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Q signals
Three-letter symbols beginning with Q. Used on CW to save time and to improve communication. Some examples are QRS (send slower), QTH (location), QSO (ham conversation) and QSL (acknowledgment of receipt).

QRL?
Ham radio Q signal meaning "Is this frequency in use?"

QSL card
A postcard that serves as a confirmation of communication between two hams.

QSO
A conversation between two radio amateurs.

Quarter-wavelength vertical antenna
An antenna constructed of a quarter-wavelength long radiating element placed perpendicular to the earth.

Radio Amateur Civil Emergency Service (RACES)
A part of the Amateur Service that provides radio communications for civil preparedness organizations during local, regional or national civil emergencies.

Radio-frequency interference (RFI)
Disturbance to electronic equipment caused by radio-frequency signals.

Radioteletype (RTTY)
Radio signals sent from one teleprinter machine to another machine. Anything that one operator types on his teleprinter will be printed on the other machine. Also known as narrow-band direct-printing telegraphy.

Receiver
A device that converts radio waves into signals we can hear or see.

Receiver incremental tuning (RIT)
A transceiver control that allows for a slight change in the receiver frequency without changing the transmitter frequency. Some manufacturers call this a clarifier (CLAR) control.

Receiver overload
Interference to a receiver caused by a strong RF signal that forces its way into the equipment. A signal that overloads the receiver RF amplifier (front end) causes front-end overload. Receiver overload is sometimes called RF overload.

Reflection
Signals that travel by line-of-sight propagation are reflected by large objects like buildings.

Reflector
An element behind the driven element in a Yagi and some other directional antennas.

Repeater station
An amateur station that automatically retransmits the signals of other stations.

Resistance
The ability to oppose an electric current.

Resistor
Any material that opposes a current in an electrical circuit. An electronic component specifically designed to oppose or control current through a circuit.

Resonant frequency
The desired operating frequency of a tuned circuit. In an antenna, the resonant frequency is one where the feed-point impedance contains only resistance.

RF burn
A burn produced by coming in contact with exposed RF voltages.

RF carrier
A steady radio frequency signal that is modulated to add an information signal to be transmitted. For example, a voice signal is added to the RF carrier to produce a phone emission signal.

RF overload
Another term for receiver overload.

RF radiation
Waves of electric and magnetic energy. Such electromagnetic radiation with frequencies as low as 3 kHz and as high as 300 GHz are considered to be part of the RF region.

RF safety
Preventing injury or illness to humans from the effects of radio-frequency energy.

Rig
The radio amateur's term for a transmitter, receiver or transceiver.

RST
A system of numbers used for signal reports: R is readability, S is strength and T is tone. (On single-sideband phone, only R and S reports are used.)