Racal Instruments 9081 Maintenance Manual page 33

FINE
TUNE
(Lever)
Switch
and
SLOW
SWEEP
Socket
FINE
TUNE
Control
AM
(lever)
Switch
FM/0M
(lever)
switch
MODULATION
LEVEL and
FM COARSE
(Concentric)
Controls
(l3)
PEAK DEVIATION
(Rotary)
Switch
This
switch connects
the
required
fine
tuning
source as follows:
(1)
I
NT
position:
the
ON
indicator
illuminates
and
the
adjacent
FINE
TUNE
control
is
operative.
(2)
OFF
position;
both
internal
and
external fine tuning
is
disabled.
The
ON
indicator extinguished.
(3)
EXT
position: the
ON
indicator will
illuminate
and an
external fine
tuning
voltage
can be applied
via the
SLOW
SWEEP
socket.
A
ramp
voltage with
an
excursion of 0
to
10V and
frequency
not exceeding
2Hz
is
suitable.
The
control
is
operative
when
the
adjacent
lever switch
is
set to
INT.
This switch selects the
amplitude modulation
mode.
The INT
position
connects
the internal
^
modulation
oscillator
to
the
modulation
system.
The EXT
position permits the
appli-
cation of external
modulation
via the
adjacent
600Q
BNC
Input
Socket.
This switch
selects
frequency and phase
modulation modes, otherwise
its
description
is
similar
to
that of the
AM
switch described
above
.
The
MODULATION
LEVEL
control adjusts the
amplitude of the selected
internal
modulation
oscillator
and
thus
sets
the
meter reading
for
the
chosen modul
ation
mode. The
FM COARSE
control adjusts the level of the modulating audio
applied
to
the
main
oscillator
on
FM
and
j£)
M.
This
switch selects the four
FM
peak
deviation
ranges
as
shown by
the
switch markings,
and
a single (10 radians)
phase modulation range.
The switch markings are coloured
to
correspond
with the appropriate
meter
scale
.
9081
&
9082 Vol. 2
2-7