Figure 94. Test setup for linearity check.

Figure 94. Test setup for linearity check.

high end of the frequency range. In

end terminal and one center ter-

each case, the change in meter

m i n a l of the potentiometer to the

i n d i c a t i o n from S704 in its nor-

terminals of S704.

mally closed-circuit position to its

(5) A d j u s t t h e v a r i a b l e a r m o f t h e

open-circuit position (with the 250,

externally c o n n e c t e d potenti-

000-ohm potentiometer across

ometer to produce an indication of

S704 terminals) must be 6 db. The

1 4 db on the AN/URM-85 panel

p o t e n t i o m e t e r arm can be set to

meter. This decrease of 6 db from

d i f f e r e n t positions within its re-

t h e panel meter. indication, given

sistance range when a different

in (3) above, must be obtained by

tuning unit is under test.

setting the arm of the potenti-

ometer to some point in its resist-

104. Interference Measurement

a n c e range.

(6) I n c r e a s e t h e 5 - d b v a r i a b l e s t e p

To perform this test, the IG-115 impulse

a t t e n u a t o r in four 5-db steps and

g e n e r a t o r is required. Set up the equip-

record the corresponding indi-

m e n t as shown in figure 95, and proceed

cation on the test set panel meter.

as follows:

T h i s indication should be within

a. Connect the IMPULSE OUTPUT jack

1 db at all steps.

o f the IG-115 impulse generator, through

t h e 20-db pad (direct connection), to the

(7) R e p e a t t h e p r o c e d u r e s g i v e n i n

SIGNAL INPUT jack of the test set under

( 1 ) through (6) above for each of

test.

t h e remaining tuning units at the

221