Tektronix 492 Operator's Handbook

Signals with large differences in amplitude that are
within the AA range can be compared without the
distortion usually introduced when signals are driven off
screen . Signals shifted off - screen by changes in the AA
reference level are not overdriving the input because the
attenuator and IF gain are not changed ; thus the mixers do
not
see any
change
in
signal levels
due to the
AA
reference
level
changes
.
To measure amplitude level differences of two signals :
1 ) Select AA mode by activating 2 dB / DIV and FINE .
2 ) Using the REF LEVEL control , set the larger amplitude
signal to a graticule line . 3 ) Press the FINE pushbutton
twice to deactivate and re - activate the AA mode . 4 ) Using
the REF LEVEL control , set the lower amplitude signal to
the same graticule line established in step 2. 5 ) The REF
LEVEL readout displays the dB difference in amplitude
level .
MIN NOISE / MIN DISTORTION
This pushbutton selects one of two algorithms that
control attenuator and IF gain settings . MIN NOISE
minimizes noise level while MIN DISTORTION minimizes
input mixer overload . To observe any change when MIN
NOISE is activated , the RF ATTEN crt readout must be
10 dB higher than that set by the MIN RF ATTEN selector .
3-8
CAUTION
With MIN NOISE activated and 60 dB of MIN RF
ATTEN
, the REF
LEVEL can be
set to +40 dBm
. The
front end of the 492 is specified at +30 dBm
maximum . Do not increase input signal level to full
screen with a REF LEVEL of +40 dBm because this
will
exceed the
attenuator rating
. DC input is limited
to
zero
( )
volt .
DIGITAL
STORAGE
(
OPTION 02 )
Digital storage provides a smooth ( flicker free ) display .
Two
complete events
can be stored
. One of these
can be
saved and then compared to subsequent updated infor
mation . A MAX HOLD feature updates the stored data in
memory when the new input is of higher amplitude thus
allowing monitoring and graphic plotting of display
changes with time . Vertical information can be divided by
a cursor , or horizontal line , that is positioned with the
PEAK / AVERAGE control . Above the cursor , video infor
mation is peak detected and displayed ; below the cursor ,
signal averaging occurs . The average ( number of
samples ) is a function of sweep speed . The slower the
sweep , the greater the number of samples averaged . This
feature
suppresses noise
in that
portion
below the
cursor
and
allows full
peak
detection of
vertical data above the
cursor . An intensified spot on the cursor indicates the
horizontal position at which memory is being updated .
492
Operator's
Handbook

Tektronix 492 Specifications

General

Brand	Tektronix
Model	492
Category	Measuring Instruments
Language	English