The changes I made have been useful especially when it comes to taking out the mast which I do every 2/3 years. You simply disconnect the hydraulic back-stay tensioner from the isolator which is at cockpit level. I have put a plastic sleeve over the wire part of the back-stay so reducing the likely impact of getting burns during transmission by the SSB.

I also held onto the back-stay frequently and found that I was constantly getting hold of the Ariel cable pulling it out of shape from the old spacers. This is why I made the change in the first place.

My only unknown is there any specific distance between the top and bottom isolators? The top isolator is one meter away from the mast measured along the horizontal plane
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Here is the best writeup I know about ssb 's on sailboats

http://www.farallon.us/webstore/Pcup%20SSB.pdf

One meter is pretty close to the recommended 4 ft. for distance from the masthead. As for distance between the isolators, the antenna should be at least 20 ft. which isnt going to pose a problem on most cruising boats using a backstay. Longer than that is better.
Alex Blackwell
Alex Blackwell
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Thanks for posting that article - very informative
jgbailey (Past OCC Member)
jgbailey
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There has been a pretty serious set of mails previously on the forum on the type of electrical wire to use for the connection and why. I had fitted by "EXPERTS" TV coaxial which worked but was not optimum. Apparently even a metal coat hanger will work.

Thanks for the PDF which is clear and confirms the change I made is acceptable. I think trying to get watt meter and test could be an interesting exercise.
GO

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