If. Step Attenuator, Detailed Analysis

+150-volt bus; C78 is the t r a n s i e n t bypass

b e c a u s e of t h e inherent 6-db loss

c a p a c i t o r . The output of e i t h e r if. trans-

o f the step a t t e n u a t o r subassem-

f o r m e r T22 or T23 is coupled from jack

bly.)

J6 through interconnecting cable assembly

(2) When SIGNAL ATTENUATOR DB

W1 to jack Jl, on if. step attenuator AT1.

s w i t c h S701 is placed at 40, 60,

and 80 DB, both relays K3 and K4

a r e energized. This action places

28. If. Step Attenuator, Detailed Analysis

r e s i s t o r s R34 and R36 in series

(fig. 17)

with the signal path, with the other

resistors in the ladder network

T h e if. step attenuator is basically a

still retaining their shunting effect.

network of resistor pads together with two

T h e result is a 20-db increase in

relays (K3 and K4) which switch different

s i g n a l attenuation with respect to

combinations of these pads into the signal

t h e deenergized condition of both

path to achieve three steps of attenuation.

r e l a y s K3 and K4. (Actually, the

T h i s subassembly also contains a third

signal is attenuated 26 db relative

r e l a y , K5, which switches the attenuated

to the original incoming signal

if. signal to the input of either the 455-kc

level because of the inherent 6-db

or the 1,600-kc if. amplifier.

l o s s of the step attenuator subas-

a. Attenuator Action. S e r i e s r e s i s t o r s

sembly.)

R34 and R36, together with shunt elements

b. Relay K4 Coil Circuit. Resistor R32

R 3 3 , R35, and R37, constitute the ladder

and capacitor C87 form a decoupling net-

n e t w o r k which furnishes the desired

work for the coil of relay K4. Feedthrough

amount of attenuation to the incoming if.

capacitor C86 functions as an rf filter.

s i g n a l . Relay K4 is energized from the

- 1 5 0 - v o l t source when SIGNAL ATTEN-

c. Relay K3 Coil Circuit. Resistor R31

UATOR DB switch S701 (rear section) is

and capacitor C84 form a decoupling net-

p r o p e r l y positioned. Relay K4 is deener-

work for the coil of relay K3. Feedthrough

gized with this switch in the 0 CW ONLY

capacitor C85, connected in the -150-volt

or in the 0 SUBST. ONLY position (para

e n e r g i z i n g line, functions as an rf filter.

1 2 ) . The signal path is directly through

d. If. Sigal-Switching Relay K5. Relay

the upper contact of relay K4 and through

K5 is energized from the +150-volt source

the movable contact of relay K5 to either

when MEGACYCLES band switch S1 (rear

output jack J2 or J3. There is no resistance

section) is at 0.15-0.36 mc or 0.87-2.1 mc

in series with the signal path, but 6 db of

(band 1 or 3). In either of these positions

i n s e r t i o n loss is present because of the

o f S1, the movable contact of relay K5

shunting effect of the resistors to ground.

p r o v i d e s a path of continuity for the at-

(1) When SIGNAL ATTENUATOR DB

t e n u a t e d if. signal through jack J3 and

s w i t c h S701 is rotated to 20, 40,

mating plug P4 to the input of the 455-kc

60, or 80 DB, the coil of relay K4

i f . amplifier. When band switch S1 (rear

is energized, and its movable con-

section) is rotated to positions 2, 4,5, and

t a c t creates a signal path through

6 , the +150-volt bus is disconnected and

t h e movable contact of relay K3

relay K5 is deenergized; the movable con-

( s t i l l deenergized) to the junction

t a c t of relay K5 then provides a path of

of resistors R35 and R36. Resistor

continuity for the 1,600-kc if. signal

R 3 6 is now placed in series with

through jack J2 and mating plug P3 to the

the signal path, with the remaining

input of the 1,600-kc if. amplifier.

resistors in the ladder network

p r o v i d i n g a shunting effect. This

e. Relay K5 Coil Circuit. Resistor R38

s e r i e s - p a r a l l e l network results in

and capacitor C89 form a decoupling net-

an additional 10-db loss in signal

work for the coil of relay K5. Feedthrough

amplitude. (Actually, the signal is

capacitor C88, connected in the +150-volt

a t t e n u a t e d 16 db in relative level

e n e r g i z i n g line, functions as an rf filter.