- Below are two diagrams illustrating the
IEEE coordinate system for antenna field strength measurement.
- Note that nowhere in either is the
orientation of the antenna considered. To analyze this
antenna, I will assume the antenna lies from X=0,Y=0,Z=0 at
the feed point to X=34,Y=-32.5,Z=-20. The interior angle
of the radiator to horizontal is 36 degrees.
- Below is the 20M radiation pattern of the
JPole jr provided by Alpha.
- NOTE: dBic is decibels gain referenced
to a circularly polarized, theoretical isotropic radiator.
- In the horizontal plane then maximum gain
is 5.36 dBic which occurs at +5 and +172 degrees. Given
the installed orientation is feed point North radiator South
then actual gain angles would be 352 True and 175 True.
- In the vertical plane the maximum gain is
5.36 dBic at -40 and +40 degrees (Theta) relative to the end
of the radiator, at a vertical angle (Phi) of 80 degrees.
- NOTE: If the antenna was analyzed as an
isotropic radiator (no reference to a ground plane) then the
36 degree slope would subtract from the 80 degrees giving a
departure angle of 44 degrees toward the South Southwest and
South Southeast with only minor power change between 125 True
and 235 True.
- NOTE: If you look at some of my 'signal reports'
screen captures from PSKReporter you will see that this setup
prefers Southern California, and an arc across North America
from North of Chicago to The Gulf of Mexico on 20M nearly
anytime. Only occasionally does it get signal into
Central and South America, but Hawaii, New Zealand, Australia
and Japan are regular openings on 20M after sunset.