Tektronix 491, Maintenance Manual

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SECTION 1
CHARACTERISTICS
The Type 491 Spectrum Analyzer is a wide band,
general purpose portable spectrum analyzer with an RF
center frequency range from 10 MHz to 40 GHz. The ana-
lyzer displays signal amplitude as a function of frequency
for a selected portion of the
played along the horizontal
amplitude on the vertical axis
spectrum, Frequency i
S
dis-
axis
of a
(dispersion) and signal
self-contained system.
The following electrical characteristics apply at an ambient
temperature of 25° C (±5°C) after an initial warmup period
of approximately 20 minutes.
ELECTRICAL CHARACTERISTICS
Characteristic
Performance Requirement
S u p p l e m e n t a l I n f o r m a t i o n
RF Center
Frequency Range 10 MHz to 40 GHz—See Table 1-1
CW Sensitivity See Table 1-1
I
( S + N = 2 N )
Dial Accuracy Within ± (2 MHz +1% of dial reading) IF CENTER FREQ central at 000, FINE IF
I
CENTER FREQ control and FINE RF CENTER
FREQ controls centered.
TABLE 1-1
Minimum CW
S e n s i t i v i t y ( S + N = 2 N )
Band and
Supplemental
Scale RF CENTER FREQUENCY 1 kHz RESOLUTION 100 kHz RESOLUTION
Information
A-1
10-275 MHz –100 dBm –80 dBm
B-2 275-900 MHz
–110 dBm –90 dBm
3 800-2000 MHz –105 dBm –85 dBm
C-4
1.5-4.0 GHz
–110 dBm –90 dBm
5 3.8-8.2 GHz –100 dBm -80 dBm
6 8.0-2.4 Ghz –95 dBm –75 dBm
7
12.4-18.0 GHz
–90 dBm –70 dBm
8 18.0 -26,5 GHz –80 dBm -60 dBm
!
26.5-40.0 GHz –70 dBm -50 dBm
50
Ω
source impedance.
All voltages are RMS.
TABLE 1-2
D I S P E R S I O N / D I V
Setting
Accuracy
Remarks
1 0 M H z
—
± 3 % ( ± 0 . 3 M H z / D i v )
Over the ±25 MHz of the IF Center FREQ control ex-
5 MHz
± 3 % ( ± 0 . 1 5 M H z / D i v ) cept the 10 MHz/DIV position (± 10 MHz). The DIS-
2 MHz
PERSION CAL adjust can be reset to improve the ac-
± 5 % ( ± 0 . 1 M H z / D i v )
curacy at a specific IF CENTER FREQ control setting
1 MHz
±7% (±70 kHz/Div)
by using the front panel 1 MHz CAL MARKERS OUT as
.5 MHz
±10% (±50 kHz/Div)
a calibrated signal.
.2 MHz
±15% (±30 kHz/Div) Measured over the center 8 divisions of the graticule.
1-1