|To:||"Tom Rauch" <firstname.lastname@example.org>,"Guy Olinger, K2AV" <email@example.com>,"TowerTalk" <firstname.lastname@example.org>|
|Subject:||Re: [TowerTalk] elevated short vertical dipole orquarterwave monopole?|
|From:||Jim Lux <email@example.com>|
|Date:||Fri, 03 Dec 2004 14:17:20 -0800|
At 11:10 AM 12/3/2004 -0500, Tom Rauch wrote:
> > The basic sleeve principle is proven at VHF, but the practicalities at > > HF overwhelm it, and one is left with all of Tom's objections.
Unpredictable in the design sense, but probably reasonably stable, once installed. With a sufficiently sophisticated phasing system, one can probably cancel the effects sufficiently. However, I'm not sure how you'd go about actually doing the adjustments. The usual "current probe on the element" strategy wouldn't work. One could adjust on the basis of incoming signals using any of a variety of adaptive array techniques, but that might leave you with huge peaks or nulls in places that you couldn't predict.
I really think the number one shortfall in amateur antenna design is not understanding or dealing with feedlines and common mode currents properly. The problem is there over a broad range of products, from log periodics that tell users to route feedlines along a hot balanced boom to no or poor counterpoise verticals. I'm sure it includes most vertical dipoles.
I think it's mostly the whole thing of any antenna design sold in a "mass market" sort of way (i.e. at retail) is going to embody some amount of compromise, both in terms of installation tolerance, expected performance (which itself can be defined a lot of ways), and so forth.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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