[TowerTalk] Takeoff angle
Joe Subich, W4TV
lists at subich.com
Mon Jul 24 09:13:43 EDT 2017
On 7/24/2017 8:58 AM, StellarCAT wrote:
> Now that stated I'd say this really is for a 2 stack ... with a 3
> stack you see more of a difference between 3IP and TOP... and with a
> 4 stack as well ... so although with a 4 stack you might have just
> over 4 db gain with all in phase you'd have a AOR that was measurably
> lower with the top antenna alone.
The trend is very much the same for all stacks according to HFTA. The
low angle response follows the curve for the top antenna alone but the
"all in phase" curve tends to reach a greater maximum and a higher
take off angle.
The difference in the full stack in phase and parts of a stack or part
of the stack out of phase shows up in the higher angle response. For a
good example, model a stack with antennas at 1.5, 3, 4.5, and 6 (or 1,
2, 3 and 4) wavelengths with all in phase, top two out of phase, middle
two out of phase and alternate antennas out of phase. One can "steer"
the take off angle rather dramatically in that configuration (at least
up to 30 degrees or so).
... Joe, W4TV
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