Repeater Coordination Terminology

A-B || C || D-E || F-J || K-O || P-S || T-Z

AM (amplitude modulation)

a radio transmission mode in which the strength of the speech signal controls the strength of the transmitter signal. This normally resuilts in two sidebands containing the modulation energy.

APRS (Amateur Packet Reporting System)

a system which supports plotting of station positions on screen maps.

ASL (above sea level)

a method of measuring antenna height

access code

one or more numbers and/or symbols that are keyed in with a telephone key pad to activate a repeater function e.g autopatch, link etc.

antenna separation

the physical spacing between transmit and receive antennas, when separate antennas are used


a device that interfaces a repeater to the telephone system to permit repeater users to make telephone calls. Often called a "patch"

auxilliary station

Auxiliary operation, at the very basic level, is inherently closed operation, which means that all auxiliary stations are part of a system of stations. All operators of the system must be authorized control operators. There are several forms of auxiliary operation, which encompass a number of different types of activities, such as:

    1. Remote control of a station, where a radio link is used. This means sending some form of signals, such as DTMF tones, to another station to change is operating parameters, turn it on or off, change frequencies or power, rotate antennas, etc. These control signals are considered to be a form of "primary" control of the station, or the control of those parameters for which the station licensee and/or any other control operators are primarily responsible. This does not include various "secondary" control functions, such as those which may be used by "users" of a repeater, i.e., to access an auto-patch, etc.

    2. Voice links between two or more stations within a system of stations, such as;

        1. Point-to-point links from a repeater's remote receiver(s) back to the main repeater site (Here, the repeater and its associated remote receivers, link transmitters and receivers, and any associated control stations, constitute the "system". "Users" of the repeater are NOT part of the system.);

        2. Dedicated point-to-point links between different repeaters in a "system" of either full-time or part-time linked repeaters;

        3. Combination remote-control and voice point-to-point links intended to control and carry the voice signals to the transmitter(s) of a remotely-controlled station (this is the equivalent to replacing the wire between the microphone and the transmitter with a radio link from the mike to the remotely located transmitter). This form of auxiliary operation is commonly referred to as an "up-link" (from the control point up to the remote station);

        4. Point-to-point links from the receiver(s) of a remotely located station back to the control point (the equivalent of replacing the wire between the receiver's audio output terminals and its loudspeaker with a radio link from the receiver to a remotely located loudspeaker). This form of auxiliary operation is commonly referred to as a "down-link" (from the remote station down to the control point).

band (amateur radio frequency band)

the range of contiguous frequencies over which amateurs may communicate.


a condition that results in greater-than-normal communication range on the VHF and UHF bands. CTCSS tones are used to minimize the effects of co-channel interference due to band-openings causing reception of distant signals.


a voluntary system of frequency allocations in each amateur radio band.

CAS (carrier activated switch)

see COR

COR (carrier-operated relay)

a device that causes the repeater to transmit in response to a received signal

CTCSS (Continuous Tone-Coded Squelch System)

CTCSS stands for Continuous Tone Coded Squelch System, often referred to as "PL" for Private Line (Motorola's trade name). GE calls it Channel Guard.

This is a sub-audible tone transmitted by your radio in addition to your voice signal. When it is equipped with a CTCSS decoder, a repeater will not function unless it hears the CTCSS tone and the "carrier" signal from your transmitter. Different CTCSS tones are in use for different repeaters or areas. These may be applied to input or output frequencies, or both. CTCSS tones are used to minimize the effects of co-channel interference due to band-openings causing reception of distant signals.

Many repeaters require the use of a PL tone to access the repeater.

Contrary to popular belief, many repeaters that require the use of a specific PL tone to access the repeater are NOT closed repeaters. PL is often used as a means of solving an interference problem, or preventing one in the first place. Some repeaters may also generate a PL tone on the repeater output so that repeater users who are equipped with a radio capable of decoding PL will not hear other interference sources on the channel that would otherwise open the user's radio's squelch.

We strongly recommend the use of PL on repeaters' receivers. PL is a minor inconvenience when you consider how many potential problems it can eliminate. The use of PL may be required for a coordination to be granted if conditions so warrant, such as proximity to a co-channel repeater, or in an area where band openings frequently aggrevate co-channel interference problems.

This chart shows each PL tone's two-character alphanumeric designator and corresponding tone frequency in Hertz.


an unmodulated (no speech) transmitter signal.

cavity resonator

a sharply tuned circuit using the physical dimensional resonance of one or more tuned cavities.


a pair of frequencies (input and output) used by a repeater.

channel spacing

the frequency spacing between adjacent frequency allocations may be 50, 30, 25, 15 or 12.5kHz, depending upon the convention in use in the area of the repeater.

closed repeater

a repeater whose access is limited to a select group (see also open repeater).

co-channel interference

the interference resulting when a repeater receives signals from a distant repeater on the same frequency pair.


the control system within a repeater which may include turning the repeater on-off, timing transmissions, sending the identification signal, controlling the autopatch and CTCSS encoder/decoder.

control operator

the amateur radio operator who is designated to control the repeater.

courtesy tone

an audible indication that the repeater user may go ahead and transmit.


the geographic area within which the repeater provides communications.


the process of transmitting on one band and receiving on another.


see tone pad.

desense (desensitization)

the reduction of receiver sensitivity due to overload from a nearby transmitter.

digipeater (digital repeater)

a packet radio repeater

dropping out

the situation, while using a repeater, when your signal does not have enough strength to keep the repeater triggered.


a mode of communication in which you transmit on one frequency and receive on another frequency (see also half and full duplex).


highly selective filter which allows a repeater's transmitter and receiver to share one antenna.

EIRP (effective radiated power referred to isotrope)

ERP plus 2.14 dB to correct for reference to isotrope.

ERP (effective radiated power)

radiated power, allowing for transmitter output power, line losses and antenna gain.


see frequency modulation.

frequency coordinator

an individual or group responsible for assigning channels to new repeaters with minimal interference to existing repeaters.

frequency modulation

a method of modulation, where the strength of the signal is constant, but the frequency varies with the strength of the voice, and the rate of change varies with the frequency of the voice.

full duplex

a mode of communication in which you transmit on one frequency while you simultaneously receive on another frequency.

full quieting

a received signal that contains no noise.


a link or bridge between one communication network and another. Can be repeater to satellite.

HAAT (height above average terrain)

a method of measuring antenna height.

half duplex

a mode of communication in which you transmit at one time on one frequency and receive at another time on another frequency.

helical resonator

a compact resonant filter circuit to block multiple interfering signals.

horizontal polarization

the antenna elements are horizontal (used at vhf/uhf for weak signal CW/SSB operation).

Hz (Hertz)

a unit of frequency measurement equal to one cycle per second.

ID (identification)

the means by which a station identifies its call sign by Morse code or speech.

input (frequency)

the frequency of the repeater's receiver.

intermod (intermodulation distortion or IMD)

interference that results when strong signals from nearby transmitter(s) mix with the desired signal in a radio receiver.


the difference in level (measured in dB) between a transmitted and received signal due to filtering.


a theoretical antenna with zero dimensions and a spherical radiation pattern. Gain is2.14 dB from dipole.

kHz (kilohertz)

a unit of frequency measurement equal to 1,000 cycles per second (Hertz).


to key up a repeater without identifying.

key pad

see tone pad.

key up

to turn on the repeater by transmitting on its input frequency


the process of connecting repeaters in a permanent network, or one controlled by access codes.

MHz (megahertz)

a unit of frequency measurement equal to 1,000,000 cycles per second (Hertz).


a slang expression meaning a repeater system.


the region of the radio spectrum above 1 gigahertz (GHz).

negative offset

the repeater input frequency is lower than the output frequency.

odd split

unconventional frequency separation between input and output frequencies.


see separation.

open repeater

a repeater whose access is not limited.

output frequency

the frequency of the repeater's transmitter (and your receiver).


the word used to indicate the end of a voice transmission.

positive offset

the repeater input frequency is higher than the output frequency.

PTT (push to talk)

the use of the microphone button or control line to key the transmitter on.


Private Line (trademark of Motoroal Inc) see CTCSS.


an automatic relay station, generally in a high location, which is used to increase the range of mobile and handheld FM transmitter/receivers.

A "repeater", at the very basic level, is an open station which the F.C.C. Rules say is available for ANY other amateur licensee to use (this basic concept ignores any usage limits or access codes which, according the Rules, may be imposed by the repeater's sponsor). All receiving and transmitting frequencies used by repeaters, including any secondary inputs, must be within specific repeater sub-bands of the 29 MHz and higher bands (refer to Section 97.205(b) of the Rules).

reverse patch

when a call is received on its incoming telephone line this special autopatch rings over the air and may be answered by tone access.

SSB (single-sideband)

a type of AM transmission which occupies half the spectrum of a standard AM signal.

separation (split)

the difference, in kHz, between the repeater's transmit and receive frequencies. Conventional separations by amateur band are:

    • 29 MHz 100 kHz

    • 50 MHz 1 MHz

    • 144 MHz 600 kHz

    • 220 MHz 1.6 MHz

    • 440 MHz 5 MHz

    • 902 MHz 13 MHz

    • 1270 MHz 12MHz


a mode of communication in which you take turns to transmit and receive on the same frequency. A frequency set aside for non-repeater use.


a circuit within a radio that keeps the speaker silenced (squelched) until the signal level exceeds a certain point, set by the squelch control. Normally you set the squelch to just block out noise and allow signals to pass.

sub-audible tone

see CTCSS.


the brief signal transmitted by a repeater transmitter after someone stops talking.


to cause the repeater, or a repeater function, to turn off because you have transmiited too long.


a device which measures the length of each transmission and causes the repeater, or a repeater function, to turn off, after a transmission has exceeded the preset time.

tone pad

an array of 12 or 16 numbered keys that generate the standard telephone dual-tone multi-frequency (DTMF) dialing signals.

touch tone

trade mark of AT&T. See DTMF.


to activate a repeater by transmitting on its input frequency (see also key up).

translator (linear translator)

a device used to directly convert and retransmit a block of received frequencies.


the term used for a linear translator in a satellite. Inverting transponder transmits received upper sideband as lower sideband. Non-inverting transponder transmits received upper sideband as upper sideband.

UHF (ultra high frequency)

the region of the radio spectrum between 300 and 1000 MHz or 1 GHz.

vertical polarization

the antenna elements are vertical (used at vhf/uhf for FM and repeater operation).

VHF (very high frequency)

the region of the radio spectrum between 30 and 300 megahertz (MHz).