Well I started by contacting a few hams that have had experience with
stacking. The main reasons they had for stacking antennas are:
In my earlier C4 / C3 setup I used one single feedline, hence only one
StackMatch. Now with the individual feedlines, I needed three for the HF
high bands (20, 15 & 10 meters).
Normally the StackMatch units are plug and play, but with multiple bands
on each antenna the focus was shifted to stacking distances. Also
since the antennas are not exactly identical, I had to look at potential
phasing problems. These phasing problems are due to the fact that the driven
element was forward or behind one another on the antenna.
See Figure 1...
My prime concern of antenna separation would be favor the top
two rotatable antennas and also focus on the gain and front-to-back ratios
on each band. I used AO and NEC Wires from K6STI to help solve these
problems. Below is a table of results for stacking the C-31XR antennas.
C-31XR
.Main
Lobe
. Secondary Lobes
.
@90' Gain F/B @ 1/2PwrLobe
#2 Lobe #3 Lobe #4
28.600 15.6dBi 22 5° 3-8°
17° @ -1dB 28° @ -2dB 42° @ -4dB
21.200 14.3 26 7° 4-11°
22° -1 40° -2
62° -6
14.200 14.0 24 11° 5-17°
34° -1 65° -7
Stack @ 90' & 54' (36' spacing)
28.600 18.1dBi 17 6° 3-10° 18°
@ -7dB 38° @ -10dB 54° @ -9dB
21.200 16.0 16 9° 4-13°
26° -7 57° -11
14.200 15.9 18 13° 6-20°
38° -8
@ 96'
28.600 15.7dBi 23 5° 3-8°
15° @-0.5dB 26°@ -1dB 38° @ -3dB
21.200 14.4 25 7° 4-10°
21° -0.5 36° -2 54°
-5
14.200 14.1 23 10° 5-15°
32° -1 58° -5
Stack @ 96' & 48' (48' spacing)
28.600 17.7dBi 21 6? 3-10° 17°
@ -13dB 25°@ -16dB 36° @ -4dB
21.200 16.1 22 8? 4-12°
23° -13 34° -17 51°
@ -5dB
14.200 16.0 13 12? 6-19°
34° -13
@ 120'
28.600 15.7dBi 22 4° 2-6°
12° @ -1dB 21° @ -1dB 30° @ -2dB 21.200 14.3
23 6° 3-8° 17°
-1 28° -1 42° -3
14.200 14.1 22 8° 4-12°
25° -1 45° -3
75° -7
Stack @ 120' & 80' (40' spacing)
28.600 18.4dBi 18 5° 2.5-7° 14° @
-4dB 37° @ -8dB 50° @ -7dB
21.200 16.3 21 6° 3-9.5°
19° -4 55° -8
14.200 16.4 16 9° 4.5-14°
28° -5 50° -20
Stack @ 120' & 70' (50' spacing)
28.600 18.1dBi 22 5° 2.5-7.5°13° @ -8dB
28° @ -7dB 38° @ -4dB
21.200 16.1 26 6° 3-10°
19° -8 39° -7
57° -5
14.200 16.4 17 10° 5-15°
28° -8 67° -11
Stack @ 120' & 80' & 40' (40' spacing)
28.600 18.8dBi 27 5° 2.5-8° 21°@
-13dB 30° @-14dB 48° @ -6dB
21.200 16.7 13 7° 3.5-11°
29° -14 42° -15 80°
-9
14.200 17.0 20 10° 5-16.5° 46°
-15
After reviewing the data I decided to go with a stack separation of
40'. This separation appeared to be the best compromise for all three
bands (20, 15, & 10 meters). The lower C-3E was mounted about
25' below the middle antenna. If you notice , even with a larger
C-31XR, the lower antenna provided minimal gain and front-to-back benefit,
so the height was determined more on an individual basis. The C-3E
mounted around 38' would provide a great multiplier antenna to the Caribbean
and South America.
The view of all three antennas modeled on AO looks like:
Figure 1 (WN9O Antenna Stack)
-
C-51XR (102'), C-31XR (62'), & C-3E (38')
To see the advantages of stacking, view a few pattern files for a C-31XR
stack.
Just click of the following link: <<
View Stack Patterns >>
To see the effects of phasing adjustments, check out my AO pattern
files.
Just click on the following link: <<
View Phasing Patterns >>
Jay's, WX0B, StackMatch units are shown
below and are easy to install. The units require a control cable
(5 wire) to connect to the phasing box on the tower. Of course you
will
need a 12 volt supply to power the units...
-
Figure 2 (WX0B StackMatch System)
For more information on the StackMatch check out the Array
Solutions web site.
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