Cross-field antenna
Gray Frierson Haertig
Gray
Roy Lewallen wrote:
>
> Among the subscribers to the NEC-LIST mailing list are a number of
> professionals who are experts in the field of antennas and antenna
> modeling. There were recently several postings on that list regarding
> the cross-field antenna. I've asked the authors of some of the most
> interesting postings for permission to re-post them in this newsgroup.
> This is the first one for which I received permission.
>
> Roy Lewallen, W7EL
>
> --- [slightly modified by the author from the original NEC-LIST
> posting, as noted] ---
>
> Bonjour,
>
> I've first heard of this thing at the IEE International Broadcast
> Conference IBC'97 in Amsterdam. I had only attended
> the [large] trade show, the number of papers and the technical level
> of the conference being very far from being worth
> the rather dear registration fee. Buying the (relatively thin)
> proceedings for 75 UKP would be about as far as I'd go,
> on the grounds that since I was there, I'd just as well know what's
> going on, just in case.
>
> When I returned home, I tried to find out more about this, as it
> really sounded way too good to be true. My interest was
> piqued and I went to the library to look up the references (see the
> reference list at the end, which complements the one
> by Mr. Belrose.)
>
> I couldn't reconcile the claims which were made with the design which
> was presented. One just can't get both high
> bandwidth and high gain simultaneously from a small antenna. If the
> input impedance of the so-called E and H terminals
> vary very much depending on their excitation, whis would indicate that
> might also be a large circulating current in the
> matching circuit and the between two ports.
>
> If the antenna works, then the implication would be that there is
> something which is overlooked in Schelkunoff's
> equivalence theorems, and in all these theorems on superdirective
> antennas, and those fundamental theorems relating
> dimensions, Q bandwidth, and gain, which I had studied and thought to
> understand. I could look up in my library, and
> throw in a pile of references in several languages, but it "ain't"
> worth it...
>
> The papers published in Wireless World did not appear to the entire
> backing of the magazine's editors - each page had
> the heading "Hypothesis", and the title "CFA: Working assumption"
> carries some of the interrogation this raises. The
> authors try to address some of the issues, but basically say that "it
> works - believe me".
>
> To wit, this quotation from [2]:
>
> << Crossed field antennas look to have major advantages over
> conventional antennas in terms of size, efficiency, and
> lower working voltages. The CFA is not a resonant antenna as its
> structure is substantially smaller than the radiated
> wavelength, and it is low Q and broad banded. Fundamental differences
> to conventional wire antennas mean it is not
> surprising that the CFA has attracted hostility from some experts.
> However, the fact that it works, indicates its basis
> is credible. Furthermore the theory may be said to have passed the
> most severe test of a new hypothesis in that it can
> be used to design new devices. Poynting vector synthesis has universal
> application as a design method for compact,
> efficient. electrically-small antennas. with demonstrated successful
> application at MF and HF, and experiments af VHF
> and LF. The technique could provide the solution to the difficult
> problem of efficient ELF radiation. >>
>
> No radiation patterns or other conventional antenna measurements are
> presented in any of the papers I found. (Unless you
> consider the "plot" on [5, p. 423] as a radiation pattern...)
>
> In [5], there is this curious statement:
>
> << It is thought that the high efficiencies measured are due to the
> absence of the "missing power" integrated from the
> field strength graph by Kraus in Ref.4. We calculate that the quarter
> wave monopole never exceeded 38% efficiency. >>
>
> What do they mean here about "efficiency" ?
>
> I had borrowed the first edition of Kraus from a friend to check this,
> but couldn't see which figure there's referring
> to. I can't find anything either right now in the second edition which
> I own. Could this be an attempt to compare the
> "CFA" to an an electrically short dipole of similar dimensions, with
> losses?
>
> Has any learned reader of this mailing list any clue as to what
> they're referring to? (This is a serious question, not
> just a rhethorical one.)
>
> But the field strength and installation records can't just be
> dismissed off-hand. Unless this whole thing is a hoax,
> which is difficult to consider if there *really* is a dozen stations
> on the air connected to this "thing". This is the
> part which truely bothers me. How can they really measure such field
> strengths? I suppose they use some sort of
> calibrated commercial instrument, and that this part is less fishy
> than the rest.
>
> But yet... There are measurements performed supposedly with 30kW of
> drive, with a statement of the improvement over a
> lambda/4 monopole. (Where are these monopoles relative to the CFA? Did
> they actually remove towers to put these things
> in? The values are in "dB". What kind of dB is that? dWuV? dBW?
> dBWm^(-2) ? dB-over-my-thumb? How many measurements did
> they make?
>
> The description of the "barrel shape CFA" states that the synthesis of
> "H component of the field" is achieved by the
> displacement current flowing between the "D plates". But they seem to
> ignore that an eventual displacement current
> flowing between the plates is exactly balanced by that carried by the
> feed wire (right in the center) connecting the
> upper plate to the source, placed somewhere below the ground plane,
> thus rendering extremely unlikely that a significant
> H field could be induced "at some distance" from the structure,
> interacting with the "synthesized E field"...
>
> Finally, ref. [2] contains the following assertion :
>
> << Input impedances :
>
> When the CFA is operating, input impedances seen at the two separate
> input ports are moderately valued, and contain
> resistance, which is itself a cogent evidence of real radiation. >>
>
> I could make the same statement about a dummy load, but I don't think
> this is a "cogent evidence" of radiation...
> (There used to be a scam in the late 1970's carried in ham radio
> magazines (73, QST, HR, etc.), which advertised "a high
> speed fully automatic antenna tuner, with no moving parts", sold by a
> company with a PO box address in Florida, which
> could really tune *anything*. Seductive stuff. The QST staff opened
> one, and found an attenuator inside... An X ray
> showed that there was also a piece of scrap PC board potted with the
> rest...)
>
> My feeling is that *if* they really measured some encouraging result,
> (field strength and input impedance), the ground
> might play a significant role, especially since they are basically
> doing away with the usual set of radials. What is the
> ground conductivity in the lush and wet Nile valley? How about just
> outside the valley in the desert? Could the ground
> be resistive enough to lower enough the Q of the antenna to make it
> look good? (All this good electricity used to heat
> the Egyptian earth?) And the feedlines might also play a part. (How is
> the station grounded, and is the equipment
> "hot"?)
>
> IMVHO, this whole thing isn't very encouraging. (I initially put in a
> less mildly worded opinion, but I feared the
> moderator wouldn't let it through). The WW paper [1] was followed by
> an ad from "Hately Engineering" for a meter high SW
> antenna. I'd say that a scale model made with a pineapple tin can,
> some copper foil, and a two port VANA could place the
> issue to rest in a day... And rereading VE2CV's contribution, I see
> this was done already.
>
> 73,
>
> Alexandre
> VE2GDC
>
> References :
>
> [1] F.C. Kabbary, M.C. Hately, B.C. Stewart, "Maxwell's Equations and
> the Crossed-Field Antenna", Electronic & Wireless
> World, March 1989, pp. 216-218
>
> [2] F.C. Kabbary, M.C. Hately, B.C. Stewart, "CFA: working
> assumption?", Electronic & Wireless World, December 1990, pp.
> 1094-1099
>
> A critical rebuttal:
>
> [3] Letter by K. Donaldson (Sevenoaks), Electronic & Wireless World,
> October 1992, pp. 837-838
>
> [4] Reply by the authors, Electronic & Wireless World, December 1992,
> p. 1007
>
> The title of the paper from the IBC was:
>
> [5] 'Extremely small high power MW broadcasting antennas', F M Kabbary
> and M Khattab (Egyptian Radio & TV Union, Egypt),
> M C Hately (Hately Antenna Technology, UK), IBC'97 record, page
> 421-426
>
> post scriptum: Rereading my original post to NEC-LIST, I realize I
> forgot to include this other nugget from [2] :
>
> <<
> A proper equivalent circuit for the CFA has not yet been evolved but
> will be the electrical equivalent of a chemical
> reaction or a thermodynamic change of state. Departure of power to
> space from the two interacting fields represents a
> unique form of load. The prime fields interact to produce radio waves
> which fly away to the infinite energy sink of
> space. An appropriate equivalent circuit must behave in a manner
> exactly similar to these unusual characteristics.
> >>
>
> Whew! I knew it, there's something terribly wrong with Maxwell! Or
> ether must have some unknown non-linear property,
> unless we're talking about phlogistics.
--
Telecommunications Engineering
Gray Frierson Haertig & Assoc.
820 North River Street, Suite 100
Portland, Oregon 97227
503-282-2989
503-282-3181 FAX
g...@haertig.com
REMOVETH...@ix.netcom.com
For most of us there is no additional cost, and it is often very helpful
to see the entire text of the original message. So, please don't
represent YOUR OPINION as the proper manner of responding. At the very
least, your post was quite rude.
Do you play "Cop" in the DX pileups too?
73 de Mike, AA3RL
----------------------------------------------------------------------
Gary McDuffie, Sr. wrote:
>
> On Sun, 07 Feb 1999 18:32:02 -0800, Gray Frierson Haertig
> <g...@haertig.com> wrote:
>
> > Thanks for your posts, Roy. Interesting stuff.
>
> Please learn to properly clip quotes. Repeating all 200+ lines of Roy's
> post is not necessary and costs many people money for no good reason.
>
> gm
> --
> Delete "nospam." from the domain name (if present) for proper return address.
AMDX
just to say
"Thanks for your posts, Roy. Interesting stuff."
> Tut, Tut Gary...
>
> For most of us there is no additional cost, and it is often very helpful
> to see the entire text of the original message. So, please don't
> represent YOUR OPINION as the proper manner of responding. At the very
> least, your post was quite rude.
Thanks for your posts, Roy. Interesting stuff
Mike
Please refer to previous letters with over 200+ lines for context. ;-)
Dan Richardson
mcduffie_d...@nospam.scottsbluff.net (Gary McDuffie, Sr.)
wrote:
>On Thu, 11 Feb 1999 13:06:05 -0500, REMOVETH...@ix.netcom.com
>wrote:
>
>> So, please don't
>> represent YOUR OPINION as the proper manner of responding.
>
>My opinion? You need to do a little research before making such a
>comment. It has always been rude to include a 200 line text when
>posting a one line reply. You must be new to usenet.
>
>I stick to my post. Check your netiquette.
>
>gm
To include what you replying to is, for the most part, the standard
way its done on most news groups.
Maybe it is you are new to the news groups.
Danny
Gary Coffman
>To include what you replying to is, for the most part, the standard
>way its done on most news groups.
To quote Emily Postnews, it is never good netiquette to include
more quoted material than original material in a post. We all do
it from time to time, but it is still not appropriate newsgroup
behavior to include 200 lines of quoted material in order to add
a one-liner.
Gary
Gary Coffman KE4ZV | You make it |mail to ke...@bellsouth.net
534 Shannon Way | We break it |
Lawrenceville, GA | Guaranteed |
Reg Edwards
internet publications entirely wasted as there has been
during the last 12 months on this subject.
The so-called "experts", "old wives" and 'gurus', are so
insecure, uncertain and afraid of stating outright that the
whole idea is a load of rubbish, in case they might
eventually be proved to be wrong, merely demonstrates what
a set of such dismal, ill-educated "experts" and "old
wives" contribute to this newsgroup.
The half-published ridiculous description of the so-called
cross-field antenna and its 'performance' is a load of
worthles piffle. Its about time the 'gurus' stopped
perpetuating its imaginary existence, wasting everybody's
time trying to be 'knowlegeable' and passing 'learned'
comments about it.
Reg G4FGQ.
Richard Harrison
The so-called "experts", "old wives", and "gurus", are so insecure,
uncertain, and afraid of stating outright that the whole idea is a load
of rubbish (cross-field antennas), in case they might eventually be
proved to be wrong, merely demonstrates what a set of dismal,
ill-educated "experts" and "old wives" contribute to this newsgroup.
Hi Reg,
Why don`t you quit beating about the bush on this subject?
Best regards, Richard Harrison, KB5WZI
Reg Edwards
Reg
da...@psilink.co.uk
said:
>--- --- -- -- - - - and there has never been so many
>internet publications entirely wasted as there has been
>during the last 12 months on this subject.
Whilst I'm not yet convinced that the cross-field antenna idea works,
there is a problem in categorically stating that something 'cannot
work'.
After all, 'experts' also declared that telegraphy would not be
possible across the Atlantic and, a few years later, that radio waves
would never be able to make the same journey either.
Dave (G0DJA)
Philip de Cadenet
>I also have watched this crossed field antenna thing...Me and every other
>ham person
>I know who builds antennas have always been under the impression that:BIG
>ANTENNA BIG SIGNAL,,small antenna ..small signal.....
Not strictly true.
Have you listened to some of the HF mobile stations out there?
Phil G4ZOW
dave reynolds
ham person
I know who builds antennas have always been under the impression that:BIG
ANTENNA BIG SIGNAL,,small antenna ..small signal.....
I just wanted to put my 2 cents worth in.. 73 Dave K6WRF
da...@psilink.co.uk wrote in article <36c592f...@news.psilink.co.uk>...
Reg Edwards
sufficient to drive people away.
As we say on this side : ANY bloody thing will work. What
matters is how WELL it works. In dBs or even S-units.
--
******************************
Reg, G4FGQ For free software go to:-
http://www.btinternet.com/~g4fgq.regp
******************************
Irv Finkleman
Irv VE6BP