Tektronix 492 - Page 23

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28
29
POWER . Pull type switch that switches the main
power
supply on
.
A
RF
INPUT . A 50
2
coaxial
input
connector
for signals 21 GHz or below . The maximum , non
destructive input signal level to the input mixer is
+13 dBm or 30 mW . Signals above - 10 dBm may
cause signal compression .
CAUTION
The maximum rating of the RF attenuator is
+30 dBm ( 1 watt average , 75 watts peak , pulse width
< 1 us , with a duty cycle that does not exceed 0.001 ) .
Burn - out occurs above 1 watt .
If MIN NOISE is activated and RF ATTEN is 60 dB ,
the +30 dBm rating could be exceeded . If the input
signal level is increased for a full screen display the
input level will be +40 dBm . Reduce high level
signals with external attenuators if the RF attenuator
rating may be exceeded . Use external attenuators
and the MIN RF ATTEN to reduce the level into the
1st mixer to
-10 dBm or
less . Input
voltage
to
the
input
mixer must not
contain any dc
component .
Refer to Signal Application ( under General
Operating Instructions ) discussed later in this sec
tion .
30
POSITION
31
32
33
These
controls
position
the
display on the horizontal and vertical axes .
CAL OUT ( Calibrator output ) . The source of a
calibrated -20 dBm ( ± 0.3 dB ) 100 MHz
( + 0.01 % ) signal , and a comb of frequency
markers 100 MHz apart . The calibrated 100 MHz
marker is used as a reference for calibrating
reference level and log scale . The comb of
100 MHz
markers
is used
to check
span and
frequency
readout
accuracy .
OUTPUT 1st and 2nd
LO . These
connectors
provide access to the output of the respective
local oscillators . The connectors must be ter
minated into 50 when they are not connected to
some
external
device
.
EXT MIXER . When the EXT MIXER button is
activated , bias is provided out the EXT MIXER
port for external waveguide mixers . The IF output
from the external mixer is then applied through
the EXT MIXER port to the 2nd converter . Exter
nal mixer connection and operation is described
under
General
Operating
Information
.
492
Operator's
Handbook
2-11