Jim,
The first YO file below is for my existing 3 element 40M Yagi. The second
file is for the same antenna with a fourth element added to significantly
improve the VSWR bandwidth of the antenna per a design originally
developed by K3LR. I plan to implement the 4 element Yagi this year.
The antenna is built on a 48 foot boom consisting of two pieces of 24 ft
x 3"od x 0.188" wall thickness 6061T6 aluminum tubing. The elements are
insulated from the boom, mounted on 12" x 12" x 1" Type LE phenolic
plates.
The elements use .058" wall 6061T6 aluminum tubing. The center
24 feet of each element uses many fully telescoped pieces of 6061T6
aluminum tubing for greatly increased strength. For example, the longest
element uses a total wall thickness of 0.290" near the center. The
detailed design of the elements is available as an NI6W YS (Yagi Stress)
file.
73
Frank
W3LPL
donovanf@sgate.com
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W3LPL 3 Element 40 Meter Yagi (as Built)
Height 2280.000
7.000 7.100 7.300 7.100 MHz
3 elements, inches
2.0000 1.8750 1.7500 1.6250 1.5000 1.3750 1.2500
1.1250 1.0000
0.0000 72.0000 121.5000 16.5000 16.5000 17.0000 17.5000 18.0000
18.0000 134.0000
258.0000 72.0000 121.5000 16.5000 16.5000 17.0000 17.5000 18.0000
18.0000 110.0000
564.0000 72.0000 96.0000 15.0000 15.5000 16.0000 16.0000 16.5000
17.0000 125.0000
Use the H key to set the elevation angle to 10
degrees. Use the M and Tab keys to enter the
following T-match parameters:
Rod Diameter 0.5"
Rod Spacing 10"
Rod Length 144"
Lead Length 6"
Series Cap 99999 pf
Feed Z 200 ohms
Experience indicates that the driven must be
lengthened to 125 inches, the length that
produces a modelled impedance of +j20 at 7.1 MHz
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W3LPL Wideband 4 Element 40M Yagi (construction planned in 1997)
Height 2280.000
7.000 7.100 7.300 7.100 MHz
4 elements, inches
2.0000 1.8750 1.7500 1.6250 1.5000 1.3750 1.2500
1.1250 1.0000
0.0000 72.0000 121.5000 16.5000 16.5000 17.0000 17.5000 18.0000
18.0000 134.0000
234.7897 72.0000 121.5000 16.5000 16.5000 17.0000 17.5000 18.0000
18.0000 120.0000
317.9102 72.0000 121.5000 15.0000 15.5000 16.0000 16.0000 16.5000
17.0000 117.0000
564.0000 72.0000 96.0000 15.0000 15.5000 16.0000 16.0000 16.5000
17.0000 125.0000
This design illustrates how a 4th element radically
improves the bandwidth of a 40M Yagi (thanx K3LR !)
Use the H key to set the elevation angle to 10
degrees. Use the M and Tab keys to enter the
following T-match parameters:
Rod Diameter 0.5"
Rod Spacing 10"
Rod Length 144"
Lead Length 6"
Series Cap 99999 pf
Feed Z 200 ohms
Experience indicates that the driven element tip
must be lengthened to 134 inches, the length that
produces a modelled impedance of +j20 at 7.15 MHz.
--
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