W7RH wrote: Further with the T portion as top loading the feed point
radiation resistance will be greater for a given vertical
height. This when coupled with an excellent ground system of 1/4 wave
radials will make the antenna substantially more efficient than other
types of loading. (Less Loss)
Why does NEC not confirm this statement? An example: A T antenna and an
L, both with the same ground loss, the same vertical section length
(49.5 ft), and the same resonant frequency. The T calculates as a
feepoint impedance of 18.1 ohms at 1.81 MHz. The L calculates as 20.2
ohms at 1.81 MHz. If you calculate the radiation resistance, the L will
be 1.5 to 2 ohms higher.
Note: If you do these calculations with a Mininec ground, you will get
in incorrect answer because there will be a low horizontal wire over a
Mininec ground. That always produces an impedance that is too low and a
gain that is too high. You have to use a real ground and simulate the
radials, or do the calculations in free space.
Jerry, K4SAV
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