T865 Circuit Operation; Introduction - Tait T860 Series II Service Manual

M860-00-Preliminary
2.1

Introduction

Mixer
Front
End
Synthesised
Local
Oscillator
12.8MHz
Master
Oscillator
The T865 receiver consists of a number of distinct stages:
• front end
• mixer
• synthesised local oscillator
• IF
• audio processor
• mute (squelch)
• regulator circuits
• received signal strength indicator (RSSI).
These stages are clearly identifiable in Figure 2.1. Refer to the circuit diagrams in Sec-
tion 6 for further detail.
Copyright TEL
Mixer
21.4MHz 455kHz
IF IF
Second
Local
Oscillator
Figure 2.1 T865 High Level Block Diagram

T865 Circuit Operation

Noise
Mute
Limiter
Audio
Processor
FM
Detector
Carrier
Mute
RSSI
B2.3
Speaker
} 600Ω
Line
30/06/98