Tektronix 1L40, Инструкция по эксплуатации

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Performance Check/Calibration— Type 1L40
c. Set the Tens Step Attenuator for 20 dB and the Units
Step Attenuator for 12 dB attenuation.
d. Adjust the G A IN control for a signal amplitude of 4 cm
on the indicator oscilloscope.
e. CHECK— the accuracy of the IF ATTEN dB selectors as
follows:
(1) Switch the 1 dB attenuator switch to O N and switch
out 6 dB attenuation by means of the Units Step Attenuator.
(2) Check the display amplitude. Must equal 4 cm ± 0.5
mm (0.1 dB/dB).
(3) Switch the 1 dB IF ATTEN switch to the OFF position,
then check the remaining IF ATTEN steps as directed in Table
5-3A.
TABLE 5-3A
Spectrum
A n a ly z e r
IF ATTEN
Switch on
Step
A tte n u a to rs
Signal A m p litu d e
Limit (.1 d B /d B )
Units Tens
1 dB 11 20
3.95 cm to 4.05 cm
2 dB 10 20
3.90 cm to 4.1 cm
4 dB 8 20 3.8 cm to 4.2 cm
8 dB 4
20
3.6 cm to 4.4 cm
16 dB 6 10
3.2 cm to 4.8 cm
20 dB
2 10
2.95 cm to 5.05 cm
The 1 and 2 dB measurements are very difficult because
of signal stability and the noise level. Over these small
signal levels the square law mode may be used. This ex­
pands the display changes for the same level change by the
square power as listed in Table 5-3B.
TABLE 5-3B
dB
1
2
4 8 16 20
Signal 3.95 3.9 3.6 3.2 2.2 1.7
amplitude to to to to to
to
limits 4.05 4.2 4.4 4.8 5.8 6.3
An alternative method which is not as accurate but
is sufficient for most applications is as follows:
(1) A pply a —6 dBm, 200 MHz signal directly from the Sig­
nal Generator to the RF connector via the proper adapter.
Adjust the Spectrum Analyzer G A IN control for a signal
display amplitude of 5 cm.
(2) Switch the 1 dB ATTEN switch on and adjust the Sig­
nal Generator Attenuator control to return the signal display
amplitude to 5 cm.
(3) Check the new reading of the Attenuator dial. It should
read — 59 dBm ± 0 .1 dBm.
(4) Turn the 1 dB ATTEN to OFF. Check the remainder of
the IF ATTEN selector steps as directed in Table 5-3C.
TABLE 5-3C
Spectrum A n a lyze r
IF ATTEN switch O N
RF G e n e ra to r A tte n u a to r
C ontrol Setting
2 dB —58 dBm ± .2 dBm
4 dB
— 56 dBm ± .4 dBm
8 dB —52 dBm ± .8 dBm
16 dB —44 dBm ± 1.6 dBm
20 dB —40 dBm ± 2.0 dBm
8. Check/Adjust Dynamic Range of Vertical
Display Modes
a. The equipment setup for this step is given in the alter­
native method portion of step 7.
b. Change the VERTICAL DISPLAY selector to LOG position
and apply a — 100 dBm, 200 MHz signal directly from the
Signal Generator to the RF INPUT connector.
c. Adjust the Type 1L40 G A IN for a signal that is
just discernible above the noise peaks (approximately 1 mm).
Position the top of the signal to the bottom graticule line
with the POS control.
d. Decrease the Signal Generator Attenuator setting 40 dB
so the generator output is — 60 dBm.
e. CHECK— Signal display amplitude must equal or exceed
6 cm. The difference between the attenuator reading for a
full screen (6 cm) display amplitude and the attenuator set­
ting for the barely discernible signal in (c) above is the
dynamic range. This must be > 40 dB for LOG mode. If this
check is satisfactory, proceed to step (i).
f. ADJUST— Log Cal R666, (Fig. 5-9) for a signal amplitude
of 6 cm.
g. Change the Signal Generator attenuator control so a
signal of — 100 dBm is again applied to the RF INPUT.
h. CHECK— Signal should be discernible above the noise
and at the bottom graticule line. Repeat step (f) through
(h) until the dynamic range of 6 cm graticule height is > 40
dB.
i. Change the VERTICAL DISPLAY slector to LIN. Position
the top of the noise peaks at the bottom graticule line with
the POS control.
j. Change the Signal Generator Attenuator setting so — 40
dBm signal is applied to the RF INPUT of the Type 1L40.
Adjust the G A IN control for a signal with an amplitude of
6 cm (full screen display).
k. Increase the Attenuator setting until the signal is again
just discernible above the noise level. Note the Attenuator
reading.
l
. CHECK— The difference in the two attenuator readings
must equal or exceed 26 dB.
m. Switch the VERTICAL DISPLAY selector to SQ LAW
position and repeat the procedure to check the dynamic
range of the SQ LAW position. The range must equal or
exceed 13 dB.
®
5 -1 9