Tho, both will work, the correct one, from my experience with useing DB
Products "Green Hornet" series antennas, is the one with the 1/4
wave/shorted piece of coax to the 1/4 wave stinger. Ans as a aside, in
vhf service, check for a dead short to the antenna (they flex in the
wind, -if you see it go open, or high resistance, when the wind blows,
needs replaceing) one thing NOT mentioned, in either of these sites, is
the application of Ground Plane radials , however, again, the shorted
antenna has a 1/4 wave decoupling sleeve, which should do the same as
the radials! All in All, I'd go with the shorted one- and a caution:
the pattern of these is VERY NARROW- and close to the HORIZON
(omni-directional) - look like drop a doughnut over the antenna! want
to mount this as straight up-down (verticle) as possible for max range!
As info, Jim NN7K

farzad wrote:
Hi,

I have read about collinear antennas within the two web sites below:

http://www.guerrilla.net/reference/a...ollinear_omni/

http://wireless.gumph.org/articles/homemadeomni.html

I have made the first one. But before testing it, I have noticed that
there is a very essential difference between them. In the first design
there is a short circuit between the central conductor and the
shielding in all segments as the final 1/4 wavelength segments is a
short circuit itself. But in the second design, there is a strict
advice that check the complete antenna before using it in order to
prevent any short cross connection between the central connector and
shielding.

Can anyone describe me what design wil actually work? and if both will
work what is the reason of that difference?

Very sincerely,
Farzad