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Re: phasing two arrows



Yes, I should have said on one of the two bands, the stacking gain will not
be realized, and if the spacing is too wide, you (as I recall), get multiple
forward lobes.

The point being, if the goal is to get the best gain, you can't do it for
both bands at the same spacing. If the goal is strictly circularity, that
one might be met (but not with the values he mentioned for coax, without
introducing some matching problems.) For the amount of effort involved, I
think the arrows are not a good choice. My own experience with having used
both circular and linear polarization (to include switching circularity at
one point), is that linear polarization can do rather nicely with minimal
effort.

I ran a pair of k1fo 22 el 70cm yagis stacked horizontally and a single k1fo
12 el 2m with my elevation rotor on a horizontal fiberglas mast and it
worked wonderfully. Increased spin mod at times, but most of the time there
was no problem.

In fact, I'm going to put up that same array in the spring.

Good input, Ed. 73

hasan schiers, N0AN
schiers@netins.net


----- Original Message -----
From: Edward R. Cole <al7eb@ptialaska.net>
To: <amsat-bb@AMSAT.Org>
Sent: Friday, December 01, 2000 4:21 AM
Subject: Re: [amsat-bb] phasing two arrows


> Hi guys,
>
> First to answer Chris:  You state "I have had luck with using nothing more
> than a 1/4 wave section of
> RG-62 joining the driven elements through a BNC T-connector. Worked
great."
>  Are you sure you used RG-62?  It is 93 ohm impedance which would not
match
> two 50 ohm antennas with 50 ohm coax at a Tee.  RG-11 or RG-59 which are
75
> ohm are close to the right value for a two-way splitting 1/4 wave
> transformer line.  Page 8-22 in the original edition of the Satellite
> Experimenters Handbook shows the right set up in fig. 8-11b.  Note that
> RG-62 is used in fig. 8-11a for a polarity switching configuration.
>
> Hasan:  Your comments about stacking two yagis are correct when the object
> is increasing gain.  The object being to space them so their aperatures
> just touch for max increase in gain.
>
> 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}
>
> I hope someone will try this out and tell us how it worked.
>
> Ed
> PS: per usual there were some comments after Hasan.  Spacing farther than
> optimum does produce bad side lobes, but under spacing, up to a point,
> usually has the effect of reducing sidelobes.
>
> If someone would fwd me the dimentions of the Arrow antenna: element dia,
> lengths, spacing; boom dia. and length and driven antenna matching method
> {i.e. gamma, T,...}, I will attempt to analyze a two antenna phased system
> with NEC4WIN.
>
> >From: "hasan schiers" <schiers@prairieinet.net>
> >If you're talking about the dual band antennas, you can't stack them for
> >both bands. The spacing will only be correct for one of the two bands.
> >
> >If you do stack two single band yagis, you have to decide on what
> >polarization you want. You can get linear vertical, linear horizontal, or
> >circular. The circular will require a delay line to one of the two
antennas.
> >
> >The dual band arrow antennas are not suitable for stacking because of my
> >initial comments above. I wouldn't bother, it can't possibly work right
on
> >one of the two bands.
> >
> >73,
> >
> >hasan schiers
> >schiers@netins.net
> >N0AN
> >
> >
> >----- Original Message -----
> >From: "Christopher Cox" <cobox@urec.net>
> >To: "Cordill,Jim" <JCORDILL@cerner.com>; "'amsat-bb@amsat.org'"
> ><amsat-bb@AMSAT.Org>
> >Sent: Thursday, November 30, 2000 3:49 PM
> >Subject: Re: [amsat-bb] phasing two arrows
> >
> >
> >> Well, it depends.
> >>
> >> Are you going to try 2 stock Arrows, or put all the 2 meter elements on
> >one
> >> boom and all the 70 cm on the other?
> >>
> >> I have not tried 2 stock Arrows, but I would make sure they where
canted
> >45
> >> degrees from each other instead of 90 degrees.
> >>
> >> If you are going to combine 'like kind' elements onto their respective
> >> booms, I have had luck with using nothing more than a 1/4 wave section
of
> >> RG62 joining the driven elements through a BNC T-connector. Worked
great.
> >>
> >> Regards
> >>
> >> Christopher Cox
> >> KC8FRJ
>
> ----
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