[amsat-bb] Re: Horizontal stacking distance question

[Edward R. Cole]

At 11:21 AM 12/16/2010, John Geiger wrote:
>I know that when stacking antennas for different bands on the same mast, the
>general rule of thumb is to space them at least 1/2 of the boom length for
>the higher frequency antenna.  Does this rule also hold true for stacking 2
>antennas on a horizontal crossboom?  If I want to put a 2m and 70cm yagi on
>the same crossboom, how far apart should they be spaced?
>
>73s John AA5JG

John,

For satellite use that is fine.  I have my 2m and 70cm yagis 
separated 5-feet horizontally.

The current setup (before high winds busted the mast) was with my 
436CP42  mounted on a 4-foot vertical boom with 1268 loop yagi.  The 
70cm antenna is 18-foot long and loop yagi 12-foot long.  This boom 
was mounted at right angles to the 5-foot elevation cross boom with a 
8-element 2m yagi (vertical pol) at the other end of the cross 
boom.  Not exactly conforming to the half-length rule.

Normally, If you are stacking linear-pol antennas the stacking 
distance in the plane of polarization needs to be further apart than 
if stacked in the direction right angles to polarization (e.g. two 
horz pol antennas stacked horizontally need more separation to avoid 
interaction, whereas, it they are vertical pol antennas stacked 
horizontal you can stack them closer than the rule.  If they are 
circular pol stacking there is no difference what direction stacking is done.

4 to 5 foot separation on the elevation cross-boom of a B5400 az-el 
is common for satellite.



73, Ed - KL7UW, WD2XSH/45
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