Re: NEC-LIST: cross field antennas

Kok,

        I think I need a 50 unbalanced to 377 balanced transformer. It
seems that whilst the source impedance can vary eg 55 or 45 is fine
the output impedance must be very close to 377 ohms eg +/- 0.5 ohms
over wide bandwidths.

The antenna seems to radiate and receive similiarly to a quarter wave
vertical. However I want to get my matching right as described above
before I can be sure.

There seems to be a certain amount of hysteria in some of the
documentation regarding the CFA however I have a genuine scientific
curiosity regarding the behaviour of the antenna.

regards.

----------
> From: Kok Chen <kchen_at_apple.com>
> To: paul moody <paulmoody_at_onaustralia.com.au>
> Subject: Re: NEC-LIST: cross field antennas
> Date: Friday, February 12, 1999 6:33 AM
>
> Paul,
>
> Are you looking for a 50:377 match that is unbalanced
> on both ends? Or balanced on the 377 ohm end?
>
> Amidon Corp (they advertise in QST and CQ magazine)
> makes some ready made Baluns and "Ununs" (unbalanced
> input and unbalanced output) that are close to what
> you need.
>
> I have been curious about the CFA ever since it
> appeared on Wireless World. However, I have not tried
> experimenting by building one. The problem is,
> when I do a gedanken experiment, I couldn't bring
> myself to believe it could work. Viz: assuming the
> law of reciprocity works; consider the CFA as a receiving
> antenna. Since the output of the antenna is a vector
> sum of the E and D plates, and the antenna is not an active
> device, the output can be no larger than the amplitude
> of what can be obtained from the E plate alone summed
> with the amplitude obtained from the D plate alone.
> Thus, either the antenna cannot work as well compared
> to a full sized vertical? (I know, you can use preamps
> to fix the receive problem in the low-HF region).
>
> I wonder if you are receiving signals from your version
> of the CFA that are comparable in signal strength to a full
> sized vertical?
>
> I would be very interested in what your have discovered
> (the additional crucial physical element :-) when you are
> ready to reveal it.
>
> Finally, the scheme shown in the Henf US Patent 5796369
> appears to be a better way of generating a B field than
> using the D-plates. Everything from that patent (you can
> read the patent on the IBM Patent web site) appears to
> me to be doing the right thing. I.e., the big hole in the
> ground plane to reduce E field lines close to the B-field
> generator, etc. However, the scheme presented there does not
> seem to have any independent control of the phases between
> the E and B fields. The phase shifts seems to be determined
> by the geometry of the Henf antenna itself. BTW, this is the
> antenna that the Gap Antenna web page shows as their
> Super-C antenna.
>
> The Antennex articles have renewed my interest in the CFA,
> even though the articles themselves appear amateurish to
> the extreme.
>
> 73
> Kok Chen, AA6TY
Received on Fri Feb 12 1999 - 10:15:56 EST