Chapter 3 Basic Theory of Operation
This chapter discusses the basic operational theory of the ASTRO APX 7000 radio, which is a
wideband, synthesized radio available in the VHF (136–174 MHz), UHF1 (380–470 MHz),
UHF2 (450–520 MHz), 764 to 870 MHz, VHF/764 to 870 MHz, UHF1/764 to 870 MHz and VHF/
UHF1, UHF2/764 to 870 MHz and VHF/UHF2, frequency bands.
All ASTRO APX 7000 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 (25 kHz only).
3.1 Major Assemblies
The ASTRO APX 7000 radio includes the following major assemblies (see Figure 3-1):
• VOCON Board – contains a dual-core processor which includes both the microcontroller unit
(MCU) and a digital signal processor (DSP) core, the processor's memory devices, an audio
and power supply support integrated circuit (IC), a digital support IC, external audio power
amplifier, and Type III secure IC.
• Transceiver (XCVR) Board – contains all transmit, receive, and frequency generation circuitry,
including the digital receiver back-end IC and the reference oscillator.
• Expander Board – contains the internal audio power amplifier circuitry and the Global
Positioning System (GPS) IC and support circuitry.
• Option Board – capability for future expansion for additional features and functionality.
• Top Display – 112 pixels x 32 pixels, transflective monochrome liquid crystal display (LCD).
• Control Top – contains five switches: On/Off & Volume Knob, a 16 position Channel/
Frequency Knob with concentric 2 position switch (for Secure Enable/Disable operation), a 3
position toggle switch for Zone Selection, and a push button switch used for Emergency calling.
The control top also includes an TX/RX LED that is solid amber upon receive, red on PTT, and
blinks amber on secure TX/RX.
• Front Display (Dual-Display Version only) – 320 pixels x 240 pixels, transflective color LCD.
• Keypad (Dual-Display Version Only) – Dual-Display version has a 3 x 2 Menu keypad with
4-way navigation button, and a 3 x 4 alphanumeric keypad.
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