Vertex VX-10 Service Manual

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Circuit

Description---------------

noise

is

removed

from

the

output,

causing

pin

96

of

Q2001 to

go

high

and

the

microprocessor

to

turn

onthe

busy

LED via Q2008.

The

microprocessor

then

checks

the

CTCSS

chip

on

the

Key

Unit,

the

DTMF

decoder

chip

and

the

CDCSS

code

for

CTCSS

or

CDCSS

or

DTMF

code

squelch

information,

if

enabled,

re-

spectively.

If

not

transmitting

and

tone

squelch

or

CDCSS is

not

activated,

or

if the received tone

or

code

matches

that

programmed,

the

micro-

processor

stops

scanning,

if active,

and

allows

audio

to

pass

through

the

audio

amplifier Q2021

(TDA7233D) to

the

loudspeaker

by

enabling

the

supply

voltage

to it via Q2018

and

Q2020.

Transmit

Signal

Path

Speech

input

from

the

microphone

is deliv-

ered

to

the

CNTL

Unit,

where

itis

amplified

by

Q2025-4 (NJM2902V),

then

applied

to

one

of the

user

selected Key

Unit

for

pre-emphasis

(see the

Key

Unit

Circuit

Description).

The

pre-emphasized

audio

then

returns

to the

CNTL

UNIT,

to

provide

IDC

(Instantaneous

Deviation

Control),

and

the

splutter

filter

which

filters

the

speech

signal to

remove

any

high

fre-

quency

components

that

might

result

in

over-

deviation.

The

processed

audio

is

then

mixed

with

a

CTCSS

tone

generated

by

the

microprocessor

Q2001

and

delivered

to 01001

(155314)

for fre-

quency

modulating

the PLL carrier

up

to±

5kHz

from

the

unmodulated

carrier

at

the

transmit-

ting frequency.

If

an

external

microphone

is used, PTT switch-

ing

is

controlled

by

Q2022 (UMZ2N),

which

sig-

nals

the

microprocessor

when

the

impedance

at

the

microphone

jack

drops.

If

a CDCSS

code

is

enabled

for

transmission,

the

code

is

genera

ted

by

the

microprocessor

Q2001

and

delivered

to

D1017

(HVU202A)

for

'-'

CDCSS

modulating.

If

DTMF is

enabled

for

transmission,

the

tone

is

generated

by

the

microprocessor

Q2001

and

applied

to

the

splutter

filter

section

in

place

of

speech

audio.

Also,

the

tone

is

amplified

for

monitoring

in

the

loudspeaker.

The

modulated

signal

from

the

VCO

Q1002

(25C5231

C8/C9)

is

buffered

by

Ql

003

(25C5231

C8/C9)

and

amplifieu

by

Ql

001

(25C5226-4/5).

The

low-level

transmit

signal

is

then

applied

to

the

PA

module

Q1005 for final

amplification

up

to 5

watts

output

power.

The

transmit

signal

then

passes

through

the

~

antenna

switch

D1006 (RL5135)

and

is

low-pass

filtered to

suppress

away

harmonic

spurious

ra-

diation

before

delivery

to

the

antenna.

Automatic Transmit

Power

Control

RF

power

output

from

the

final

amplifier

is

sampled

by

C1026, C1027

and

is

rectified

by

D1004

(1

55321

).

The

resulting

DC

is fed

back

through

Q1004 (NJM2904V) to

the

PA

module,

and

thus

the

power

output.

The

microprocessor

selects

either

high

or

one

of

three

low

power

levels.

Transmit Inhibit

When

the

transmit

PLL is

unlocked,

pin

2

of

PLL

chip

Q1015

goes

to

a logic low.

The

result-

ing

DC

unlock

control

voltage

is

passed

to

pin

98

of the microprocessor Q2001. While

the

trans-

mit

PLL is

unlocked,

pin

47

of

Q2001

remains

low,

which

then

turns

off the

Automatic

Power

Controller

Q1014

and

Q1004

(UMCSN,

NJM2904V)

to

disable

the

supply

voltage

to

the

transmitter

RF

amplifier

Q1005,

disabling

the

transmitter.

'-._/

1-18

VX-10VHFBandServiceManual

~

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Vertex VX-10 Specifications

General

Brand	Vertex
Model	VX-10
Category	Radio
Language	English