NEC-LIST: Stark Raven Rad -- Mystic Fiction

On Thursday last week Roy Lewallen copied to the NEC-List a WEB site
and a US Patent number 6,025,810 which gives us a flight into the
world of electomagnetic fantasia. The hyper-speed antenna is another
piece of pseudo-science. If we are to counter this sort of thing it's
up to those who know something about EM antennas and radiating systems
to study carefully what is being claimed and focus sharply on the
essential faults.

Clifford Kraft has told us that the patent office apparently gets
several applications for perpetual motion machines each year in which
they always demand proof. They should have done that here too, or for
any invention that claims to overcome an established scientific
principle. The cold fusion crossed field antenna, which I have been
struggling with, was also patented. The office should demand the
inventor to prove it works (synthesizing the Poynting vector for
maximum power transfer to the propagation medium, or in the present
incidence sending messages faster than the speed of light, etc.)
before it issues a patent. They are supposed to do this.
Nevertheless, if the examiner (and usually his/her boss) accepts the
inventor's claim, it can get by. This is usually because the examiner
simply does not have the specialized knowledge to challenge the claim.

The hyper speed antenna is definitely a very useful invention:

(1) because it brings to our attention (at least for me) WEB sites
where one can find intellectual property --- and hence engage in the
exercise of chasing patents. A better WEB site, than the one given in
Roy's memo, since Netscape 4.6 allowed me to view/and print all
figures, and text for the referenced patent, is the IBM Intellectual
Property Network <http://www.patents.ibm.com>; and

(2) it brought a lot of fun to people on the NEC-List.

Or is there something more to it??

The CFA remains a mystery. There are clearly two camps, those that
say its great, providing unbelievable performance, and those that
who-haw. The inventors/and those that would like to market the
antenna are obviously playing to the gallery and trying to address
potential customers who are probably not into the minutiae of
electromagnetic theory. In engineering, you always get found out
sooner or later, but for now it seems to be later, since for the
present we see only a few reports disclaiming the high efficiency for
antennas in Egypt.

Jack

Trying to come to Grips with Meaured Performance
___________________________________________

A team of Brazilian BC Engineers visited Egypt last summer and
measured field strengths for the Tana Station (near Cairo). Their
reported results are that are difficult to believe. They were unable
to observe the transmitter power, but estimated it to be 24 kW.

The *measured* FSs equal to 225 mV/m (107.04 dB microvolts/m), 68 mV/m
(96.65 dB microvolts/m), 50 mV/m (93.98 dB microvolts/m) for distances
equal to 13.2 km, 40.9 km, and 55.4 km, power equal to 24 kW,
correspond to a FS at 1 km, power 1 kW equal to 116.8 dB microvolts/m.
The theoretical maximum FS for a quarter wave is 314 mV/m. (109.9 dB
microvolts/m) ---- so the *measured* FS corresponds to a gain of 6.8
dB over a quarter wave monopole. That is impossible!!

Dr. Kabbary must have a silver wand. But, on the other hand Benjamin
F. Dawson [private communications] measured FSs a factor of four
smaller.

Kabbary [reference Radio World, March 2000. p. 48] is now saying "We
think a little confusion has arisen (concerning the efficiency of a
CFA). The efficiency of CFAs appears to be greater than 95 percent,
similar to very good vertical antenna systems. The above remarks
(efficiencies as high as 9 dB) arose when comparing to a "fictitious"
or non-realistic antenna systems in the past. We are quite happy to
say that a CFA appears to be just as efficient as a vertical." So
what does this say about the published Brazilian results?

The only measured FSs that are (at least) in accord with my view are
those measured in Australia, for a Sidney Narrowcast Station,
operating on 1665 kHz. The relative difference in dB was measured
with reference to three Narrowcast Stations operating on similar
frequencies, employing standard broadcast antennas (efficiency
unknown). I tabulate results below measurements reported by Steve
Olney, VK2ZTO ( on 10 February 20000).

TABLE

Frequency Narrow Cast Station kHz 1620 1630 1683

Distance km 42 21 53

Distance Correction dB (1) -1.8 -7.9 0.17

Field Strength Difference dB 13 18 12

Transmitter Power Difference -3 -3 -3
dB

Corrected Difference in FS dB (3) 8.15 7.9 9.16

1) Distance Correction, since when making measurements at one site
the distance to the CFA Station and the distance to the Standard
Station were not the same.
2) The CFA Station was (apparently) operating at half power level.
3) Standard Station Compared with CFA Station.

So the CFA is about - 8 dB with reference to stations employing
standard antennas. I have heard that the Station Owners are very
dissatisfied, have closed down their station and want their money
back.

I have seen a photograph of this station. It is on the roof of a
building. Height of CFA 2.4 m. In fact the GP is on a platform about
2m above the roof. The transmitter appears to be underneath.
Connection to ground, or to the building's ground unknown?? The
performance of a CFA on the roof of a building is improved due to
radiation from wires connecting the antenna system to ground. In fact
the building itself may be a re-radiator, since in effect for MF the
building is a wire grid structure. The electrical wiring system has a
ground wire, and the electrical grounding of buildings is usually
fairly good.

My original calculations (very poor efficiency) are for a very small
antenna, the 1991 original Tanta antenna, which was 0.014 wavelengths
high. The radiation efficiency is a strong function of antenna
height. That is my statement, the inventors say antenna height is
unimportant (insofar as efficiency and bandwidth). But, I have added
the conical sections to my numerical model, added wires connecting to
ground stakes (height of building 4.3 m, length of ground stakes 4.3
m) --- and the best I can do (according to NEC-4) is - 10 dB
referenced to a theoretical quarter wave monopole.

So we have a problem regarding efficiency. But in my view there is a
major problem problem (according to our numerical and experimental
modelling), with power surging back into the tuning network and the
transmitter.

One can experimentally tune and phase the antenna so that one sees
50-ohms looking into the antenna, and when connected to a transmitter,
with a phase lag feeding the disc, one can measure currents 90-degrees
different in phase --- but the transmitter certainly does not see all
of its power going forward --- something like half of that power comes
back.

This is a characteristic (according to our numerical modelling) of
electrically small antennas fed in phase quadrature (dipoles,
monopoles or the unusual "CFA" configuration). No one using the
antenna has mentioned this, excepting for our experiments. We find
this feature when we try to power our experimental CFA.

If users do not find this problem, in my view their antenna elements
are not fed in phase quadrature.

_____________________________________________
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 Mon Mar 27 2000 - 06:15:30 EST