Tektronix 492 Operator's Handbook

SECTION
3
GENERAL OPERATING INFORMATION
SIGNAL APPLICATION
Signal
frequencies up to 21
GHz are
applied through a
short , high quality , 50 2 coaxial cable , to the RF INPUT
connector
.
These
signal
pass
through
an
internal
RF
attenuator to the
first (
1st )
mixer .
Option 1
version of the
492 has a
filter
selector that
automatically
selects either a
low - pass
filter or tuned
preselector (
depending on fre
quency band ) between RF attenuator and the 1st mixer .
Signals
above
21 GHz
are
applied
to an
external
waveguide mixer . The
output
of
the
waveguide mixer is
then applied through the EXT MIXER port to the second
converter
of
the 492.
Waveguide mixers and
their
applica
tion are described later .
RF
INPUT
CONNECTOR
The nominal input impedance of the coaxial RF INPUT
is 50
.
Because
cable
losses
can be
significant at
microwave
frequencies
,
it is
important to keep
the
cables
as short as possible . Impedance mismatch between the
signal source and the RF INPUT will produce reflections
and
degrade
flatness ,
frequency
response
,
sensitivity , and
increase spurious responses . Impedance mismatch can
be
caused
by
poor
connections ,
incorrect signal
source
impedance , long or low quality coaxial cable , etc. When
optimum flatness or frequency response is desired and
signal strength is adequate , set the MIN RF ATTENuation
for 10 dB or
more . The
addition
of
the
attenuator helps
minimize
reflections
to
improve
the input
characteristics
.
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
.
492 Operator's Handbook
3-1

Tektronix 492 Specifications

General

Brand	Tektronix
Model	492
Category	Measuring Instruments
Language	English