A publication, CD ROM or WebSite, such as QRZ.com that lists licensed amateur radio operators.
Callsign.
Callsigns are designations given to licensed radio stations. Callsign groups are allotted to countries by the ITU (List of country prefixes). Individual callsigns are allocated by the national government.
Amateur Radio callsigns generally take the form of: [Prefix] [Number] [Suffix] Where:
the prefix is one or two characters. One letter, two letters or a number and letter
the number 0 through 9
the suffix of 1 to 4 letters (rarely 4)
For example:
Call sign
Country prefix
Number
Suffix
Country
VE4XCF
VE
4
XCF
Canada
M3BAU
M
3
BAU
UK (England, Foundation Class)
2M0BDW
2M
0
BDW
UK (Scotland, Intermediate Class)
MW0GKX
MW
0
GKX
UK (Wales, Full Class)
W1AW
W
1
AW
USA
(shown split for emphisis)
Prefixes are allocated to countries by international agreement but the number and suffix is decided upon by the national government. No two callsigns in the world are the same.
Capacitance.
A measure of the ability of a capacitor to store energy in an electric field. Capacatance is measured in farads.
Capacitor.
An electrical component usually formed by separating two conductive plates with an insulating material. A capacitor stores energy in an electric field. See also: Electrolytic capacitor.
Carrier / Carrier Wave .
A pure continuous radio emission at a fixed frequency, without modulation and without interruption. Several types of modulation can be applied to the carrier.
A device used to switch over a set of contacts in response to a received signal. Sometimes used in linear amplifiers to energise the output stage and preamplifiers to bypass the delicate circuitry.
Cathode-Ray Tube (CRT).
A vacuum tube with a phosphor coating on the inside of the face. CRTs are used in oscilloscopes and as the "picture tube" in television receivers and computer monitors (not LCD or Plasma types).
Cavity Resonator.
A sharply tuned circuit using the physical dimensional resonance of one or more tuned cavities.
2. Counter Clock Wise, in relation to rotary controls.
Cell.
The basic building block of a battery. An 'AA battery' is, in fact, a single cell, as are the 'AAA', 'C' & 'D' types. An 9V PP3 is a battery, it contains 6 1½Volt cells connected in series. Schematic symbol: See also: Battery Equivalents. page.
Centi.
The metric prefix for 10-2, or divide by 100.
Central Processor Unit (CPU).
The 'brain' of the piece of equipment, most radios since the mid 1980s have a CPU that controls the radios functions. Auto ATUs also have a CPU to control them.
Centre-Fed.
Connecting the centre of an antenna to a transmission line, which is then connected to the final (output) stage of the transmitter. Also known as Current-Fed as the feeder is connected to the point of the antenna with the greatest current.
Set frequencies within the bandplan for different methods of operation. For example;
The 2Mtr band in the UK has single frequency channels for simplex operation and paired frequencies (input and output) for repeaters.
Channel Spacing.
The frequency spacing between adjacent frequency allocations. This may be 50, 30, 25, 15 or 12.5 kHz, depending upon the band in use and national regulations.
Characteristic Impedance.
The ratio of voltage to current at any given point on a transmission line.
Chassis Ground.
The common connection for all parts of a circuit that connect to the negative side of the power supply. Schematic symbol:
Checksum.
A simple way to protect the integrity of data by detecting errors in data that are sent through space (telecommunications) or time (storage). It works by adding up the basic components of a message, typically the asserted bits, and storing the resulting value. Anyone can later perform the same operation on the data, compare the result to the authentic checksum, and (assuming that the sums match) conclude that the message was probably not corrupted.
Chirp.
A slight shift in transmitter frequency each time you key the transmitter.
Circular Polarisation.
Where the direction of the radio wave oscillates in a spiral pattern, can be clockwise or anti-clockwise.
CI-V.
Icom Computer Control Interface, allows multiple Icom radios to be controlled form one computer.
A repeater that restricts access to those who know a special code.
Closed, or complete circuit.
An electrical circuit with an uninterrupted path for the current to follow. Turning a switch on, for example, closes or completes the circuit, allowing current to flow.
A PSK mode which provides a full duplex simulation. It is well suited for HF operation (especially under good conditions). CLOVERs key characteristics are band-width efficiency with high error-corrected data rates. CLOVER adapts to conditions by constantly monitoring the received signal, based on this monitoring, CLOVER determines the best modulation scheme to use. See also: Digital Modes page.
Coaxial cable .
Coax (pronounced kó-aks). A type of electrical conductor which carries radio energy from a transmitter to an antenna system; the inner conductor is insulated from an external wire mesh shield. The shield minimizes electrical and radio frequency interference. 50Ω and 72Ω characteristic impedances are typical. Coaxial cable: See also: Coax explained page and Coax in depth page.
Co-Channel Interference.
The interference resulting when a repeater receives signals from a distant repeater on the same frequency pair.
Coherent CW (CCW).
Coherent CW was invented by Ray Petit, W7GHM (died June 13, 1999), who also invented CLOVER. The transmitted signal exhibits distinguishing characteristics to which the receiver is designed to respond. A CCW signal has three distinguishing characteristics:
Precise Frequency.
Accurately established pulse length.
Predetermined "turn-on/turn-off" instant, or pulse-phase.
A conductor wound into a series of loops.
See also: Inductor.
Colour Code.
A system in which numerical values are assigned to various colours. Coloured stripes are painted on the body of resistors and other components to show their value. See also: Capacitor Codes, Resistor Codes.
Conductor.
A material that has a loose grip on its electrons, so an electrical current can pass through it.
Connected.
The condition in which two packet radio stations are sending information to each other. Each is acknowledging when the data has been received correctly.
Contesting.
A competitive amateur radio activity. In a contest an amateur radio station, which may be operated by an individual or a team, seeks to contact as many other amateur radio stations as possible in a given period of time and exchange information. Rules for each competition define the amateur radio bands that may be used and the kind of information that must be exchanged in each contact.
Continuous Tone Coded Squelch System (CTCSS).
A sub-audible (below the level of human hearing) tone system used on some repeaters and internet gateways. When added to a carrier, a CTCSS tone allows a receiver to accept a signal.
Control Operator.
An amateur operator designated by the licensee of a station to be responsible for the transmissions of an amateur station.
Control Point.
The locations at which the control operator function is performed.
Coordinated Universal Time (UTC / Zulu).
The time (expressed in 24-hour format) at the 0-degree Meridian, which passes through Greenwich, England. See also: About Time page.
The material used in the center of an inductor coil, where the magnetic field is concentrated.
Courtesy Tone.
A tone or beep transmitted by a repeater to indicate that it is okay for the next station to begin transmitting. The courtesy tone is designed to allow a pause between transmissions on a repeater, so other stations can call. It also indicates that the time-out timer has been reset.
If radio waves leave an antenna at an angle greater than the critical angle for that frequency they will pass through the ionosphere instead of returning to Earth.
Critical Frequency.
The highest frequency at which a vertically incident radio wave will return from the ionosphere. Above the critical frequency radio signals pass through the ionosphere instead of returning to Earth.
Cross-Band.
The process of transmitting on one band and receiving on another.
Crowbar Circuit.
A power supply protection circuit that rapidly short-circuits ("crowbars") the supply line if the voltage and/or current exceeds defined limits. In practice, the resulting short blows a fuse or triggers other protection, effectively shutting down the supply. It is usually achieved by an SCR or other silicon device, or by a mechanical shorting device. Probably named for the concept of using a big metal bar to mechanically provide the short circuit, as might be used done in a high-current application; or from the appearance of a crowbar circuit's I-V curve.
An antenna built with its elements in the shape of four-sided loops. Developed by Clarence C. Moore, W9LZX, an engineer at HCJB (a shortwave missionary radio station high in the Andean Mountians). He developed it to resolve issues with large coronal discharges in the thin air with a beam antenna. He later received a patent for his design.
1. A communications mode transmitted by on/off keying of a radio-frequency signal.
.
2. Another name for international Morse code. In truth a Continuous Wave is an unmodulated, uninterrupted radio frequency wave. However in common usage refers to Morse Code emissions or messages which is an interrupted wave as in 2. See also: Coherent CW, Digital Modes page.
CW filter.
Used to narrow IF passband to improve reception in crowded band conditions.
Cycles.
A term used for measuring frequency prior to the term Hertz replaced it - hence kc, Mc, etc.
Cyclic Redundancy Checks (CRC).
A type of calculation which is used to produce a small, fixed-size checksum of a larger block of data, such as a packet of network traffic or a computer file. The checksum is used to detect errors after transmission or storage. A CRC is computed and appended before transmission or storage, and verified afterwards by the recipient to confirm that no changes occurred in transit. CRCs are popular because they are simple to implement in binary hardware, are easy to analyze mathematically, and are particularly good at detecting common errors caused by noise in transmission channels. See also: Digital Modes page.
