2-2

Theory Of Operation: Major Assemblies

 

 

The IFIC is a low-voltage monolithic FM IF system incorporating a mixer/oscillator, two limiting IF amplifiers, quadrature detector, logarithmic received signal strength indicator (RSSI), voltage regulator and audio, and RSSI Op Amps. The second LO frequency, 44.395 MHz, is determined by a crystal oscillator. The second mixer converts the 44.85 MHz high IF frequency to 455 kHz.

Additional IF selectivity is provided by two ceramic filters. The first ceramic filter is a 4-pole filter used between the second mixer and IF amp. The second ceramic filter is a 6-pole filter and is used between the IF amp and the limiter input. For the second ceramic filter, a wider filter is used for 20/25 kHz channel spacing, and a narrower filter is used for 12.5 kHz channels.

A ceramic resonator provides phases vs. frequency characteristic required by the quadrature detector, with 90 degree phase shift occurring at 455 kHz. The output of the IFIC is the recovered audio signal which is fed to the audio IC for amplification and signal conditioning. The output of the audio IC is injecting into the audio PA which drives the 24 Ohm speaker.

2.2.2Transmitter

When the radio is transmitting, microphone audio is passed through the audio IC, where pre- emphasis and low-pass (splatter) filtering are done. The output of the audio IC is used to modu- late the TX VCO, which creates the modulated carrier. The modulated carrier is then amplified by the pre-driver and power amplifier circuit, which transmits the signal under dynamic power control

Ref. Osc.

Frac N

 

Tx VCO

Tx

PA

 

 

Predriver

Module

 

 

Circuit

 

 

Tx Out

 

 

 

 

 

 

Loop

 

VCOBIC

 

 

Filter

 

Power

 

 

Rx Out

 

 

 

 

 

 

 

Cntr

Mod

 

Rx VCO

 

 

 

Circuit

 

 

 

 

 

 

Audio PA

 

 

 

T/R

 

 

 

Switch

 

 

 

 

Spkr

Audio IC

Mic

 

BW_SEL

 

 

Filter

Recovered Audio

 

 

Preselector

 

 

 

 

Ceramic

6G

6E

Cer Fltr

 

Rx

 

Switching

4E

 

Resonator

 

 

LNA

 

 

 

 

 

 

 

IF Amp

Crystal

 

Demodulator

 

 

Filter

Image

 

 

 

 

 

 

Filter

 

 

 

 

 

 

 

 

 

 

Mixer

RSSI

IF IC

Harmonic

Filter

Figure 2-2. Transceiver Block Diagram

December 3, 2003

HKLN4215A

Page 19
Image 19
Motorola EP450 service manual If IC

EP450 specifications

The Motorola EP450 is a robust and reliable two-way radio that has made a significant impact in the world of professional communications. Known for its solid construction and exceptional performance, the EP450 is a popular choice among various industries, including security, transportation, and event management.

One of the standout features of the Motorola EP450 is its impressive audio quality. Equipped with advanced audio processing technologies, the radio offers clear and crisp sound, ensuring effective communication even in noisy environments. This feature is particularly beneficial for users who work in fields where situational awareness and timely communication are crucial.

The EP450 operates on both VHF and UHF frequency bands, making it versatile for various communication needs. With 16 channels and a wide frequency range, users can easily switch between channels to avoid interference and ensure secure communications. Additionally, the radio offers a programmable feature, allowing users to customize button functions and settings, which enhances the overall user experience.

The battery life of the EP450 is another notable characteristic. It comes powered with a long-lasting rechargeable battery that provides extended usage on a single charge. This ensures that users can rely on the device throughout their shifts without concerns about running out of power. Furthermore, the EP450 features a battery save mode that helps conserve energy when the radio is not in use.

In terms of design, the Motorola EP450 is built to withstand tough environments. Its rugged housing is dustproof and can withstand exposure to water, making it suitable for outdoor use. Additionally, the radio's user-friendly interface includes a large display and oversized buttons, allowing users to operate it easily even with gloves or in challenging conditions.

Furthermore, the EP450 supports various accessories, such as headsets and external microphones, enhancing usability and flexibility in various operational scenarios. This adaptability allows users to customize their communication solutions based on specific needs.

In conclusion, the Motorola EP450 stands out for its superior audio quality, versatile frequency operation, long-lasting battery life, and rugged design. These features make it an indispensable tool for professionals who require reliable communication in demanding environments, proving its value across a multitude of industries.