Chapter 3 Basic Theory of Operation
This chapter discusses the basic operational theory of the ASTRO APX 3000 radio, which is a
wideband, synthesized radio available in the UHF1 (380–470 MHz), UHF2 (450–520 MHz), VHF
(136–174 MHz) and 764–870 MHz frequency bands. All ASTRO APX3000 radios are capable of
both analog operation (12.5 kHz or 25 kHz bandwidths), ASTRO mode (digital) operation (12.5 kHz
only) and X2-TDMA mode (12.5 kHz only).
3.1 Major Assemblies
The ASTRO APX 3000 radio includes the following major assemblies
(See Figure 3-1.):
• Main Board – Contains all transmit, receive, and frequency generation circuitry, including the
digital receiver back-end IC and the reference oscillator. The main board also contains a dual
core processor, which includes both the micro controller unit (MCU) and a digital signal
processor (DSP) core, the processors's memory devices, an audio and power supply support
integrated circuit (IC), a digital support IC, external power amplifier as well as combination
Global Positioning System (GPS) and Bluetooth 2.1 IC and front end circuitry.
• Control Top – Contains an ON/OFF switch and one programmable button.
• Side Control – Contains 2 programmable buttons and 2 arrow buttons.
• Back Kit– Contains one TX/RX LED that is solid amber upon receiving and red upon PTT. The
bottom LED represents the Bluetooth LED that will emit Blue color LED at certain flashing rates
for different Bluetooth events.
Figure 3-1. APX 3000 Overall Block Diagram
Bluetooth
Antenna
External Accessory
Connector
Control
Top
Main
Board
RF and GPS
Antenna
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