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Repeater Related Terminology Submissions of terminology from the users of the Repeater-Builder mailing list Formerly Maintained by Robert Meister WA1MIK (SK) Currently Maintained by Mike Morris WA6ILQ.

Contributions, comments / critiques / suggestions / corrections / updates for this page (or any page) are welcome and appreciated.
Actually that applies to any page at this web site! (even one that just points out a typo).

2G - second generation of wireless communications systems

3G - third generation

5G - Fifth generation

Access Code - Usually a series of DTMF tones transmitted to a repeater to perform control functions. In some linked systems the Access Code is the site address and then a function code is sent. (see function code)

Active High and Active Low - Active Low means that the signal is high when idle, and is pulled to ground when the function is true. Active High means that the signal is normally low when idle, at or very close to ground, and is pulled high when the function is true. In most cases low is ground, and high is either +5 or +12, but not always. Some telephone systems are powered by -48v and "low" is -48v and "high" is ground. And there was some equipment made by a company called EECO that used -3v as a high and -11v as a low.

AC - alternating current

ACPR - adjacent-channel power ratio

ACR - adjacent-channel rejection

A/D, ADC or A2D - Analog-to-digital - A circuit that converts an analog voltage to a binary number indicating the voltage at that instantant point of time.

ADPCM - Adaptive Differential Pulse Code Modulation, is a form of voice (or other audio) coding and decoding algorithm used in digital equipment to handle analog signals (like a voice). For example, a voice IDer may use ADPCM to to store the audio signal in a digital memory chip. Some ROIP systems use ADPCM to encode and decode the audio at each end of the digital link.
Another method of voice coding and decoding is GSM or PCM.

Alligator timer - A timer function of a repeater controller that limits the length of time the transmitter will remain keyed with out a pause. Typically the timer is set between 3 and 5 minutes. (Also see - Time-out Timer)

AMPS - advanced mobile phone system

Antenna - Every radio has an antenna. The antenna radiates radio frequency energy that you create when you press the push-to-talk button. Antennas come in various shapes and sizes and serve different purposes. Some direct energy all directions (omnidirectional) and some direct energy in one direction or to a general area (beam, corner reflector.)

Antenna analyzer - Test instrument designed to measure the impedance and standing wave ratio (SWR) of an antenna or an antenna and feed line combination as a function of frequency. See www.arrl.org/reviews-listed-by-issue, look for May 2005.

ASIC - application-specific integrated circuit

ASP - application service provider

ATM - asynchronous transfer mode

Autopatch - a device that interfaces a repeater to the telephone system and allows repeater users to make outgoing phone calls. Some offer incoming as well.

AWGN - additive white gaussian noise

Azimuth pattern - Plot of antenna radiation level as a function of azimuth angle around the antenna. Generally provided at a particular elevation angle.

Bandwidth - The difference between the highest and lowest frequency component of a signal waveform or highest and lowest frequencies passed in a system. In an antenna, the term band- width often refers to the difference between the highest and lowest frequency for which the SWR is below an application suitable value, often 2 to 1.

BDR - blocking dynamic range

Beam Tilt - Generally refers to the angular tilt of the main lobe of a antenna in the elevation pattern above or below 0 degrees elevation. Often considered in high repeater locations.

BER - bit error rate

The Box...A commercial grade working repeater.

Boom - Structural portion of many directional antennas. It is used to support the active elements and maintain their inter-element spacing.

Break - A term used in an emergency to interrupt a conversation in progress.

Bunker...The term often refers to the small buildings at the foot of a tower that contain the radio repeater(s). The ex-FAA or other government agencies were famous for their ones that were poured concrete and low profile.

Boom - A beam is built on a boom. A long horizontal pole on which the antenna elements are mounted. This is the one that bends in a storm.

Carrier delay - When you're monitoring a repeater and the person talking into the repeater un-keys his transmitter, you hear the squelch tail "sssssssssh" from the repeater's receiver. Then a carrier delay timer in the repeater controller keeps the transmitter keyed anywhere between 1/2 second and 5 seconds, in other words the transmitter "hangs" on during the "carrier delay" before it "drops out". Some repeaters insert a beep or other type of tone or multiple tones during the hang time. This tone or tones can be a "courtesy beep" or it can be telemetry signaling that certain links or other devices are connected. The purpose of the carrier delay timer on a repeater is to eliminate the repeater's transmitter from chattering on and off when the repeater's receiver is receiving a noisy, choppy signal. In the early days when all the repeaters were based on vacuum tubes and used mechanical relays this timer saved much wear and tear on those relays. Todays solid state repeaters do not have this issue, but a chattering transmitter combined with an already choppy fluttering signal into a repeater is even more difficult to hear. Another purpose for the carrier delay is for testing. You can "kerchunk" (key your radio into a repeater momentarily) and monitor its signal level coming back to you until thecarrier delay times out.

Cavity filter - see this page, part way down.

CCT - Carrier Control Timer (this term is used mostly in GE documentation). Also known as the time-out timer in th emobile radio. When the driver sits on his microphone this timer saves the mobile transmitter from meltdown and frees up the channel.

CDMA - code-division multiple access

CDPD - cellular digital packet data

CG - GEs abbreviation for CTCSS, called Channel Guard. Also trademarked.

Channel - This refers to to the channel on the radio that you use or ... (see Channel Pair)

Channel Busy - see COR

Channel Guard - General Electric's trademarked name for CTCSS

Channel pair - A repeater uses a pair of frequencies, one to listen on, one to transmit on (simultaneously). Frequently a repeater channels/frequencies are also referred to as a channel pair.

Chicken-Burst - this was the derogatory name given to RCA and GE for their patent-infringement-avoiding version of reverse-burst... where that Motorola patented design slammed the reed to a stop (which closed the squelch instantly) the RCA and GE method just turned off the tone, and kept the transmitter on for a quarter to half second. The reed coasted to a stop and the squelch closed. The end result was a longer burst of noise than the Motorola "reverse burst". After the Motorola patent expired GE "invented" Squelch Tail Elimination (STE), a total copy of reverse burst, but by then RCA was history.

CMOS - complementary metal oxide semiconductor

Coax - Coaxial cable. An unbalanced transmission line in which one conductor is a wire in the center of a dielectric with a circular cross section. The dielectric is surrounded by a tubular conductor, often made of flexible braid covered with a protective insulating outer jacket.

COR - "Carrier Operated Relay" A relay that is usually derived from the squelch circuit of a receiver signaling the presence of a signal at the receiver.This signal tells the repeater controller when a valid signal is present. See squelch circuit.

COS - "Carrier Operated Signal", "Carrier Operated Squelch" or "Carrier Operated Switch" is a relayless version of the COR. It's a digital signal that switched between two logic levels (usually +5v and ground). See squelch circuit.

From Ric Sohl   KK5RIC .... So What's the COR or COS??
The Carrier Operated Switch used to be called COR.... Short for Carrier Operated Relay. This is going back to the early days of repeaters in which all the repeaters had tubes in them, and all circuit switching was done by relays. Nowadays most of the repeaters are solid state, except for a few which have tubes in the final amplifier, so now we call it COS or "Channel Busy" (CB) or Receiver UnSquelched (RUS)...
So you ask how does it work and what's the purpose, and were can I find this COS on a receiver? The function of the carrier operated switch is to tell the repeater controller, if the repeater has one, that the receiver squelch is open, and that there is a signal there. If the controller is set up for Carrier Squelch (CSQ) it then turns on and off the repeater transmitter. If the repeater does not have a controller, the COS simply does the function of turning on and off the transmitter. The COS signal can be either a set of relay contacts or a voltage that swings high or low to give either a + voltage or ground with the receiver active, (noise or a signal.) On some receivers the COS uses a relay and that has a dry contact to ground, and you won't see a swinging voltage, a 5k or so pullup resistor connected either +5 volts, +12 volts or +24 volts (whatever the circuitry requires), makes the COS voltage swing. The squelch circuit rectifies the hissing noise, its the noise that we hear when the squelch is open and no signal is present on the FM receiver. Sometimes this noise is amplified and is applied to diodes to converted to a dc voltage, some other times to a voltage doubler to get a greater level of swinging voltage. That voltage is compared to the squelch pot and if it's greater the squelch stays closed, if it's less the squelch opens. There's another way to get a COS voltage from a receiver, that is with a VOX circuit on the receiver audio output, it does not work properly on a repeater, (if someone has a full quieting signal and there is a pause in the speech the VOX closes) so I won't go in detail with it here. Some AM receivers have COS's also.. not just the FM ones, the major difference between the two are the FM receivers the COS and squelch works much better and is harder to be fooled by noise....by the way, airports with towers use AM receivers with COS. The COS squelch circuit has been used in repeater receivers for years, long before the tone squelch came to be very popular. Manufacturers paid special attention to the squelch circuits in their receivers, Motorola even made a special squelch IC for their MICOR series radios.

Courtesy Beep - An audible indication that the repeater is clear and you may go ahead and transmit. This beep occurs after the squench tail and before the repeater transmitter drops out.

Courtesy Tone - see courtesy beep.

CTCSS - "Continuous Tone Coded Squelch System" CTCSS is a series of sub-audible tones which are standard on most new radios. An audible cousin of CTCSS is DTMF. These tones often perform control functions. Some repeaters may require a sub-audible tone before activating, others use it to perform functions such as turning all trunks on and off when a specific tone is present. (Also see: Tone Squelch, CG, ETS, PL, TOS)

COR / COS - A signal from the repater receiver to the repeater controller saying that there is a carrier on the receiver frequency. The controller may AND this signal with one from the subaudible decoder, or it may key up the repeater transmitter on carrier alone. A COR generally has a relay in it, a COS circuit is relayless.

CSU - channel service unit

CPE - customer premises equipment

CTCSS - Continuous Tone Coded Squelch System. This is the process by which a radio signal is transmitted containing a sub-audible tone. Only a receiver that is set up to detect the tone will un-mute its receiver. Using CTCSS is a way of limiting what you hear to only what you want to hear on the frequency you are using. The tones range from 67 to about 200 Hz.

DC - direct current

DCS - distributed communications system

DCS - Digital Coded Squelch. This is similar to CTCSS above but uses a digital signal rather than an analog signal.

DCT - digital cordless telephone

Deaf (receiver) - A receiver that requires more than 1/3 uV or more signal.

De-emphasis - The reduction in audio level in the audio circuits of a receiver at the rate of 6 dB per octave. The increase of level applied at the TX end assists in overcoming noise appearing in the higher frequencies of the audio bandpass.

Dense - An FM operator that refuses to learn proper operating procedures.

Desense - soft for "Desensitzation" - A problem characteristic of many radio receivers in which a strong RF signal overloads the receiver, reducing sensitivity.

Deviation - the act of pushing a transmitter off center frequency at an audio rate. See "Modulation"

Dipole - An antenna often, but not always, center fed with two halves along the same line. Often refers to an antenna with a length equal to half an electrical wavelength. Often a reference antenna and also used as an element of multielement arrays.

Direct - When both persons or a group of persons talk on one radio channel to each other rather than using a repeater they are said to be talking direct. Also called Simplex or Talk Around.

DDS - direct digital synthesis

DECT - digital european cordless telephone

The Dog...A repeater that keeps on breaking down, sometimes once a week.

Doubling - two or more stations transmitting simultaneously on the same channel. Sometimes the one with the strongest carrier wins, other times it's just grunge.

Downlink - The radio signal which carries information from the satellite to the satellite terminal. Can also be used to describe the signal from the repeater to the users.

DPL - Digital Private Line. Motorola's trademarked acronym for DCS.

DSP - digital signal processor

Drop Out Timer - see Carrier Delay.

DTMF - the Bell System developed the Touchtone system for dialing, and trademarked it. Someone came up with "Dual Tone, MultiFrequency"to avoid trademark infringement. It is simply a set of dual audible tones used for remote command and control of equipment. Always identify yourselfand your intent when transmitting DTMF.

Duplexer - The magic filtering device that a high level of isolation between two frequencies and allows a repeater to simultaneously transmit and receive at the same time on one antenna.

DUT - device under test

EDA - electronic design automation

EDGE - enhanced data for global evolution

EIA - electronics industry association

EM - electromagnetic

EMC - electromagnetic compatibility

EMI - electromagnetic interference

ESD - electrostatic discharge

Estate - yet another name for the repeater site, the highest building in the city or a mountain top.

ETS - "Electronic Tone Squelch" is the Canadian Marconi Company name for CTCSS, CG, Tone Squelch and PL. "ETS is a series of sub-audible tones which hasthe ability of performing control functions".

EZNEC - Proprietary software program that performs analysis of antenna systems based on the Numerical Electromagnetic Code (NEC) antenna modeling engine. There are a number of ver- sions available from www.eznec.com, including a reduced size free trial version. Many of the antenna pattern plots used in QST articles are generated using EZNEC.

FA - failure analysis

FET - field-effect transistor

FM (frequency modulation) - An operating mode commonly used on Land Mobile Radio.

Frequency Coordinator - an individual or group responsible for assigning frequencies in an area. Usually an unappreciated, overworked volunteer who gets blamed for everything.

FSK - frequency shift keying

FTAGH - Free To A Good Home - for the good stuff that you can't stand tossing in the trash.

Full Duplex - Radio communication using two frequencies simultaneously (one for receive, one for transmit)

Function Code - the DTMF sequence that does something. *808 might be a forced ID.

GaAs - gallium arsenide

GaN - gallium nitride

Geostationary - Describes the orbit position that causes the satellite to appear as if it is stationary to observers on earth. It appears this way because the orbit period of the satellite is the same as the daily rotational period of the earth.

GFSK - gaussian filtered frequency shift keying

GM300 - Motorola trademark name for a family of commercial radios that can be used on GMRS, ham and commercial frequencies among others. Other members of the product line were the M10, M120 and M130. About the size of a CB radio, usually underdash. A follow-on to the Radius product line.

GMSK - gaussian minimum shift-keying

GPIB - general-purpose interface bus, also known as HPIB

GPRS - general packet radio service

GSM - Global System for Mobile Communications is an algorithm and standardized method of voice coding and decoding used in digital equipment to handle analog signals (like a voice). For example, a voice IDer may use GSM to to store the audio signal in a digital memory chip. Some ROIP systems use GSM on-the-fly to encode and decode the audio at each end of the digital link. GSM is one of the methods used in cellphones. Another method of voice coding and decoding is ADPCM or PCM.

HT - An acronym for Handie-Talkie or hand-held radio

Half Duplex - Radio communication using two frequencies sequentially (one for receive, one for transmit). In this mode the receiver is muted while PTT is pressed.
See also: Yackaholic

Hand-held - The same as HT, walkie-talkie, portable hand held radio.

Hang-In Timer - another name for Carrier Delay.

Harmonic - A signal occurring at some integral multiple of a fundamental frequency.

HBT - heterojunction bipolar transistor

HCI - host controller interface

HDR - high data rate

Heliax - A trademarked term (by Andrew Corp) for their corrugated, semi-flexible, solid copper shielded coaxial cable with very low loss and very long life characteristics that is used to connect a repeater or base radio to an antenna. It is highly preferred over standard coaxial cable because of the low insertion loss. A "slang" term frequently (but incorrectly) used is "hard-line", but real hardline is based on a tubular pipe, not a corrugated semi-flexible feedline.

HEMT - high electron mobility transistor

HF - High frequency. That portion of the radio spectrum between 3 and 30 MHz. Often called short waves, these frequencies are characterized by long range propagation via ionospheric refraction.

HSCSD - high-speed circuit-switched data

I/O - input/output

IC - integrated circuit

IEC - International Electrotechnical Commission

IF - intermediate frequency

IM or Intermod - a contraction of "Intermodulation" an often misused term that has become a generic terms used to describe just about any type of receiver interference. Like Klenex has become the name for any brand of facial tissue. Intermod is a very specific type of phenomenon and for accuracy, should only be used to describe intermodulation issues and not mixes, adjacent channel interference, etc.

IMD - intermodulation distortion

Input Frequency - Commonly term for the frequency you use when transmitting to a repeater; sometimes called the uplink frequency.
Intermodulation - is the creation of a new frequency by mixing 2 or more >other frequencies. This mixing only takes place in either the Receiver, Transmitter or other connecting devices.

IR - infrared

ISDN - Integrated Services Digital Network, is a digital telephone connection that uses digital signals instead of analog signals to handle the transfer of signaling and speech. ISDN delivered two voice-quality lines at 64 kbit/s as well as a separate 16 kbit/s circuit for data - it is basically two channels of a T1 link plus a little bit of additional bandwidth for a control channel. It was more popular in Europe than in the USA and ISDN has largely been replaced with digital subscriber line (DSL) systems of much higher performance.
Two humorous translations of ISDN are "I Still Don't Know", and "Innovations Subscribers Don't Need".

ISM - industrial, scientific medical

IT - information technology

Jug...A cavity filter used to eliminate unwanted or clean up signals in a repeater... Moto's early ones resembled seltzer bottles.

Kerchunk Box...A repeater without a real controller, usually just a COS, a Carrier Delay timer, a timeout timer, and a morse ID.

Linking system - The linking system refers to the dedicated point-to-point radio links between repeaters on a network. These dedicated radios talk only to other link radios and usually have beam antennas on both ends, or sometimes if multiple links terminate at one site there will be a gain vertical at that site. One should not access the network via a link radio. (Also see: Trunk)

LDMOS - laterally diffused metal oxide silicon

LMDS - local multipoint distribution service

LNA - low-noise amplifier

LO - local oscillator

LOS - Line Of Sight or Loss Of Signal

LPF - low-pass filter

LSI - large scale integration

LTR - Logic Trunked Radio - an analog trunking system developed by E. F. Johnson company. Uniden made a lot of LTR radios, along with Motorola, Kenwood and Icom LMR. The big advantage of LTR is that the is no control channel, and the majority of controllers made by Zetron, CSI and Trident allowed the gradual migration of regular and community repeaters into LTR trunking systems. And a single channel LTR "system" was possible with up to 200 talk groups / user groups.

Machine - Ham slang for radio repeater.

Mast - The pole on which antennas are typically mounted. The one that bends if the wind speed exceeds the side-load of the mast.

MaxTrac - Motorola trademark name for a series of commercial quality radios that can be used on used on GMRS, ham and commercial frequencies among others. About the size of a CB radio. It followed the Motrac / Motran series.

MDS - multipoint distribution systems

MMDS - multichannel multipoint distribution service

MMIC - monolithic microwave integrated circuit

Monopole - Single vertical antenna element, typically a quarter or more wavelengths long. Often used as a transmit and receive antenna, singly or in combination with other similar antennas. Radiation resistance - Portion of antennas’ input impedance that results in transfer of electrical signal into a radiated electromagnetic wave. In general, the higher the radiation resistance, the higher the efficiency will be.

Mount - The hardware used to attach the antenna to the car body, mounting pole or tower.

Mobile - using radios in a car, truck, bicycle, or on foot.

Mobile unit number - Some GMRS licensees adopt mobile unit identifiers for use on repeaters or on simplex. This is in addition to their FCC assigned call signs.

MOSFET - metal-oxide semiconductor field-effect transistor

MOU - Memorandum Of Understanding, a legal document.

Mountain top - A reference to the location of a repeater antenna. It means literally what it says. Refers to a flat area at the top of a mountain where a radio repeater site might be located.

MTBF - mean time between failures

NTC - negative temperature coefficient

Octave - An Octave when referring to frequency is that point when the frequency is doubled. Every time we double the frequency, we increase it by 1 octave.

OEM - original equipment manufacturer

Offset - When referred to as a Repeater Frequency variable, it is the >standard frequency step needed to work a duplex repeater; the repeater receiver frequency. Each band has its own standard "offset", for example 5 MHz on the USA UHF (440 MHz) band.

Output - When referred to as a Repeater Frequency, it is a frequency which a repeater transmits on.

PA - power amplifier

PC - personal computer

PCB - printed circuit board

PCM - Pulse Code Modulation, is a form of voice coding and decoding algorithm used in digital equipment to handle analog signals (like a voice). For example, a voice IDer may use PCM to to store the audio signal in a digital memory chip. Some ROIP systems use PCM to encode and decode the audio at each end of the digital link. Another method of voice coding and decoding is ADPCM or GSM.

PCS - personal communications system

PDA - personal digital assistant

PDC - pacific digital cellular

PIM - personal information management

PL - an abbreviation for Private Line, Motorolas trademark for CTCSS or tone squelch. PL is a series of sub-audible tones which has the ability to perform control functions. (Also see: Tone Squelch, CTCSS and ETS)

PLL - phase-locked loop

Port - when referred to as a Repeater Port, it identifies a radio, serial data (COM), phone patch or other I/O option on the repeater.

Portable - Carrying radio with you, or refers to a packset or hand held radio.

Power Supply - A direct current supply that powers radios.

PPM - parts per million

From Kevin Custer W3KKC:

Precipitation Static This phenomena exists when a charged cloud is near, and an aurora is formed around the antenna. As the static is built up on the antenna, receiver desensitization occurs.

Private Line - Motorola's trademarked term for CTCSS

PSK - phase shift keying

PSTN - Public Switched Telephone Network, which refers to the international telephone system based on copper wires and switched circuits for carrying analog voice data.

PTFE - polytetrafluoroethylene

PTT - Push-to-Talk, A signal to a radio transmitter, which controls the actual transmission of radio frequency energy over the air. Historically the name comes from the Push-To-Talk button on the side of a microphone.

QoS - quality of service

QPSK - quadrature phase shift keying

Quarter Wave - An antenna typically seen on vehicles, about 9 feet on 10 meters, about 50 inches on 6 meters, about 15-18 inches on high band, and six inches on ham UHF.

Quieting - When referring to signal reports, quieting pertains to the amount of limiter quieting in an FM receiver. A full-quieting signal would be one that completely eliminates all background noise from the receiver.

Radio Technician - A frequently sought after individual who understands the inner workings, hidden mechanisms, and theory behind the operation of radio systems. Sometimes called a magician. Often called upon to build, fix, or install radio systems. Usually misunderstood, unappreciated, underpaid and overworked.

Radius - Motorola trademark name for a series of commercial quality radios that can be used on used on ham, GMRS and commercial frequencies. About the size of a CB radio, usually underdash. A follow-on to the MaxTrac.

The radio shop - The place of business of the radio tech.

Repeater - A radio transmitter and a receiver station usually located at a high place that receives a signal on one frequency and simultaneously transmits it as received on another frequency. It is almost always a full duplex device. By using a repeater a low power portable radio can retransmit a signal over a larger area. The benefit is that people can carry smaller radios and communicate with one another over a wide geographical area, a city, a county, or a region.

Repeater Network - The connecting of 2 or more repeaters which will usually increase the "footprint" or a common user area or diversify frequencies or bands.

Reset - As pertaining to the "Repeater User Codes", it means to turn the repeater controller to its normal state of operation.

Reverse Autopatch - the capability of some phone patches to initiate a call from a phone, out to a repeater user via dialing into the repeater autopatch.

From Rick Sohl - KK5RIC:
Reverse Burst was used in the Olden Golden days of yore, when we used mechanical tuned reeds to decode and encode CTCSS tones. The decode reeds would keep the squelch open as they coasted to a stop and the radio would be on open squelch, and you would hear the noise squelch close with a shorter "sssssshhhhh" sound than if it was carrier squelch. When the user released the PTT button the reverse burst circuitry kept the transmitter on for bit and turned the CTCSS tone around 180 degrees. This out-of-phase tone caused the decode reed to slam to a stop, causing the receiver squelch to instantly mute before the user heard any squelch noise. "Ker-Chunk".

Reverse Split - Operating duplex on a reverse frequency split compared to what is considered "normal" for the situation.

RFI - radio frequency interference

RFIC - radio frequency integrated circuit

RG-(some number) - Many coaxial cables are standardized with an "RG" number, for example RG-8, or RG-58.

RoIP - Radio over Internet Protocol, (compared to VoIP) not only converts voice to a digital format that can be sent over the Internet or another IP based network, but also convert PTT and COR control signals that are essential for seamless for radio interoperability. Also include are extra delay and jitter compensation.

ROIP Gateway - a device used to connect a land mobile radio device to another device over an IP-based network. The unit creates a network link that passes both voice and control signals either one direction (a one-way link) or both directions (a full duplex link).

ROM - read-only memory

RSSI - received signal strength indicator

RTT - radio transmitter technologies

Rubber Duck - A small, flexible, short, inefficient antenna used on hand held radios.

RUS - a logic signal that takes into account the presence or absence of a carrier signal, the presence or abscence of any CTCSS tone, and the position opf the CTCSS switch (in tone mode or in carrier mode). When active the signal indicates that the receiver audio is unmuted.

SA - Spectrum Analyzer

SAREX - "Shuttle Amateur Radio Experiment" An educational program in which the space Shuttle Astronauts communicate with amateurs and schools using voice and packet.

SD - sigma delta

SDH - synchronous digital hierarchy

SFDR - spurious-free dynamic range

Simplex - two units communicating direct on the same frequency. Also see Direct.

Site - "The site" often refers to the location of something like a repeater building.

SMD - surface mount device

SMS - short messaging service

SMT - surface-mount technology or surface-mount toroidal

SNR - signal-to-noise ratio

SONET - synchronous optical network

SPDT - single-pole double-throw - a type of switch.

Spectrum - A term used to describe a range of frequencies.

SPST - single-pole double-throw - a type of switch.

Squelch - The squelch control or circuits of a radio "squelch" or make quiet the noise a radio receives when a radio signal is not present on the radio channel. The radio is un-squelched when a signal is received.

Squelch circuit - All receivers have a section, called a "noise operated squelch circuit", or squelch for short. The squelch circuit samples the white noise that is on channel, and goes away when there is a signal. This section generates a DC voltage that is compared to the position of the squelch control and switches a voltage on or off when the receiver hears a carrier signal. This voltage is used to mute the speaker when there is no signal, and unmutes it when there is a signal, sometimes in concert with a tone decoder (see CTCSS). This voltage can also feed a output signal driver (COS) or a relay driver (COR). Either way, the control signal is fed to a repeater controller or in the tube days the COR contacts would key the transmitter in a repeater. By adding a large capacitor on the relay coil circuit you could add a carrier delay that keept the transmitter keyed when the receiver was receiving a weak signal that was fluttering or dropping out.

Squelch Tail - The short burst of white noise heard on an FM receiver between the time a signal ceases to be received and the squelch circuit actually mutes the audio output (the speaker audio). This term is often confused with the "carrier delay", "hang time" or "drop out delay" with respect to a repeater. When you're monitoring a repeater and the person talking into the repeater un-keys his transmitter, the short burst of white noise (rushing sound) you hear is the squelch tail from the repeater's receiver. Then, the repeater's transmitter remains keyed anywhere between 1/2 second and 5 seconds, in other words its transmitter "hangs" on during the "carrier delay" before it "drops out", this is what's known as the hang time or drop out delay. Some repeaters insert a beep or other type of tone or multiple tones during the hang time. This tone or tones can be a "courtesy tone" or it can be telemetry signaling that certain links or other devices are connected. At the end of this time when the repeater's transmitter un-keys, you will hear a squelch tail from your radio's receiver. When operating simplex with another station, every time the station(s) transmitting to you un-keys, you will hear a squelch tail from your receiver.

Squelch Threshold - The signal level at which a receiver squelch is broken. Frequently the squelch open theshold is lower than the squelch close threshold.

SSB - single sideband

SSPA - solid state power amplifiers

STE = GE's implementation of reverse-burst, called Squelch Tail Elemination.

Stubby - A slang term for a small rubber duck antenna. Generally, stubby antennas are a tradeoff - the shorter ones have a lower radiation efficiency.
See also "Tiger-tail".

SWR - Standing wave ratio. Measure of how well a load, such as an antenna, is matched to the design impedance of a transmission line. An SWR of 1 - 1 indicates a perfect match. Coaxial cables, depending on length, type and frequency can often work efficiently with an SWR of 3:1, sometimes higher. Solid state transmitters frequently require an SWR of 2:1 or less for proper operation.

Talk-Around - Same as direct or simplex except you are doing so on a repeater output frequency. Comes from the concept of "talking around" the repeater.

TCP - Transport Control Protocol is an additional layer on top of the Internet Protocol, which ensures delivery of packets, sent across the network. It can handle situations such as lost packets or packets arriving out of order.

TCXO - temperature-compensated crystal oscillator

TDD - time division duplex

TDMA - time-division multiple access

TETRA - Trans European Trunked Radio

TIA - Telecommunications Industry Association

The hill - A slang expression referring to a high location which could even be a mountain! See "Site".

Tiger Tail - An add-on to a handheld antenna to increase the radiation efficiency.
See: https://w3atb.com/tiger-tail-antenna
and: https://paratusradio.com/2020/08/building-the-tiger-tail

Time-out timer - A function of a repeater controller that limits the amount of time the transmitter will remain keyed with out a pause. Typically the timers are set to between 3 and 5 minutes. (Also see: Alligator)

Tone - Refers to CTCSS and sometimes DCS.

Tone Decoder - Depending on the usage it could be a circuit that senses the proper tone (or tone pair if DTMF) and changes a voltage level for the duration of the tone / tone pair, or it could be the tone decoder circuit that feeds some accociated circuitry to decode a function.
See Function Code.

Tone Squelch - Is a generic name for many "Sub-audible tone systems". The principle is that a receiver will not allow any audio to be routed to the speaker (or repeater transmitter) unless it is accompanied by the appropriate sub-audible tone. (Also see - CTCSS, ETS and PL)

TOR - Tone Operated Relay - a relay operated by the CTCSS decoder. GE had a TOR board for their stations.

TOS - Tone Operated Squelch - another name for CTCSS or Tone Squelch.

TOT - see Time out timer

Tower - Antennas are mounted on towers.

Trunk - Picture a star-based linked repeater system with VHF repaters and a 220 hub. The dedicated 220 link channel from the VHF repeater to the hub is sometimes called a trunk channel. trunking radios. One should not access the network via a trunk link channel. (Also see: Link)

TTL - transistor -transistor logic

UDP - user datagram protocol

UHF - "Ultra High Frequencies" - Radio frequencies from 300 to 3000 MHz.

UMTS - universal mobile telecommunications service

Uplink - Referring to Earth /Satellite communications, it is that portion that brings traffic from earth to the satellite. In repeater communications, it's the user-to-repeater frequency (the repeater receiver frequency).

UTRA - UMTS terrestrial radio access

UWC - universal wireless consortium

VCO - voltage-controlled oscillator

VCXO - voltage-controlled crystal oscillator

VHF - "Very High Frequency" Radio frequencies from 30 to 300 MHz.

VOCODER - Voice Coder / Decoder, is an algorithm use by VOIP and ROIP systems that reduces speech signals to digital signals transmittable over TCP/IP networks to conserve network bandwidth.

VOFDM - vector orthogonal frequency division multiplexing

VoIP - Voice over Internet Protocol is a method of sending voice communications across a digital network.

VSAT - very small aperture terminal (satellite service)

VSWR - voltage standing wave ratio

WAP - wireless application protocol

Watt - The measure of electrical power, in radio is usually is the output for a radio transmitter, it can also be the AC power input.

WASP - wireless application service provider

WISP - wireless internet service provider

W-CDMA - wideband code-division multiple access

WLAN - wireless local area network

Yackaholic - a pejorative or derogatory term to describe people that are always talking and never listening or refuse to learn.
See also "Half-Duplex".

THE R-S-T SYSTEM

The R S T system of signal reporting is an internationally recognized
method of reporting signal quality. The "R" stands for readability, the
"S" for signal strength, and "T" for tone in CW.

Readability
1 - Unreadable
2 - Barely readable, occasional words distinguishable
3 - Readable with considerable difficulty
4 - Readable with practically no difficulty
5 - Perfectly readable

Signal Strength
1 - Faint signal, barely perceptible
2 - Very weak signal
3 - Weak signal
4 - Fair signal
5 - Fairly good signal
6 - Good signal
7 - Moderately strong signal
8 - Strong signal
9 - Extremely strong signal

Tone (only on a morse code contact)
1 - Sixty cycle a.c. or less, very rough and broad
2 - Very rough a.c., very harsh and broad
3 - Rough a.c. tone, rectified but not filtered
4 - Rough note, some traces of filtering
5 - Filtered rectified a.c. but strongly rippled modulated
6 - Filtered tone, definite trace of ripple modulated
7 - Near pure tone, trace of ripple modulation
8 - Near perfect tone, slight trace of modulation
9 - Perfect tone, no trace of ripple or modulation

If you give a signal report of 5-by-9, you are indicating that the signal is extremely strong.

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors. All Rights Reserved, including that of paper and web publication elsewhere.