can anyone point me to an article that has the details right, for vhf/uhf
use.

i don't understand how the velocity factor of the coax used in the elements,
works in this antenna.

If you ever have the opportunity to disassemble an old Prodelin, or
Phelps-Dodge antenna, which is the commercial implementation of this
design,
you will find it very different from any of the ham construction
articles.
This design has many interdependent variables, and due to many
disappointments, the ham interest had waned by the time a real, correct
analysis was published.

As far as I know, the original disclosure of this design appeared in the
Proceedings of the IRE just after WW2, and is likely the closest to
correct.
But, for the life of me, I can't remember the inventor's name.

all that i've seen on the net just says that the vf affects the segment
lengths.
of course the radiating segments are significantly shorter than free space
half wavelengths, depending on velocity factor.

it seems the the ideal coax for this would have a very high vf, but i may be
missing something.

i can't see how it works so well, when the radiating elements are only 66pct
of what they should be.

Since the VF is 66% (or whatever the coax you use is) what
good (?)
effect would tophats have at the end of each section in an
effort
to make them resonant?

Just a thought.
Murray

Dave VanHorn wrote:

If you ever have the opportunity to disassemble an old Prodelin, or
Phelps-Dodge antenna, which is the commercial implementation of this
design,
you will find it very different from any of the ham construction
articles.
This design has many interdependent variables, and due to many
disappointments, the ham interest had waned by the time a real, correct
analysis was published.

As far as I know, the original disclosure of this design appeared in the
Proceedings of the IRE just after WW2, and is likely the closest to
correct.
But, for the life of me, I can't remember the inventor's name.

all that i've seen on the net just says that the vf affects the segment
lengths.
of course the radiating segments are significantly shorter than free space
half wavelengths, depending on velocity factor.

it seems the the ideal coax for this would have a very high vf, but i may be
missing something.

i can't see how it works so well, when the radiating elements are only 66pct
of what they should be.
Murray Kelly vk4aok

wrote in message
...
Since the VF is 66% (or whatever the coax you use is) what
good (?)
effect would tophats have at the end of each section in an
effort
to make them resonant?

it would make the antenna a whole lot larger, that's for sure.

For those, have disected (you have to when these trashed, unless have
trailer, after lightning hit them!) These are actually 1/2 wave length
sections (NOT USEING VELOCITY FACTOR!) , at least in the "Green Hornet"
versions, Alternating with the inside to outside(shield), and
outside(shield), to inside , all the way to the top of the antenna, EXCEPT,
the TOP 1/4 wave stinger, which is attached to BOTH THE SHIELD, and CENTER
of the Last section of coax in this antenna. The base (shield of coax) is
counterpoised to 1/4 wavelength radials, and a matching 1/4 wave piece of
coax (value unknown), is attached to bottom connector of antenna.
In other words, forget the velocity factor, EXCEPT for the 1/4 wave matching
section !! and, the after effects of a lightning strike are CATASTROPHIC,
as the Beeswax, that held this mess, inside the fiberglass tube has
literally evaporated . one other thing, when these go bad, measure for a
DEAD SHORT . got it?? , well, now wait for the wind to blow -- or take it
down and flex it . if it goes to "OPEN circuit, it is BAD!! Been there,
done that (in 80 mph winds, at better than 100 feet up in air, no thasnks
any more)!! Jim NN7K

"Dave VanHorn" wrote in message
...

wrote in message
...
Since the VF is 66% (or whatever the coax you use is) what
good (?)
effect would tophats have at the end of each section in an
effort
to make them resonant?

it would make the antenna a whole lot larger, that's for sure.

Harold A. Wheeler: A Vertical Antenna Made of Transposed Sections of
Coaxial Cable; March 1956, IRE National Convention Record, Part 1, Pp. 160 -
164

I seem to recall an addenda or correction published later, but It isn't
mentioned in the 1967 text where I found this.
--
Crazy George
Remove NO and SPAM from return address

I was frustrated that the ARRL design never worked right, and quite a
few years ago thought through the problem pretty carefully. Since
then, I've been able to build them "at will" since I know what's
needed now. I've posted this in the past, and you can probably find
it in the Google archives. Keys, as with essentially any antenna, are
to arrange elements to get the pattern you want and then feed them
properly, and decouple from other conductors (esp. the feedline). In
a coaxial collinear, the feed is tied closely to the elements. If you
feed between each adjacent element pair with in-phase equal-amplitude
voltages, even though the elements are shorter than 1/2 wave, the
currents in the elements will be very nearly in-phase (though of
differing magnitudes). It's fairly easy to simulate in EZNEC to see
what happens. The "end-fed" half-waves show high feedpoint impedance,
but the coax puts them all in parallel, and what I see with typical
ten element antennas is a net ROUGHLY 150 ohms with some reactance,
easily matched with an "L" network to 50 ohms.

Though I prefer using foam Teflon dielectric line (which has about
0.82 VF), the coaxial collinear DOES work with solid polyethylene line
with 0.66 VF. I prefer the foam Teflon because it's really nice to
solder, more than anything else, and an 1100' roll was very cheap...

Others have posted (on web sites) similar findings, with designs
similar to what I've used. You will find people who tell you you
can't build one, but I know better: I've simulated them and built
them, and the performance as-built matches what I expect from the
simulation.

Cheers,
Tom

"Dave VanHorn" wrote in message ...
can anyone point me to an article that has the details right, for vhf/uhf
use.

i don't understand how the velocity factor of the coax used in the elements,
works in this antenna.