GPS PreLim

wave

can be defined as a disturbance (sound, light, radio waves) which moves through a medium (air, water, vacuum).

wave motion

can be defined as a recurring disturbance advancing through space with or without the use of a physical medium. Therefore, it is a means of moving or transferring energy from one point to another point.

Transverse and Longitudinal wave

2 types of Mechanical Waves

Transverse Waves

The up and down motion is traverse, or at right angles (perpendicular) to the outward motion of the waves. This is called transverse wave motion. Radio waves, light waves, and microwaves are transverse waves. Transverse waves also travel on the strings of instruments.

LONGITUDINAL WAVES

is a wave in which particles of the medium move in a direction parallel to the direction that the wave moves. Suppose that a slinky is stretched out in a horizontal direction across the classroom and that a pulse is introduced into the slinky on the left end by vibrating the first coil left and right as shown in the figure.

compressions

high pressure regions in longitudinal waves

rarefactions.

low pressure regions in longitudinal waves

Amplitude, Wave length, Frequency, Wave period

Parts of a wave

AMPLITUDE (A)

is half the distance measured vertically (height) from the crest to the trough.

WAVE LENGTH (f..)

is the distance from the crest of one wave to the crest of the next, or between any two similar points on adjacent waves.

FREQUENCY (F)

The number of times the wave cycle repeats in a given unit of time is called the ———- of the wave and is measured in hertz (Hz).

Heinrich Hertz

To honor the German physicist ———-, the term Hz was designated for use in lieu of the term "cycles per second" when referring to the frequency of radio waves.

WAVE PERIOD (T)

is the measure of time it takes for the wave cycle to complete, measured in seconds. The ———- and frequency are inversely proportional to each other, so if the frequency increases, the period decreases, and vice-versa.

ELECTROMAGNETIC WAVES

consists of two primary components: an electric field and a magnetic field .

electric field and magnetic field

two primary components of electromagnetic waves

electric field

results from the force of voltage

magnetic field

results from the flow of current

electromagnetic field

is responsible for the transmission and reception of electromagnetic energy through free space.

Radio waves

belong to the electromagnetic radiation family, which includes x-ray, ultraviolet, and visible light- forms of energy we use every day. Much like the gentle waves that form when a stone is tossed into a still lake, radio signals radiate outward, or propagate, from a transmitting antenna and intercepted by a receiver.

Amplitude

is measured in volts, is usually expressed in terms of an average value called root-mean-square, or RMS. The RMS values of salient waveforms are shown in the figure

Extremely Low Frequency (ELF)

Frequency starting from 3Hz to 3 kHz is known as ———— in the electromagnetic spectrum.

Very Low Frequency (VLF)

is the starting range of RF and practical radio transmission systems which span from 3 kHz to 30 kHz. However, the design and implementation of the antenna system are extremely complicated due to the wavelength.

It has been used in submarines and still using in time radio stations which synchronizes clock signals between two remote locations.

Low Frequency (LF)

is in the range of 30 kHz to 300 kHz. One of the important properties of these signals is that they will get reflected by the earth’s ionosphere and thus, it is suitable for long-distance communication. Since it’s a long wavelength and less attenuation from big terrains like mountains, it is generally called a ground wave.

Medium Frequency (MF)

was one of the most popular frequency bands since the beginning of wireless radio transmission in the early nineteenth century. this operates in the range of 300 kHz to 3 MHz. The transmitters, receivers, and antenna design is relatively less complex than other high-frequency transmission bands.

High Frequency (HF)

range between 3 MHz and 30 MHz. This frequency band is also known as a short wave. It also gets reflected by the earth’s ionosphere, and it is one of the suitable bands for long-distance communication.

Very High Frequency (VHF)

is one of the most commonly used RF bands, with an operating range from 30 MHz to 300 MHz. this frequency has been widely used in analog TV broadcasting since it started a few decades ago. FM radio broadcasting from 88 to 108 MHz operates in this frequency band.

118 MHz to 137 MHz

airline pilots communicate between ————.

Ultra High Frequency (UHF)

is modern wireless communication systems’ most critical radio frequency band. It begins from 300 MHz to 3 GHz and is highly complicated to design and implement the system. UHF has many sub-frequency bands; some are restricted and assigned only to particular applications.

Super High Frequency (SHF)

is in the range of 3 GHz to 30 GHz. It can only operate in a line of sight path since any obstruction between the transmitter and receiving station will break the communication.

Extremely High Frequency (EHF)

is the highest in the RF frequency spectrum, which ranges between 30 GHz and 300 GHz. this is only used in advanced communication systems due to its complex nature and line of sight requirement.

COMMUNICATION ANTENNA, GPS ANTENNA, LORAN ANTENNA, LOOP ANTENNA, MARKER BEACON ANTENNA, NAVIGATION ANTENNA, RADIO ALTIMETERS, UHF ANTENNA

TYPES OF AIRCRAFT ANTENNA

COMMUNICATION ANTENNA

are usually mounted on either the top or bottom of the aircraft, and their only concern is being affected by the shadowing of the fuselage. Each transmitter has its own antenna, and the antenna are strategically placed mainly because their range and coverage can be negatively affected if positioned incorrectly.

GPS ANTENNA

Transmitting less than five watts of power, these antennas result in signals that are usually very weak. Because of this, most of these antennas consist of built-in amplifiers that are designed to boost the signal for the receiver. In addition, this frequency is very high, usually in the gigahertz band, which requires that this antenna to be attached to the very top portion of the fuselage.

Long-range navigation, or Loran antennas

look a lot like communications antennas until you look on the inside. Loran antennas usually contain either an amplifier built into their base so that the signal is better or a smaller amplifier located just under the skin. They are meant to be placed either on the top or bottom of the plane, but you must configure the receiver to fit the exact antenna position for them to work properly.

LOOP ANTENNA

They are also called directional antennas because they can actually determine which direction a signal is coming from. They consist of two or three separate coils that make them look like a flattened bagel, and each signal is received between the coils at various strengths.

MARKER BEACON ANTENNA

have to be on the bottom of the aircraft because to receive any signal, the antennas have to be almost directly over the transmitting ground station. There are many different types of these antennas, with the most common ones resembling little canoes that are roughly 10 inches long. They are both simple and reliable.

NAVIGATION ANTENNA

Almost always found on the vertical tail, these antennas come in three main types.

The cat whisker, the dual blade, the towel bar

Three types of navigation antennas

The cat whisker

has several rods jutting out from each side of the stabilizer at 45-degree angles. It is a good antenna to have when you’re flying low because it cannot receive signals from the side.

the dual blade

has antennas on either side of the tail.

the towel bar

is a balanced loop antenna that can easily receive signals from all directions. these antennas are found on both sides of the tail of the airplane and are often required for area navigation (RNAV) systems.

RADIO ALTIMETERS

These antennas, which look like six-inch-square plates, are placed on the bottom of the aircraft. They are usually either a single- or dual-antenna system, and the radar signal is transmitted straight down and literally bounces off of the ground. Radio altimeters include high frequencies and, therefore, require a secure electrical bond with the skin of the airplane.

UHF ANTENNA

Utilized mostly for distance-measuring equipment (DME) and transponders, these aircraft antennas are only around four inches long and are always found on the bottom of the aircraft. They can be used for both DMEs and transponders, and their two main types are blade and spike antennas.

Spike antennas

should only be used for transponders

blade antennas

work best with DMEs.

Spike antennas, blade antennas

Two main types of UHF antennas

Institute of Electrical and Electronics Engineers

IEEE

Extremely Low Frequency

3 Hz to 30 Hz

Super Low Frequency

30 Hz to 300 Hz

Ultra Low Frequency

300 Hz to 3 kHz

Very Low Frequency

3 kHz to 30 kHz

Low Frequency

30 kHz to 300 kHz

Medium Frequency

300 kHz to 3 MHz

High Frequency

3 MHz to 30 MHz

Very High Frequency

30 MHz to 300 MHz

Ultra High Frequency

300 MHz to 3 GHz

Super High Frequency

3 GHz to 30 GHz

Extremely High Frequency

30 GHz to 300 GHz