Ham Radio Extra key terms

A message passed by an amateur station on behalf of a person other than the station licensee or operator. Under Part 97, the control operator must be present and the message must not be encrypted or for business purposes.

The licensed amateur designated to be responsible for the proper operation of a station at the time of transmission. The station licensee must designate one for each transmission, and that person's privileges limit what may be done.

The person holding the amateur license under which a station is authorized to transmit. The licensee is responsible for the station's proper operation and for keeping records as required by the FCC.

A radiocommunication service for self-training, intercommunication, and technical investigation carried out by duly authorized persons interested in radio technique, with no pecuniary interest. It is defined in Part 97 and international radio regulations.

A radiocommunication service using space stations on Earth satellites for the same purposes as the amateur service. Amateur stations may use it under specific frequency and power limits in Part 97.

An amateur station located more than 50 km above the Earth's surface. Space stations, such as those on satellites, have separate privileges and power limits from Earth-based stations.

An amateur station located on or within 50 km of the Earth's surface. This category includes nearly all typical amateur installations, as opposed to stations on satellites or high-altitude platforms.

An amateur station transmitting one-way communications for the purpose of observing propagation or related experimental activities. Beacons operate under specific subbands and must be remotely controlled or automatically controlled.

An amateur station, other than a repeater, that transmits signals over a shared channel to control or communicate with another amateur station. Auxiliary stations are limited to specific bands and must be under automatic or remote control.

An amateur station that receives signals on one frequency and simultaneously retransmits them on another, typically to extend coverage. Repeaters have specific frequency bands, power limits, and control requirements in Part 97.

Operation of an amateur station by a device that controls transmissions without a control operator present at the control point. Part 97 permits it only for specific station types such as repeaters, beacons, and auxiliary stations.

Operation of an amateur station by a control operator located at a point other than the station itself, using a control link. The control operator must be able to control the transmitter and monitor its operation.

Emission on a frequency outside the necessary bandwidth that cannot be reduced without affecting the information being transmitted. Part 97 sets strict limits on spurious emissions to prevent interference.

A spurious emission at an integer multiple of the fundamental frequency. Harmonics are a common source of interference and must be suppressed by filtering or good transmitter design.

The width of a frequency band containing 99 percent of the total mean power of a given emission. It is used to describe how much spectrum a signal actually occupies under Part 97 measurement conventions.

For a given class of emission, the width of the frequency band sufficient to ensure transmission of information at the required rate and quality under specified conditions. Emissions should not exceed it unnecessarily.

An entity recognized by local amateur operators that recommends coordinated frequencies and technical parameters for repeaters and auxiliary stations. Coordination reduces interference and is referenced in Part 97.

The Radio Amateur Civil Emergency Service, a part of the amateur service established to provide emergency communications for civil defense. RACES operation is limited to stations enrolled by a government emergency management agency.

The Amateur Radio Emergency Service, a volunteer organization sponsored by the ARRL that provides emergency communications. Unlike RACES, it is not a government program and operates with broader participation.

Communications directly related to the immediate safety of human life or protection of property. Part 97 allows special operating privileges, such as using any available frequency, during declared emergencies.

A voluntary or coordinated arrangement of frequencies within an amateur band for specific modes and activities. Band plans are not FCC rules but are widely followed to minimize interference and promote efficient spectrum use.

A designated frequency where operators initiate contacts before moving to another frequency to continue. Using calling frequencies properly reduces congestion and interference on popular bands.

A technique where a station transmits on one frequency and receives on another, often used for DX or satellite contacts. Split operation avoids interference when many stations call the same station.

A communication method in which transmission and reception occur simultaneously on different frequencies. Repeaters and satellite links commonly use duplex operation to allow full two-way conversations.

A two-way communication between amateur stations. The term is often used to describe a contact, and exchanging signal reports and locations is customary in a QSO.

A standardized assessment of a received signal's readability, strength, and tone, commonly using the RST system. Signal reports help operators evaluate propagation and equipment performance during a contact.

A record of amateur contacts, typically including date, time, frequency, mode, and call signs. While logging is not required for most amateur operations, it is used for awards and required in certain circumstances.

The way radio waves travel from a transmitter to a receiver, influenced by the ionosphere, ground, and atmosphere. Understanding propagation helps operators choose frequencies and times for effective communication.

Layers of ionized gas in the upper atmosphere that can refract and reflect radio waves. It enables long-distance communication on the HF bands and varies with time of day and solar activity.

The minimum distance from a transmitter at which skywave signals return to Earth. Signals may be inaudible within the skip zone but receivable beyond the skip distance.

The relationship stating that voltage equals current times resistance in a circuit. It is used to calculate one electrical quantity when the other two are known.

The rate at which electrical energy is transferred, measured in watts. In a resistive circuit, power equals voltage times current, or current squared times resistance.

The opposition to alternating current caused by capacitance or inductance, measured in ohms. Reactance varies with frequency and combines with resistance to form impedance.

The total opposition to alternating current in a circuit, including resistance and reactance. It is expressed as a complex quantity with magnitude and phase and is central to matching and transmission-line analysis.

The condition in a circuit where inductive and capacitive reactances cancel, leaving only resistance. Resonance occurs at a specific frequency and is used in tuned circuits, antennas, and filters.

A logarithmic unit used to express ratios of power, voltage, or current. In amateur radio, decibels describe gain, loss, and signal strength changes compactly.

The increase in signal power or voltage produced by an amplifier, antenna, or circuit, often expressed in decibels. Gain describes how much a device strengthens a signal relative to its input.

A measure of how much an antenna concentrates radiated power in a particular direction compared with a reference antenna. It is usually expressed in dBi or dBd and does not create power.

The property of an antenna that describes how strongly it concentrates radiation in one direction. Higher directivity generally means a narrower beamwidth and greater gain.

The angular width of an antenna's main radiation pattern, usually measured between the half-power points. Narrower beamwidth indicates greater directivity and typically higher gain.

The ratio of maximum to minimum voltage or current along a transmission line, caused by reflections from an impedance mismatch. An SWR of 1:1 indicates a perfect match, while higher values indicate reflected power.

A measure of how much of an incident wave is reflected at an impedance discontinuity, expressed as a ratio or in decibels. It relates directly to standing wave ratio and return loss.

The ratio, usually in decibels, of reflected power to incident power at a mismatch. A higher return loss means less reflection and a better impedance match.

The impedance of a transmission line when it is infinitely long or terminated in a matched load, determined by its physical construction. Common values are 50 and 75 ohms.

A transmission line with a central conductor surrounded by a dielectric and an outer shield. It is widely used in amateur stations because it is convenient and shields against interference.

A device that converts between balanced and unbalanced transmission lines or loads. It is often used to connect a balanced antenna to an unbalanced coaxial feed line and can also provide impedance transformation.

The speed at which a signal travels along a transmission line, expressed as a fraction of the speed of light. It affects the physical length required for tuned lines and phasing harnesses.

A conductor system that carries radio-frequency energy from a transmitter to an antenna or from an antenna to a receiver. Its impedance, loss, and velocity factor affect system performance.

The highest RF exposure level considered safe for humans under FCC rules, based on frequency and averaging time. Amateur stations must evaluate compliance, especially near antennas and high-power transmitters.

Human exposure to radio-frequency electromagnetic fields. FCC rules limit exposure based on frequency, power density, and distance from the antenna to protect against harmful effects.

The fraction of time a transmitter is actually emitting during a period of operation. It affects average power and RF exposure calculations, especially for modes like CW and digital transmissions.

A filter that passes low frequencies and attenuates high frequencies. It is used after a transmitter to reduce harmonic emissions and prevent interference to other services.