Tektronix 1L30, Instruction Manual

Page: 79 / 129

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6-23. Equipment setup for checking incidental
FM
(step 151.
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Type 1L30
POS Position a free running
trace to the bottom line
of the graticule
IF CENTER FREQ
Midrange (000)
FINE
Centered
DISPERSION Pa MCE
k H z /C M
DISPERSION
5 0 0 kHz
VIDEO FILTER
OFF
G A IN
M id ran g e
VERTICAL DI3PI. AY
LIN
IF ATTEN
Switches off
FINE RF CENTER i-RcQ
Centered
1NT 1 MH?. £SF FEED
INT
Oscilloscope
s Time/Cm
t
J Triggering
'1 Horizontal Position
■ |
j 6-22
50 ms
Adiu:.:ed fo r a free
running sweep
Centered trace
15. Check Incidental Frequency Modulation
N O T E
Signal source must supply a very stable 2 0 0 M H z
signal to accu rately measure incidental FM and
the Type 1L30 must b e on a v ib ra tio n -fre e p la t­
form .
a. Equipment setup is shown in Fig. 6-23.
b. Set the DISPERSION RANGE switch to kH z/C M and the
DISPERSION to 500kH z/cm . Set the Time/Cm to 50 ms.
c. Apply a 200 M H z signal from the Time-Mark Gener­
ator (2nd harmonic of 10 ns marker) through a 20 dB atten­
uator and a 50 Q termination to the RF INPUT connector.
Center the IF feedthrough signal on screen.
d. Change the DISPERSION-COUPLED RESOLUTION to
1 kHz/cm position. Adjust ’the IF CENTER FREQ control if
required to keep the signal centered on screen.
e. Adjust the G A IN control for a full screen 6 cm signal
amplitude.
f. Check the amount o f frequency modulation (see Fig.
6-24) in the IF feedthrough ’signal. Must not exceed 2 milli­
meters or 1 minor division ( < 2 0 0 Hz).
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