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1 , 0 0 0 - or 10,000-microvolt signal
b. Connect the output of the audio oscil-
( a s required) at the SIGNAL IN-
lator (para 100) to the input of audio am-
PUT jack (any frequency).
plifier V701A in the main unit of the test
(3) S e t the variable 5-db step atten-
s e t . A convenient point for injecting the
uator to the 25-db position.
a u d i o oscillator signal is at the unnum-
(4) Rotate the SIGNAL ATTENUATOR
b e r e d feedthrough terminal at the bottom
D B switch to 60 and adjust the
r i g h t corner of the filter box assembly
GAIN control on the tuning unit to
( f i g . 45). This terminal is essentially the
p r o d u c e a 0-db indication on the
same circuit point as terminal Al of con-
main unit panel meter.
n e c t o r J701.
(5) D e c r e a s e the setting of the 5-db
c. Connect Voltmeter, Meter ME-30B/
variable step attenuator in four
U across a 600-ohm, l/2-watt resistor,
steps, from 25- to 5-db, and record
connected from PHONES jack J702 to
the corresponding indication of the
c h a s s i s ground.
d. Adjust the output of the audio oscil-
A N / U R M - 8 5 panel meter.
lator to produce a signal of O l-volt am-
(6) C h e c k the panel meter for a 5-db
1 increase for each step decrease
plitude from terminal Al of J701 to ground.
of the 5-db variable step at-
e. Tune the audio oscillator to 1,000 -
tenuator.
cps and record the voltage indication shown
on the ME-30B/U.
b. CW AVERAGE Test. This test is de-
s i g n e d to check the test set for linearity
f. Repeat procedure e above at the test
f r e q u e n c i e s of 150, 500, 2,000, 3,000,
w h e n a 100-percent modulated cw signal
4 , 0 0 0 , and 5,000-cps. Note the voltage
i s received at the SIGNAL INPUT jack.
reading at each test frequency. The audio
Signal sources capable of producing such
r e s p o n s e curve must be flat, within 8-db
a signal are not readily available. The
following test procedures, when used with
o f the 1,000-cycle value, with a gradual
a n unmodulated cw source, will simulate
s l o p e - o f f at each end. There must be no
the conditions above. For this test, change
r e s o n a n t peaks.
the setting of the function switch to the CW
AVERAGE position.
103. Linearity Test
(1) S e t the tuning unit signal gener-
a t o r output level control to pro-
Two tests are required to check the
d u c e  a  2,000-microvolt, or a
l i n e a r i t y of the test set; one checks the
2 0 , 0 0 0 -microvolt signal (as re-
linearity in the PULSE PEAK position of
quired) at the SIGNAL INPUT jack.
the function switch, and the other checks
(2) Set the frequency of the tuning unit
t h e linearity in the CW AVERAGE posi-
signal generator and the frequency
t i o n of the function switch. Remove the
dial of the tuning unit under test to
main unit from its instrument case (para 40
a frequency at the high end of the
b, item 12, TM 11-6625-351-12). Set up the
band under test.
equipment as shown in figure 94 and pro-
(3) A d j u s t the GAIN control on the
ceed as follows:
tuning unit to produce a full-
a. Pulse Peak Test. Connect the appli-
scale, 20-db indication on the main
c a b l e tuning unit signal generator (de-
unit panel meter with the variable
pending on the tuning under test) through
5 - d b step attenuator set to the 5-
a 5-db variable step attenuator (para 100),
db position.
o r equivalent, and through the RG-5B/U
(4) P l a c e t h e I F . C A T H O D E F O L -
cable, to the SIGNAL INPUT jack of the
LOWER ADJ switch S704, a chassis
t e s t set.
adjustment control (fig. 51) in its
(1) Set the main unit function switch to
o p e n - c i r c u i t position (check with
the PULSE PEAK position.
a multimeter). Shunt its terminals
with a 250,000-ohm potentiometer.
(2) Set the tuning unit signal generator
Use alligator clips to connect one
o u t p u t level control to produce a
220


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