Wavetek 3000 - M9 W - Sweep Oscillator; Wide Oscillator; Narrow Oscillator; Levelers

Section
3 .6 is
deleted .
3 .7
M9W
-
SWEEP
OSCILLATOR
TheM9W is the origin of the instrument's
RF output frequency . This
frequency is
generated by heterodyning the
signals
from two higher frequencyvoltage con-
trolled oscillators .

SeeFigure
3-12 .
3.7 .1 Mixer
The narrow oscillatorapplies a
signal
of 1198 MHz
to themixer (except in the
FM mode)
. The wideoscillator provides
between 1199 and 1718 MHz
. The differ
ence

(1-520 MHz)

is applied to a wide
band pre-amp and then sent to the M10W .
3.7.2 WideOscillator
Thewide range of oscillation
is achieved
by applying to varactor
diodes in the
tank circuit an analog signal which is
dependent
upon
the setting of the fre-
quency switches onthe
instrument's front
panel . An additional
signal is applied
to this
VCO from
the phasedetector in
the
M34 .
This is the fine tuningsignal
which locks the wide oscillator on the
properfrequency .
3 .7 .3 Narrow Oscillator
This oscillator also uses a varactor
diode so that the frequency can
be
vol-
tage controlled for
phase locking and
for FM
operation .
The coarse modulating
signal (FM) is
applied to the varactorfrom the modula-
tion board (C316) . The frequency of
this oscillator is accuratelycontrolled
by a "fine tuning" bias voltage from
the
M33 phasedetector .

The
deviation can
be controlled up to 500 kHz .
3 .7
.4 Levelers
THEORY OF OPERATION
This
module
contains three
RF
leveling
circuits as shown in the diagram
.
These
maintain a constantamplitude RF
over
the frequency range and withtemperature
variation . The output of a peakdetec-
tor is compared to a constant DC level .
Any error is amplified and applied to a
PIN diode attenuator
in series with the
RF signal .
3-11