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2.3
OPERATING
CONTROLS
The
operating controls
and
electrical
connections
for
the
Model 144
are
shown
in
Figure
2-1.
The
listing
below
discusses
each
control
and
its
function.
1.
Frequency Range/Power Switch
—
This
11
position
switch
selects
the generator
frequency
range.
The
extreme
counter-clockwise
position
is
the
power
off
position.
2.
Frequency
Dial
—
The
main
frequency
control.
The
setting
on
this dial
multiplied
by
the frequency
range
setting
(above) equals the
output frequency
of
the
generator.
The
frequency
vernier
(3)
and
the
symmetry
control (11)
also affect
the generator
fre-
quency.
Note
their effect
in
the
listing
below.
3.
Frequency
Vernier
—
This control allows
precision
control
over the
output
frequency.
A
complete
turn
of
this
vernier
is
equivalent to
approximately
one
half
of the
smallest division
on
the
main frequency
dial.
When
in
the
full
clockwise
position
(CAL),
the
set-
tings
on
the
main
dial will
be
accurate.
4.
Frequency
Index
—
The
scribe
line
indicates
the
fre-
quency
dial
setting.
The
index
is
illuminated
when
the unit
is
on.
5.
Waveform
Selector
—
This
selects
the
waveform
that
appears
at
the 50L2
output
connector.
The
waveforms
are sine
^
,
triangle
\
,
square
'Xi
.
positive go-
ing pulse,
and
negative going
pulse.
6.
Amplitude
Vernier
— A
vernier control
of the
output
amplitude.
Maximum
clockwise
position gives
the
full
output amplitude
of
30
V
peak-to-peak
into
an
open
circuit
or
15
V
p-p
into
a
50J2
load,
except
positive
and
negative pulse
which
are
7.5
V
zero to
peak
ampli-
tude
into
50£^
load.
Counter-clockwise
rotation
will
continuously reduce the output amplitude.
The
con-
trol
gives
a
minimum
of
20
dB
variation (10:1).
This
control operates
in
conjunction with the
output
atten-
uator
(9).
For
maximum
amplitude output
this
vernier
must
be
full
clockwise
and
the
output
attenuator
in
the
"0
dB"
position.
7.
50f2
Out
—
This connector provides the
selected
generator
output
function.
The
generator
may
oper-
ate into
an
open
circuit
providing
30
V
peak-to-peak
maximum,
or
into a
50fl
load providing a
15
V
peak-to-peak output.
8.
Sweep
GCV
Output
—
When
the generator
is
in
continuous,
trigger,
or gated
mode
(control 12)
this
output
provides
a
fixed
0
to
-i-5
V
sawtooth
out-
put.
The
frequency
of
this
output
is
controlled
by
the
sweep
rate
controls
(11).
When
the generator
is
in
continuous
Swp,
Trig
Swp,
or
Swp
Hold
modes
the
output
becomes
the
Generator Control Voltage
(GCV)
that
is
proportional to frequency.
The
fre-
quency
is
controlled
by
the
sweep
rate
controls (11)
and
the
amplitude
is
determined by
the
main
fre-
quency
dial,
VCG
input,
and sweep width
controls.
9.
Output
Attenuator
—
Attenuates the
output from
0
dB
(15
V
p-p
5012
max)
to
-60
dB
(15
mV
p-p
into 5012)
in six,
10
dB
steps.
The
vernier
(6)
adds
an
additional
—20
dB,
thus, a
maximum
of
—80
dB
(1.5
mV
p-p into
5012).
10.
Sweep
width
control
—
Determines
the
amount
of
sweep
when
in
Cont Sweep,
Trig
Swp,
or
Swp
and Hold modes. Clockwise
rotation increases
sweep
width, counter clockwise
rotation decreases
sweep
width.
11.
Sweep
rate
control
—
Determines the frequency
of
the
144
ramp
generator appearing
at
the
SWP/GCV
OUT. The
frequency
of
this
generator
is
independent
of the
frequency
of the
main
generator.
When
in
any
of the
sweep modes,
this
ramp
determines
the
duration
of the
sweep
cycle.
The
outer
dial
deter-
mines
the
frequency range and
the
vernier
(inner)
dial
provides a
fine
adjustment.
Note
diat the outer
switch detent position
is
located
between
two
time
ranges.
With
the
vernier
in
the
full
clockwise
position,
the
sweep
time
is
equal to the time to the
right
of
the detent
setting.
However, moving
the
vernier to
the
full
counterclockwise
results
in
sweep
time
ap-
proximately
100
times
the
sweep time
to
the
left
of
the detent.
12.
Trigger Level
Control
—
Adjusts the
sensitivity
of the
Trigger
Input
Circuitry.
When
in
the
full
counter
clockwise approximately
—7.5
V
is
required
for
triggering.
In
the
full
clockwise
position approxi-
mately
-1-75.
V
is
required for
triggering.
At
the
mid
point,
extremely low
voltages
will
trigger
the
instru-
ment.
By
rotating
the
dial,
it
is
possible
to
manually
trigger
the generator.
In
the gated
mode,
the generator
will
begin
to
run continuously
as
the
control
is
rotated past the
mid-point
in
a
clockwise
direction.
13.
Generator
Mode
Control
—
Selects
the operating
mode
of the
main
generator
as
follows:
a)
Cont = Continuous
Mode
—
The
generator operates
at
a
fixed
frequency
and
runs continuously.
The
SWP/GCV
output
is
a fixed
0
to
5
V
ramp.
22
8/73
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