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Figure 3-5
-
Sweep
GEN,
CONT
SWP,
TRIG
SWP,
& SWP HOLD
modes
DIAL,
the
VERNIER,
and
the
FREQ HZ
selector.
As
the
Sweep
Generator output
starts
moving
positive,
the
fre-
quency
increases
linearly
because the
output
of the
Sweep
Generator
is
coupled through
the
SWEEP WIDTH
control
to
the
first
VCG
Amplifier
summing
node.
Maximum
fre-
quency
is
determined by the
basic
frequency and
the
setting
of the
SWEEP WIDTH
control.
It
should be noted
that the
maximum
SWEEP WIDTH
(fully
clockwise)
is
usable
only
when
the
basic
frequency
is
set
to
less
than
1/1
00th
of the
maximum
frequency
in
the
selected range.
The
swept output waveform
repeats for as long
as
the
MODE
switch
is
set
to
CONT
SWP.
SWEEP TIME
switch
and
VARIABLE
control
determine
the
sweep
repetition
rate.
(b)
Triggered
Sweep
Mode
Refer
to Figure
3-5.
In
the
TRIG
SWP
mode,
the
Main
Generator runs continuously
at
the
minimum
frequency
set
by
the
FREQ
DIAL,
VERNIER,
and
FREQ HZ
selector.
The Sweep
Generator
is,
initially, in
a
standby
condition.
When
an input
trigger signal
is
applied
at
the
TRIG
IN con-
nector,
the
output
of the Trigger
Level
Comparator/
Squaring
circuit
changes
the
state
of the Trigger/Gate
Control
circuit.
The
output
of the Trigger Level
Com-
parator/Squaring
circuit
is
coupled through
a
capacitor to
release
the
Sweep
Generator
Clamp
for a
single cycle.
Thus,
a single
sweep
of the
Main Generator
is
accomplished.
The
operation of the
SWEEP WIDTH
control
is
the
same
as
in
the
CONT
SWP
mode.
(c)
Sweep
and Hold
Mode
The
operation
in
this
mode
is
similar
to
operation
in
the
triggered
Sweep
Mode
except the output
of
the Trigger
Level
Comparator/Squaring
circuit
is
not coupled through
a
capacitor,
and
the
Sweep
Generator
Clamp
is
removed
for
the duration of the
trigger (or gate) signal.
When
the
gate
signal
drops, the
Main
Generator
again runs continu-
ously
at
the
frequency
set
by
the
frequency
controls.
3-5
1/74
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