LESSON THREE
RESONANT CAVITIES AND MAGNETRONS
TASK
Describe resonant cavities and magnetron operations, recognize coupling and
tuning techniques employed with resonant cavities and magnetrons, identify
different types of magnetrons and describe their modes of operation.
CONDITION
Given this lesson, pencil, and paper.
STANDARD
Demonstrate competency of task skills and knowledge by correctly responding
to 75 percent of the multiple-choice test covering radar transmitters.
REFERENCE
TC 11-67
Learning Event 1:
RESONANT CAVITIES
1.
General.
a. A coil and capacitor form a resonant circuit when connected together
either in a series or parallel arrangement.
The higher the resonant
frequency you want, the smaller are the capacitor and coil that you need.
Resonant circuits operating at ultra-high frequencies (UHF) have extremely
small values of inductance and capacitance.
The values are so small in
fact, that at about 500 megahertz, the use of coils and capacitors becomes
impractical.
So, instead of using a coil and capacitor at these UHF
frequencies, we can use a section of transmission line as a resonant
circuit.
b. You learned in a previous lesson how a transmission line section
serves as a resonant circuit.
Transmission lines are similar to resonant
circuits, except that the inductance and capacitance are distributed instead
of being lumped values. Just like ordinary resonant circuit components,
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