[TowerTalk] C31 ant file - query
Wed, 23 Feb 2000 17:06:28 EST
In a message dated 02/23/2000 11:39:25 AM Pacific Standard Time,
> 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
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