CT Systems Wavetek 2500 - Page 54

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3.4.10

Tuning

Sub-Audible

Transmitter

Tones

CTCSS

tones

may

be

identified

using

the

SUBTONE

function

as

described

in

Section

3.4.7

(Off

Air

Monitoring).

This

task

may

also

be

more

rapidly

performed

by

using

an

oscilloscope

to

create

a

lissajous

pattern

during

tuning.

I

NOTE

I

1

The

Model

2500

is

designed

to

take

transmitter

measurements

based

on

1

what

is

presented

at

the

RF

IN/OUT

port.

The

user

must

take

into

1

consideration

the

potential

inaccuracies

introduced

by

the

cables

1

used

to

hook

up

the

system

under

test.

To

reduce

cable-related

1

errors,

use

only

good

quality

50

ohm

coax

cables

of

the

minimum

I

length

required.

I

Refer

to

Figure

3-12

for

the

following

test

procedure.

1)

Select

REC

mode.

2)

Set

frequency

for

transmitter

frequency

in

MHz

using

numerical

keys

followed

by

ENTER

key.

3)

Select

AUDIO

SYNTH

.

4)

Use

the

numerical

keys

to

program

terminate

the

data

with

the

ENTER

the

desired

subtone

in

Hz

and

key.

5)

Cable

the

Antenna

Port

of

the

transmitter

under

test

to

the

"RF

IN/OUT"

port

of

the

Model

2500.

6)

Cable

the

demod

out

of

the

Model

2500

to

the

oscilloscope

vertical

input.

7)

Cable

the

audio

synthesizer

output

to

the

osci~loscope

horizontal

input.

8)

To

prevent

overheating

the

instrument,

see

the

specifications

for

applying

·

power

to

the

wattmeter.

9)

Key

the

transmitter.

10)

Adjust

the

audio

synthesizer

level

control

for

a

lissajous

pattern

on

the

oscilloscope.

11)

Adjust

the

transmitter

subtone

frequency

for

a

stable

lissajous

pattern.

2500-MANUAL

PAGE

42 SECTION-3