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Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its phase, as in phase modulation.
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a separate signal called the modulation signal that typically contains information to be transmitted. For example, the modulation signal might be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing a sequence of binary digits, a bitstream from a computer. The carrier is higher in frequency than the modulation signal. In radio communication the modulated carrier is transmitted through space as a radio wave to a radio receiver. Another purpose is to transmit multiple channels of information through a single communication medium, using frequency-division multiplexing (FDM). For example in cable television which uses FDM, many carrier signals, each modulated with a different television channel, are transported through a single cable to customers. Since each carrier occupies a different frequency, the channels do not interfere with each other. At the destination end, the carrier signal is demodulated to extract the information bearing modulation signal.
In amateur radio, QRP operation refers to transmitting at reduced power while attempting to maximize one's effective range. QRP operation is a specialized pursuit within the hobby that was first popularized in the early 1920s. QRP operators generally limit their transmitted RF output power to 5 Watts or less regardless of mode be it CW operation or SSB operation.
In radio communications, single-sideband modulation (SSB) or single-sideband suppressed-carrier modulation (SSB-SC) is a type of modulation used to transmit information, such as an audio signal, by radio waves. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. Amplitude modulation produces an output signal the bandwidth of which is twice the maximum frequency of the original baseband signal. Single-sideband modulation avoids this bandwidth increase, and the power wasted on a carrier, at the cost of increased device complexity and more difficult tuning at the receiver.
Frequency-shift keying (FSK) is a frequency modulation scheme in which digital information is encoded on a carrier signal by periodically shifting the frequency of the carrier between several discrete frequencies. The technology is used for communication systems such as telemetry, weather balloon radiosondes, caller ID, garage door openers, and low frequency radio transmission in the VLF and ELF bands. The simplest FSK is binary FSK (BFSK), in which the carrier is shifted between two discrete frequencies to transmit binary information.
In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, that are the result of the modulation process. The sidebands carry the information transmitted by the radio signal. The sidebands comprise all the spectral components of the modulated signal except the carrier. The signal components above the carrier frequency constitute the upper sideband (USB), and those below the carrier frequency constitute the lower sideband (LSB). All forms of modulation produce sidebands.
PSK31 or "Phase Shift Keying, 31 Baud", also BPSK31 and QPSK31, is a popular computer-sound card-generated radioteletype mode, used primarily by amateur radio operators to conduct real-time keyboard-to-keyboard chat, most often using frequencies in the high frequency amateur radio bands (near-shortwave). PSK31 is distinguished from other digital modes in that it is specifically tuned to have a data rate close to typing speed, and has an extremely narrow bandwidth, allowing many conversations in the same bandwidth as a single voice channel. This narrow bandwidth makes better use of the RF energy in a very narrow space thus allowing relatively low-power equipment to communicate globally using the same skywave propagation used by shortwave radio stations.
A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration. It may refer to e.g. a laser or particle accelerator having a continuous output, as opposed to a pulsed output.
In a radio receiver, a beat frequency oscillator or BFO is a dedicated oscillator used to create an audio frequency signal from Morse code radiotelegraphy (CW) transmissions to make them audible. The signal from the BFO is mixed with the received signal to create a heterodyne or beat frequency which is heard as a tone in the speaker. BFOs are also used to demodulate single-sideband (SSB) signals, making them intelligible, by essentially restoring the carrier that was suppressed at the transmitter. BFOs are sometimes included in communications receivers designed for short wave listeners; they are almost always found in communication receivers for amateur radio, which often receive CW and SSB signals.
A linear amplifier is an electronic circuit whose output is proportional to its input, but capable of delivering more power into a load. The term usually refers to a type of radio-frequency (RF) power amplifier, some of which have output power measured in kilowatts, and are used in amateur radio. Other types of linear amplifier are used in audio and laboratory equipment. Linearity refers to the ability of the amplifier to produce signals that are accurate copies of the input. A linear amplifier responds to different frequency components independently, and tends not to generate harmonic distortion or intermodulation distortion. No amplifier can provide perfect linearity however, because the amplifying devices—transistors or vacuum tubes—follow nonlinear transfer function and rely on circuitry techniques to reduce those effects. There are a number of amplifier classes providing various trade-offs between implementation cost, efficiency, and signal accuracy.
Multiple frequency-shift keying (MFSK) is a variation of frequency-shift keying (FSK) that uses more than two frequencies. MFSK is a form of M-ary orthogonal modulation, where each symbol consists of one element from an alphabet of orthogonal waveforms. M, the size of the alphabet, is usually a power of two so that each symbol represents log2M bits.
Amateur radio frequency allocation is done by national telecommunication authorities. Globally, the International Telecommunication Union (ITU) oversees how much radio spectrum is set aside for amateur radio transmissions. Individual amateur stations are free to use any frequency within authorized frequency ranges; authorized bands may vary by the class of the station license.
A radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. Radio waves are electromagnetic waves with frequencies between about 30 Hz and 300 GHz. 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. Transmitters are necessary parts of all systems that use radio: radio and television broadcasting, cell phones, wireless networks, radar, two way radios like walkie talkies, radio navigation systems like GPS, remote entry systems, among numerous other uses.
In radio, a detector is a device or circuit that extracts information from a modulated radio frequency current or voltage. The term dates from the first three decades of radio (1888-1918). Unlike modern radio stations which transmit sound on an uninterrupted carrier wave, early radio stations transmitted information by radiotelegraphy. The transmitter was switched on and off to produce long or short periods of radio waves, spelling out text messages in Morse code. Therefore, early radio receivers did not have to demodulate the radio signal, but just distinguish between the presence or absence of a radio signal, to reproduce the Morse code "dots" and "dashes". The device that performed this function in the receiver circuit was called a detector. A variety of different detector devices, such as the coherer, electrolytic detector, magnetic detector and the crystal detector, were used during the wireless telegraphy era until superseded by vacuum tube technology.
Yaesu FT-101 is a model line of modular amateur radio transceivers, built by the Yaesu Corporation in Japan during the 1970s and 1980s. FT-101 is a set that combines a solid state transmitter, receiver and a tube final amplifier. Its solid state features offer high-performance, low-current characteristics and its tube amplifier provides an almost mismatch-resistant transmitter and tuner stage. FT-101s were made with plug-in circuit boards that could be sent to the dealer or factory for replacement or repair. Until then, modular design was unprecedented in the amateur community. This also explains the fact why so many FT-101s are still in use today. The rig was sold worldwide as Yaesu FT-101 and in Europe as Yaesu FT-101 and as Sommerkamp FT-277. Because of its reliability it earned its nickname "the workhorse".
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The Yaesu FT-ONE is an all-mode solid state general coverage HF amateur radio (HAM) transceiver. The use of FM required an optional FM board to be installed. The unit was designed for fixed, portable or mobile operation, although the size and weight (17 kg) made it more suitable for fixed use. The FT-ONE was built by the Japanese Yaesu-Musen Corporation from 1982 to 1986. At its release, the FT-ONE was launched as the successor to the FT-902 and as the new Yaesu top-of-the-line transceiver. The FT-ONE was not only Yaesu's first fully synthesized, computer-controlled amateur band transceiver but it was also the first transceiver with a general coverage receiver. The FT-ONE was sold in the U.S., Asian and European markets. It was released in 1982 with a list price of $2800.00 US.
CESSB is a narrowband modulation method using a single sideband, whose peak envelope level is controlled so that the peak-to-average power ratio of CESSB is much reduced compared to standard SSB modulation and offers improved effective range over standard SSB modulation while simultaneously retaining backwards compatibility with standard SSB radios.
The ICOM IC-7300 is a multimode 6 meter and HF base station amateur radio transceiver. The IC-7300 was announced to the public at the Japan Ham Fair in 2015. The radio has 100 watts output on CW, SSB, and FM modulations and 25 watts of output in AM. Although not the first SDR radio on the market The IC-7300 was the first mass-produced mainstream amateur radios to use SDR technology instead of the older superheterodyne transceiver design. Designed to replace the older IC-746PRO the IC-7300 is smaller and significantly lighter than its predecessor. Like many other radios of its class the IC-7300 has an internal antenna tuner and contains an internal audio card accessible over USB. This allows the radio to be used for popular digital modes such as PSK31, Winlink, and FT8. The radio has received praise for its easy to use menus, large readable screen, and excellent audio processing.