I have been working with Jim, WA3FET for many years on antenna designs and he
asked me to pass
along this important update. It is unfortunate that an error was reported early
on
in the design of Jim's OWA 20 meter Yagi (Nathan, NW3Z was involved as well),
but it never got
corrected and distributed to everyone.
What happened was that a typo mistake was made on the 2nd
director spacing where a 2 was typed instead of the correct 6 in the number.
Also, there
was an incorrect file put in for the stacking design as well. Jim is
deeply sorry that these errors propagated out through the internet on various
websites and he apologizes for any inconveniences that this has caused,
especially to those
who built these with the wrong numbers. The effect on the free space design is
to still
give a good pattern but to have the SWR be around 2 or so. Once the errors are
corrected,
the antenna performs as specified.
TAPER SCHEDULES (Corrected)
The spacing of each element is shown from the reflector and all lengths
represent
the exposed length of tubing. Double wall sections are indicated below the
table.
The taper schedule of the elements can be adjusted using YO (using the W6QHS
algorithm).
All element lengths assume the use of the plate clamps discussed previously.
The 20m Antenna Optimized for Free-Space or Stand Alone Operation
The original table had a typing mistake and had 226.70 as the position of the
2nd director.
It should have been at 266.70 inches. All other dimensions are correct.
1 0.875 0.75 0.625 0.5
0.00 48 24 44 36 65.73
90.00 48 24 44 36 58.70
139.52 48 24 44 36 48.80
266.70 48 24 44 36 42.62
388.44 48 24 44 36 42.63
570.00 48 24 44 36 35.39
* The 1.000", 0.875" and 0.750" sections are double wall sections
The 20m Antenna Optimized for Stacking
The original table for the OWA Yagi optimized for stacking at K3CR was for
another file
and incorrect as listed. The corrections have been made below. Note that the
tip lengths
were corrected and the element positions were correct as given before.
All other dimensions were corrected as given before.
1 0.875 0.75 0.625 0.5
0 48 24 44 36 66.05
90.05 48 24 44 36 58.66
137.74 48 24 44 36 50.82
238.04 48 24 44 36 43.14
348.84 48 24 44 36 42.73
570 48 24 44 36 38.17
* The 1.000", 0.875" and 0.750" sections are double wall sections
73!
Tim K3LR
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