The following is a copy of an E-mail reply that wasn't posted to
topband by Lew, and my response.
> To:
w8jitom@postoffice.worldnet.att.net
> From: Lew McCoy <mccoy@zianet.com>
> Cc: n5nug@ix.netcom.com
> Subject: Re: TopBand: Unihat
To: <topband@contesting.com>
> Date: Wed, 30 Apr 97 05:03:08 +0000
> I should not do this because you apparently don't read what is written. I
> am n0t saying any of the things you outlined below--what I am saying is that
> the antenna does an excellent job--it is extremeluy efficient--I kmnow--I
> know--you want some technical figures but forget it.
Why should I "forget it?" I'd like to know exactly what "extremely
efficient" means. Is you claimed based on the fact it might beat a
180 ft long dipole 60 feet above ground on 160, or a shortened loaded
rotatable dipole on 40, about "50% of the time"??
If the 60 ft high 180 ft long dipole is your reference (as your
review claimed), I would hardly call that "extremely efficient".
The 160 meter loop radiation resistance of this antenna is about 5
ohms at best (Antenna Engineering Handbook, Jasik, pages 20-4 through
20-9, 19-3 and 4; EM waves and Radiating Systems, Jordon-Balmain page
325, et cetera ).
With only a few 1/8 WL radials over even the best soil, , the ground
loss would be MORE than 5 ohms (Brown, Lewis and Epstein) plus there
would be radiation field losses. With eight ohms ohms of conductor and ground
loss normalized to
the point where loop radiation resistance is taken, efficiency would
be under 38% NOT counting field induced absorption losses (that can
amount to six dB all by themselves).
> All the tests that I
> have made and many, many others who are not fools--find that the UniHat is
> an excallent performer and perfroms very well agfainst a fullsize 160 meter
> antenna. That is all I am saying but you cannot seem to get hat point
> through your head.
We both agree a top loaded vertical, especially with a large hat,
is the most efficient form of top loading. The antenna under
discussion certainly appears to be very well constructed.
So I apologize if I didn't make my point well. My point is this.
Your review (and the early advertisements) plainly stated the folded
wires improved efficiency, and reduced the dependence on a good
ground. Such claims are based on pure unvarnished ignorance of
antenna theory. They "paint" incorrect mental images of how any
antenna works, and mislead people trying to understand theory.
> I have read and heard the continuing argument about the
> impedance and I know that Krause, Jasyk and all the rest are correct--but
> again--bottom line--this is a damn good performer and you shouldn't knock
> until you have put one up and tried it.
Since you agree with the published experts, I assume you now
agree with the text on page 403 of Electromagnetic Waves and
Radiating Systems. In that section it explains the radiation
resistance of a folded dipole or monopole is exactly the SAME as a
single element of the same dimensions, and the SUM of currents
flowing into the ground is the same.
If the sum of currents is the same, ground loss is exactly the same.
Nothing is changed by using the folded element, except feedpoint
impedance characteristics.
When I read your review, you plainly did not understand or agree with
the well established facts surrounding folded antennas.
73 Tom
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