Motorola MAG ONE Manuel - Page 19

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Overview

Section 2

THEORY OF OPERATION

1.0

Overview

1.1

Purpose

This section defines the theory of operation (or the Circuit Description) for the radio. At the same

time, it provides a description of the circuit theory and analysis of the radio hardware design.

1.2

General Description

The radio comprises of one main PCB. This main PCB contains the RF and digital circuits. The VHF/

UHF compliant handheld transceivers consists of a receiver, a transmitter, a phase-locked loop

(PLL) frequency synthesizer, control circuits and power supply circuits.

2.0

Receiver System

LPF

ANT-SW

CR301,2

The receiver is a double conversion super heterodyne with first IF frequency at 45.1MHz and

second IF frequency at 455kHz.

2.1

Front-End

The front-end consists of a low pass filter, pre-selector filter, RF Amplifier, and a post-selector filter.

The receive signal from the antenna is applied to TX LPF (L409, L410, C426, C427, C428, C429,

C430) and then routed to an RF amplifier (Q301) after passing transmit / receive switch (CR401,

CR301, CR302) and the pre-selector. The signal from the pre-selector is amplified around 13dB at

PRESLECTOR

LNA

FILTER

Q301

F.T.V.

POST SELECTOR

1'ST MIX

Q302

FILTER

VCO

Inj FILTER

Recovered AUDIO

MCF

45.1MHz

DESCRIMI

NATOR

455C24

IF AMP

IF,MIX

U201

Q303

CF1,2

X-TAL

44.645MHz

N/S

2-1