Re: NEC-LIST: cross field antennas

Gentlemen:

The CFA can be put to rest by a simple exercise. Try this and see:

The inventors claim that it "works" because the E field from the disc
plates when crossed into the H field from the fat dipole/monopole,
(which has a 90 phase shift forced by the phasing network) shows the
required "in-phase relationship and quadrature space relationship" for
an outward going poynting vector! (Sounds and looks good! Real
in-phase power!)

But they conveniently "forgot" to include the remaining E from the
quadrature shifted dipole and the H from the discs! Those cute little
devils just so happen to produce and INWARD GOING poyinting vector,
which adds up to NO real power over that from a small dipole! (SIGH!)

Any radiation measured in the original experiment (at 80 meters) had
to come from the"phasing coils of coax" mounted on a nearby cart, and
from the "instrumentation" which was a scope sitting beside the
antenna feed point, which was used to measure the 90 degree phase
tweak.

A group of SRI engineers assembled a "kit" obtained from the inventors
(for 400 pounds sterling) and tested it under very carefully
controlled conditions. They used a very good ground plane (no loss)
and hardline coax to prevent leakage radiation and loss-induced feed
point resistance terms and removed the phasing networks from the
vicinity of the antenna to prevent currents from the antenna from
flowing on the outer conductors of the cables. Results: A very short
antenna with typical highly reactive input reactance and very low
resistance and no surprises in field strength measured. (These
results are not available as they were funded by an agency that
remains very low profile.)

I have followed this little fairy tale since its first telling and
have not seen any data that can be verified. In a recent trip to the
middle east, a very competent broadcast engineer was not able to
witness the output power from the transmitter nor able to verify the
antenna current nor the input impedance due to some "unfortunate
situations" during a scheduled proof of performance visit for a major
MF/HF U.S. company. "And the music goes round and round...."

R W Adler

-----Original Message-----
From: John Belrose <john.belrose_at_crc.ca>
To: Grant Bingeman <DrBingo_at_compuserve.com>
Cc: nec-list_at_ee.ubc.ca <nec-list_at_ee.ubc.ca>; Stephen White
<stephen.c.white_at_xtra.co.nz>
Date: Tuesday, February 09, 1999 4:09 PM
Subject: Re: NEC-LIST: cross field antennas

>Hello Grant,
>
>On Friday you wrote:
>
>> Jack, I recall seeing an article showing the cross-field concept to
>> be a fraud, but can't put my finger on it at the moment. Do you
>> recall where that might have been published? I think there were
>> some similar debunking articles perhaps 15 years ago in the IEEE
>> Transactions on Broadcasting, re the Bibey antenna.
>>
>> Grant Bingeman
>> Continental Electronics
>> Dallas
>
>I do not know anything about the Bibey antenna, but I do know a little
>bit about the Hatley antenna.
>
>In 1989 (see Electronics + Wireless World, March, July and November,
>1989, and December 1990) and in following years, Maurice C. Hatley,
>GM3HAT describes a cross-field antenna (CFA), in which quadrature E
>and H fields are separately generated. In the words of the inventor,
>reversing the form of Maxwell's equations led to the "realization and
>development of this revolutionary new antenna system". Quite small
>versions of it have (apparently) been fabricated and tested,
>cf. reference [1], to demonstrate its ability to efficiently couple EM
>energy to space --- but, notwithstanding, in my view this antenna fits
>the category of a hoax.
>
>The Hatley, Kabbary and Khattrab paper claims that the field strengths
>and service area for a small (1.6 percent of a wavelength high) MF CFA
>in Egypt is identical to that provided by a 75 m quarter wavelength
>vertical. The antenna was a ground-plane type CFA on the roof of the
>transmitter building, and after listening to the paper I questioned
>whether the radiation realized was in fact generated by the GP CFA, or
>by currents flowing on the outside surface of the coaxial cable
>feeding the antenna --- since E X H fields in the far field are
>produced naturally whether the radiating antenna was a dipole,
>monopole or loop (?).
>
>At a more recent IEE ICAP Meeting (Edinburgh, April 1997), I was
>presenting a paper on elevated radials, I met Hatley and his Egyptian
>colleague (Khattrab), or should I say they cornered me; and I learned
>that the Broadcaster was happily still using the antenna --- or should
>I say the authors still believed in the results of their experiment
>--- in retrospect I am not sure now which is which.
>
>Maurice told me that he was developing HF versions of this antenna for
>use by radio amateurs, for mobile communications, and he would send me
>details on it. I told him I would be glad to measure the radiation
>efficiency of his amateur version --- but, no correspondence has to
>date been received.
>
>In 1992 Colin Davis, University of Surrey [2], conducted a study of a
>VHF dipole version of the CFA, his model was a 50-percent scaling of
>Hatley's original. His work, carried out to investigate whether the
>CFA does operate as an efficient radiator, casts doubts about it,
>which seem overwhelming. Despite his best efforts to make it work,
>the best he could achieve was - 23 dBd.
>
>["The great tragedy of science --- the slaying of a beautiful
>hypothesis by an ugly fact", T.H. Huxley].
>
>So, is the debate concluded, should the CFA RIP?
>
>73, Jack, VE2CV
>
>
>References
>
>1. M.C. Hately, F.M. Kabbary and Khattab, "An Operational MF Antenna
>using Poynting Vector Synthesis", Proceedings of 7TH International
>Conference on Antennas and Propagation, Part 2, Conference Publication
>No. 333, April 1991, pp. 645-648.
>
>2. Colin Davis, "CFA --- RIP?", Electronics World + Wireless World,
>May 1993, pp. 405-407.
>
>_____________________________________________
>John S. (Jack) Belrose, PhD Cantab, VE2CV
>Senior Radioscientist
>Radio Sciences Branch
>Communications Research Centre
>PO Box 11490 Stn. H
>OTTAWA ON K2H 8S2
>CANADA
>TEL 613-998-2779
>FAX 613-998-4077
>e-mail <john.belrose_at_crc.ca>
>_____________________________________________
>
>
>
>
Received on Wed Feb 10 1999 - 02:45:10 EST