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From: Quote from Jack Belrose
Date: 12 Jan 2000
Time: 11:43:02
Remote Name: 208.21.128.214
....in the interest of fairly & correctly quoting Jack Belrose's current view of the Tanta Station CFA measurements & his follow up discussions with Sylvio of the observation team, Jack Belrose sent me this message to post... regards, Jack L. Stone:
Correspondence with Sylvio Damiani is not new for me, I have corresponded with him on numerous occasions in the past, on the subjuct of MF folded monopoles, MF BC antennas with elevated radials, and other topics of interest.
It is true that I have been discussing the subject of his measurements of the FSs for the Tana CFA in Egypt.
What I have learned follows:
1) The NEAR FIELD measurements are RELATIVE VALUES only. The BC antenna engineers accompanying Sylvia all turned the gain of their FS meters to zero --- frightened to damage their instruments.
Re measured relative values Sylvia said:
Let me copy directly from my personal notes. These relative values are: distance from CFA (m) relative F.S. measured (V/m) 50 3.4 100 2.6 200 2.1 250 1.5
2) The FAR FIELD measurements are ABSOLUTE VALUES.
Sylvia said, "yes, they are Jack. With *full calibration* of the three FIM-41s. Here again the values of F.S. extracted from my personal notes: distance from Tanta(km)* measured F.S. (mV/m) 13.2 225 40.9 68 55.4 50 76.9 14 Note: * distances calculated by two different GPS receivers".
The measured values for distances 13.2 -55.4 km fall on a 1/d curve, almost exactly, the conductivity in the Nile delta must be super, and hence my projected FS value at 1 km is 115 dB microvolts/m, for a transmitter power of 1 kw. Note: The measured data correspond to a transmitter power of 24 kW.
The theoretical maximum FS for a quarter wave monopole at 1 km, 1 kW is 314 mVm, which corresponds to 109.94 dB microvolts/m.
Hence the "measured" value of 115 dB microvolts/m is 5 dB greater than a 100-percent efficient quarter wave.
This I say is absolutely impossible for an antenna so small (the CFA).
3) The results of my studies to date, which will be published when the AD 2000 Conference Proceedings is available on CD ROM, are all for the original 1991 barrel shaped CFA. But I have modelled the Tana antenna, my best guess. A CFA with the conical extension, total structure height as stated, GP on roof of building, connected to stake grounds in 4-places (stake length 3.6 metres), ground conductivity 10 mS/m, inductor Q-factors 500.
The calculated FS at 1 km, transmitter power1 kW (according to NEC-4D) is 78 mV/m (97.83 dB microvolts/m). Hence the measured values are 17 dB greater than NEC-4D predicts. The predicted FS (according to NEC-4D) is 12 dB down on a quarter wave.
Conclusion:
1) We have a problem to explain the unacceptably high values of FSs measured.
2) We have a problem to explain why the antenna works so well in Egypt, but not elsewhere (c.f. my detailed experimental study).
For our wire grid models see:
http://members.home.net/propagation/cfa.html
Experiments are described in:
http://members.home.net/propagation/CFA2.rtf
3) Finally, consider the general concept of this antenna. Power from a transmitter is fed into a phasing unit from which two voltage feeds are taken to two separate electrodes, the D-plate and the E-plate. The E-plate, a hollow metal cylinder that is fed against the GP, produces curved E-field lines to the GP. The D-plate is a circular metal disk, which, in conjunction with the GP, forms a parallel-plate capacitor. The time varying E-field lines between the D-plate and the GP produce H-field lines surrounding the capacitor, which link with the E-field generated by the E-plate to produce, in the view of the co-inventors of the CFA, an out-going Poynting vector, resulting in significant radiation.
This description of the theory of operation of the CFA is a bit naive. The D-plate electrode, designed to generate H-field also generates a strong E-field of its own. The electrode E-plate, that is intended to generate an E-field, also generates an H-field. We therefore have to consider in-going as well as out-going Poynting vectors, and, integrating (ExH) over a hemispherical surface, it is not at all clear what the outcome will be.
Continuing, in the words of the co-inventors of the CFA, the circular disk capacitor plate (H-Plate) above a GP is used to convey displacement current dD/dt. Hence it said that unlike assumptions in most antenna theory books, it is the displacement current which gives rise to the magnetic field, rather than conduction current on the antenna elements. Thus it is said that the numerical electromagnetic code NEC (we use here NEC-4D) cannot be used to analyze the CFA. But their claims that a new theory is needed and that NEC cannot be used to analyze the CFA are wrong. The relation of H to varying D and the relation of E to varying B is contained in Maxwell's equations and is exactly satisfied in the NEC solution. The only source terms in Maxwell's equations are electric current (and magnetic current if you can find any) and that is what NEC uses. Of course, on the plates the large D is produced by charges, but that is related to current through the continuity equation, and is taken into account by NEC. That is why NEC uses Green's functions for E and H due to J, such that Maxwell's equations are guaranteed to be satisfied.
The so-called Hately-Kabbary-Stewart "heavy theory" that is supposed to to explain how the CFA works is flawed. Simple and fundamental knowledge in mathematics and physics are missing and the results would contradict the foundations of electrodynamics and relativity, which have been proven to be reliable and are confirmed by many experiments within the last 100 years. If that is the theory the CFA is based on, then one can conclude, without believing my detailed numerical modelling, that the CFA does not work, did never work and will never work.
It so far works only in Egypt. It did not work in Australia. We have yet to learn from Ing. Alberto Fassio about his experiences with his CFA in San Remo, Italy (Fathi Kabbary is there now to tune the antenna, so if it does not work, one cannot say that Alberto did not tune it correctly).
And, we have yet to learn about the performance of the MF CFA in Kiel, Germany. The report, see radiotoday, October 1999, p. 12, that Deutsche Telekom are delighted with its performance is premature, or wishful thinking. The setting up of the CFA system and measured performance is presently ongoing.
The radiotoday article makes performance claims which are absolutely unbelievable.
Regards, John S. (Jack) Belrose, PhD Cantab, VE2CV