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Stacked Antennas
Stacked Antennas analyzed using 4nec2 to determine:

1. Minimum tolerable separation for some "typical" vertically stacked UHF and Hi-VHF antennas.

2. Optimum stacking distance for matched antennas: http://www.grantronics.com.au/docs/StkYagis.pdf
Also see Cebik's article (FREE registration required): http://www.cebik.com/content/a10/yagi/stacksup.html
Date(s): March 4, 2010. 1 - 5 of 5 Total. Shared
Horizontally Stacked UHF Antennas
1. Horizontally Stacked UHF Antennas  (19 Dec 2013)
Horizontally Stacked UHF Antennas analyzed using 4nec2, including:

a) Stacking for GAIN.

b) Stacking for a NULL along the X-Axis (which also results in TWO, SPLIT BEAMS).
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Vertically Stacked UHF Antennas
2. Vertically Stacked UHF Antennas  (23 Jun 2013)
Vertically Stacked UHF Antennas analyzed using 4nec2.
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Vertically Stacked Hi-VHF Antennas
3. Vertically Stacked Hi-VHF Antennas  (16 Jul 2014)
Vertically Stacked Hi-VHF Antennas.
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Vert. Stacked A-D UHF 91XG + A-C FM-6
4. Vert. Stacked A-D UHF 91XG + A-C FM-6  (14 Aug 2013)
Stacked Antennas-Direct 91XG UHF Corner-Yagi and Antennacraft FM-6 Antennas analyzed
using 4nec2 to determine amount of interaction between them at various Separation Heights
(measured Boom-Boom Centers).

Since there was no noticeable degradation to the A-C FM-6, no FM Band charts are provided here.

Significant degradation to 91XG Raw Gain, F/B & F/R Ratios & SWR did not occur until Boom-Boom
Center Separation was just 1-foot.  Minor degradation was observed at 1.5, 2-ft and 3-ft separation.
Negligible degradation was observed for separations of 4-feet or more.
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Vert. Stacked UHF and Hi-VHF Antennas
5. Vert. Stacked UHF and Hi-VHF Antennas  (4 Mar 2010)
"Typical" Hi-VHF and UHF Vertically Stacked Antennas analyzed using 4nec2 to determine minimum "tolerable" separation.
Best vertical spacing for either combination is 6-ft or more.

For CM4228 8-Bay (with Reflector Screen) stacked on top of K6STI's 5-element Hi-VHF Yagi, impact on Gain and SWR were minimal, even at 3-inch separation.
When separation was less than 4-ft, UHF CM4228's F/R Ratio was degraded 2-3 dB, mostly at lowest frequencies.
F/R Ratio for K6STI's 5-El Hi-VHF Yagi was slightly degraded, beginning at 4-ft separation, but did not become excessive until 3-inch separation.
[Separation is measured to the bottom of CM4228's Reflector Screen.]

For kgb's 13-Element UHF Yagi stacked on top of K6STI's 5-Element Hi-VHF Yagi, the impact to Gain and SWR were minimal at even small (1-foot) separations.
However, 13-El UHF Yagi's Front/Rear (F/R) Ratio was significantly degraded when they were any closer than about 4-feet.  5-El Hi-VHF Yagi's F/R Ratio was minimally impacted.

EDIT (6Mar2010 at 5:15pm): Updated some charts with 5, 6, 8 and 100-ft separations.
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