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Re: phasing two arrows



I previously wrote:
>But what if your object is to provide a set of orthogonal positioned
>elements to generate circular polarization?  The classic case has the two
>sets of elements mounted on the same boom {i.e. zero spacing}.  
>
>Therefore, I think you could space the two Arrows for 0.8 wavelength {as
>recommended on page 7-8, Fig. 7-7} at 436 MHz and feed the 2m and 70cm
>sections separately using normal 90 degree phasing harnesses to produce
>circular pol.  Since the two antennas are at right angles the proximity of
>the 2m elements should not produce much coupling or detuning providing that
>the cross boom and mast are non-metallic.  I would mount the antennas in
>the / and \ position vs H and V.  I think you would get fairly clean
>patterns but little or no stacking gain.  {you would gain 3 dB for matching
>circular polarization, though}

Well theoretically I believe this is correct, but got to thinking this
morning about physical dimentions.
I goofed!
  
0.8 wavelength on 436 is 0.8*27 inches = 21.6.
...whereas the spacing needed between the 2m elements {40.5 in long}
slanted at 45 deg. would be 28.6 inches if the tips just touched!

Clearly the spacing will have to be more, maybe 1.25 wavelengths at 436
{33.75 inches} to provide some clearance between the 2m antennas.  The
effect on the 436 pattern is unclear without analysis.

So if someone could send me the physical info on the arrow so that I could
model it on NEC4WIN, I will check it out.  It may turn out that using
separate 2m and 70cm antennas is better.

73, Ed

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