[TowerTalk] Re: tt
Sun, 20 Feb 2000 15:42:10 -0500
Be very careful with the wholesale acceptance and propagation of what
is being written in the some foreign and ham literature, by some rather
unorthodox people, about the CFA antenna and some of it's variations.
The claims of it's proponents for: very wide bandwidth, substantial
"gain", well above that of conventional antennas, all with very small
size, are not well founded.
Numerous people have tried to duplicate the results with no objective
evidence of anything close to the claims of the originators. The main
reason given where the feed systems weren't accurately built, etc.
This has caused some to correct the supposed "errors" with several
"revised" feed approaches. No confirmable success has been proven yet.
The CFA within the US broadcast industry, has been characterized by
many, as "voodoo" science. None of the claims by the inventors have
been duplicable by responsible broadcast antenna engineers in this
No antenna synthesis program such as NEC* or the like, confirms
anything close to the claims of the inventors. In fact quite to the
contrary. Most responsible attempts to simulate the results have shown
performance 10 db or worse, below typical ground plane figures and
severely restricted bandwidth. Claims that current CAE methods are at
fault are not supportable.
For something to be "scientific" it has to be observable and
reproduceable with good methodology.
The CFA is yet to show it can stand this sort of testing. So far it
appears to be a myth or at least an erroneous series of conclusions by
On July, 1999, Dr. Grant Bingeman, in comments to firstname.lastname@example.org,
made the statement: "As a member of the audience, (attending the 1999
NAB engineering forum, on the CFA), my conclusion is that apparently
there are no concrete supporting numbers for the CFA claims."
Recent attempts by myself, to obtain an HF prototype for some serious
testing, have been unsucessful, so far. The design wasn't finished yet
was the reason given.
If you are really interested in the subject, drop Roy Lewellan or Tom
W8JI, a line and see their comments. They've been into antenna design
a long time. Their comments are worth serious consideration.
Please also note the interesting challenge made on the NEC list by Chip
N1 and copied below: (I haven't heard of any takers yet).
Ray LaRue, W4BYG
Consolidated Media Systems, Inc.
Chip N1IR wrote:
"For many months now we have heard on Antennex that CFA's are
remarkably efficient antennas. This is despite presentations
from Jefferies(also given here on Antennex), Belrose, and others
that the 'new physics' explanation for the CFA's alleged performance
is incorrect; that model and measurements of the CFA show very
poor efficiency; and that a high efficiency (very electrically
small) antenna cannot be broad band.
I thus pose the following challenge: I will pay $10,000 to
the first person or group who can demonstrate--using one or more of
standard metrological methods--that the efficiency of a CFA less than
2% of a wavelength in size is in excess of 90%. Such an alleged
radiator must also possess the broad band characteristics also ascribed
to the CFA.
This is a serious challenge, with absolutely no malice, spite, or
'agenda', other than to reveal: 1) the claims for CFA performance are
not accurate and thus; 2) the requirement for 'new physics' to explain
such alleged performance is not needed.
Only an accurate, scientific, and repeatable demonstration of
the alleged high efficiency of the CFA will allow one to consider
exotic new explanations. This challenge is a clear incentive to show
that for those who believe it can be shown."
73 Chip N1IR
> In a message dated 20.02.00 02:29:56 Pacific Standard Time, email@example.com
> << Hi again Ken,
> I already forget what the CFA antenna is. What is AntenneX and how do I see
> It's a very small antenna designed for the BC Band--using different theory
> which is very sound.. Stations in Europe are taking down their 1/4 wave
> verticals and installing the CFA.. There are really 2 different types. One
> can go in ones attic. They are in the "AntenneX" Web Site. It's a Web Site
> Antenna Mag. Bring it up and subscribe. There are 5 articles on the CFA.
> There is great stuff in there. They announced the CFA a year ago. It hasn't
> been in QST They may not have anyone that can cover it. k7gco
> FAQ on WWW: http://www.contesting.com/towertalkfaq.html
> Submissions: firstname.lastname@example.org
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: email@example.com
> Search: http://www.contesting.com/km9p/search.htm
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Administrative requests: towertalk-REQUEST@contesting.com