Motorola XTL 1500, Detailed Service Manual, Page: 38 / 452

Chapter 2 Product Overview
2.1 Introduction
The ASTRO Digital XTL 1500 radio is a dual-mode (trunked/conventional), microcontroller-based
transceiver incorporating a Digital Signal Processor (DSP). The microcontroller handles the general
radio control, monitors status, and processes commands input from the keypad or other user
controls. The DSP processes the typical analog signals and generates the standard signaling
digitally to provide compatibility with existing analog systems. In addition it provides for digital
modulation techniques utilizing voice encoding techniques with error correction schemes to provide
the user with enhanced range and audio quality all in a reduced bandwidth channel requirement. It
allows embedded signaling which can mix system information and data with digital voice to add the
capability of supporting a multitude of system features.
The XTL 1500 radios are wideband, synthesized, fixed-tuned radios and are available in the VHF
(136–174 MHz), UHF Range 1 (380–470 MHz), UHF Range 2 (450–520 MHz), 700 MHz, and
800 MHz bands. All XTL 1500 radios are capable of both analog operation (12.5 kHz, 20 kHz, and
25 kHz bandwidths) and ASTRO mode operation (12.5 kHz bandwidth).
NOTE: The UHF radio does not support 20 kHz bandwidth.
2.2 Functional Blocks
The XTL 1500 radios contain the following functional blocks:
• Control-Head Assembly (Dash)—is connected directly to the front of the transceiver. This
assembly is divided into three main sections, the controller (applications processor, RAM and
Flash), power management (Power Control Processor, and Voltage Regulators) and user
interface (GCAI Accessory Connector, Keypad, STN Display, Volume and Frequency Knob)
section.
• Radio Power Distribution—contains voltage-regulation circuitry for power distribution
throughout the radio.
• Receiver Front-End section—contains the preselector, low-noise amplifier (LNA), and mixer.
• Receiver Back-End section—contains the receiver intermediate-frequency (IF) amplifier/filter
and the digital receiver back-end integrated circuit (IC).
• Transmitter section—contains the antenna switch, directional coupler/ detector, and power
amplifier circuitry.
• Frequency Generation section—contains the synthesizer, voltage controlled oscillators (VCOs),
reference oscillator, and receive and transmit buffers.
• Controller section—combines a vocoder and a controller into a single section containing the
following elements: