Sencore CB42 User Manual

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Fig. 5()-Scope

hookup

for

trape:zoidal display.

TRAPEZOIDAL

MODULATION

MODULATION

SIGNAL

0

0

0

VERT.

HORIZ.

'~

"

..

.;

"'''''

ADAPTER

Fig. 51--Tropezoldal

modulation

envelope,

A'loeCf)nd

method

of

modulation

analysis

is

Ihe

use

of

the

"trapezoidal

method"

of

waveform

analysis.

The

hookup

for

this

test is shown in Fig. 50 ,The horizontal

inpUI

of

an

oocilloscol""

i!s

connected to

the

modulation

line running

to

Ihe RF stage

of

the

transmitter,

The

scope

adapwr

OUlpul

i~

run

to

the

vertical input. A

vec_

tor

seOI""

such

as

the

Sencol'\!

PSZ9

or

l'S163

can

be used

no signal applied to

the

microphone, To

te8t

for this tondi-

lion.

key

the transmitter,

and

make sure

that

no

audi

...

sig-

nal

reachee

the

microphone. Shielding the microphone

from

audi

...

signals may be n":l!AAary fnr

this

tellL

If

modulation

apl""al"ll

on

the

wa,'eform (which would also

read as modulation using the modulation

poo;ition

of

the

DIGITAL

READOUT

SELECTOR.

residual

carrier

noise

is

io,licat>«L

With

tlO

modulation

signal applied

10

the

input

of

the

tranamitter,

the

result

should

be

the

dean

carrier

signal

shown in

Fig,

49

If

the

modulation

sta~e8

contain

residual noise.

the

r\!!lull

is

modulatioo

of

the

carrier. with

Fig. 48-Nef1.ltiue

c/ippiTlf1.

d~

to

O(l('r-modulation.

Fig.

4~rrwr

with

no

,...,idUQI /loi6e.

NOTE,

When

determining

positiVf!

or

negatiVf!

modu.

Iation,

the

digilal

readout

of

pen:ent

modulation

prove.

to

be

a

more

accurate

method

than

!oope

interpretations_

The

reason

is

the

circuitry

of

the

per-

cent

modula.tion

test

determines

the

average earner

power

to

calculate

positive

and

negatiVi!

modulation.

Any

distortion

of

the

WlIVf!form

will

show

~

a

differ.

ence

in

positive

and

negative

modulation

when

a

!ymetrical

wave

is

used

to

modu.late

tbe

transmitter.

Since

the

negative

modulation

detector

..

ill

not

'lhow

more

than

100%

modulation,

however,

the

scope

adapter

mouk!

be

used

for

chceking

n..gativ.. over-

modulation.

RESDJAL

CARRIER

NOISE CHECK

44

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Sencore CB42 Specifications

General

Brand	Sencore
Model	CB42
Category	Measuring Instruments
Language	English

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