Amateur Radio and All about Ham Communication

In this video, viewers will learn the basic principles of FREQUENCY MODULATION. This video is from U.S. Department of Defense 1964 - At the end of this video, viewers will learn the Fundamentals of AM and FM of Radio Communication, details on how FM eliminates the problem of electrical interference and functions of FM Radio. Many thanks to PublicResourceOrg for allowing the reuse of this video. License Creative Commons Attribution license (reuse allowed) Source videos View attributions

In this video, viewers will be able to understand what Radio Frequency is all about. - Meaning of Radio Frequency -In-depth explanation about Radio Frequency. At the end of this video, viewers will learn about Radio Frequency and how it is relevant to Amateur Radio Practices. What is RADIO FREQUENCY? What does RADIO FREQUENCY mean? RADIO FREQUENCY meaning - RADIO FREQUENCY definition - RADIO FREQUENCY explanation. Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/... license. Radio frequency (RF) is any of the electromagnetic wave frequencies that lie in the range extending from around 3 kHz to 300 GHz, which include those frequencies used for communications or radar signals. RF usually refers to electrical rather than mechanical oscillations. However, mechanical RF systems do exist (see mechanical filter and RF MEMS). Although radio frequency is a rate of oscillation, the term "radio frequency" or its abbreviation "RF" are used as a synonym for radio – i.e., to describe the use of wireless communication, as opposed to communication via electric wires. Electric currents that oscillate at radio frequencies have special properties not shared by direct current or alternating current of lower frequencies. The energy in an RF current can radiate off a conductor into space as electromagnetic waves (radio waves); this is the basis of radio technology. RF current does not penetrate deeply into electrical conductors but tends to flow along their surfaces; this is known as the skin effect. RF currents applied to the body often do not cause the painful sensation of electric shock as do lower frequency currents. This is because the current changes direction too quickly to trigger depolarization of nerve membranes. However they can cause superficial but serious burns called RF burns. RF current can easily ionize air, creating a conductive path through it. This property is exploited by "high frequency" units used in electric arc welding, which use currents at higher frequencies than power distribution uses. Another property is the ability to appear to flow through paths that contain insulating material, like the dielectric insulator of a capacitor. This is because capacitive reactance in a circuit decreases with frequency. In contrast, RF current can be blocked by a coil of wire, or even a single turn or bend in a wire. This is because the inductive reactance of a circuit increases with frequency. When conducted by an ordinary electric cable, RF current has a tendency to reflect from discontinuities in the cable such as connectors and travel back down the cable toward the source, causing a condition called standing waves. Therefore, RF current must be carried by specialized types of cable called transmission line. To receive radio signals an antenna must be used. However, since the antenna will pick up thousands of radio signals at a time, a radio tuner is necessary to tune into a particular frequency (or frequency range). This is typically done via a resonator – in its simplest form, a circuit with a capacitor and an inductor form a tuned circuit. The resonator amplifies oscillations within a particular frequency band, while reducing oscillations at other frequencies outside the band. Another method to isolate a particular radio frequency is by oversampling (which gets a wide range of frequencies) and picking out the frequencies of interest, as done in software defined radio. The distance over which radio communications is useful depends significantly on things other than wavelength, such as transmitter power, receiver quality, type, size, and height of antenna, mode of transmission, noise, and interfering signals. Ground waves, tropospheric scatter and skywaves can all achieve greater ranges than line-of-sight propagation. The study of radio propagation allows estimates of useful range to be made. Radio frequency (RF) energy, in the form of radiating waves or electrical currents, has been used in medical treatments for over 75 years, generally for minimally invasive surgeries using radiofrequency ablation including the treatment of sleep apnea. Magnetic resonance imaging (MRI) uses radio frequency waves to generate images of the human body. Many thanks to The Audiopedia License Creative Commons Attribution license (reuse allowed)

In this video, viewers will understand a potential harm of static electricity that can be harmful to their communication equipment. Potentially, hundreds of Volts in just a few seconds can have significant effect on your rig. Consider disconnecting your antenna during adverse static conditions. Many thanks to Rodrigo A B Freire for letting me reuse this video. License: Creative Commons Attribution license (reuse allowed)

In this video, viewers will learn What a TRANSMITTER is, meaning, pronunciation, definition and explanation. At the end of this video, viewers are expected to have a deeper knowledge about Transmitter. Source: Wikipedia.org article, adapted under https://creativecommons.org/licenses/... license. In electronics and telecommunications a transmitter or radio transmitter is an electronic device which, with the aid of an antenna, produces radio waves. The transmitter itself generates a radio frequency alternating current, which is applied to the antenna. When excited by this alternating current, the antenna radiates radio waves. In addition to their use in broadcasting, transmitters are necessary component parts of many electronic devices that communicate by radio, such as cell phones, wireless computer networks, Bluetooth enabled devices, garage door openers, two-way radios in aircraft, ships, spacecraft, radar sets and navigational beacons. The term transmitter is usually limited to equipment that generates radio waves for communication purposes; or radiolocation, such as radar and navigational transmitters. Generators of radio waves for heating or industrial purposes, such as microwave ovens or diathermy equipment, are not usually called transmitters even though they often have similar circuits. The term is popularly used more specifically to refer to a broadcast transmitter, a transmitter used in broadcasting, as in FM radio transmitter or television transmitter. This usage typically includes both the transmitter proper, the antenna, and often the building it is housed in. An unrelated use of the term is in industrial process control, where a "transmitter" is a telemetry device which converts measurements from a sensor into a signal, and sends it, usually via wires, to be received by some display or control device located a distance away. A transmitter can be a separate piece of electronic equipment, or an electrical circuit within another electronic device. A transmitter and a receiver combined in one unit are called a transceiver. The term transmitter is often abbreviated "XMTR" or "TX" in technical documents. The purpose of most transmitters is radio communication of information over a distance. The information is provided to the transmitter in the form of an electronic signal, such as an audio (sound) signal from a microphone, a video (TV) signal from a video camera, or in wireless networking devices a digital signal from a computer. The transmitter combines the information signal to be carried with the radio frequency signal which generates the radio waves, which is called the carrier signal. This process is called modulation. The information can be added to the carrier in several different ways, in different types of transmitters. In an amplitude modulation (AM) transmitter, the information is added to the radio signal by varying its amplitude. In a frequency modulation (FM) transmitter, it is added by varying the radio signal's frequency slightly. Many other types of modulation are used. The antenna may be enclosed inside the case or attached to the outside of the transmitter, as in portable devices such as cell phones, walkie-talkies, and garage door openers. In more powerful transmitters, the antenna may be located on top of a building or on a separate tower, and connected to the transmitter by a feed line, that is a transmission line. Many thanks to "The Audiopedia". License Creative Commons Attribution license (reuse allowed)

In this video, viewers will learn what Frequency Modulation is. At the end of this video, viewers will learn how Frequency Modulation is related to all Amateur activities. What is Frequency Modulation? Frequency modulation is a technique or a process of encoding information on a particular signal (analogue or digital) by varying the carrier wave frequency in accordance with the frequency of the modulating signal. As we know, a modulating signal is nothing but information or message that has to be transmitted after being converted into an electronic signal. Much like in amplitude modulation, frequency modulation also has a similar approach where a carrier signal is modulated by the input signal. However, in the case of FM, the amplitude of the modulated signal is kept or it remains constant. If we talk about the applications of frequency modulation, it is mostly used in radio broadcasting. It offers a great advantage in radio transmission as it has a larger signal-to-noise ratio. Meaning, it results in low radio frequency interference. This is the main reason that many radio stations use FM to broadcast music over the radio. Additionally, some of its uses are also found in radar, telemetry, seismic prospecting and in EEG, different radio systems, music synthesis as well as in video-transmission instruments. Source: IIT JEE Study Materials:https://creativecommons.org/licenses/... Many thanks to "The Audiopedia". License: Creative Commons Attribution license (reuse allowed)

Analog Transmission is the transmission of signals that vary smoothly with time. An analog signal can take on any value in a specified range of values. A simple example is alternating current (AC), which continually varies between about +110 volts and -110 volts in a sine wave fashion 60 times per second. A more complex example of an analog signal is the time-varying electrical voltage generated when a person speaks into a dynamic microphone or telephone. Analog signals such as telephone speech contain a wealth of detail but are not readily accessible to computers unless they are converted to digital form using a device such as an analog-to-digital converter (ADC). Analog signals are usually specified as a continuously varying voltage over time and can be displayed on a device known as an oscilloscope. The maximum voltage displacement of a periodic (repeating) analog signal is called its amplitude, and the shortest distance between crests of a periodic analog wave is called its wavelength. SOURCE: Network Encyclopedia #Many thanks to The Audiopedia for this video License: Creative Commons Attribution license (reuse allowed)

In this video, Amateur Radio and Military Radio Communications helped the Military turn the tide of WWII. At the end of this video, viewers will learn the importance of Amateur Radio Communication during Word War II. This is an RCA 1944 documentary video depicting importance of radio communications during World War II. Many thanks to #carnradio for finding this video. License Creative Commons Attribution license (reuse allowed)