NEC-LIST: Further Update on the CFA

Hello to all, from my Desk,

The CFA Successful Deployment an Enigma
_____________________________________

In the October 1999 issue of Radio Today, pp. 11-13, another article
tells us once again that this electrically small antenna, less than
3-percent of a wavelength, has GAIN over a quarter wavelength tower
mast (1.25 dB field strength at 1 mile; 4-9 dB distant field
strengths); little or no RFI (a photograph shows two MF broadcast
antennas on the roof of the same building, operating at powers of 30
kW and 100 kW); and greater bandwidth compared with a quarter wave.
The reason for the greater gains observed for the distant fields was
said in earlier papers to be due to the fact that the ground wave
field falls off more slowly for the CFA then for conventional
antennas. This is even more unbelievable.

The article begins with statements that we should forget about
everything we know about antennas, because otherwise we will say
impossible!! But (in the view of the inventors), the *CFA does all
this, and more*, and it really does work.

In my view the characteristics of the CFA are: very intense E-fields
in the near field, and relatively weak H-fields; it is very
inefficient radiator (one percent or less); and difficult to feed.
The large (large compared with radiated power) circulating reactive
powers, surging out one terminal and surging back into the other
terminal, creates problems for the transmitter. And, while disagreeing
with the wild claims above regarding performance, I find it incredible
that this small antenna can be operated at such high power levels
(30-100 kW); and two of them can be operated in close proximity (only
6-metres apart).

Never in my experience, in my fifty years of research in the field of
antennas and propagation, have I seen such a difference between
performance claimed, and performance predicted by simulation and
experiment (simulation and experiment performed by me not by the
inventors).

I have now completed my paper, which will be presented at the AP 2000
Conference, to be held in Davos, Switzerland, in April. If you would
like a preprint, I can send it in two ways: a) as a postscript (level
2) file. The file size is under 3MB; or 2) by mail. Whatever, let me
know. If I send it by mail I will need a postal address.

The paper is gone, so it is too late to make changes, however, I will
be be pleased to receive comment.

Regards, Jack

_____________________________________________
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 Fri Dec 10 1999 - 18:28:13 EST