Electromagnetic Waves Quiz

Aircraft Communication System

• Radio theory focuses on transmitting and detecting electromagnetic waves. These waves travel in a straight line or reflect off the ionosphere or a communications satellite.
• A wave is a progressive disturbance in a medium, moving outward and possessing energy. Energy is lost due to friction.

Electromagnetic Wave

• Electromagnetic waves form when electric and magnetic fields interact. These fields are perpendicular (at right angles) to each other.

Radio Wave

• Radio waves are a type of electromagnetic wave. They fall within the portion of the electromagnetic spectrum that has lower frequencies than microwaves.
• Radio waves are used in various applications: broadcast radio, television, shortwave radio, navigation, air traffic control, cellular telephony, and remote-controlled toys.

Radio Wave Characteristics

• Low Frequency: Has long wavelengths, low energy, and poor quality.
• High Frequency: Has short wavelengths, high energy, and good quality.

Factors Affecting Radio Waves

• Diffraction: Bending of radio waves, primarily in low-frequency waves.
• Reflection: Bouncing of radio waves, mainly in high-frequency waves.
• Refraction: Change in direction of radio waves due to disturbances like rain, high and low frequencies.
• Attenuation: Loss of signal strength during transmission, caused by friction, impacting radio waves' energy.

Radio Wave Propagation

• Radio waves are transmitted in various directions as omni directional, directional or pulse & echo method.
• These waves travel following three paths: surface waves (follow earth's curvature), sky waves (stronger than ground waves, overcome gravity but cannot penetrate ionosphere), and space waves (overcome gravity and penetrate ionosphere but limited by "line of sight").

Types of Radio Waves

• Ground Waves/Surface Waves: Follow Earth's curvature, limited by gravity, VLF, LF, MF frequencies.
• Sky Waves: Stronger than ground waves; overcome gravity but cannot penetrate the ionosphere. HF frequency.
• Space Waves: Overcome gravity and penetrate the ionosphere. Primarily limited by line of sight, VHF, UHF, SHF, EHF frequencies.

Frequency Bands - Common Applications

• Different frequency bands (VLF, LF, MF, HF, VHF, UHF, SHF, EHF) are used in different applications like Loran, NDB, Radio Stations, VHF Nav/Comm, VOR, Tacan, DME, LOC/GS (Microwave is mentioned).

Radiotelephony

• Pilots, engineers, and air traffic controllers communicate using standardized words and phrases (ICAO approved) for routine aircraft situations.
• Standardized phrases facilitate communication on common and work-related topics.

VHF and HF Communication

• VHF and HF communication systems use transceivers (self-contained transmitter and receiver).
• Transceivers operate at the same frequency.
• The microphone button switches the transmitter.
• Saves space and weight, leading to wide use.

VHF Communication

• VHF is the 30MHz-300MHz portion of the radio spectrum; offers short-range line of sight communications.
• The range is determined by the equipment, antenna height, and terrain (typically 2 to 20 miles).

HF Communication

• HF (3-30MHz) is used for long-range communication by reflecting signals off the ionosphere.
• HF transmitters generate higher power outputs than VHF.
• A tuner adjusts impedance matching between the transceiver and antenna.

Service Interphone System

• The service interphone system enables two-way voice communication between ground crew and aircraft crew during servicing and flight operations.
• Handset jacks are located throughout the aircraft.
• Pilots use overhead panel P5 to disconnect these jacks.

Communication methods

• Transmission of information between parties using various methods (radio, METAR, ATIS).

Basic Communication equipment

• VHF Radio.
• Transponder
• Emergency Locator Transmitter(ELT)

Transponder

• A transponder is a device that receives a radio signal and responds by sending out a signal.
• Offers different modes for various purposes:
• Mode A: Identification (Squawk Codes).
• Mode C: Identification and altitude (pressure altitude).
• Mode S: Identification, altitude, and data exchange.
• Includes codes for specific situations (eg., VFR, unlawful interference, emergency).

Emergency Locator Transmitter (ELT)

• An emergency locator transmitter (ELT) broadcasts signals on specific frequencies.
• Can be Automatic (activated by impact) or Manual.
• Self-contained, self-powered, and frequently uses frequencies for civilian, new ELTs, and military transmissions.

Categories of Messages

• Distress messages (MAYDAY)
• Urgency calls (PAN PAN, often with a medical designation)
• Direction finding
• Flight safety messages
• Meteorological messages
• Flight regularity messages

Weather Reports

• ATIS (Automatic Terminal Information Service)
• METAR (Meteorological Aerodrome Report)
• TAF (Terminal Aerodrome Forecast)

Light Gun Signals

• Various signals (steady, flashing, colors) used for communication between the air traffic control tower and aircraft.