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RADIO TERMINOLOGY
ABBREVIATIONS
& DEFINITIONS
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I am indebted to Richard Vaughan who kindly send in some suggestions for the site, including these very useful definitions of some often used radio terms.  So if you hear any strange expressions while listening to Single Side Band on the amateur bands, you'll know where to look them up...

  • A.B.C. - Automatic Band Control. This feature will automatically switch the active band (the one with receive activity) to the main band position. This feature is present on dual band radios.

  • ALC - Automatic Limiting Control. This feature will automatically limit (reduce) the output power of a transmitter. This feature will protect the transmitter in the event of high SWR.

  • Alternate key command - This refers to the secondary function of a key. The alternate or secondary function is selected by first pressing (and sometimes holding) a [FUNCTION] key.

  • Band - This refers to a group of frequencies. Many of the "DUAL BAND" radios can operate on two or more bands. The 2 meter band is the group of frequencies between 144 MHz and 148 MHz. The 440 Band contains the frequencies between 440 MHz and 450 MHz.

  • Bank - Some radios store memories into memory banks. A 100 memory radio may have the memories grouped into 10 banks with 10 memories in each bank. Memory banks can be useful to help group "classes" of frequencies. Fire, Police frequencies are often grouped into separate banks.

  • BEEP- This refers to an audible sound that occurs signaling a specific event, ie. Keyboard key pressed, Signal received or other event.

  • Bell- A bell symbol is often used on an L.C.D. display to show that the "BELL ALERT" function is active. In Bell Alert mode, the speaker is turned off and an audible bell sound will signal the reception of a signal.

  • Burst- Tone "BURST" is a signaling mode used in Europe in place of the PL (sub audible tone) we use in America. In tone burst mode, a tone or group of tones is transmitted each time the P.T.T. key is pressed. The receiving radio will only turn on the speaker when the proper "Tone Burst" is received.

  • Busy - When a signal is present on a frequency, the channel is "BUSY". The "BUSY" light will light when a signal is present or when the squelch is set too low to block out the background noise on a frequency.

  • Call Channel - This is a specific memory channel used to store your favorite frequency. It is often selected with a single key.

  • Carrier- A signal on a frequency. In the scan mode, carrier scan will stop the scan whenever a signal is present.

  • Check- This is the same feature as "REVERSE". Refer to Duplex or repeater operation. It is often desirable to "CHECK" the repeater input frequency. The [CHECK] key, while pressed, will monitor the input.

  • Clock- Many of the new radios have a clock feature. The presence of a clock will also provide automatic power off and power saver functions.

  • CTCSS - Continuous Tone- Coded Squelch System. Also the same as PL (private line) or DECODE. CTCSS refers to a mode where the speaker is muted unless a specific PL tone is present on the received frequency. A radio can be set in three CTCSS modes: 1) Not using any form of CTCSS. 2) PL Encode only mode. This places a sub audible tone on the transmitted signal only. 3) CTCSS Decode mode. The PL is encoded on the transmitted signal and the speaker is muted unless the received signal has the proper tone.

  • Decode - See CTCSS. This is a term also used to describe DTMF and Tone Burst signaling features.

  • Decoder- The electronic component used to find a PL, DTMF or Tone Bursts. A decoder is often an optional accessory.

  • Digital Squelch - Digital Squelch operates in the same faction as CTCSS. The squelch will remain closed until the specific digital (often DTMF ) tones are received. A digital Squelch is usually an optional accessory for a radio.

  • Dim -A button used to lower the illumination of the display screen.

  • DTMF- Dual Tone Multi Frequency. A DTMF keypad is a standard accessory on most modern radios. When a DTMF key is pressed along with the P.T.T. key, a two tone sound is transmitted. A receiver with a DTMF decoder can convert the tones back into an electronic command.

  • Dual- Two. Some radios can operate on two different bands. It is called a dual band radio. Some radios have two VFO modes. It is called dual VFO's.

  • Duplex - Transmission and reception on different frequencies. Repeater operation requires simultaneous reception and transmission. When a radio is in duplex mode, reception is on the displayed frequency and transmission is offset from the receive frequency by a predetermined amount and direction. On 2 meters the offset is set at 600 kHz. The direction of the offset (up or down) is determined by local practice.

  • Encoder - To encode a tone (sub audible) on the transmitted signal. Often called to as PL. See CTCSS.

  • Function - The objective of the key, lever or switch. The [FUNCTION] key is often pressed to select an alternate key command.

  • Hertz - Cycle per second. Hz

  • Hide - Hiding a memory may prevent it from being used in normal operation. This feature will allow you to skip unused memories during scanning and operation.

  • KiloHertz - 1000 cycles per second kHz

  • LCD Display - Liquid Crystal Display. This type of display requires external lighting to see properly. LCD display consumes very little power and are present on most modern radios.

  • Limit - See Programmable Scan. Certain scan modes will allow you to select a frequency range to scan. The lowest frequency is called the lower limit and the highest frequency is called the upper limit. These limits are often stored in two specific memory locations.

  • Lockout - A memory may be locked out from the memory scan mode. You may wish to lockout a memory if it contains a busy repeater.

  • Megahertz- 1 million cycles per second. MHz

  • Memory - A memory can store a frequency, offset direction, PL tone and other related items. Most modern radios have at least 10 memories. The desired frequency, etc. is set up in the VFO mode and is then transferred to a memory with a set of keyboard commands.

  • Mute - To silent a speaker. A mute key is pressed to silence the speaker.

  • Odd-Split - see duplex and offset. It is sometimes useful to change the value of the offset in Duplex mode. Storing an Odd-Split repeater means to store in a memory channel a separate receive and transmit frequency. Some radios allow you to enter the receive and transmit frequencies directly into a memory channel. Other radios require you to enter the receive frequency and the value of the offset.

  • Offset - The value of the difference between the receive and the transmit frequency in the Duplex mode. On 2 meters the offset is 600 kHz. The direction of the offset (Up or down) is set by local convention. On the frequency 147.00MHz. A positive (+) offset will transmit on 147.600 MHz. A down (-) offset will transmit on 146.400MHz.

  • PL - (Private line) Sub- audible tone. A PL tone is encoded on a transmission. A PL decoder (CTCSS) can identify the PL tone and act accordingly. The are 38 suggested PL tones.

  • Power saver - Many of the newer radios have a feature called Power saver. This feature will conserve power by entering a limited "off" mode for a short duration and then quickly turn on for a few seconds to check for channel activity. If no activity is found, the cycle starts over. The period of "off" time conserves a great amount of power. This assumes that the channel be monitored is not constantly busy.

  • Priority - Many radios have a Priority memory channel and a priority watch feature. When the priority watch mode is active, the radio will regularly jump to the Priority memory channel to check for activity. If no activity is found, the radio will return to the last frequency.

  • Programmable band scan - Certain scan modes will allow you to select a frequency range to scan. The lowest frequency is called the lower limit and the highest frequency is called the upper limit. These limits are often stored in two specific memory locations.

  • PTT- Push To Talk. This is the key used to cause the radio to transmit.

  • Reset- To restart with the default features, functions and data. Most modern radios utilize a microprocessor. Resetting the microprocessor will often clear all memory and VFO data.

  • Reverse - see Offset, Duplex and Check. The Reverse key will cause the Transmit and receive frequencies to be exchanged. The radio will the receive on the repeater input and transmit on the repeater output.

  • RF- Radio Frequency

  • RIT - The control that shifts the receiver up or down in frequency to improve the reception. Most often used in 1.2 GHz equipment.

  • Save- see Power Save

  • Scan Time operated, Carrier operated - See Programmable band scan. Scanning a frequency range of a memory bank can be performed in a number of ways. You may wish to scan and stop on a busy frequency for a time period and then continue scanning (Time operated), or until the signal on the frequency stops (Carrier operated).

  • Search, Busy, Clear - See Programmable band scan, Scan Time operated Scanning a frequency range of a memory bank can be performed in a number of ways. You may will to scan for a Busy channel or for a clear channel.

  • Shift - see Duplex, Offset.

  • Signal Strength - The relative amount of RF signal received by the radio antenna. Signal strength is measured in "S" units

  • Simplex - see Duplex. When operating in the Simplex mode, The radio will receive and transmit on the same frequency.

  • Squelch - The control on a receiver that automatically quiets a receiver by reducing its gain.

  • Step - The amount of increase in frequency when a radio's tuning dial is increased or decreased. Common steps are 5, 10, 12.5, 15,20 and 25 Khz. Most modern radios allow you to change the amount of the frequency step.

  • Sub- see Band, Dual. On a dual band radio, one band is selected as the main band and the other is then called the Sub-Band.

  • S.W.R. - Standing wave ratio. see A.L.C. When a transmitter is connected to an antenna, it is hoped that all the RF signal will be radiated from the antenna. In practice, some of the RF energy is reflected back to the transmitter. Reflected energy can damage the transmitter components. The radio of the forward power and reflected power is the S.W.R. value.

  • Sub audible tone - see P.L., Encoder, Decoder, CTCSS. Sub audible means that it is a tone frequency that is too low, or too high to be heard by the human ear - or is filtered out by the radio receiver so that it is inaudible to the listener. The tone is often transmitted on a radio frequency along with voice information.

  • Toggle - A Flip-Flop. To change states or functions alternately. Press to turn on press again to turn off is an example of a toggle switch.

  • Tone alert - see Beep. When a radio is placed in Tone Alert mode. A beeping will sound when a signal is present on a frequency. This feature may be used along with CTCSS.

  • Tone squelch - see CTCSS, PL, Decoder. When a radio is placed in Tone Squelch mode, the speaker will only sound when a signal is present and that signal contains the proper PL tone.

  • Thumb Wheel - Some radios make use of Thumb wheel controls to select the desired frequency. Each wheel has 10 positions numbered 0-9.

  • Tuning Step - see Step

  • Unlock - Unlock has two different meanings.

1. To unlock the keyboard and allow keyboard functions. It is often desirable to lock a keyboard to prevent accidental changes. The Lock/Unlock feature is often a toggle feature selected by one key.
2. When the tuning circuits can not turn the selected frequency. A "U" symbol will often appear on the L.C.D. display to show that the radio can not accept the selected frequency.

  • VFO - Variable Frequency Oscillator. In the VFO mode, frequency, step, shift and all other changes are allowed. Once a frequency and related options are entered in the VFO, the VFO can be copied into - a memory location.



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