Try the old Frank Jones VHF handbook ,he was a "6", (if you can find one)
he did more than a few colinears (includeing an 18 El one for 432) can't
renmember his call, and this NOT modern, (from the 60's) but what you are
essentially trying to do is: from top of element, to bottom of NEXT element,
create a 180 deg phase shift! can do that with a out of (radiation) plane
1/2 wave long (like the center piece of a cushcraft ringo), or RESONATE
CIRCUIT (but, this if high "q" can cause problems, this is also how the
multiple stacked 1/2 wave sections on commet, and many commercial antennas
work! those configured out of stacked , center conductor to shield, and
vice versa coax pieces , all the way to the top, (EXCEPT at the top, they
shorted together, and hit a 1/4 wave rod)! been in handbooks for years--
Jim NN7K


"Tom Bruhns" wrote in message
m...
mike wrote in message
news:c1ac07f922537b76bdd0efbf47136f6b@TeraNews.. .
After much searching (Google and books) I have yet to find an answer.

Does anybody have the formulas for making a phasing coil for collinear
antennas?

I would like to use coils instead of stubs, easier to make enclosures
and mounting points.

Surprised you haven't gotten any other answers on this yet.

Suggest you look for a program that will tell you the self-resonant
frequency of a solenoid coil and use that to _estimate_ the coil you
should use. Try to make some measurements with that and with some
coils a little longer and a little shorter, and also for comparison,
against a measurement of just a simple quarter wave (assume you want
to run it against a ground plane).

Consider also that you could use a coaxial phasing stub: make one of
the elemens from coax whose center shorts to the outer an electrical
quarter wave away from the end; outer is the radiator of that section
and the inner connects to the end of the other section.

But I'd also suggest you read the part of the "Antennas" chapter in
King, Mimno and Wing's "Transmission Lines, Antennas and Waveguides"
that talks about phasing stubs, and suggests that coaxial stubs (and
by implication, phasing coils) do NOT work as well as stubs
perpendicular to the axis of the antenna.

I'm personally partial to the "coaxial collinear" construction in
which transmission line characteristics ensure proper phasing of the
feedpoint voltages between each pair of elements.

Cheers,
Tom

Frank Jones (W6AJF) - Google is your friend

I was thinking about the coax collinear but I never could make them
work.
I did find a reference about the velocity factor if the center being
different from the sheild. This messed up the phase relationship.

It appear the original antenna this was copied from had the whole
antenna potted in wax to fix that. Maybe build one out of the air
dielectric coax I have in the garage?

I guess I'll just drag out the formulas for parallel line and stubs.
Whip something out of copper pipe and the wife poly cutting board she
don't use.

So, how does one mount a 10' copper pipe antenna to a mast? Beside on
a dare....


Mike

(Mike) wrote in message . com...
Frank Jones (W6AJF) - Google is your friend

I was thinking about the coax collinear but I never could make them
work.
I did find a reference about the velocity factor if the center being
different from the sheild. This messed up the phase relationship.

It appear the original antenna this was copied from had the whole
antenna potted in wax to fix that. Maybe build one out of the air
dielectric coax I have in the garage?

The coaxial collinear works fine if done properly. You do NOT have to
put the thing in wax to make it work. I wrote a paper on how to do it
properly, but the key is to use sections 1/2 wave long taking into
account the VF of the line, so that the voltage across each gap
between adjacent sections is the same, and all in phase. The
feedpoint impedance will be somewhat reactive since the elements are
shorter than a half-wave, and the impedance will depend on the number
of sections (since they are all fed in parallel, and there's a mutual
impedance to consider), but you just provide the proper matching
network for that, and you provide proper decoupling from the feedline.
It's easy to put together an eznec or similar model to show that it
works fine in air, no wax needed. And it works in practice as well as
in theory.

The old ARRL writeup on the coax collinear was rather messed up, and
my lack of success building them a couple times led me to think it
through much more carefully and learn HOW to do it.

Cheers,
Tom