Calibration as Two-Terminal RF Voltmeter

impulse g e n e r a t o r output level controls;

of the band under test; then check at two

t h e sum o f the settings is the reference

other equally spaced frequency points

within the band.

sensitivity.

k. Repeat the procedures in e through

g. Now disable the local oscillator in the

j for each band of the tuning unit under test.

tuning unit under test. Each tuning unit re-

quires a different procedure for this oper-

110. Calibration as Two-Terminal RF

a t i o n . Perform the procedure outlined in

Voltmeter

the following chart:

This procedure is used to calibrate. the

t e s t set as a two-terminal rf voltmeter.

S e t up the equipment as shown in figure

94; however, use the 10-db pad instead of

the 5-db variable step attenuator. The 10-

d b pad can be connected directly to the

tuning unit signal generator.

a. If tuning units 1, 2, or 3, are used,

c o n n e c t the applicable tuning unit signal

g e n e r a t o r (recently calibrated for power

o u t p u t ) to the test set and proceed as

follows:

(1) S e t t h e f u n c t i o n s w i t c h t o C W

A V E R A G E a n d the calibration

switch to SERIES CAL &OP-

ERATE.

(2) I f tuning unit 1 is used, set the

h. With the local oscillator of the tuning

SIGNAL ATTENUATOR switch to

u n i t disabled (g above), readjust the im-

0 CW ONLY; if tuning units 2 or

p u l s e generator coarse and fine output

3 are used set the SIGNAL AT-

l e v e l control settings to again produce a

TENUATOR switch to 20 DB.

2-db indication on the panel meter. Record

(3) Set the tuning unit signal generator

t h e sum of the two output level control

output level to produce a 10-

s e t t i n g s : t h i s is the rf intermodulation

m i c r o v o l t signal at the SIGNAL

sensitivity.

INPUT terminal of the test set for

i. S u b t r a c t t h e v a l u e o f t h e r f i n t e r -

t u n i n g unit 1, or a 100 microvolt

modulation sensitivity (h above) from the

signal for tuning units 2 or 3.

r e f e r e n c e sensitivity (f above) to deter-

N o t e : If the 10-db pad is too large to

mine the difference in db. This difference

p r o v i d e a signal of proper amplitude at

in settings for the impulse generator out-

the test set SIGNAL INPUT terminal, use

p u t level controls must be the same or

a Pad of a smaller value (AT-50-8) to pro-

duce the proper signal amplitude.

h i g h e r than the values shown in the fol-

(4) Adjust the GAIN control to obtain

lowing chart:

a 20-db reading on the test set

p a n e l meter.

(5) S e t t h e f u n c t i o n s w i t c h t o C W

P E A K and the calibration switch

to SHUNT CAL.

(6) Set the IMPULSE GENERATOR DB

ABOVE lV/MC switch to ON

a n d adjust the impulse generator

output controls (coarse and fine) to

again obtain a 20-db reading on the

j. R e p e a t t h e p r o c e d u r e g i v e n i n e

t e s t set panel meter.

through i above for the high-frequency end

(7) Record the settings of the impulse

225