A wide spaced array offers many benefits when possible. In general the
is less coupling between the elements results in better less mutual
impedance interdependence. When enough space is available a simple Ham
array would be 1/2 wave spaced elements fed from the center point with
open wire. This will produce familiar figure 8 pattern where the major
lobe is perpendicular to the line of the towers. Basically the energy if
equal from both towers will cancel along the line of the towers but
since the towers are in phase, points perpendicular, beginning at 45
degrees between the line of the towers will add in phase with the
resultant lobe at 90 degrees. If the phasing is 180 degrees the energy
will add along the line of the towers and also produce a figure 8 but
rotated 90 degrees. A useful unidirectional mode with 180 degree spaced
towers is 45 degree phasing which produces a wide forward lobe with deep
nulls at an angle to the rear and a 'tail' peaking up at the rear.
Towers spaced around 90 degrees produce better cardioid patterns. The
ARRL Antenna Handbook goes into pretty detailed explanation of phased
arrays and gets into multitower arrays, showing three and four tower
designs.
I would also suggest EZNEC as good entry modelling software. while with
modeling the devil is always in how close to life the modeling details
are, simple two towers models play out pretty well with basic models.
If I had the space I would consider a 180 deg spaced two tower array
with as I mentioned earlier open transmission with 4 positions. The
first in the center for normal figure 8 operation, the second a
transmission line to either one of the towers to rotate the figure 8 90
degrees and the third and forth to taps in either direction along the TX
line to achieve 45 degree phasing for quasi unidirectional operation
along the line of the towers in either direction. This would be one of
the least expensive arrays that could be built with a minimum parts
count. But have 360 deg coverage.
On 11/22/11 8:06 PM, Gerry Treas, K8GT wrote:
> Hi Dale,
>
> I'm no antenna expert, but certainly read as much of the experts publications
> as I can get my hands on, but having a Teflon brain, it doesn't stick very
> well.
>
> That said, the ARRL Antenna Book has a page that shows the patterns of
> various spacings and phasings of vertical antennas, which I found very
> enlightening.
>
> 73, Gerry, K8GT
>
>
> ---- Dale Long<dale.long@prodigy.net> wrote:
>
> =============
> Gentlemen:
>
>
>
> I am not one who thinks the whole world revolves around my concerns. And I
> recognize that some research on my part may be necessary. ( I have read
> ON4UN's Low-Band Dxing)
>
>
>
> But I do think this is a reasonable question, and think that there are
> knowledgeable folks who might provide some advice. Unfortunately I have
> never done any antenna modeling.
>
>
>
> Please let me know your thoughts.
>
>
>
> Thanks,
>
>
>
> Dale N3BNA
>
>
>
> From: Dale Long [mailto:dale.long@prodigy.net]
> Sent: Saturday, November 19, 2011 3:05 PM
> To: 'Topband@contesting.com'
> Subject: feeding phased verticals at half wave spacing
>
>
>
> Gentlemen:
>
>
>
> I have been told repeatedly that phased verticals should be spaced 1/4
> wavelength apart. Ok, I am willing to accept that.
>
>
>
> My question is if you have verticals that are 1/2 wave apart, would it not
> give some pattern, whatever that should be?
>
>
>
> If you were looking for an endfire pattern how should you feed such
> verticals?
>
>
>
> If you have specific questions, you may contact me directly at
> dale.long@prodigy.net
>
>
>
> Thanks and 73,
>
>
>
> Dale N3BNA
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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