Model 618B Sect. I11 Page 7
I FROM SYNC bMP V-10- 3-4 RF OSCILLATOR
2 MICROSEC
R-146
1 - 120u
A. REFLEX KLYSTRON
The rf oscillator is a reflex klystron V114
operating with a parallel-plane resonator. The
resonant section is coupled to the resonator grids
of the klystron as shown in Figure 3-13, and in
the equivalent circuit, Figure 3-14.
It may be seen how oscillation occurs when it is
assumed that a small amplitude rf voltage exists
FM across the resonator grids which has its origin
I
-3OOdOC "0 as thermal agitation noise. The electron stream
directed through the resonator grids from the
cathode will be velocity modulated by this small
rf voltage. The stream will cease to be uniform
in nature, and may be thought of as having some
Figure 3-12. Internal Frequency Modu-
of its electrons accelerated and some retarded.
lating Circuit
The resultant stream in the drift space past the
resonator grids will possess bunches of electrons,
and is therefore said to be velocity modulated.
fm sweep rate and the internal pulse repetition
rate may be controlled by the same knob.
The relaxation oscillator is triggered by a posi- As this bunched stream, or velocity modulated
tive pulse from the cathode of the pulse shaper stream moves toward the negative repeller, it is
and when activated, delivers a rising saw-tooth turned about and shot back through the resonator
voltage to the repeller, sweeping the frequency grids. Since the stream is bunched, it produces
and providing a saw-tooth frequency modulation. an rf voltage across the grids.
A-F ATTENUATOR AND
POWER PICK-UP LOOP
MOVABLE SHORTING PLUNGER
PLUNGER
ACTUATING
ROD
LYIRON ABSORPTION CARDS
LLER VOLTAGE CONNECTOR
ENTER CONDUCTOR
RESONATOR GRIDS RO
Figure 3-13. Cross Section of RF Oscillator |
ACEC
