Using Tuning Wand

Working from the bottom of the 10.7-

p a n e l meter indication. This pro-

m c if. amplifier subassembly, adjust the

cedure completes the alignment of

t h e 10.7-mc if. amplifier.

c o r e s of if. transformers T206 and T207

f. Disconnect the fabricated cable as-

f o r a further maximum indication on the

sembly (a(2) above) from input jack J1 on

p a n e l meter.

d. Repeat the procedures given in b a n d

the if. step attenuator. Reconnect plug P209

on cable assembly W201 to input jack J1 on

c a b o v e , a s necessary, until no further

the if. step attenuator.

peaking can be observed. Proper if. align-

ment is evidenced when an output of ap-

p r o x i m a t e l y 40 to 70 microvolt from the

90. Using Tuning Wand

tuning unit 2 signal generator produces a

f u l l - s c a l e pointer deflection on the panel

A tuning wand is required for aligning

t h e 70-200-mc band of tuning - unit 2 and

meter (with the SIGNAL ATTENUATOR

DB switch at the 20 db position).

for the complete frequency range of tuning

unit 3. This tuning wand, which is commer-

e. After completing the p r o c e d u r es

given in a through d above, adjust signal

c i a l l y available, c o n s i s t s of a plexiglas

p e a k i n g coil L229 in the cathode circuit

r o d approximately 7/32 inch in diameter

of V211, as follows:

by 6 inches long. One end of the wand ter-

(1) I F . CATHODE FOLLOWER ADJ

minates in a powdered iron core slug; the

switch S704 is mounted on the

other end terminates in a brass slug. Use

m a i n unit power supply partition

the wand as described below:

a. Tuning Unit 2 (70- to 220-Mc Band

(fig. 51). Set this toggle switch to

(fig. 65)).

the open-circuit position to place a

resistor in the metering signal path

(1) I n s e r t the brass slug end of the

and make the panel meter (M701)

tuning wand into the separate mag-

l e s s sensitive.

netic field of variable coils L208 at

(2) Observe that the meter pointer now

the input to V204, L211 at the input

d e f l e c t s to approximate midscale,

to V205, and L213 at the input to

with the tuning unit 2 signal gener-

V206A. Watch the change in indica-

ator i n j e c t i n g a 50-microvolt

tion on the main unit panel meter.

output signal (at 10.7 mc) into the

An increase in the meter indication

i f . amplifier.

shows that the coupling between the

(3) Rotate the tuning unit 2 signal gen-

individual loops of wire comprising

e r a t o r MICROVOLTS control to

t h e particular coil under measure-

ment should be reduced. This effect

o b t a i n the full-power level capa-

is obtained by spreading the loops

bility (approximately 100,000

m i c r o v o l t ) , and adjust the core of

of wire farther apart from each

other.

L229 for a maximum output indica-

(2) Insert the powdered iron core end

tion on the panel meter.

o f the tuning wand into the same

(4) S e t switch S704 to its closed-cir-

v a r i a b l e coils, one coil at a time.

c u i t position. This action short-

Watch the change in panel meter in-

c i r c u i t s the series resistor in the

dication. An increase in the panel

metering signal path and causes the

meter indication with the powdered

p a n e l meter to be more sensitive.

iron core inserted in the magnetic

(5) D e c r e a s e the tuning unit 2 signal

field of the coil now shows that the

generator MICROVOLTS control to

coupling between the loops of wire

t h e setting that produces approxi-

shoul be increased. This effect is

mate mids c ale panel meter

obtained by bending the loops

reading.

c l o s e r to each other.

(6) Readjust Z202 to obtain a maximum

p a n e l meter indication.

b. Tuning Unit 3 (200 to 400 Mc ( f i g .

69)).

(7) Repeat the procedures given in (1)

t h r o u g h (6) above for final peak

1 ) Insert the brass slug end of the

199