Coupler Antenna CU-893/URM-85

coaxial cables, one for each dipole

calibration of the test set i s a c -

a r m , to the balun. The input side

c o m p l i s h e d by injecting a S i g n a l

o f the balun is also balanced so

f r o m the impulse generator to the

that both arms of the antenna s e e

a t t e n u a t o r network housed in the

the same impedance. The length of

c o u p l e r . The signal path is from

t h e coaxial cables is critical for

t h e main unit IMPULSE OUTPUT

optimum phasing and a low voltage

front-panel jack, through the green

s t a n d i n g wave ratio over the fre-

color-coded cable of Cable As-

q u e n c y band. Since the phenolic

s e m b l y Set, Electrical MX-3410/

b o o m is too short for a straight

URM-85 and connector jack J2003.

run of coaxial cables over the 20-

The calibrating voltage is then

applied to a 10-to-1 voltage-

to 220-mc band, the remaining

lengths of the cables are wound on

d i v i d e r network which consists of

a bakelite form within the balun

R2001 shunted by R2002; this

results in a 20-db signal loss. The

housing.

(2) U n b a l a n c e d output connector. E s-

calibrating signal from the impulse

s e n t i a l l y , the actual coupling be-

generator circuit is injected in

t w e e n the input and output cir-

series with the incoming rf signal

cuits consists of two 1-turn loops

(identical with the method used in

o f wire coupled together. The rf

l o o p antenna and the vertical an-

e n e r g y from the balanced coaxial

tenna and the vertical antenna, para

c a b l e s is coupled into the N-type

5 9 a and b). Therefore, the cali-

o u t p u t connector, P1701, which

brating voltage causes a current to

mates with the input end of the red

flow through the same circuit path

color-coded cable of Cable As-

a s that of the unknown signal. In

s e m b l y Set, Electrical MX-3410/

t h i s manner, a direct comparison

URM-85. The far end of this cable

of the amplitude of the rf incoming

a p p l i e s the rf signal to the main

signal, w i t h r e f e r e n c e t o t h e

unit SIGNAL INPUT jack for ampli-

i m p u l s e generator signal, is ob-

ficiation, detection, a n d m e t e r

t a i n e d without introducing trans-

Presentation on the test set.

f o r m a t i o n factors.

d. Coupler, Antenna CU-894/URM-85

c. C o u p l e r Antenna CU-893/URM-85

(E, fig. 38). Coupler, Antenna CU-894/

(E, fig. 38). Coupler Antenna CU-893/

U R M - 8 5 is used for picking up radiated

signals over the frequency range from 200-

signals over the frequency range from 20

to 400-mc (corresponding to the range of

to 220-mc (corresponding to the range of

tuning unit 3). This coupler functions

tuning unit 2). It consists of a phenolic tube

i d e n t i c a l l y with the CU-893/URM-85 (c

w h i c h functions as a supporting boom, a

above). At one end of the boom, its block

block assembly at one end of the boom, and

assembly is physically constructed of

a balanced-to-unbalanced transformer

p l e x i g l a s s instead of phenolic material;

(balun) at the opposite end of the boom, the

i n addition, the CU-894/URM-85 output

purpose of the block assembly is to serve

connector at the balun end of the boom is

a s a means of physical attachment and

d e s i g n a t e d reference symbol J1803.

electrical connection for the two arms of a

e. Antenna AT-1030/URM-85. Antenna

telescopic dipole antenna. The purpose of

AT-1030/URM-85 is used for picking up

the balun is to convert the balanced input

r a d i a t e d signals over the frequency range

feeding system, which consists of the two

f r o m 400- to 1,000-mc (corresponding to

dipole arms, into an unbalanced feed which

the range of tuning unit 4). Although this

c o n s i s t s of the single coaxial terminating

a n t e n n a is not shown in figure 38, it is

c o n n e c t o r P1701.

identical in cirouit analysis with the CU-

(1) Balanced input system B a l a n c e d

8 9 3 / U R M - 8 5 (C above) and the CU-894/

output frowm the center of the an-

URM-85 (d above) except for the addition

tenna is fed through a pair of