c. Another kind of window tuning called inductive window tuning is
shown in Part B of Figure 126. This time, the metal partitions, or irises,
are placed near the side walls of the waveguide. These irises obstruct the
magnetic field, and act as an inductive reactance.
The further we extend
the irises into waveguide, the more inductive reactance we get.
We place
metal partitions near the side walls of the waveguide to cancel any
undesirable capacitive reactance.
d. Both types of window tuning are usually done at the factory, and it
won't be necessary for you to adjust them. However, we do have waveguide
that you, as a repairman, will have to tune.
Most adjustable waveguide
tuning is done with a slug.
29. Slug tuning.
You tune waveguide with a slug the same way that you tune a resonant
cavity with a slug.
If the slug is inserted in the side wall of the
waveguide as in Part A of Figure 127, it affects the magnetic field and
tunes the waveguide inductively. If the slug is inserted in the top of the
waveguide, as in Part B of Figure 127, it affects the electric field and
tunes the waveguide capacitively. Besides adjusting waveguide to change its
impedance, you sometimes adjust the power level inside a waveguide by using
an attenuator.
Figure 127.
Waveguide Tuned With a Slug.
180
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