[Boatanchors] Fw: Slightly OT: What is the optimum "twist ratio" inwindow-line

[Jim Wilhite]

Proximity to other objects, particularly metal, will unbalance any 
window or open wire line no matter the orientation Brian.  Twist will 
not mitigate that unbalance, but it might minimize the exposure at a 
given point as you suggest.  Never the less the exposure is there and 
will cause an unbalance.

Twist in the line was something my mentor and all his friends did back 
in the 40s and 50s to help minimize the exposure to the wind and 
equalize the stress on the attach points at the antenna.  The practice 
was suggested in discussions and literature on the antennas at the time. 
It may not have worked but that was the rational, and I wonder why wind 
sail manufacturers would test open wire line.  I know nothing about 
sailing so don't explore those sites.

Jim/W5JO





----- Original Message ----- 

> Not so, Jim.
>
> The purpose of the twist in window feedline is to balance the line 
> with respect to all possible unbalancing materials, such as metal 
> masts, metal downpipes, metal rooves and gutters.
> Go to any wind sail manufacturer's wind tunnel results to see the 
> effect of uni-directional spiral twisted lines.
>
> 73 de Brian, VK2GCE.
>
> ----- Original Message ----- 
> From: "Jim Wilhite" <w5jo at brightok.net>
>>
>> Mac you hit the nail on the head.  The purpose of the twist is
>> resistance to air flow not radiation nor pickup of extraneous 
>> signals.
>> If you have an interfering signal, it won't care what orientation the
>> feedline is.  One, obviously, does not want to twist the line
>> excessively, that can cause problems.  The amount you suggest is 
>> good.
>>
>> Jim/W5JO
>>> ----- Original Message ----- 
>>>
>>>>
>>>> I generally use a full twist around 8 feet. Somewhere,
>>>> there is probably some sort of formula that is based
>>>> on the wavelength at the highest frequency being used
>>>> on that feedline.
>>>>
>>>> I am more concerned about flutter and accompanying
>>>> fatigue of the conductors in high Oklahoma winds than
>>>> I am about any radiation or pickup considerations.