Coaxial Relays and Attenuators.

c. Coaxial Relays and Attenuators.

the setting of six-step signal atten-

(1) Coaxial relay K702. With this relay

uator AT702. The division of atten-

in its energized condition, the out-

u a t i o n between the rf and the if.

signal paths maintains an optimum

put of the impulse generator is

coupled through a set of relay

s i g n a l - t o - n o i s e ratio.

c o n t a c t s to 20-db fixed attenuator

d. Typical Tuning Unit. The attenuated

AT701.

signal is coupled from six-step signal

(2) F i x e d a t t e n u a t o r A T 7 0 1 , 2 0 - d b .

attenuator AT702 to the-input of the tuning

u n i t in use, through multipin connector

T h i s fixed attenuator, coaxial in

structure, attenuates the signal

J701 (on the main unit) and its mating plug

from the impulse generator by 20-

(on the rear of each tuning unit). The tyical

d b and couples the signal to de-

tuning unit shown is representative of

energized coaxial relay K701. With

tuning units 1 through 4; however, circuit

t h i s 20-db fixed attenuator in the

v a r i a t i o n s exist in each because of the

c a l i b r a t i n g signal path, the output

d i f f e r e n t frequency ranges encountered.

of tie impulse generator agrees

(1) R f section. In the tuned rf ampli-

with the engraved numerals on the

f i e r , the signal is amplified and

front-panel coarse and fine impulse

c o u p l e d to the mixer stage, which

g e n e r a t o r controls.

also receives a signal from the

(3) Coaxial relay K701. With this re-

local oscillator. Sum and difference

f r e q u e n c i e s are produced in the

l a y in its deenergized condition,

the output of 20-db fixed attenuator

mixer stage, but only the difference

AT701 is coupled through one set

f r e q u e n c y is accepted by the if.

of relay contacts to six-step signal

amplifier.

a t t e n u a t o r AT702.

(2) I f . step attenuator. The output of

(4) Six-step signal attenuator AT702.

t h e mixer stage is coupled to a

This cartridge-type attenuator has

three-step if. attenuator, which

a flat response to the complete fre-

operates with rotation of the signal

quency range of the test set, from

attenuator control (c(4) above).

1 5 0 kc to 1,000 mc. Six steps of

(3) If. amplifier. The difference fre-

attenuation are provided by the use

quency from the mixer stage is

o f coaxial networks, which result

amplified by a conventional trans-

in a low-voltage standing wave

f o r m e r - c o u p l e d if. amplifier. The

ratio (swr) at any input frequency.

output signal is applied to the sealed

E a c h attenuator section is a re-

detector-electrometer assembly.

(4) D e t e c t o r and electrometer as-

s i s t i v e T-pad, in which the series

elements are rod resistors, and the

s e m b l y . This assembly is identical

s h u n t element is a disk-type re-

a n d is interchangeable in all four

sistor. The geometry of the innter

tuning units. Two detectors are in-

and outer conductors of each atten-

c l u d e d within the assembly. One

u a t o r section produces a 50-ohm

detector provides drive for the

line impedance at the input and out-

a u d i o amplifier in the main unit e

put of each network. Two settings

The other detector provides drive,

o f the six-step signal attenuator

t h r o u g h high-impedance electro-

control provide zero attenuation of

m e t e r stages, for the vacuum-type

the calibrating signal. The four re-

v o l t m e t e r indicating circuit in the

maining settings provide 10-, 20-,

main unit.

40-, or 60-db loss in the rf signal

e. Indication Circuits. Two indicating

path; additional attenuation of 10 or

c i r c u i t s are provided in the main unit.

20-db is inserted into the if. signal

(1) A u r a l . The aural indication is de-

r i v e d from electrometer assembly

path (fig. 2). This loss is introduced

by operation of relays in the if. step

audio detector V1. Its output signal

attenuator, which are controlled by

i s coupled through terminal A1 of