Performance Check— Type 1A1
j. Set the MODE switch to CH 2.
k. CHECK— Using steps 18d through 18g as a guide,
check Channel 2 upper bandwidth for a limit of 50 MHz
or higher.
l
. Set the Type 191 Frequency dial to 25 MHz, and the
Frequency Range switch to 50 kHz ONLY, and the Ampli
tude Range switch to 5-50 mV.
m. Set the Channel 2 VOLTS/CM switch to .005.
n. If necessary, adjust the Type 191 Variable controls
so the display is exactly 4 cm in amplitude. This is the ref
erence amplitude (see Fig. 6-7A).
o. Set the Type 191 Frequency Range switch to 18-42.
p. Without changing the Type 191 output amplitude, in
crease the output frequency until the vertical deflection is
reduced to 2.8 cm (see Fig. 6-7B).
q. CHECK— Channel 2 upper bandwidth limit at a verti
cal deflection factor of 0.005 volts/cm should be 28 MHz
or higher.
r. Disconnect the signal from the Channel 2 INPUT con
nector and connect it to the Channel 1 INPUT connector.
s. Set the MODE switch to CH 1 and set the Channel 1
VOLTS/CM switch to .005.
t. Set the Type 191 Frequency dial to 25 MHz and the
Frequency Range switch to 50 kHz ONLY.
u. CHECK— Using steps 18n through 18q as a guide,
check Channel 1 upper bandwidth for a limit of 28 MHz
or higher.
19. Check Upper Bandwidth Limit of
Channel 1 Signal Out Amplifier
a. Requirement— Upper bandwidth limit should be equal
to or greater than 35 MHz at the 3dB down point.
b. Set the controls as follows:
MODE
INPUT SELECTOR
(channel
2
)
VOLTS/CM
(both channels)
Type 1A1
CH 2
AC
.05
Frequency dial
Frequency Range
Amplitude
Amplitude Range
Type 191
35 MHz
50 kHz ONLY
20
50-500 mV
c. Connect an 18-inch 50-ohm cable from the CH 1 SIG
NAL OUT connector to the Channel 2 INPUT connector.
d. Adjust the Type 191 Amplitude controls so the display
is exactly 4 cm in amplitude.
e. Disconnect the end of the 18-inch cable that connects
to Channel 2 INPUT connector.
f. Disconnect the signal from the Channel 1 INPUT con
nector and connect it to the Channel 2 INPUT connector.
Note the exact amount of vertical deflection.
g. Set the Type 191 Frequency Range switch to 18-42.
Check that the Frequency dial is set to 35 MHz.
h. Adjust the Type 191 Amplitude controls to obtain the
same vertical deflection as that noted in step 18f.
i. Disconnect the signal from the Channel 2 INPUT con
nector and reconnect it to the Channel 1 INPUT connector.
j. Reconnect the 18-inch cable to the Channel 2 INPUT
connector. Check that the signal is applied from the CH 1
SIGNAL OUT connector to Channel 2.
k. CHECK—The CRT display should be 2.8 cm in ampli
tude or more. This indicates the upper bandwidth limit
for the Channel 1 Signal Out Amplifier is 35 MHz or higher.
NOTE
Steps 19f through 19h in the procedure use a
technique that eliminates Channel 2 and the os
cilloscope as factors when determining the upper
bandwidth limit for the Signal Out Amplifier alone.
l
. Disconnect the signal from the Channel 1 INPUT con
nector and turn off the Type 191 Constant Amplitude Sig
nal Generator. Remove the coaxial cable from CH 1 SIG
NAL OUT connector to Channel 2 INPUT connector.
20. Check— AC Coupled Low Frequency
Response
a. REQUIREMENT— The —3dB response point is less than
2
hertz.
;b. Set both Channel 1 and 2 VOLTS/CM switches to 5,
INPUT SELECTORS to AC, and the MODE switch to CH 1.
c.
Set the Time Base B Time/Cm switch to .1 sec and turn
the Time Base B Triggering Level control fully clockwise.
6-10
Fig. 6 -8 . Measuring AC coupled low-frequency response using an
RC curve.
