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  #11  
Old 01-27-2010
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Zan,

I merged them. You can go back and delete any duplicate posts now, if you feel like it.
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Old 01-27-2010
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I scanned the article. I am home with a yucky cold, so I have the time. But I have never had luck posting photos here. It is a jpg 87k, meets requirements. There was a post once about the vodoo req'd to post, but I cannot find it.
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Old 01-27-2010
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If this is a direct repro of copyrighted material, you can not verbatim paste it here. Sorry. I have no problem with you linking it, but copyrighted material is, well, copyrighted for that very purpose.

Sorry.

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Old 01-27-2010
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OK gotcha
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Old 01-27-2010
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Quote:
Originally Posted by Zanshin View Post

K1VSK - what sort of interactions are you referring to? If I were to embed an antenna into the nonconductive Dyneema, could you envision that the structural integrity might suffer over time? Dyeema doesn't like temperatures of over 150C, could those be reached somehow when transmitting?
The most common form of interaction is parasitic and takes the form of effectively changing both the impedance and electrical wavelength of the antenna. This is a lot more complex set of interactions than is worth going into here but hopefully it will suffice to say that in erecting various forms of antennas over the years, we have found that virtually any material in close proximity to an antenna has an effect.
You will not find any measurable temperature change.

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Old 01-27-2010
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I found a page on the web showing physical characteristics of Dyneema and they stressed that it makes an optimal covering for radar and sonar as its dielectric constant is a low 22oC/10GHz: 2.25 and Loss tangen: 2. 10-4 {which means nothing to me, but sounds impressive} so perhaps that is a point in its favor if used around a SSB antenna.

Here is the link to the manufacturer's factsheet: http://www.dyneema.com/en_US/public/...ext.src=search
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Last edited by Zanshin; 01-27-2010 at 10:18 AM.
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Old 01-27-2010
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Zanshin, I'm not aware of any numbers for longwire antennas, but in general IIRC as the antenna "tubing" gets thicker, the antenna can work a wider frequency range with lower SWR.

I'm probably getting something not-quite-right with that description, but for conventional antennas thicker tubing has definite advantages, and the same physics behind it would tend to indicate a thicker wire for wire antennas might also have some real benefit. (Aside from being thick enough to carry power without heat damage.)

Something you might want to check into.
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Quote:
Originally Posted by Shortman View Post
There is an interesting note on SSB antennas in the current issue of Sail by Gordon West. BoatWorks Ask Sail p.87. References GAM/McKim antennas that don't need an insulated backstay, the use of a whip antenna, or running a GTO-15 cable inside a double braid sheath & hoisting up the mast when you need.
It is not online yet. Just got it in the mail.
G. West says in this note that the Gam/McKim antenna "is a nice alternative for temporary installations". In my mind this translates to "not as good as a typical insulated backstay installation". Any thoughts on why he might use the word 'temporary'.
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Old 02-07-2010
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Julie, I think I have heard Mr. West comment on this antenna before, some years ago. The antenna is nothing new or magical, and Mr. West sometimes says more than what he is saying, or just what he is saying, if you read between the lines.

As I recall it, he said the antenna was very well made, that he had in fact used one, and that's important because no antenna works well if it takes water damage, etc. But he did not make any comment or judgement about comparable performance or price, and to "read" more about that you only need to know basic antenna design theory. He doesn't do Consumer Reports type comparisons.

There's no $400 worth of antenna there, nicely jacketed and insulated and able to be taken down and moved and raised repeatedly and still work as well as it does on day one. Unless you figure, someone has to pay for low volume hand production, distribution, and retail market, as usual.

You could build the equivalent by trimming some wires yourself for a fraction of the cost, or you could probably outperform it with a permanent installation tuned to your preferred frequencies and matched to your rigging. No matter what antenna you use, the rigging that is unique to your boat will uniquely affect performance and make it extremely difficult for any "one size fits all" solution to work as well on any two different boats.

Antennas all share the same physics, anything that works by "magic" or that isn't described in conventional terms by antenna type and theory, probably is all sizzle and no steak.

But, for the folks who don't want to crunch the numbers and solder the wires...sometimes a well-made "average" performer is still the right product. Sometimes "reliable" is worth having.
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