- From Frank, W3LPL, the initial antenna propagation specification was obtained: The 20M beam must be located at a height of 100 ft.
This became the specification that drove the rest of the system design. This 100 ft 20M spec became the determining factor in ALL of the other antennas loactions
on the tower, including the tower height itself.
- The tower, because of the 90% guying requirements needed to be guyed no higher than approximately 140 feet. This was necessary due to the physical
constraints in the property. With a gas pipline right-of-way and a septic building restriction line, the tower would need to be designed and implemented
with precision.
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The design proceeded |
With the 20M antenna at 100 ft and 90% guying limited by property restrictions to approximately 140 feet, the next specification that
could be determined was the lower antenna in a 20M two-stack: 50 feet. This particular spacing was a solid performer at W3LPL's station, so it
became the 2nd spec we "fixed". The models looked very good: |
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Then, I decided to install CushCraft 40-2CDs initially, rather than design and build a 40M beam myself because I had never designed and/or
built a beam antenna from scratch. The upper 40M antenna would be at one wavelength above ground (134 ft) and the lower 40M antenna at 67ft.
The EZNEC model looked pretty good for the 2/2 stack: |
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Now that 40 and 20 had been decided, that meant that the tower must be at least 134 feet high. Now what about 160, 80, 15, and 10?
I still had plenty of real estate on the tower, so the decision on those locations would need to wait for the determination of the guy wire locations
on the tower so as to not interfere with the beams. As far as rotating the beam antennas, I had a choice between side mounts or Ring Rotors - a decision
that would be made later.
Much of these remaining decisions about antenna placement on the tower will need to wait for other design decisions to be made. The Tower decision
would be next.
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