Marconi Instruments TF 2502 - Terminating Load; Chapter 5 CALIBRATION; Apparatus Required; Preliminary Checks

Marconi Instruments TF 2502

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Calibration

The

following

information,

based

on

abstracts

from

the

Company

Test

Schedule,

is

intended

to

enable

you

to

carry

out a

series

of

tests

by

which the

main

points

of

performance

of

the

instrument

can

be

checked;

it

also

gives

details

concerning

adjust-

ment

to

preset

components

and

the

choice

of

value

for

individually

selected

components.

5.1

APPARATUS

REQUIRED

(a)

Resistance

bridge,

e

..

g.

mT

type

TF

2700.

'(b) Signal

generator,

400 MHz

and

1 GHz, 50 Q output;

e.g.

mf

types

TF

801

and

TF

1060.

(c) V. S.

W.

R.

measuring

device,

50 Q

characteristic

impedance

with

residual

v.

s.

w.

r.

of

better

than

1.

01

at

1 GHz.

(d)

Variable

a.

c.

source,

capable

of

delivering

10 W;

e.

g.

a

Variac.

(e)

Dynamometer

wattmeter,

0 to 10 W,

0.5%.

5.2

PRELIMINARY

CHECKS

(Apparatus

required:

item

a)

NOTE: When

carrying

out

these

checl{s,

it

is

advisable

to

set

the

Range

switch

to 10 W

to

avoid

the

possibility

of

overloading

the

meter.

1)

.

Connect

the

termi,nating

load

and

measure

the

·cold d.

c.

resistance

of

the

terminating

load

(R4)

between

the

centre

and

outer

conductors

of

the

socket

(SKTB).

The

resistance

should

be

49 Q ±2%.

2)

Measure

the

resistance

of

the

complete

power

meter

(i.e.

,

in-line

detector

and

the

terminating

load)

between

the

centre

conductor

of the input

socket

SKTA and

chassis.

The

resistance

should

be

53

Q ±3%.

5.3

STANDING

WAVE

RATIO

(Apparatus

required:

items

b

and

c)

For

the

power

meter

to

act

as

a good

match

to a

transmission

line

its

v.

s.

w.

r.

must

be

as

close

to

unity

as

possible.

In

the

TF

2502, v.

s.

w.

r.

is

a function of

the

2502 (1a)

17