[amsat-bb] Re: Horizontal stacking distance question
Edward R. Cole
kl7uw at acsalaska.net
Thu Dec 16 12:59:50 PST 2010
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
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
BP40IQ 500 KHz - 10-GHz www.kl7uw.com
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