On Mon, 03 Oct 2005 09:11:37 -0500,
Bob Bob wrote:
Yes!

The "there and back" is often seen as phasing coils on mobile UHF
verticals. Also the same kind of logic as a colinear J pole (for
example) that has the hairpin shaped thing about half way up the
radiating section of the antenna.

You can also get colinear effects by using alternate halfwaves of very
thick vs very thing elements (eg 25mm pipe and 2mm wire on 144MHz) but
as one long "element" rather than bending it back and forth. (Yes the
gain is lower for a given length)

Keep in mind that it is prudent to feed in the middle of the antenna,
probably at one of the hairpins sections. Its a good place as somewhere
along the phasing section the Z will be that of your feedline. If you
feed at the end the pattern tends to skew away from the feedpoint.

Cheers Bob VK2YQA

Jim Richardson wrote:
...

something like this.

Feed __||__||__||__


Very enlightening responces, thanks all. I have access to a nice HP
vector NA at work, and plan on building a couple of VHF antennas for the
boat (marine band, so centered around 159MHz). The colinear was one I
was considering, "just because". Primary is going to be a copper pipe
j-pole.

--
Jim Richardson http://www.eskimo.com/~warlock
I have plenty of talent and vision. I just don't give a
damn.