{"id":14510,"date":"2025-06-07T16:27:29","date_gmt":"2025-06-07T10:57:29","guid":{"rendered":"https:\/\/ibexaviation.com\/pilot-training\/?p=14510"},"modified":"2025-07-20T07:28:37","modified_gmt":"2025-07-20T01:58:37","slug":"electro-magnetic-waves","status":"publish","type":"post","link":"https:\/\/ibexaviation.com\/pilot-training\/electro-magnetic-waves\/","title":{"rendered":"Electro-Magnetic Waves (EM Wave)"},"content":{"rendered":"\n<h2>Electro-Magnetic Waves<\/h2>\n\n\n\n<h3>Electrical and Magnetic Field in EM Waves<\/h3>\n\n\n\n<ul><li>EM waves are created by movement of Alternating current (AC) in a wire<\/li><li>Radio aids in aviation use Electro Magnetic Waves (EM Waves)<\/li><li>Alternating current creates a magnetic field perpendicular to electric field<\/li><li>EM Radiation is transmitted through air if the wire is connected to an Ariel<\/li><li>EM Radiation consists of electrical and magnetic components<\/li><li>Electrical field in the same plane of the ariel<\/li><li>Magnetic field perpendicular to the electrical field<\/li><\/ul>\n\n\n\n<h3>Electro Magnetic Spectrum<\/h3>\n\n\n\n<ul><li>EM waves has a wide spectrum with differing wavelength, frequency and energy<\/li><li>Visible light is the only part of EM Spectrum seen by a naked eye<\/li><li>X Ray spectrum have higher frequencies and lower wavelength<\/li><li>Long wave audio spectrum have lower frequencies and higher wavelength<\/li><li>Short waves have high levels of energy, hence harmful to body<\/li><li>EM waves travel at the speed of light in vacuum irrespective of their spectrum<\/li><li>Speed of light in vacuum is 1,62,000 nm\/sec or 3 x 10\u00c2\u00b2 m\/sec<\/li><\/ul>\n\n\n\n<h3>Horizontal and Vertical Polarisation<\/h3>\n\n\n\n<ul><li>Polarisation is the plane of the electrical component which carries the message<\/li><li>Electrical and magnetic components of EM waves are perpendicular to each other<\/li><li>Vertical and Horizontal ariels transmit vertically and horizontal polarised waves<\/li><li>Vertically polarised wave can be received only by a vertical ariel<\/li><li>Horizontally polarised wave can be received only by a horizontal ariel<\/li><\/ul>\n\n\n\n<h3>Circular Polarisation<\/h3>\n\n\n\n<ul><li>Circular polarisation can be received by both horizontal and vertical antenna<\/li><li>Circularly polarised waves are created by a helical antenna<\/li><li>These are used if the polarisation changes during transmission<\/li><li>Circular polarisation reduces rain clutter but requires high power transmitters<\/li><\/ul>\n\n\n\n<h3>Speed of EM Wave<\/h3>\n\n\n\n<ul><li>Speed of an EM wave is the same as speed of light<\/li><li>The speed of EM waves is maximum in vacuum at 3 x 10\u00c2\u00b2 m\/sec<\/li><li>Speed over water higher than that its speed over land<\/li><\/ul>\n\n\n\n<h3>Time Period of EM Wave<\/h3>\n\n\n\n<ul><li>Time period is the time taken by the wave to complete one cycle<\/li><li>EM radiation is transmitted as a sinusoidal or sine wave form<\/li><li>Amplitude of a wave is the maximum displacement of wave from its mean position<\/li><li>One cycle of the wave is means one complete set of values<\/li><li>For example, mean position to maximum to minimum and back to mean position is called one cycle<\/li><li>Time period is the time time taken to complete one cycle in micro seconds<\/li><\/ul>\n\n\n\n<h3>Frequency &#8211; Wavelength<\/h3>\n\n\n\n<ul><li>Frequency of the wave is same as the current which caused the wave<\/li><li>Frequency in hertz is the number of cycles of the wave in one second<\/li><li>Wave length in meters is the distance travelled by the wave in one cycle<\/li><li>Frequency and wavelengths are inversely proportional to each other<\/li><li>Speed is the distance travelled by an EM wave in one second<\/li><li>Speed = Wave length x Frequency<\/li><\/ul>\n\n\n\n<h3>Formula connecting Speed, Frequency and Wavelength<\/h3>\n\n\n\n<ul><li>Speed of an EM Wave is a product of its wavelength and frequency<\/li><li>Speed of EM Waves in Meters per Sec = Frequency in Hertz x Wavelength in Meters<\/li><li>Frequency in Hertz = Speed of Light in Meters per sec \/ Wave Length in Meters<\/li><li>Wave Length in Meters = Speed of Light in Meters per sec \/ Frequency in Hz<\/li><\/ul>\n\n\n\n<h3>Units of Frequency Measurement<\/h3>\n\n\n\n<ul><li>Frequency is measures in Hertz, Kilohertz,<\/li><li>1 Hertz = 1 Cycle Per Second and 1 Kilo Hertz = 1000 Hz = 10\u00c2\u00b3 Hertz<\/li><li>1 Mega Hertz = 1000 K Hz= 106 Hertz and 1 Gigha Hertz = 1000 M Hz= 109 Hertz<\/li><\/ul>\n\n\n\n<h3>Radio Wave Frequency Bands<\/h3>\n\n\n\n<ul><li>Frequencies and Wavelengths are used to distinguish between various bands<\/li><li>VLF Band &#8211; Frequency 3-30 KHz &#8211; Wavelength 100-10 KM &#8211; Used in Submarine Communication<\/li><li>LF Band &#8211; Frequency 30-300 KHz &#8211; Wavelength 10-1 KM &#8211; Used in Non-Directional Beacon NDB<\/li><li>MF Band &#8211; Frequency 300-3000 KHz &#8211; Wavelength 1000-100M &#8211; Used in Long Range NDB<\/li><li>HF Band &#8211; Frequency 3-30 MHz &#8211; Wavelength 100-10 M &#8211; Used in Long Range Communication<\/li><li>VHF Band &#8211; Frequency 30-300 MHz &#8211; Wavelength 10-1 M &#8211; Used in VHF Communication<\/li><li>UHF Band &#8211; Frequency 300-3000 MHz &#8211; Wavelength 100-10 CM &#8211; Used in Instrument Landing System<\/li><li>SHF Band &#8211; Frequency 3-30 GHz &#8211; Wavelength 10-1 CM &#8211; Used in Radar<\/li><li>EHF Band &#8211; Frequency 30-300 GHz &#8211; Wavelength 10-1 M &#8211; Used in Satellite Communication<\/li><\/ul>\n\n\n\n<h3>Phase Difference between EM Waves<\/h3>\n\n\n\n<ul><li>Phase Difference is the difference in Phase between two waves<\/li><li>Phase of a EM wave is a defined position on the sine wave form expressed from 0 to 360 degrees of a circle<\/li><li>Phase difference is obtained by phase comparison of two waves of same frequency and wavelength<\/li><li>Principle of phase comparison is used in some radio navigational equipments<\/li><\/ul>\n\n\n\n<h3>Power of Radio Wave and Polar Diagram<\/h3>\n\n\n\n<ul><li>Inverse square law of electro magnetic radiation defines the power required<\/li><li>Power of a radio wave reduces with increase in distance from the transmitter<\/li><li>Power available is inversely proportional to the square of the range<\/li><li>Therefore, power transmitted has to be increased four times to double the range<\/li><li>Polar diagram is the line joining points of equal power or intensity<\/li><li>Polar diagram can be drawn for both transmitter as well as receiver<\/li><li>Polar diagram of transmitter connects points of half of the the power transmitted<\/li><li>Polar diagram of receiver connects points of half the power received<\/li><li>Shape of ariel determines the shape of polar diagram<\/li><\/ul>\n\n\n\n<h3>Surface Attenuation<\/h3>\n\n\n\n<ul><li>Surface attenuation occurs due absorption of energy by the earth\u00e2\u20ac\u2122s surface<\/li><li>Attenuation is the weakening of radio wave during transmission with distance<\/li><li>Attenuation of radio waves follow inverse square law of electro magnetic radiation<\/li><li>Vertically polarised waves have lesser surface attenuation since they have lesser contact with earth<\/li><li>Horizontally polarised waves have greater surface attenuation due to constant contact with earth surface<\/li><li>Surface attenuation is least in very low frequency and increases with frequency of the radio wave<\/li><li>Therefore, Very Low frequency bands are used for submarine communications<\/li><\/ul>\n\n\n\n<h3>Factors affecting Surface Attenuation<\/h3>\n\n\n\n<ul><li>Surface attenuation greater over land surface than over smooth sea surface<\/li><li>Land range is proportional to twice times the square root of power<\/li><li>Sea range is proportional to thrice the square root of power transmitted<\/li><li>Reflection attenuation is a form of surface attenuation which is caused due reflections from buildings and hills<\/li><li>Installation of tall ariels for transmission reduces reflection attenuation<\/li><\/ul>\n\n\n\n<h3>Fading of Signals<\/h3>\n\n\n\n<ul><li>Fading causes Waxing and Waning of audio signals or increase and decrease in voice signals<\/li><li>Fading is caused by out of phase signals from the same transmitter received through different paths<\/li><\/ul>\n\n\n\n<h3>Atmospheric Attenuation<\/h3>\n\n\n\n<ul><li>Atmospheric attenuation causes weakening of radio waves due to Atmospheric Absorption and Static Interference<\/li><li>Atmospheric absorption or scatter is caused by small particles in atmosphere<\/li><li>High frequency radio waves are affected more by atmospheric absorption<\/li><li>Frequencies around 5 GHz are affected badly by absorption due to their wavelength similar to water droplets<\/li><\/ul>\n\n\n\n<h3>Static Interference<\/h3>\n\n\n\n<ul><li>Static interference is reduction in signal strength caused due to negatively charged particles in atmosphere<\/li><li>Negative charges build up due to rain, thunderstorm or solar activity<\/li><li>Static interference is higher in lower frequencies affecting voice clarity<\/li><li>Equipment\u00e2\u20ac\u2122s electronic circuits also cause static interference<\/li><\/ul>\n\n\n\n<h3>Signal to Noise Ratio<\/h3>\n\n\n\n<ul><li>Signal to noise ratio is the ratio of strength of audio signal to static noise in decibels<\/li><li>Better signal to noise ratio is achieved by increasing Transmission Power or improving Receiver Sensitivity<\/li><li>Increasing transmission power would be as per Inverse Square Law of Electromagnetic Radiation<\/li><li>Therefore, doubling the range requires four times increase in power<\/li><li>Improving receiver sensitivity reduces internal noise by better manufacturing quality<\/li><li>Receiver sensitivity improves receiver\u00e2\u20ac\u2122s ability to receive weaker signals<\/li><\/ul>\n\n\n\n<h3>Diffraction and Refraction<\/h3>\n\n\n\n<ul><li>Radio waves alter their path during propagation by Diffraction and Refraction<\/li><li>Diffraction is bending of radio waves around the surface of earth<\/li><li>High diffraction is seen in lower frequencies like VLF, LF and HF<\/li><li>Refraction is bending of radio waves due to change in speeds with density of medium<\/li><li>For example, density of air over land and sea surface have different densities<\/li><\/ul>\n\n\n\n<h3>Ionospheric Attenuation and Refraction<\/h3>\n\n\n\n<ul><li>Radio waves are Attenuated and Refracted by the Ionosphere and a part of radio wave returns to earth<\/li><li>Ionosphere is a layer of free electrons in the upper levels of Stratosphere<\/li><li>Ionospheric Refraction is caused by slowing down of radio waves in ionosphere<\/li><li>Increasing frequency reduces Ionospheric Refraction and exit the atmosphere as Escape Rays<\/li><\/ul>\n\n\n\n<h3>Super and Sub Refraction<\/h3>\n\n\n\n<ul><li>Super and sub-refraction increase the range of VHF band unexpectedly<\/li><li>Normally only lower frequencies are affected by ionospheric refraction<\/li><li>Special atmospheric conditions cause super and sub refraction in higher frequencies<\/li><li>Super refraction is caused due to High pressure system and Warm air flowing over cold surface<\/li><li>Sub refraction is caused due to Low pressure system and Cold air flowing over warm surface<\/li><\/ul>\n\n\n\n<h3>Coastal Refraction<\/h3>\n\n\n\n<ul><li>Coastal refraction causes an error in radio aids located close to coast line<\/li><li>Bending of radio waves while crossing coast line result in coastal refraction<\/li><li>Speed of radio waves is faster over sea due to change in medium<\/li><li>Radio waves bend towards land which is the slower speed medium<\/li><li>Coastal refraction is lesser in comparatively higher frequencies<\/li><li>Therefore, Non directional beacons near coastline use higher frequencies<\/li><\/ul>\n\n\n\n<h2>Best of luck<\/h2>\n","protected":false},"excerpt":{"rendered":"<p>Electro-Magnetic Waves Electrical and Magnetic Field in EM Waves EM waves are created by movement of Alternating current (AC) in a wire Radio aids in aviation use Electro Magnetic Waves (EM Waves) Alternating current creates a magnetic field perpendicular to electric field EM Radiation is transmitted through air if the wire is connected to an Ariel EM Radiation consists of electrical and magnetic components Electrical field in the same plane of the ariel Magnetic field perpendicular to the electrical field Electro Magnetic Spectrum EM waves has a wide spectrum with&hellip;<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"disable_featured_image":false},"categories":[326],"tags":[],"_links":{"self":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14510"}],"collection":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/comments?post=14510"}],"version-history":[{"count":0,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/posts\/14510\/revisions"}],"wp:attachment":[{"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/media?parent=14510"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/categories?post=14510"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibexaviation.com\/pilot-training\/wp-json\/wp\/v2\/tags?post=14510"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}