[Moon-net] Orthogonal polarization???

[Edward Cole]

Bill,

Obtaining 45 degree linear polarization is merely driving both V and 
H equally in-phase.  Because the Vertical elements are physically 
spaced ahead of the Horizontal elements (approx. 1/4 WL) you must 
delay the signal to the Horizontal elements by 90-degrees (1/4 WL 
longer coax line x velocity factor).  If You want -45 degrees (this 
is equivalent to +135 degrees as far as polarity is concerned) you 
must delay the Horizontal signal by 270-degrees (3/4 WL x vel. factor).

RG-8 and RG-58 clear polyethylene insulated coax has a velocity 
factor of 0.66.  Foam type insulation is something like 0.85 (you 
need to look this up so you make the delay line exact).  Or you can 
use a grid-dipper or the MFJ antenna analyzer to determine the correct length.

At 05:47 PM 1/14/2008, you wrote:
>Thanks to all who replied publicly and privately to my
>question.  Several people said that orthogonal
>polarization could be obtained by feeding one of the
>yagis out of phase, but others pointed out that this
>just produces circular polarization, which is not what
>we want for eme.
>
>Orthogonal polarization is supposed to be linear
>polarization at 45 degrees between horizontal and
>vertical.  This is supposed to be possible with the M2
>XP antennas, but I called M2 and could not get a clear
>explanation how to accomplish this.
>
>As for the "exceeds 6-dB stacking gain" claim, I think
>they don't really mean "stacking gain."  My guess is
>they were trying to say that due to the XP's ability
>to send and receive at the correct polarity, the
>antenna is effectively more than 6 db better than a
>horizontal only array.
>
>73, Bill NZ5N
>--- graham <graham.d at orange.fr> wrote:
>
> >
> > >.  I do not know how
> > >one exceeds 6-dB stacking gain
> >
> > There are a number of antennas that display this
> > characteristic during
> > array modelling.....whether they actually realise
> > the result in the real
> > world would be difficult/impossible to verify on an
> > amateur range.
> >
> > It happens 'typically' in some older designs that
> > were not computer
> > optimised, the old Tonna 16/17 can be easily made to
> > display this if anyone
> > wants to play with it..... I forget the stacking
> > parameters that give
> > this > 6dB result.
> >
> > It occurs because coupling of the antennas together
> > in an array has
> > influence on  each part of the array.
> >
> > But one has to be careful because poor segmentation
> > can also distort
> > results, either way,  as can 'short cut' modellers (
> > such as YO)  and the
> > most popular g/t  modeller ( yagi 3.54) which has a
> > 3dB 'assumed' gain in
> > one plane also....
> >
> > Graham F5VHX
> >
> >
> >
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>
>
>
> 
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73,
Ed - KL7UW
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