Amateur Radio Foundation Glossary

Here’s a short summary of some of the terms that you may experience when studying towards your amateur radio Foundation exam:

Term Description
AM Amplitude Modulation. This is a method of combining audio (e.g. speech) with a carrier to create a radio signal. The audio changes the amplitude (height) of the carrier’s waveform
AMU Antenna Matching Unit. Used to “match” antenna impedance to the transmitter, to reduce VSWR
Attenuate To reduce the energy of a radio signal. As an example, heavy rain attenuates (reduces the strength of) radio signals at UHF and above
Balun A device that couples balanced and unbalanced feeder / antennas. For example, you would use a balun to connect a balanced antenna (such as a dipole), to unbalanced feeder (such as co-ax cable)
BNC Type of connector used for connecting between radio equipment and an antenna (bayonet connector, twist-and-click)
CQ A general call asking for someone to make contact with you. Derives from “I Seek You”.
CW Continuous Wave – Also known as Morse Code
CTCSS Continuous Tone Coded Squelch System. Sub-audible tone by your radio sent alongside a transmission, to allow a repeater to “open”. The helps to ensure that the repeater will only forward genuine messages
dB (Decibels) Unit associated with the measurement of gain (or loss). At Foundation, recall that Yagi (beam) antennas have a gain measured in dB, for example, a Yagi with a 3dB gain would double the radiated power
Dummy Load A device that plugs into a transmitter’s antenna socket to allow you to test a transmitter without radiating a signal into an antenna
EMC Electro-Magnetic Compatibility. A device’s immunity to interference. EMC issues relate to electrical or radio interference to other equipment.
EMF Electro-Magnetic Fields. Antennas generate EMF when transmitting and amateurs are required to ensure that EMF they generate is below recommended international limits.
EIRP Effective Isotropic Radiated Power – How much power is being radiated by your antenna (compared to a theoretical “isotropic” antenna)
ERP Effective Radiated Power – How much power your antenna is outputting (calculated by multiplying the power in watts, by the “gain” of the antenna when compared to a half-wave dipole antenna)
FM Frequency Modulation. Method of combining a radio signal with a carrier. The signal changes the frequency of the carrier’s waveform
Impedance An antenna has an impedance, which is measured in Ohms at the feed point. The impedance depends on the size, shape of the antenna, how it’s positioned, and the frequency transmitted. You would use an AMU (Antenna Matching Unit) to match the impedance of the antenna and feeder, with the transmitter, to ensure that the system is as efficient as possible.
Ionosphere Layer of conductive gases 70-400km above Earth, that refracts radio signals back to Earth – Used to make HF contacts beyond line-of-sight
Ohm’s Law The Voltage equals the Current multiplied by the Resistance (V = I x R). Need help? Ohm’s Law Triangle Explained
PL-259 Type of connector used for connecting between radio equipment and an antenna (screw-thread)
PME This stands for Protective Multiple Earthing, and relates to one of the ways that electricity companies connect houses to Earth. Special care is needed with RF earthing arrangements if your house has PME. More details can be found in the RSGB’s guide: RSGB UK Earthing Systems and RF Earthing
Q Codes Shorthand codes used on amateur radio dating back to early Morse Code days. Common codes are: QTH (Location) ; QSL (Acknowledgement of receipt) ; QRZ (Who is calling) ; QRM (Man-made interference) ; QRP (Reduced power) ; QSY (Change frequency) ; QSO (communication / contact). Can be a question or a statement- e.g. “QSL?”… “QSL” (Did you get that? Yes, I got that)
RF Radio Frequency
SSB Single Sideband. There are two types: USB (Upper Sideband) and LSB (Lower Sideband). These are methods of transmission, like FM and AM
VSWR Voltage Standing Wave Ratio. Often shortened to SWR.  An SWR of 1:1 would indicate that all of the power from the transmitter is being radiated by the antenna. An SWR reading of 2:1 or higher would indicate that a significant amount of power is reflected back to the transmitter from the antenna (indicating an antenna mismatch).
Yagi A beam antenna. Typically has a gain (measured in dB), and focusses energy in a single direction

This list can be downloaded as a PDF – See

Anything you’d like us to add, or that’s not clear? Let us know!

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  1. Christopher fancett 22 September 2016 Reply
    • Pete SippleAuthor 23 September 2016 Reply
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