f. Now, look at the 2J51 magnetron shown in Part B of Figure 86. You
can see that the magnet for the 2J51 is part of the magnetron proper. So
the 2J51 is called a packaged magnetron.
Packaged magnetrons have an
advantage over those having separate magnets in that they use a smaller
magnet for a given field strength.
There is no air gap between the pole
pieces, so the magnetic lines of force are more concentrated.
g. Another difference you will notice is that the 2J51 magnetron uses
waveguide instead of rigid coaxial line to couple out the RF energy. The
reason is that the 2J51 oscillates at frequencies between 8500 and 9600
megahertz.
5.
Brief review on magnetron construction.
a. A magnetron is a microwave oscillator that consists of a diode and a
magnet.
b. The magnet is either
part
of
the
magnetron
proper
(packaged
magnetron) or is separate.
c. The diode section of the magnetron consists of a cathode, a filament
to heat the cathode, and an anode.
d. The
cathode
is
oxide-coated
and
is
indirectly
heated
by
the
filament.
e. The anode is a circular copper block containing six to eighteen
resonant cavities.
f. Magnetrons use loop coupling or slot coupling.
g. RF
energy
is
coupled
out
of
the
magnetron
by
coaxial
line
or
waveguide.
h. The long filament leads of the magnetron are insulated from the
chassis by a glass enclosure.
i. Now that you have seen typical magnetrons, let's find out how they
work. You are already familiar with other types of oscillators, so we will
start by comparing these other types with magnetrons. This way you will get
a better idea of magnetron operation.
6.
Comparing magnetrons with other oscillators.
A magnetron is like any oscillator in
that it generates an
alternating current at some particular frequency.
Magnetrons differ from
other oscillators in that their output
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