Marconi Instruments TF 2502 - Remote Operation; Determination of Modulation

Marconi Instruments TF 2502

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4)

Tune

the

source

under

test

for

maximum

reading

on

the

DETECTOR

meter.

5)

If

the

probe

was

inserted

in

(3)

above,

turn

the

INSERT

PROBE

control

back

to

its

fully

counter-clockwise

position.

Then

read

the

power

of

the

source

on

the

WATTS

meter.

2.6

REMOTE

OPERATION

If

the

power

meter

has

to

be

connected

directly

to

the

power

source

it

may

be

inconvenient

to

read

or

operate

the

instrument.

If

so,

it

may

be

better

to

use

it

with

the

detector

unit

and

load

detached

from

the

monitor

unit.

To

do

this,

pull

out

the

INSERT

PROBE

knob

to

disengage

the

dog

clutch,

depress

the

catch

on

the

ternunating

load

and

withdraw

the

load

and

detector

assembly

as

far

as

the

interconnecting

lead

will

allow.

Operation

is

the

same

as

in

Sect.

2. 5

except

that

probe

insertion

is

controlled

directly

by

the

slotted

knob

on

the

detector

unit.

2.7

DETERMINATION

OF

MODULATION

DEPTH

The

depth

of

amplitude

modulation

of

an

r.

f.

signal

having a

sinusoidal

envelope

can

be

determined

as

follows:

1)

Measure

the

output

power

of

the

source

under

test

with the

signal

unmodulated.

Let

this

reading

be

Pc

watts.

2)

Modulate

the

signal

and

again

measure

the

output

power.

Let

this

reading

be

Pm

watts.

3)

Calculate

the

modulation

depth.

This

can

be

evaluated

since

P

c,

P

m,

and

the

%modulation,

m,

are

related

by

2502 (1a)

p

m

p

c

m2

(1 +

2)·

.................... (1)

9