[TowerTalk] phasing question

[alsopb]

Tom,

I recently persued this in EZNEC.  I have two towers of identical
height with 10 M antennas on them.  Their spacing is 10 wavelengths on
10M.

Case 1 - It is like a 6 element beam with 10 wavelengths between the
two "beams"
AZIMUTHAL
It turns out that for this combo you can get "rhombic" like pattern
with 270 degree phasing.  The description is hard to put in words.  It
had a single forward pencil beam of about 20 degrees width and then a
large number of vary narrow secondary beams each with decreasing
amplitude.  The largest of these lobes is down 2 db from the main
lobe.  If one connects the peaks with a dashed line, it approximates
the normal beam pattern for a single antenna.
ELEVATION.
The height of these antenns is 2.5 wavelengths.  That gives 5 lobes in
the forward quadrant. Phasing it as above accentuates the lowest lobe
and suppresses the others significantly.  The nearest secondary lobe
is quite narrow and 6 db down from the max.  The pattern is quite
dirty.

The overall gain was 3db relative to a single antenna.

Case 2 (both beams 90 degrees from above).  This is the usual
horizontal stacking configuration.  What is formed is an
inteferomenter where you get many, many lobes azimutally.  Again, if
you connect the peaks with a dashed line, it approximates the pattern
of a single beam.  PHASING DOESN'T MATTER MUCH.  I can't find the
elevation plots.  This looked like a looser to me.

Based on these studies, unless you have the good fortune to have two
towers line up in a perferred direction (JA), neither is too useful. 
The first case is more useful than the second.

By the way, if the antennas are space 1 wavlength, one can get a neat
"inteferometer pattern" with only 3 lobes in the forward half-space. 
The secondary lobes are down 15 db!  The forward lobe has a beam width
of about 30 degrees.  So if one want's to stack horizontally.  This
type of spacing is useful.

73 de Brian/K3KO

n4kg@juno.com wrote:
> 
> Yes you can phase antennas on different towers.
> Seems like there was an article on phasing 2 or 3
> 80M(?) beams in line.
> 
> One useful approach would be to phase them in-line
> to SouthernEurope which would be broadside to JA,
> where the more narrow broadside pattern is not a problem.
> 
> de  Tom  N4KG
> 
> On Fri, 17 Nov 2000 "Bill Heinzinger" <w9ol@billnjudy.com> writes:
> > Purely a theoretical question.
> > I have no plans nor have heard of any to do this.
> >
> > I know you can phase multiple beams on one tower.
> > Can you phase a beam on multiple towers?
> >
> > I'm purely guessing that you could carefully calculate the proper
> > coax
> > between the towers but also guessing that the increased length and
> > it
> > subsequent loss would defeat the idea.
> >
> >

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