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VHF Enhanced Transmitter Instruction Manual VT-3 132 - 174 MHz

2-5

2.3.2

Frequency Change

The

transmitter

initially

aligned

at the factory for the frequency stamped on the 'Factory Set

Operating Frequency'

label

(see section 3.1). This

label

should list the frequency at

which

the last

complete

transmitter

alignment

was performed. For a

small

frequency

change,

simple

channel

change (see section 2.2) may be all that is required. A larger frequency change may

involve

the

realignment

of other modules. The frequency change in question is the

accumulated

frequency

change in

relation

to the frequency stamped on the

label.

For

example,

if the frequency is changed

by 0.5 MHz from that stamped on the

label,

then a second frequency change of 1 MHz in the same

direction

would result in a

total

change of 1.5 MHz. The

action

taken would be on the basis of the

1.5 MHz

value.

Failure to perform a

realig

nment after a large frequency change could result in

unreliable

transmitter

operation

transmitter

operation

that does not conform to the published

specifications.

The

allowable

frequency change is

summarized

below.

Note: It is

advisable

to confirm these frequency ranges

with

the

individual

module

manuals,

notably the

Amplifier

and Synthesizer

Module,

as they are subject to change

with

updated

versions. The

values

in the module manuals take

precedent

over

those

tabulated.

FOR MODEL

ALL

VT-3 132 - 174 MHz Transmitters

Size of Frequency Change Modules to be

Aligned

less than

0.2 MHz

Transmitter

Main Board (Channel Change)

between

0.2 and

0.5 MHz

Transmitter

Main Board (Channel

Change),

Audio Processor (see section 2.3.4)

between

0.5 and

1.0 MHz

Transmitter

Main Board (Channel

Change),

Audio Processor (see section 2.3.4), Synthesizer

check RF

alarm

thresholds (section 2.3.5)

1.0 MHz or

greater

Complete

alignment

2.3.3 Output Power Adjustment

The RF power output of the

amplifier

is set to its rated

value

of 2.0 Watts or 8.0 Watts at the

factory. This should not require

adjustment

under normal

circumstances.

However,

should it be

necessary to

correct

the output

power,

the 'Output Power

Adjustment'

which

is described in the

Amplifier

Manual can be adjusted

accordingly.

If the Synthesizer module is

replaced,

it is strongly

recommended

that the

amplifer

undergo a

realignment

as described in the

Amplifier

Module,

unless

it is

confirmed

that the

original

and

replacement

nthesizer

module

have

identical

output power

(within

0.5 dBm).