This is a brief list of some commonly used terms and expressions used by radio enthusiasts and resellers. It is not an exhaustive list and many of the terms can be found in greater detail in the Wikipedia.
Amplitude modulation – a method of encoding an audio signal by varying the amplitude of the carrier wave. The term AM is often (incorrectly) used to describe the medium frequency or medium wave band. AM is common on low frequency/longwave, medium frequency/medium wave and high frequency/shortwave bands. AM is also used for the VHF aircraft band.
Bandwidth control on a short-wave radio receiver allows you to control the selectivity of the receiver so that interference can be reduced considerably.
Carrier ware or continuous wave. This is used for Morse code transmission.
Enhanced other network – allows you to listen to an RDS programme without missing news even from other networks.
Frequency modulation. This is where an audio signal is encoded by slightly varying the frequency of the carrier wave. The term FM is often used (incorrectly) to describe the VHF wave band. However, many countries also use frequency modulation for UHF television sound.
Shortwaves travel around the earth by bouncing between the earth and the ionosphere (The part of the earth’s atmosphere that reflects shortwave back to the earth).
Liquid crystal display – many digital radio’s and radio scanners have LCD displays.
DX stands for distance. This switch adjusts the sensitivity of the radio to improve reception of distant stations or prevent over loading of the radio by a very strong local transmitter.
Narrow frequency modulation – as distinct from WFM, wide frequency modulation. This is used in communications radio such as UK citizens band radio. It allows a lot of channels for a small bandwidth but the audio quality is poor in comparison to wide FM.
A notch filter removes a very narrow slice from a received signal. either from the radio frequency itself (RF notch) or from the audio output (audio notch) of the receiver.
With so many stations broadcast on adjacent frequencies, its is possible to adjust the signal bandwidth and sharpen the tuning to reduce unwanted noise.
This allows you to programme your favourite stations on you radio.
Phase Lock Loop – an Electronic circuit in digital radios that locks onto your chosen station to give clear drift free reception.
Radio Data System – this enables the radio receiver to display the radio station name and depending on the model of radio, some program information as well.
Radio frequency gain control is a control that permits the sensitivity of the reciver to be continuously varied.
Single Sideband ability to receive signals from the upper or lower part of the carrier wave. This is needed to listen to ham radio and utility stations. Single side band operation makes it possible to concentrate the full transmission energy with suppressed carrier noise.
This feature allows the receiver to automatically tune through a desired frequency range, stopping on all frequencies where a signal is present.
The ability of the receiver to select the station it is tuned to, and to reject signals from all the other stations broadcasting on a nearby frequency.
The ability of a shortwave radio to pick-up weak signals. It is usually measured in microvolts. The lower the measurement in microvolts, the weaker the signal the radio can receive.
This mutes the receiver audio when the strength of the signal drops below a preset level.
This feature is found on some modern shortwave receivers such as the Grundig Satellite 800, Sony SW7600 and SW100E. It is a circuit that replaces the carrier in an AM signal with an internally generated replacement signal to reduce the effects of fading.
Variable Bandwidth Tuning
This is a circuit that allows the selectivity of a receiver to be continuously varied.
Wide frequency modulation – as distinct from NFM. WFM is used for high quality audio on the broadcast VHF & UHF bands for FM Radio and analog television.
Another name for the high frequency or shortwave band.