LIN; ≥ 2 6 δ Β .
LOG; ≥40 d B .
SQ LAW; ≥ 1 3 δ Β
Limits (.1 dB/dB)
b. Apply 200 MHz signal that has an amplitude less than
5.93 to 6.07 div
-40 dBm, from a VHF Signal Generator that has a cali-
5.86 to 6.14 div
brated variable output attenuator, to band B RF INPUT con-
5.6 to 6.3 div
5.5 to 6.6 div
c. Adjust the GAIN control and the variable attenuator
5.0 to 7.2 div
of the Signal Generator for a display amplitude of 8 divi-
4.7 to 7.6 div
sions (full screen).
The 1 and 2 dB measurements are very difficult, because
d. Increase the output attenuation of the VHF Signal Gen-
of signal stability and the noise level. For these small signal
erator until the signal is just visible (about 0.5 minor divi-
sion) on the display. Note the difference in the attenuator
levels, the square law mode may be used to expand the
screen changes, for the some level change by the square
e. Check the dynamic range of each VERTICAL DISPLAY
switch position. Must equal or exceed the range listed in
f. Return the VERTICAL DISPLAY switch to the LIN posi-
An alternate method which is not as accurate but is suf-
ficient for most applications is as follows:
18. Check Accuracy of IF ATTENUATOR
1. Apply a 200 MHz signal (at 60 dB below 1 mW, as
shown an the Attenuator dial) from the signal generatar
Accuracy of the IF ATTENUATOR dB selectors is checked
to the RF INPUT connector. Adjust the Spectrum Analyzer
at the factory to insure that they are within 0.1 dB/dB specifi-
GAIN control for a signal amplitude of 5 divisions.
cation. Any change in this tolerance should be a large one and
2. Switch the 1 dB IF ATTENUATOR switch on and adjust
due to component failure. Step attenuators with rigid
the signal generator output attenuator control to return the
specifications are, therefore, not recommended. However, if
signal amplitude to 5 divisions.
the user desires a precise check of the attenuator error, he
must either accurately calibrate the recommended equipment
3. Check the new reading of the attenuator dial. Should
or use step attenuators with more rigid specification.
read -59 dBm.
4. Turn the 1 dB IF ATTENUATOR switch to OFF. Check
the remainder of the IF ATTENUATOR selector steps as
b. Apply a 200 MHz signal from the signal generator that
is 10 dB below 1 mW, through a 2X attenuator (6 dB), a Tens
and Units step attenuator and a 10X attenuator (20 dB) to the
c. Set the Tens attenuator far 20 dB attenuation and the
Units attenuator for 12 dB attenuation.
d. Adjust the GAIN control far a signal amplitude of 6
divisions on the analyzer screen.
e. Check the accuracy of the IF ATTENUTOR dB selectors
19. Check Attenuation Range of IF GAIN
1. Switch the Type 491 1 dB attenuator siwtch to ON and
switch out 1 dB of attenuation through the units step attenua-
a. Requirement-The IF GAIN control range should equal
or exceed 50 dB.
2. Check the display amplitude. Must equal 6 div. 0.7
b. Turn the GAIN control fully counterclockwise. Adjust
minor division (.1 dB/dB).
the VHF Signal Generator output for an 8 division signal
amplitude. Note the variable attenuator dial reading.
3. Switch the IF ATTENUATOR switch to OFF position,
c. Increase the output attenuation 50 dB from the noted
then check the remaining IF ATTENUATOR switch steps