Chapter 5 435 - 480 Mhz Uhf2 Theory Of Operation; Introduction; Uhf2 Receiver; Figure 5-1. Uhf2 Receiver Block Diagram - Motorola P100 Series Detailed Service Manual

Chapter 5 435 – 480 MHz UHF2 Theory of Operation
5.1

Introduction

This chapter provides a detailed theory of operation for the radio components. Schematic diagrams
for the circuits described in the following paragraphs are located in Chapter 7 of this manual.
5.2

UHF2 Receiver

The UHF2 receiver design covers the frequency range of 435 – 480 MHz and it is a double
conversion super heterodyne with 1st IF 45.1 MHz and 2nd IF 455 kHz. The receiver is divided into
two major blocks, Front End and Back End as shown in Figure 5-1.
RX from
Antenna Switch
from Synthesizer
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Preselector RF Postselector
Filter Amp
First LO
N/S_SW
Descriminator
Recovered Audio
RSSI

Figure 5-1. UHF2 Receiver Block Diagram

Crystal
Filter 1st Mixer
Filter
Inj Filter
455C24
LPF
Quadrature
Detector
IF
Amp
Ceramic
Filter
455FW
455HW
IF
Amp
Crystal
44.645MHz