Block Diagram of Signal Attenuator AT702 Circuitry

below) is required when the dipole antenna

through six-step signal attenuator AT702

before application to the input of the tuning

o r coupler devices are used. Series cali-

bration (b below) is required when the dis-

u n i t . The purpose of the signal attenuator

i s to insert either zero or a fixed amount

cone, loop, or vertical antenna is used. In

either series or shunt calibration, the

o f resistive attenuation in the rf and if.

s e t t i n g of the six-step signal attenuator

s i g n a l path. This circuit arrangement is

(c below) affects the signal path.

d e s c r i b e d in paragraph 12.

a. Shunt Calibration Condition (fig. 1 and

12. Block Diagram of Signal Attenuator

2 ) . The following two circuit conditions

exist with the calibration switch set at the

AT702 Circuitry

SHUNT CAL position.

(fig. 4)

(1) The calibrating signal voltage from

Figure 4 shows the threefold functioning

impulse generator G701 has a path

of the six-step SIGNAL ATTENUATOR DB

of continuity through coaxial relay

c o n t r o l . This block diagram is based on

K 7 0 2 to the input of 20-db fixed

p l a c i n g the front-panel calibration switch

a t t e n u a t o r AT701. The calibrating

in the SERIES CAL & OPERATE position

signal is decreased in amplitude by

(fig. 2). The s h a f t of the front-panel

a ratio of 10 to 1 (20-db), and is

SIGNAL ATTENUATOR DB control drives

applied through coaxial relay K701

three separate switches, which operate

t o the input of six-step signal at-

c i r c u i t s as described below:

t e n u a t o r AT702.

a. Rf Attenuating Circuit. The incoming

(2) T h e incoming rf signal applied to

r f signal is coupled through front-panel

SIGNAL INPUT jack J705 (fig. 2)

SIGNAL INPUT jack J705 and coaxial relay

is effectively removed from the

K701. This relay is energized in the

input to the test set. Therefore, no

SERIES CAL & OPERATE position of the

i n c o m i n g signal from the antenna

calibration switch, and a path of continuity

or coupler can affect the meter in-

is created to the input of rf six-step signal

dication when the test set is being

attenuator AT702. The six positions of the

calibrated by the shunt method.

S I G N A L ATTENUATOR DB control have

b . Series Calibration and Operate Con-

t h e following effect on the incoming rf

d i t i o n (fig. 2 and 3). The following two

signal:

circuit conditions exist with the calibration

(1) I n the 0 SUBST. ONLY position,

switch set at the SERIES CAL& OPERATE

z e r o attenuation is inserted in the.

position.

r f signal path. Since the test set

(1) A n incoming signal, applied from

input circuit is not terminated with

the antenna or coupler through

a 50-ohm impedance in this position

S I G N A L INPUT jack J705, has a

of the attenuator, quantative

p a t h of continuity through coaxial

m e a s u r e m e n t s are meaningful only

relay K701 to six-step signal atten-

if the substitution method of opera-

u a t o r AT702.

tion (para 6b) is used. The 0 SUBST.

(2) The calibrating signal voltage from

ONLY position of the attenuator is

i m p u l s e generator G701 is inter-

usually used for taking relative

rupted from the input to 20-db fixed

measurements of broadband

a t t e n u a t o r AT701 (fig. 1) by de-

( n o i s e ) signal amplitude with the

energizing c o a x i a 1 relay K702

m a g n e t i c field probe, the electric

T h e r e f o r e , 20-db fixed attenuator

field probe, or the conductive cou-

AT701 is effectively removed from

plers.

the calibrating signal path and the

(2) In the 0 CW ONLY position, 10-db

f u l l calibrating signal voltage is

of attenuation is inserted in the rf

a v a i l a b l e at front-panel IMPULSE

s i g n a l path. This position of the

OUTPUT jack J717 (fig. 3).

c. Signal Attenuating Circuit. Figure 3

c o n t r o l provides a 50-ohm termi-

s h o w s that the incoming rf signal passes

n a t i o n to match the characteristic