Motorola MDH65SDF9AA3AN Informationen zum Dienst - Seite 9
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1.0
Introduction
This Chapter provides a detailed theory of operation for the UHF circuits in the radio. Schematic
diagrams and board layout diagrams are included in Chapter 4 in this Section of the manual.
2.0
UHF (465-495MHz) Receiver
The UHF receiver covers the range of 465-495 MHz and provides switchable IF bandwidth for use
with 20/25/30 kHz or 12.5 kHz channel spacing systems. The receiver is divided into two major
blocks, as shown in Figure 2-1.
Front End
Back End
RX from
Antenna Switch
Preselector
RF
Filter
Amp
First LO
from Synthesizer
Recovered Audio
RSSI
Figure 2-1 UHF Receiver Block Diagram
THEORY OF OPERATION
Interstage
Crystal
Filter
1st Mixer
Inj Filter
6G
Ceramic
Resonator
Demodulator
12.5kHzFilter
Chapter 2
IF
Amp
Filter
BW_SEL
6E
Cer Fltr
Switching
4E