Re: NEC-LIST: Ingoing-Outgoing Poynting Vectors -- 2

> Yes, you are correct. I do not have the original, but I must have
> flipped one of the E & H terms if you had to fix it. Sorry about
> the confuser.
>
> RWA
>
> BTW did you get a copy of the NAB paper on the CFA?
>
> RWA
> -----Original Message-----
> From: John Belrose <john.belrose_at_crc.ca>
> To: RW Adler <rwa_at_ibm.net>
> Date: Wednesday, April 28, 1999 11:22 AM
> Subject: Re: NEC-LIST: cross field antennas

Dick,

No I have not seen the NAB paper. John Stanley told me that according
to Dr. Kabbary at NAB (brochure handed out), there are now 10 CFAs in
service in Egypt and other places with three under construction. The
saga of the CFA becomes more and more unbelievable with time.

Jerry does not seem to agree with your statement --- which seems okay
insofar as I am concerned --- but I will compute E and H for the disk
and for the monopole separately.

Clearly the CFA does not produce much H-field. And, certainly the CFA
is not doing what the inventors claim. They say that the near field
ratio of Ez/Hy is about the same as that for the far field; which is
very different from that for a conventional monopole. These two
antenna systems are very different, but the difference is not in the
sense anticipated. For the CFA the ratio of Ez/Hy at a distance of 3
metres from the antenna is 3473 (>> 377 ohms), and this ratio
decreases with increase in distance, to a value of 361 at 200 m. For
a 75 m monopole, the ratio of Ez/Hy at 3 m is 212, increasing to 357
at 200 m (all according to NEC-4D).

73, Jack, VE2CV

PS

Okay, I have calculated the E- and H fields for the disk alone, and
the monopole alone. See Table below.

Pt = 1000 watts
PEC Ground
No loss except copper loss (which is small)

Distance Disc Alone Monopole Alone
metres
               Hy-field Ez-field Hy-field Ez-field
                A/m V/m A/m V/m

3 4.066 21,957 2.996 8467

4 1.946 7463 1.801 4623

5 1.152 3436 1.197 2739

6 0.765 1873 0.851 1732

40 0.205 5.42 0.027 7.31

Recall that the disc has a radius of 2m, so I have not calculated
fields closer than 3m (height is 0.3 m, half the distance between the
disk and the GP). The feed for the disk is off centre, since I have a
1.25 m diameter hole in the centre of my disc --- 0.625 m in the
X-direction. I have calculated the fields in the X-direction.

Curiously (?) close to the antenna (the so-called interaction region,
reference Hately et.al.), the disk has the strongest E and H fields.

The Table below gives the results for the CFA (quadrature feed),
compared with a 75m Monopole.

Distance CFA 75m Monopole
Metres
              Hy-field Ez-field Hy-field Ez-field

                A/m V/m A/m V/m

3 0.4355 1513 0.184 39.1

4 0.2533 702 0.14 28.2

5 0.166 395 0.113 21.8

6 0.1174 244 0.095 17.5

40 0.0037 0.992 0.0172 3.817

200 0.00053 0.191 0.00386 1.38

In the very-near field, the 75m monopole is the only antenna that has
a reasonable value for the ratio Ez/Hy. And, with increase in
distance the H-field for the CFA rapidly becomes vanishing small ---
even for a no-loss antenna!! Notice that at 200 m (which I consider
the far field) the Ez field for the CFA is -17.2 dB wrt the 75 m
monopole.

And, concluding with this line of thought, I do not think we can
ignore your insight re out-going and in-going Poynting vectors (see
below).

J

Statement under Discussion:

"The inventors claim that it "works" because the H field from the disc
plates when crossed into the E 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 H field from the
quadrature shifted dipole and the E field from the discs! These
fields result in an INWARD GOING Poynting vector, which adds up to
little real outgoing power over that from the small dipole! [Adler,
private communications, 1999]."

_____________________________________________
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 Thu Apr 29 1999 - 16:53:59 EDT