C316 - Modulation Board - Wavetek 3000 Instruction Manual

3 .3 .2
Modulation
The modulating signal from assembly C316
is applied to the VERNIER which ultimately
causes the RF level to
change . The
leveler in the M10W
does not cause the
RF level to respond linearly to changes
in the level program voltage . To com-
pensate for this,
a stage is included
to shape the modulation signal before it
is applied to the VERNIER .
3 .3 .3 Meter
The output level meter (front panel) is
controlled by the level program from the
VERNIER . The meter and its driver cir-
cuit are designed to display a reading
which corresponds to the actual RF level
from the M1OW.
3 .3 .4 "Unleveled" Light
A
light emitting
diode is mounted on
this assembly and appears on the front
panel of the instrument . Refer to the
MOGUL AT/ON
/NPUT
M10W description for an explanation of
the circuit driving this light .
3 .4 C316 - MODULATION BOARD
This assembly provides the modulating
signals used in the AM and FM modes .
The front panel ACCURACY lights and as-
sociated circuitry are also on this as-
sembly . See Figure 3-9 .
3 .4 .1 Modulating Signals
The AM or FM modes are achieved by simply
routing essentially the same signal to
the
appropriate circuitry by means of
the front panel MODE switch .
The front panel MODULATION FREQ switch
selects one of four sources of modulating
frequency, one external and three inter-
nal . The internal signal can be selected
from one of two CW oscillators or a man-
ually variable DC control .
FROM
PHASE L OCKEO
L OOiL5
Figure 3-9 . C316 Modulation Board
THFORY OF OPFRATION