c.
insure that only the desired mode is propagated through the waveguide.
d.
remove a sample of the transmitted or received energy for test purposes.
20.
The use of a single antenna, both to receive and transmit energy, is based on the property known as
a.
reciprocity.
c.
waveguide radiation.
b.
compatability.
d.
two-way propagation.
21.
Additional dipole elements may be added to the simple dipole antenna to
a.
provide an impedance match between the waveguide and space.
b.
form the energy into the desired radiation pattern.
c.
make antenna reciprocity possible.
d.
prevent mode changes.
22.
waveguide-to-horn impedance. It also serves as a
a.
filter.
b.
polarizer.
c.
mode launcher.
d.
dielectric guide.
23.
Parabolic reflectors are used to control energy in the microwave frequency ranges because
a.
they are nonresonant at microwave frequencies.
b.
they provide a simple all-purpose antenna system.
c.
there is no other way to control microwave energy.
d.
microwave energy can be handled in the same manner as light energy.
24.
In a cassegrainian antenna system, the final narrow RF beam is formed by the
a.
paraboloid.
c.
horn antenna.
b.
hyperboloid.
d.
polyrod feed system.
344 L2
102
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