MORE 130 FT TOWER OPTIONS de N4KG
The new Force 12 C31XR tribander offers some interesting
hybrid stacking options with monobanders since it is composed
of stagger interlaced monobanders that can be fed separately.
This allows simultaneous operation on different bands with
appropriate band pass filters in line.
The following arrangement offers a 3 high stack of 3L on 20M
equally spaced at 45 ft, a 4 high stack of 4L on 15M equally
spaced at 30 ft, and a 2 high stack of 6/7L 10M spaced at
20 ft plus a high 10M rotary. These spacings are near optimum
for each band / configuration.
130 ft C31XR
100 ft 4L15
85 ft 3L20
70 ft 4L15
60 ft 6L10
40 ft C31XR
Guy at 130 / 100 / 70 / 40 ft.
With this many antennas, not all of them can be rotated under
the guy wires. In particular, the 6L10 and 3L20 would likely hit guys
if turned. The simplest option is to rotate only the high and low
C31XR's.
If simultaneous operation on separate bands is not required,
a 4 high stack of tribanders is an attractive option with some
added flexibility. With a C31XR stack, each band can still be
fed separately if desired.
Consider the following:
130 ft C31XR or other large tribander
100 ft C31XR "
70 ft C31XR "
40 ft C31XR "
Gain should be comparable to the hybrid stack on all bands
with the added flexibility of 360 degree rotation if the tower is
rotated, 300 degree rotation if swinging gates are utilized or
150 degree rotation if individual rotors are side mounted at
each level.
Guy at 4 levels, just under each tribander. Place the guy
anchors out far enough to allow rotation of all antennas.
Single feedlines can be used on each C31XR simplifying
switching requirements. Feed options should include
all 4, upper pair, lower pair, or individual feed. During
high MUF daytime operation, I would not be surprised
to find the lower single antenna or lower pair to be the
best configuration.
A 2L40 could be added above the top C31XR and/or
a fixed 2L40 at 85 ft. A large 3L40 could be placed
at 130 ft with tribander heights juggled to allow
equal spacing for a 4 high stack or simply delete the
high tribander. 40M Delta Loop arrays can be supported
between two tall towers with the apex at 120 ft.
I like the C31XR 4 high stack for the primary target area(s).
With 30 ft spacing and forward stagger, interactions are minimal.
A second 130 ft tower with a large 3L40 on top and individually
rotated tribanders at 40 / 70 / 100 ft offers directional flexibility
for chasing multipliers in less populated directions.
At my home station, which has evolved over the years using
acquired antennas (as opposed to designed to a particular goal)
I have single monobanders for 10 / 15 / 20 which I rotate between
Europe and Japan and several tribanders which I park due East
for Africa (TH7 at 40 ft), SE for the Caribbean / S.A. (TH3 at 40 ft),
SOUTH for C.A. / S.A. (TA32 at 60 ft), and WSW for VK / ZL
(TH6 at 80 ft overlooking a 20 ft rise). During high sunspots I rarely
have to rotate the monobanders away from the primary targets
as the low tribanders seem to do the job. The 40 ft TH7 is a
giant killer to Africa.
de Tom N4KG
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