[2m] Re: 2 meter stacking question

Thu, 11 Jul 2002 12:42:30 -0400

Hi John:
First, what polarity are you going to use Horizontal or Vertical ???
Second, are you planing to use it for weak signal or repeater work ???

If you are going stack the 13B2's for vert. pol. on the horz.
boom, you don't need to use a non conductive boom. Also you
will be throwing away about 99% of you power if you try to work
weak signals as the cross pol. loss is about 20 Db (1 in 100)!!!

If you are going stack the 13B2's for horz. pol. on the horz.
boom, you will have to think about how you are planning to route
the coax.
Remember that if you run the coax from the ant. feed point, along the
ant. boom, to the non conductive boom, and then down the Vert. rotor
mast, you will be negating the whole premise of using the non-conductive
boom.� You will be placing a conductive media, the outer shield of the
coax, in the same plane as the radiation plane.� Usually in this mounting
configuration, it is best to route the coax to the rear of the beams about
a 1/4 WL and then try to figure out a method of supporting the coax and
let it drop vertically and then over to the rotor mast.

In my opinion, for weak signal work you would do better to stack them
vert with horz. pol. !!!� You will get a lower take off angle and you
won't have such a narrow horz. beamwidth.

After you figure out your optimum mounting, to make your phasing lines
reach, you can always add an extra 1/2 WL (electrical) to both and keep
the same impedance to the common feed point.� An other option is to use
a real 2 port power divider and then you can run any length of 50 ohm
coax you need from the power divider to the ant. feed point, just remember
to keep both lines the same length.

If you can clarify exactly what you are trying to accomplish, it will
make it easier for those on the list to advise you.

73 
Bob, K1VU
FN42ma At 12:13 AM 07/10/02 , John Geiger wrote:
>I am planning on stacking a pair of 13B2 antennas side
>by side.� Will be using a non-metallic stacking boom
>to lessen interaction between each yagi and the boom. 
>Here is my questions:
>
>The stacking distance in the manual is 9 1/2 feet.� I
>can get a phasing harness and power divider used for
>stacking 2 3219 antennas.� I used to have a pair and
>seem to remember that the stacking distance was around
>12 feet or so.� Will this phasing harness work for
>stacking the 13B2?� I am not sure if the length of the
>matching section of coax will change with the decrease
>in stacking distance or not.� 
>
>Does anyone have any experience or thoughts on this?
>I have looked at a few websites, but could find no
>conclusive evidence about this.
>
>
>73s John NE0P
>
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