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SECTION 3
Operation
actual center frequency value. The center frequency is the
center frequency on the linear scale, and it is not the cen-
ter frequency based on the sweep time in the log sweep
mode.
Sweep Function
Three sweep functions
are available: A
(ascending, de-
scending),/l
(ascending), andI
(step). The A
sweep
is generated by sweeping from the start frequency to the
stop frequency and then sweeping back to the start fre-
quency. Then
sweep is generated by sweeping from the
start frequency to the stop frequency and then returning
to the start frequency instantly.
The1
sweep alternates
between the start frequency and the stop frequency.
Sweep Time
Sweep time will vary depending
on the selected sweep
function.
When the sweep function
is A
:
Sweep time = time of transition from start frequency to
stop frequency
= time of transition
from stop frequency
to start fre-
9U-7
= half of repetition
period of continuous
sweep
When the sweep function
is n
:
Sweep time = time of transition from start frequency to
stop frequency
= repetition
period of continuous
sweep
When the sweep function
is 1:
Sweep time = duration
of start frequency in continu-
ous sweep
= duration
of stop frequency in continuous
sweep
= half of repetition
period of continuous
sweep
When the sweep times for then
and/\
sweep functions
are identical, the sweep rate along the equivalent
sloped
portions
of the two waveforms
will also be identical.
Note, however, that the continuous-sweep
repetition
pe-
riod for the two functions is different. See Figure 3-14 for
more details on sweep progression.
Sweep Operations
Model 3930A sweep operations
include
the following
eight types of sweeps:
Starting a continuous
sweep (CONT START key).
Starting a single sweep (SINGL START key).
Holding
and resuming a sweep (HOLD/RESM
key).
Turning
a sweep off to enable normal frequency
pro-
gramming
(SWEEP OF'F key).
Setting the output
waveform
to the start frequency
(START STATE key).
Setting the output
waveform
to the stop frequency
(STOP STATE key).
Starting a single sweep with
external
signals (SINGL
START IN BNC jack).
Holding
and resuming
a sweep with external signals.
(HOLD IN BNC jack).
starting
a continuous
Sweep
To start a continuous
sweep, press SHIfl
CONT START.
During the sweep, the Model 3930A displays the sweep
frequency,
and the following
message is displayed:
"CONT
SWEEP EXEC (EXIT:SWI'
OFF)". When the
Model
3930A is in this mode, you cannot set the fre-
quency with the FREQ key.
3-30
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