ICOM IC-245E Block Diagram and Circuit Schematics

Block Diagram

The following describes the functional blocks of the ICOM IC-245E transceiver. The diagram illustrates the signal flow and interconnections between various electronic modules.

Main Block Diagram Components:

PLL Unit U-116: Controls frequency synthesis.
Modulator/Demodulator: Processes audio signals for transmission and reception.
Transmitter/Receiver Sections: Handle signal amplification and filtering.
Local Oscillator (LO): Generates carrier frequencies.
Harmonic Filter: Reduces unwanted harmonic emissions.
Antenna Switch: Selects between transmit and receive paths.
Buffer Amplifiers: Maintain signal integrity.
Filters: Select desired frequencies and reject interference.
Mixers: Combine or separate frequencies.
Detectors: Extract information from signals.
Control Circuits: Manage various operational modes (e.g., AGC, AFC).
Audio Amplifier (AF): Amplifies the final audio output.
Speaker (SPK): Outputs the received audio.
Microphone (MIC): Input for voice transmission.
PTT Switch: Push-to-talk control.
Photo Sensor: Likely for display illumination control.
LED Display: Shows operating frequency and status.
Reference Voltage: Provides stable voltage references.

Logic Circuits Block Diagram

This section details the digital logic and control functions within the IC-245E.

Key Logic Components:

Display (IC9, IC10, IC11): Drives the frequency display.
Decoder Driver (IC1, IC2, IC3, IC4, G1, G2, G3): Decodes signals for display and control.
Counter (IC2, IC3): Counts frequency-related signals.
Space Select (IC2, IC3): Manages channel or frequency spacing.
D/A Converter: Converts digital signals to analog.
Varicap Diodes (D7, D8): Voltage-variable capacitors used in tuning circuits.
Shift Switch (Q8): Controls data shifting.
Diode Switch (D9, D10): Switches signals based on diode conductivity.
Oscillator (Q9): Generates a stable clock signal.
Triplers (Q10, Q11): Multiply frequencies.
Mixer (IC4): Combines signals.
Amplifier (IC5): Amplifies signals.
Low Pass Filter (Q4, Q6): Filters out high frequencies.
Buffer (Q7, Q2): Isolates and strengthens signals.
VCO (Voltage Controlled Oscillator) (Q1, Q3): Generates frequencies controlled by voltage.
One Shot (IC8): Generates a single pulse.
Flip-Flop (IC8): Stores binary data.
OR Gate (IC7): Performs logical OR operation.
UD Differencer / UD Square: Logic gates for signal processing.
Dual Phase Generator: Creates phase-shifted signals.
Driver (U-11B, U-119): Amplifies signals for driving other components.
DC Regulator (IC6): Stabilizes DC voltage.
DC-DC Converter (IC7): Converts DC voltage levels.
Delay (Q1): Introduces a time delay.
TS Switch: Transmit/Receive switch control.
FMBV: Likely a frequency modulation related signal.
Duplex Switch: Manages duplex operation.

Detailed Circuit Schematics

The detailed schematics provide component-level information for various sections of the IC-245E, including the PLL unit, RF stages, audio stages, and control logic. These diagrams show specific component values, part numbers (e.g., transistors like 2SC245, 2SC1947, ICs like SC3062, MC14013), and interconnections.

Key Circuit Sections Depicted:

PLL Unit (U-116): Shows the integrated circuit (SC3062) and associated components like transistors (2SC965), resistors, and capacitors that form the phase-locked loop for frequency control.
RF Amplifier Stages: Illustrates transistors (e.g., 2SC1971, 2SC2630, 2SC245) and passive components forming pre-amplifiers, driver amplifiers, and final power amplifiers.
Mixer and Oscillator Circuits: Details components like transistors, diodes, and LC tanks used in frequency mixing and oscillation.
Audio Frequency (AF) Amplifier: Shows the circuitry for amplifying the received audio signal, including operational amplifiers and transistors.
Control and Logic Circuits: Depicts the implementation of digital logic gates (ICs like MC14011, MC14001), flip-flops, and drivers that manage the transceiver's functions.
Power Supply and Regulation: Includes DC-DC converters and voltage regulators (e.g., IC6, IC7) to provide stable operating voltages.
Display and Interface Circuits: Shows the connections to the display driver and other interface components.

The schematics are highly detailed, indicating component placement and connections crucial for understanding the internal workings and for repair or modification purposes.

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