Tektronix 1L30, Instruction Manual

Page: 55 / 129

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POS
DISPERSION RANGE
DISPERSION . .
RESOLUTION
VIDEO FILTER
VERTICAL DISPLAY
Position the trace lo I he
bottom line of the grati­
cule
M H z /C M
1 M Hz/cm
Uncoupled fully clockwise
O ff
LIN
c. Plug the special phone plug, with the 600 Q load re­
sistor across the output, into the TO RECORDER jack. Con­
nect the Vertical Input of the test oscilloscope through a
1 X probe, across the 600 Q load resistor.
d. Check-—Signal amplitude at the TO RECORDER con­
nector across the 600 Q load should measure between 12 mV
and 20 mV with a full screen signal display.
e. Disconnect the test oscilloscope probe and remove the
test phone plug.
11. Check Video Frequency Response
a. Requirement— Video frequency response is < 1 6 Hz to
> 10 MHz.
b. Apply a 50 kHz signal from the Constant Amplitude
(Type 191) Signal Generator through a coaxial cable,
T connector and a 50 Q termination, to the Video INPUT
connector on the Type 1L30.
c. Monitor the input signal amplitude to the Type 1L30
by connecting a DC coupled test oscilloscope to the open
end of the T connector.
d. Switch the VERTICAL DISPLAY selector to the VIDEO
position, turn the G A IN control fully clockwise and adjust the
Signal Generator output control for a signal amplitude of
4 cm on the analyzer plug-in oscilloscope. Adjust the test
oscilloscope vertical gain to establish a signal reference
amplitude of 4 divisions.
e. Increase the frequency of the Signal Generator (main­
tain a constant input amplitude) until the signal amplitude on
the plug-in oscilloscope decreases to 2.8 cm (— 3 dB point).
f. Check the input signal frequency. Must equal or exceed
10 MHz.
g. Disconnect the Constant Amplitude Signal Generator
and apply the signal from an Audio Signal Generator to
the Type 1130 Video IN P U T ./
h. Set the frequency of the Audio Signal Generator to.
50 kHz and adjust its output for the reference 4 cm signal
amplitude.
i. Decrease the generator frequency (maintaining a con­
stant input amplitude) until the signal display on the analyzer
oscilloscope screen is again 2.8 cm.
j. Check the input signal frequency. Must equal or be less
than 16 Hz. Remove the signal to the Type 1L30 Video IN
t
PUT and the test oscilloscope.
12. Check Incidental Frequency Modulation
a. Requirement— W ith the DISPERSION RANGE switch at
the kH z/C M position, the IF incidental FM should not exceed
©
Performance Check— Type 1L30
200 Hz. The incidental FM of the local oscillator plus the
IF incidental FM with phase lock must not exceed 300 Hz.
NOTE
Signal source must supply a very stable signal to
accurately measure this perform ance and the Type
1 L30 and plug-in oscilloscope must be on a stable,
v ib ra tio n -free p latform .
b. Set the DISPERSION RANGE switch to kH z/C M , the
DISPERSION to 500 kHz/cm and the VERTICAL DISPLAY to
the LIN position. Set the Time/Cm to 50 ms or slower.
c. Apply a 200 M Hz signal from the Time-Mark Gener­
ator through a 20 dB attenuator to the RF INPUT connector.
Center the IF feedthrough signal on the screen.
d. Change the DISPERSION-COUPLED RESOLUTION to
1 kHz/cm. Adjust, if required, the IF CENTER FREQ control
to keep the signal centered on the screen.
e. Adjust the G A IN control for 6 cm signal amplitude.,
f. Check the amount of signal frequency modulation at
the steepest.slope of the signal resp.onse (see Fig. 5-6). Inci­
dental FM is displayed as short term horizontal jitter. Dis­
regard long term horizontal drift. Must not exceed 2 mm
( < 2 0 0 MHz).
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Fig. 5-6. Typical display showing incidental frequency modulation.
Measure the horizontal displacement of the signal at the most ver­
tical slope of the signal.
g. Change the DISPERSION to 100 kHz/cm and move the
IF feedthrough signal off screen with the IF CENTER FREQ
control. Adjust the RF CENTER FREQ controls to Center ‘a
a tunable signal on screen.
h. Turn the INT 1 M Hz REF FREQ on and phase lock the
display. Adjust the MIXER PEAKING for maximum signal
amplitude.
i. Decrease the DISPERSION to 1 kHz/cm, keeping the
phase locked signal on screen by adjusting the IF CENTER
FREQ conlrols.
j. Check the frequency modulation in the display. Must
not exceed 3 mm (300 Hz).
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