Topband: Elevated Radials
zr at jeremy.mv.com
Wed Mar 6 11:54:57 EST 2013
Since the radial field for any height vertical has equal importance the only
way to get 1/4 wave efficiency is to have zero RF loss in the loading coil
and matching network. Cryogenics anyone?
There is no magic wire minimalist radial or counterpoise that accomplishes
that. All they provide is some improvement over a poor on ground radial
attempt; I wont call it a radial system.
----- Original Message -----
From: "Rick Karlquist" <richard at karlquist.com>
To: <topband at contesting.com>
Sent: Tuesday, March 05, 2013 8:42 PM
Subject: Re: Topband: Elevated Radials
> One of the problems with discussing this topic is that
> nearly all studies of radials deal with 1/4 wave verticals.
> Most ham stations including mine don't have the luxury of
> a height of 130 feet.
> There are many cases where some "novel" grounding scheme
> is touted as "just as good as 120 radials" and indeed it
> may be for the 1/4 wave height case.
> What is scarce is advice for the owner of a short vertical
> as to what to do about grounding. What grounding scheme
> would it take to make the proverbial 43 foot vertical play
> as good as a 130 foot vertical? Whatever that scheme is,
> we know that it will have very narrow bandwidth. This is
> a good litmus test to separate short vertical installations
> worthy of additional testing from low efficiency ones. Of course, narrow
> bandwidth is merely necessary, but not sufficient, to
> prove high efficiency. The advantage of the bandwidth
> criterion is that it is easily and unambiguously measured,
> as opposed to field strength. The bandwidth should ideally
> be determined by measuring the antenna drive impedance
> directly, rather than looking at it through a matching
> network. A matching network will to a greater or lesser
> extent decrease the bandwidth of the antenna. Alternately,
> the matching network can be modeled to remove its effect
> on bandwidth.
> I think it is less likely that you can be fooled by a bandwidth
> measurement than you can with base impedance measurements.
> Topband Reflector
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