Chuck Counselman, ccc_at_space.mit.edu, wrote,
>
> Unless I missed something or something was missing in Paul's
> drawing, you don't need NEC-4 to understand this antenna.
Paul was kind enough to also email the small JPEG drawing to me.
Adding to what Chuck described, it is a heavily end loaded
off-center-fed vertical.
It reminded me of the disc-loaded vertical dipole that Rich
Littlefield described in Communications Quarterly a couple of years
ago, but with a much different aspect ratio. The diameter of Paul's
discs are the same as the separation between the discs.
Using NEC2's Example 6 as a guide for describing surfaces, I did a
NEC2 model for Paul's antenna. I sent him a set of NEC2 outputs
yesterday.
At 28.1 MHz, I found the feedpoint to be predominantly capacitive,
with the real part of the feedpoint about 0.2 ohms, I think [I don't
have the numbers with me here].
I also did not find anything unusual in terms of fields.
The curious thing is, I don't know how he had managed to resonate the
structure using the matching circuitry he described.
Paul's antenna is not as "small" as the classic CFA, as described in
the AntenneX articles. The antenna described in AntenneX is of the
order of a foot in size, and operates on 80 metres. When someone
claims success with that antenna, I will spend time to attempt to
model it on NEC2.
Regards,
Kok Chen
aa6ty_at_arrl.net
Received on Thu Feb 25 1999 - 06:48:30 EST
This archive was generated by hypermail 2.2.0 : Sat Oct 02 2010 - 00:10:39 EDT