[TowerTalk] antenna decisions

[Dick Green]

>>> 1.  TH6 @ 70' and three 40m ground mounted phased 1/4 wave verticals in
an
>     equilateral triangle.
>
>      A bunch of work to install the verticals and get them working IMO.
Does
>the performance pay off for the investment? Vertical array owners?


Cheers and GL,  Steve  K7LXC


Well, I've got a 40M 4-square with 60 radials on the ground for each
element. It only took these 30 easy steps to build:

1) Find a suitable 100' x 100' square of land using compass and tape measure
(measure, measure, measure.)

2) Determine feasibility of element and radial placement while tromping
around amongst a thicket of trees and sticker bushes on a steep hill, making
sure elements are not too close to tower, property lines or trees (measure,
measure, measure.)

3) Lay it all out on graph paper and re-measure, re-measure, re-measure --
do it again for various array placement angles.

4) Determine property lines with compass, tape measure and deed (measure,
measure, measure.)

5) Run up and down steep hill each time steps 1-4 are attempted (dozens of
trips in all.)

6) Discuss plan to clear forest with abutting neighbor and secure agreement
on location of property lines. Try not to laugh when he looks confused.

7) Clear a 100' x 100' square of forest, chip all debris and place in neat
piles at least 25 feet from property lines.

8) Determine final element placement (measure, measure measure.)

9) Dig four 3' deep post holes in exactly the right places (measure,
measure, measure), removing huge rocks and praying that a big boulder or
ledge will not appear.

10) Insert four pressure-treated 4x4 element supports and backfill, keeping
the posts level (measure, measure, measure.)

11) Lay out two 100' radial bus wires (measure, measure, measure.)

12) Measure, cut, roll, solder, unroll, and pin 240 36' radial wires
(measure ad infinitum.) Try not to cry too many times while doing this step
over a period of several *months*. Realize how lucky you are that this isn't
an 80M or 160M ground-mounted 4-square (even though you wish you had one of
each.)

13) Cut and solder 144 radials inside square to bus wires.

14) Weatherproof solder joints.

15) Build four telescoping aluminum vertical elements (7 sections, 2" - 1
1/4" diameter -- cross cut, clean, deburr and clamp each section -- drill
hole in each bottom section for RF terminal.)

16) Mount elements to 4x4s with conduit clamps.

17) Mount current balun at base of each element.

18) Extend each element and tune for resonance (50KHz - 100KHz below desired
frequency.)

19) Cut four 75-ohm RG/11U phasing lines (measure, measure, measure with a
noise bridge.)

20) Attach 16 PL-259 connectors for 4 phasing lines, feedline, 180 degree
line, phase corrector, and dummy load (it's an old Colatchco, so it needs
those two extra lines.)

21) Run 350' feedline and control line (actually part of a larger antenna
farm project, which included digging a 250' long 4' deep trench, pounding
out three seams of ledge, laying 250' of 1/0 ground wire, buring three 250'
runs of conduit, building and installing three termination boxes complete
with lightning suppressors, and pulling 10 runs of coax/AC/control wire.)

22) Pound in 6' 1 1/2" dia. water pipe at center of square.

23) Mount control box and attach all lines.

24) Set up dummy load and remote dumped power monitor (procure discontinued
Radio Shack RF/SWR meter with remote coupler -- perfect for the job.)

25) Procure and install plastic garbage can to protect control box.

26) Refinish old Colatchco switch box.

27) Test array and fine tune elements.

28) Weatherproof connector joints.

29) Whack 4' high weeds once per year to keep forest from returning.

30) Enjoy, enjoy, enjoy.

Yes, it's a lot of hard work. A simpler installation or an elevated radial
system would take less work. It took nearly a year from conception to
completion. The reason I did it was that I needed a directional antenna for
40M, couldn't install a tower capable of handling a 40M beam (got a 70'
tubular crankup), and a friend traded me the old Colatchco phasing system
for an old TA-33 (who got the better end of that deal?)

Was it worth it? Yes, Yes, Yes, and YES!!!!!

I love this antenna. Forward gain over the old vertical monopole is just as
science would predict -- 5-6dB (but don't forget that a monople is -3dB to a
dipole). I guess that amounts to maybe 2-3 dB over a dipole. That's pretty
comparable to a 2-element shorty forty beam. Gain over my old GAP Titan is
15-20 dB (some antenna, huh?) F/B is 20+ dB. The antenna sings on receive.
Need to go through the fall/winter contest season to see how it transmits,
but broke through pileups on SMOM and Midway with 150 watts. Electronic beam
rotation just beats the heck out of using a rotor! Mechanical stability and
ease of repair make it a very desirable alternative to a 40M beam here in
New England.

Besides, I really enjoyed the project -- sometimes the building is half the
fun!

73, Dick, WC1M



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