[TowerTalk] Re: linear loading

Guy Olinger, K2AV k2av@qsl.net
Wed, 18 Nov 1998 16:52:29 GMT

On Wed, 18 Nov 1998 01:59:04 +0000, "w8ji.tom" <w8ji.tom@MCIONE.com>
(by way of Pete Smith <n4zr@contesting.com>) wrote:

>A linear loaded antenna should be no more or no less sensitive to
>surroundings than any other loading method that has the loading at a
>similar point in the element, unless something is wrong with one of the

This is the one point I'm having problems with. A loading coil does
not radiate significantly, and it's properties will not vary with
distance from the ground (say 65 feet vs. 100 feet on 40m). 

I suspect (preliminary looks) that a wide spread, angled,  linear
loading like F12 & M2 *does* radiate significantly, and therefore is
subject to variations in environment, to the degree that it radiates.
This is not a design flaw, or something wrong. It is not lossier than
a lumped solution, unless it has physical implementation problems. It
does have certain physical advantages (eg, doubling as a truss) that
are very attractive. 

Having significant radiation will cause it to have it's own nature as
regards tuning and keeping on spec. Also since it *is* shortened, it's
settings are more variance-critical to performance than a full-sized
version. Therefore it's divergence from a lumped solution like the
XM240 means it needs to be dealt with in it's own paradigm, with it's
own tuning methods, etc.

I will have more runs with the unlimited mininec in NEC4WINVM before
long, and may be able to quantify this a lot better.

>73 Tom

Likewise, Guy.


Guy L. Olinger
Apex, NC, USA

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