wrote:
On 7 Feb 2005 21:27:32 -0800, wrote:


I couldn't find anything there that was similar
to this:

http://www.drslick.org/Temp1/yagiplot.jpg

You can lead a horse to water, still can't get it damp.


I would like an H-plane plot, if possible,
and i'm looking for a cardiod pattern, as above,
but with higher dBi if possible.



You'd have to look at the data sheet. All the commercial people
are aware of this and it's accepted practice.

What you missed is a 2 or 4bay dipole is a really nice antenna
that can offer gain and pattern control. The usual use is a 4 bay
vertically oriented with each of the 4 dipoles spaced 90 degrees
around the mast for 5.6db omnidirectional gain. Now, if you want a
directional pattern, such as cartioid then put all four on one side,
also expect slightly higher gain as well. The commercial version are
expensive but are known for their durability but, the good news is
they can be built using copper pipe and will give the same
perfomance. I might add, the gain numbers I gave are not theory,
they are real numbers from proven designs.


2 bays is big and heavy enough! 4 would be
a bit overkill in this situation.



http://dipole.w4zt.com/ look at the plumbers dipole page.
This can be built as a 1/2/4/8 dipole array. The limit is 4


I've tried using an SO-239 attached to the
antenna itself (as they have done here), and it's
a bad idea...pot metal is very weak.



direction. These designs will you get away from theory and use
practical designs.


The theory is close to reality in my case! Except
for the F/B ratio, which seems a bit exaggerated.





A repeater group I work with locally used the DBproducts 4bay and
found it the best antenna they've put on the tower to date. It
wasn't
cheap and it was heavy. Experience at that site was anything less
robust would barely stand a year before the SWR went to unacceptable.
I've built the 4bay for UHF and it's a solid performer. The all
copper design weathers very well, is very cheap to build
and performs just as well as the commercial versions which are welded
up from aluminum.


yeah, but UHF versus VHF is gonna be a huge
difference weight and size wise!



I'm sure your getting results from the Jpole but, I can be certain
from using them myself that your results are part luck and can easily
be attributed to the added height (the 70+inches can really help)
and
placement more than the presumed gain. If you compare a yagi or
dipole to a J-pole the radiating element must be the same height.
Since the J-pole is really an end fed dipole it has a 38 inch
advantage. For a yagi the centerpoint is the boom.. In direct
comparisons the yagi you built would have to be minimally 3ft higher
to compete on fair ground.


The Super J-pole was actually about 5 ft. lower than the
Yagi, so it evened out in the end.


S.