Direct Energy, 2018a

4 ANTENNAS 89
(a) Assume a person 100 m away and receiving signal from the antenna
in the front direction (along the â x axis) receives a signal
of 15 W. Approximately how strong of a signal would the person
receive by standing 100 m away from the transmitter along the
â y axis (in watts)?
(b) Find the (power) F/B ratio in dB.
(c) According to the azimuth plot, at approximately what angle are
the nulls for this antenna?
(d) What wavelength is this antenna designed to operate at?
4.7. Figure 4.4 show the radiation pattern plots for a quad antenna designed
to operate at f =21.2 MHz. The upper left plot shows the
azimuth plot, the upper right plot shows the elevation plot. The
lower left plot shows the 3D radiation pattern, and the lower right
plot shows the antenna elements. They were plotted with EZNEC
software.
(a) Find the wavelength the antenna is designed to operate at.
[
−→
]
| E front|
(b) Find
| −→ , the eld front to back ratio of the antenna in
E back|
dB
dB.
[
Pfront
(c) Find
P back
]dB, the power front to back ratio in dB.
[
Pfront
(d) Find
P back
]lin, the power front to back ratio on a linear scale.
(e) Assume the electric eld intensity 50 m away measured along
the φ =45 0 axis (in the z =0plane) is 5 m V . Find the electric
eld intensity 50 m away measured along the φ = 135 0 axis (in
the z =0plane).