[Elecraft] easy simple portable antennas?

Tue Jun 4 20:45:01 2002

On Tue, 4 Jun 2002, Vic Rosenthal wrote:

> Trevor Day wrote:
> > 
> > Funnily enough, I have just been playing with a pole antenna (courtesy
> > W0KPH web site) just to prove to myself that its surely not possible to
> > radiate a decent signal on 20m using an antenna that is:
> > 
> > contained within a tube of 2 inches diameter by 14 inches long,
> > fed with 4 feet of coax,
> > and leaning against the inside of my shack window!!!
> 
> The link is http://www.qsl.net/w0kph/ if anyone's interested.  What he's done,
> it seems to me, is make a dipole with a large amount of capacity between the
> (small) halves and resonate it with a coil.  This dipole would be expected to
> have a very low radiation resistance, which he matches via a link.  Probably the
> circulating current in the coil is quite high, which means that for reasonable
> efficiency it should be made of copper strap or tubing.
> 
> I think I'll try it -- I'll use tubing for the coil and put a capacitor in
> series with the link to simplify tubing.  If it works at all, its small size
> makes it interesting!
> 
> 73,
> Vic, K2VCO
> Fresno CA

Vic, et all:

I looked into this antenna a few weeks ago.  From everything I can find
with testing, it acts like any other short, fat dipole.  IE; It is not a
very efficient radiator.  Sure, it will load up.  That is a function os
the loading coil and the capacitance between the two elements.  It doesn't
appear to radiate nearly as well as a *low* half-wave dipole
though.  Additionally, I think if you do some searching at google or
whatever other search engine you desire on the EH and the CFA antennas
(the EH design is apparently the prior work of Dr. Fathi Kabbary on his
way to designing the CFA antenna) you'll find that there has been NO
real-world testing done that shows results anywhere NEAR the claimed
performance of either EH Antenna Systems or CFA Limited.

Take a look at this article from Radio World Newspaper:

http://www.rwonline.com/reference-room/special-report/rw-antenna3.shtml

73 de John - KC4KGU
K2/100 #2490