Foundation Glossary of Terms
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. Low-frequency tone sent with your transmission that can be used to access a repeater. This 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. The avoidance of interference between various pieces of electronic 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 – transmitted power taking account of antenna gain, referenced to a theoretical isotropic antenna |
| ERP | Effective Radiated Power – transmitted power taking account of antenna gain, referenced to a half-wave dipole |
| 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 | A region of the upper atmosphere containing ionised particles that can refract some HF radio signals back towards Earth, allowing 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 indicates a perfect impedance match, with no power being reflected back towards the transmitter because of a mismatch. 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 |
Anything you’d like us to add, or that’s not clear? Let us know!