[TowerTalk] C31 ant file - query

K7LXC@aol.com K7LXC@aol.com
Wed, 23 Feb 2000 17:06:28 EST

In a message dated 02/23/2000 11:39:25 AM Pacific Standard Time, 
00tlzivney@bsuvc.bsu.edu writes:

> K2AV claims that some of the dimensions of the C31XR are critical to 1/4" -
>  this seems to be extremely uncommon in a HF antenna - given that the holes
>  to adjust a C3 are 1" apart for adjustment purposes!  And the swaying of
>  the elements in the breeze could conceivably change the effective spacing
>  by at least that amount.  
>  I would be disinclined to purchase a HF antenna that required that degree
>  of accuracy to make it work.

       Hold on there, pilgrim. Your sweeping generalization has little basis 
in fact. In the old days, most antennas were designed by 'trial-and-error' - 
a notoriously slow process. But with a decent antenna range, some terrific 
antennas were produced (the TH6DXX probably the most popular) although it 
took six months and 4 hours per iteration.

      The newest generation of antenna electrical designs have been designed 
with computer modeling and the NEC program. With this ability to really 
scrutinize a design (along with being able to run literally hundreds of 
iterations), sometimes a quarter-inch dimension difference can cause an 
unwanted change. And that's particularly true with the newest sleeve feed 
systems; they are dimensionally critical. 

      And, yes, I think the sleeve feeds in F12 antennas should have some 
sort of device to hold the elements in place because they DO move in the wind 
and the SWR DOES change. 

Cheers,   Steve   K7LXC
Tower Tech

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