Wavetek 3000 - Programmable Divider; Unlock Indicator

"K HZ'
SWITCHES
phase or frequency
in the signals
applied to the
phase detector inputs
produces an error
voltage at the phase
detector
output, which controls the
VCO . The system is stable only
when
the phase and frequency
error is zero,
so that the output
frequency is phase
locked to the 1 kHz
reference signal .
3 .12 .3 PROGRAMMABLE DIVIDER
In order for the M31A to perform prop-
erly, the
divider is designed to divide
the VCOfrequency by (10,000-Sk) where
S k
is the number set on
the "kHz"switches .
The divider
counts the number of cycles
at its
input and puts out a pulse when
the countreaches 10,000 . The
starting
count is the number
shown on the "kHz"
switches .
For
example, if the instrument
is
set for 222 .500 MHz, this circuitwould
divide by 9,500 (count from
500 to
10,000) . Therefore, the
variable input
to the phasedetector
wouldbe correct
(1 kHz) only if
the VCO output were 9 0 500
MHz .
1 KHZ REF
SK =
SETTINGOF 'KHZ ° SWITCHES
Figure
3-17, M31A - kHz
Steps
3
.12
.4
UNLOCK INDICATOR
THEORY OF
OPERATION
When the phase-locked loop is unlocked,
the LED on top of the module will light
and the front-panel
ACCURACY lights will
flash .
A window detector monitors the voltage
level which
is being fed
from
the phase
detector to the
VCO
.
If
the voltage
exceeds the normal operating range,
power is applied to the module light and
the flasher circuit on the Modulation
Board .
3-17