Tektronix 492 Operator's Handbook

USING THE VIDEO FILTERS
The video filter restricts the video bandwidth so that
noise or beat signals are reduced ( see Fig . 3-1 ) . When
signals are closely spaced , the filter may be useful to
reduce modulation between two signals so they can be
more
easily analyzed .
The filters
can also be
used to
average the
envelope of pulsed
RF
spectra that has
a
relatively high prf ( pulse repetition frequency ) ; however ,
because the filter is basically an integrating circuit ,
selecting a Video Filter when measuring low prf spectra
produces
poor
results .
The WIDE filter reduces the bandwidth to approximate
ly
1 / 30th the
selected
resolution bandwidth
; the NARROW
filter about 1 / 300th . Using the filter may require a reduc
tion in the sweep rate to maintain a calibrated display .
Again the UNCAL indicator will light if the sweep speed is
too
fast
for
video
filtering .
TIME DOMAIN OPERATION
When the FREQ SPAN / DIV is reduced to zero , the
analyzer functions as a tunable receiver to display time
domain characteristics within the capabilities of the
resolution bandwidth . The TIME / DIV selector can now be
used to analyze such characteristics as modulation
pattern , pulse repetition rates , etc.
3-4
TRIGGERING
THE
DISPLAY
Triggering is
usually FREE RUN
for
spectrum displays ;
however , it may be desirable or necessary to trigger the
display when the event is time related to some source or
when the frequency span has been reduced to zero for
time domain analysis . In the FREE RUN mode the sweep
will not synchronize with any input signal .
The
sweep
can be
triggered
internally
from the
vertical
or
video signal
, at the line
frequency rate
of the power
supply , or from
an
external signal
applied to the EXT
IN
HORIZ / TRIG jack on the back panel . The amplitude of
trigger signal required to trigger the sweep is one ( 1.0 )
division or more , for internal triggering , and 0.5 volt to a
maximum of 50 volts ( dc + peak ac ) for external triggering .
Trigger source is selected by activating one of the
triggering
pushbuttons . In
addition to the
four trigger
source
selections ,
SINGLE SWEEP
mode can be
selected .
The
sweep will run
once
after
the
circuit
has
been
armed
and
trigger
signal
arrives .
The
READY indicator lights
when the circuit is armed and waiting for a trigger signal
and remains lit until the sweep has run . Pushing the
SINGLE SWEEP button once activates single sweep
mode ; pushing it again arms the trigger circuit so it is
ready for a trigger signal .
492
Operator's
Handbook

Tektronix 492 Specifications

General

Brand	Tektronix
Model	492
Category	Measuring Instruments
Language	English