In a previous message, I recommended a 160 foot tower with
2L40's at 160/80 ft and TH7's at 120/40 ft.
Obviously, most people are not able to put up such a tall tower on
limited real estate.
Another suggestion with wider application would be the following:
Put up 80 ft of Rohn 45, guyed at 40 and 80 ft. using Philystran or
adequately insulated steel guys.
Place TH7's (or other tribanders/5 banders) at 40 and 80 ft.
Using a strong mast with at least 1/4 inch wall and 90,000 psi
yield strength, put a 2 element "shorty forty" 10-12 ft above the
top TH7. Omega match the boom of the TH7 as a rotary dipole
on 40M. This provides instant direction change of +/- 90 degrees
without having to rotate the antennas. Matching the boom of the
lower TH7 on 40M may be useful for domestic contests.
A sloping 3/4 inch arm to the 10 or 15M director position and a
pair of WX proof capacitors (can be made from RG-213 or equiv)
will do the job. Capacitance values will need to be determined
"in place" since they will depend on matching arm length, position,
and height of the antenna above ground.
It is definitely worthwhile to rotate the lower antenna.
Another (small) tribander could be placed at 60 ft, fixed on South
America/Caribbean.
de Tom - N4KG
.
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