Advanced Amateur Radio (Canada) key terms

Defined ranges of radio spectrum that Canadian amateurs may use, such as 160, 80, 40, 20, 15 and 10 metres, plus VHF and UHF bands, each with rules on power and permitted modes.

The format of Canadian amateur call signs, beginning with VE or VA, followed by a digit indicating the call area and then letters, with suffixes distinguishing individual operators from clubs or special-event stations.

A voluntary or recommended arrangement of modes and activities within an amateur band, such as reserving narrow segments for CW or weak-signal work, so that operators avoid interfering with one another.

Messages passed on behalf of someone other than the licensed operator. International rules restrict such traffic to countries that have agreed to permit it, so amateurs must know which destinations are allowed.

Use of amateur stations to pass messages during disasters or other emergencies when normal services fail. Special provisions may permit operation outside normal rules, but only to the extent genuinely needed.

The requirement to transmit your assigned call sign at specified intervals and at the end of a communication, so that any listener can determine who is operating the station.

A written or electronic record of contacts showing date, time, frequency, mode and the other station's call sign. It supports awards, confirms contacts and helps resolve interference complaints.

A postcard or electronic confirmation sent between amateurs to verify that a two-way contact took place, often used as proof for operating awards and for confirming long-distance contacts.

Safety limits on human exposure to radio-frequency energy, expressed as field strength or power density. Operators must evaluate their station's emissions and keep people away from excessive fields.

The fraction of time a transmitter is actually emitting energy during a period of operation. It matters for exposure calculations and for estimating average power and heat in amplifiers.

The average power supplied to the antenna during one radio-frequency cycle at the crest of the modulation envelope. It is the standard limit used for SSB and other amplitude-modulated transmissions.

The process of varying a carrier wave's amplitude, frequency or phase to carry information such as voice or data, allowing the signal to be transmitted efficiently through space.

One of the two bands of frequencies produced above and below the carrier when a signal is amplitude modulated. Single sideband suppresses the carrier and one sideband, saving power and bandwidth.

A transmission consisting of an unmodulated carrier switched on and off to send Morse code. It is highly efficient and can be copied at very low signal levels.

The weakest signal a receiver can detect and reproduce usefully, usually quoted in microvolts or dBm for a given signal-to-noise ratio. Better sensitivity allows reception of fainter stations.

The background level of noise in a receiver or at an antenna, arising from thermal noise, atmospheric noise and man-made interference. Signals below it cannot be distinguished reliably.

The ratio of desired signal power to noise power at a point in a system, often expressed in decibels. Higher values mean the signal is easier to copy.

A logarithmic unit used to express ratios of power or voltage. In radio it describes gain, loss, signal strength and noise, allowing very large ranges to be handled with convenient numbers.

The way radio waves travel through the atmosphere, especially by refraction from ionized layers high above the Earth. Solar activity, time of day and frequency determine which paths are open.

The highest frequency that can be refracted back to Earth by the ionosphere over a given path at a given time. Above it, signals pass into space rather than returning.

The highest frequency that is reflected straight down from the ionosphere when a signal is sent vertically upward. It indicates the ionospheric layer's maximum electron density.

The increase in signal strength in a particular direction compared with a reference antenna, expressed in dBi or dBd. Gain comes from concentrating energy, not from creating extra power.

A plot or description of how an antenna radiates or receives energy as a function of direction, showing lobes, nulls and the main beam direction.

The angular width of an antenna's main radiation lobe, usually measured between the points where power falls to half its maximum value. Narrower beamwidth generally accompanies higher gain.

A measure of impedance mismatch on a transmission line, equal to the ratio of maximum to minimum voltage along it. A value of 1:1 indicates a perfect match.

The impedance a transmission line presents to a travelling wave, determined by its conductor spacing and dielectric, typically 50 ohms for amateur coaxial cable.

A transmission line with a central conductor surrounded by insulation, a braided shield and an outer jacket. The shield confines the field, reducing radiation and pickup.

A transformer or choke that connects a balanced antenna or line to an unbalanced line such as coaxial cable, preventing unwanted currents on the outside of the coax shield.

A simple antenna made of two straight conductors fed at the centre. A half-wave dipole resonates when its total length is slightly less than half a wavelength.

The physical distance between successive crests of a wave, equal to the speed of light divided by frequency. It sets antenna dimensions and explains band naming such as 20 metres.

A complex number describing how much of a wave's voltage is reflected at an impedance discontinuity, including its phase. Its magnitude relates directly to standing wave ratio.

The relationship stating that current through a conductor equals voltage divided by resistance. It underlies nearly every calculation of current, voltage and power in station wiring.

The total opposition a circuit presents to alternating current, combining resistance with reactance from capacitors and inductors. It determines how power transfers between stages.

The condition in which a circuit's inductive and capacitive reactances cancel, leaving only resistance. It occurs at a particular frequency and is used to tune antennas and filters.

A network of components that passes signals in some frequency ranges while attenuating others, used to remove interference, shape emissions or separate bands.

The rate at which electrical energy is transferred, equal to voltage multiplied by current, or current squared times resistance. It is measured in watts.

Connecting equipment chassis and station grounds together and to earth to reduce shock hazard, minimise RF burns and prevent unwanted currents that cause interference.

The generation of unwanted signals at sums and differences of two or more frequencies when they pass through a nonlinear device, causing interference that may be hard to identify.