Re: NEC-LIST: cross field antennas

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> From: Kok Chen <kchen_at_apple.com>
> To: paul moody <paulmoody_at_onaustralia.com.au>
> Subject: Re: NEC-LIST: cross field antennas
> Date: Saturday, February 13, 1999 4:52 AM
>
> Paul,
>
> > 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.
>
> I have been reading feedback to the AntenneX articles. Except
> for the author (Ted Hart) of the articles, no one else has managed
> to obtain any radiation within 18 dB of a quarter wave vertical.
> I.e., everyone was getting the performance of a 1% tall vertical.
>
> Your independent results are thus, indeed, EXTREMELY encouraging.

Well I have yet to do comparative field strength tests.

>
> Except for loops, I don't know of any antenna that is 1/100 a
> wavelength in the larger dimension to be capable of anywhere close
> to the efficiency of a 1/4 wave vertical. And the bandwidth of
> your antenna far exceeds that of a tiny loop. EVEN if CFA theory
> is suspect, your design has much merit in amateur circles.
>
> If you can't get the proper balun (I suspect the baluns designed for
> folded dipoles would be good enough) I would suggest sticking to
> your present arrangement and installing a whole bunch of ferrite
> beads where the feedline is connected to the CFA. Even better, wind
> a few turns of the coax through a large ferrite core at the point
> the coax is attached to the CFA. That should prevent much of the
> coax shield from radiating, it it is currently.

This is exactly what I do.
>
> Since you posted to the NEC group, have you succeeded in modelling
> the CFA for NEC? If so, are you seeing a large coincident E and B
> field somewhere in space?

I am not an RF guru however I am using a small adcock ( I think
spelling correct ) antenna for E detection and a small loop for B
detection. I get extremely large E at 10 meters radius around the
antenna. The Loop gives similiar results.

I joined the list to find out how to model the antenna under NEC but
have yet to do so. Which version of NEC is best? ( and prefer free ).

I am going to publish the full specification on my website in a few
days ( I hope ) .. I will post a notice on the NEC list when I do so.

regards ..
Received on Mon Feb 15 1999 - 19:32:45 EST