A-index / A index / A_P-index

See

absorption

• Intake or assimilation (acceptance, unlike either or passing through) of by the or other object
• Rate or amount of deposited in the human body as a result of exposure

AC

alternating current : electric charge flow () that periodically reverses direction; see also

AC coupling

See

ACDS

automatically controlled digital station : unattended that communicates primarily in , similar to a , and typically on ; see also

AC line noise / AC line interference

See

AC power

See

AC power line / AC line

See

across the pond

Slang for the other side of the ocean or across the ocean (typically the Atlantic, and often between the US and the UK, but not necessarily)
We might need to start sending across the pond again

ACSSB

amplitude-companded single-sideband : narrowband technique that uses to compresses an signal and it with a pilot signal prior to transmission, then expand (decompress) the signal during reception, using the pilot signal as a reference, which improves the effective audio range of the signal; see also

activation

Act of alerting, intiating, mobilizing, and setting in motion a trained service (such as and ) to provide their services in a timely manner

active element

See

active power

See

adaptive filter

used in to remove unwanted from a received signal; see also

ADC

admittance

Quantity of allowance for flow in a circuit, expressed in siemens (symbol S) and defined as the reciprocal of , such that Y = G + jB, in which Y is the admittance, G is the real , j is the imaginary unit, and B is the see also

aerial

AF

affirmative / affirm

yes; see also

AFSK

audio frequency-shift keying : type of in which digital is represented by changes in the frequency (pitch) of an tone (typically from a sound card) to shift the of the transmitted (typically ) signal; see also and

again

repeat it : request to repeat a or other identifying information
Again? (please repeat that)
Again, again? (please repeat that at least two more times)

AGC

AGM absorbed glass mat : type of whose acid electrolyte is held in fiberglass mesh mats that surround conductive lead plates, and often used in radio as electric storage; see also

AIP

advanced intercept point : feature introduced by , in which the can be manually adjusted, to help extend its while reducing both nearby signal and

air waves

Slang for organized or in general; see also and and
You should announce that over the air waves

A_L / AL

See

ALC

ALE

alien

• Person residing in the US, but is not a US citizen (also called a resident alien)
• Person living within the borders of a country, but is not a citizen of that country; see also

alien reciprocal operation

See

alkaline Most popular type of non-rechargeable battery (there are some rechargeable ones, too) that offers a higher energy density and longer shelf life than do carbon-zinc batteries, but at a higher cost; see also

alkaline batteries

alligator

Slang for a , especially a , that seems to transmit farther than it could receive a signal (think big mouth, little ears); see also

AllStar

Software-based system that radio around the world through your cell phone or other computing device using Voice over IP; see also and the

alpha

parameter (also known as common-base current gain, symbol α) defined as the change in collector with respect to emitter current; see also and

alphabet

See

altazimuth

See

AM

• Nickname (also called AM broadcast and AM band) for the portion of the that is dedicated to , which in the US spans 530 kHz to 1700 kHz, using 10 kHz spacing; see also

amateur

• Person who is to a for communication within the spectrum, often synonymous with ; i.e., a ham operator
• Practitioner, hobbyist, or promoter who is not paid for performing a particular service

Amateur Auxiliary

American radio organization consisting at one time, of and now , and operated by the , working in conjunction with the to in the US to help self-police their compliance with rules; see also and

Amateur Extra

Highest level radio obtainable in the US and some other countries, whose privileges cover all of all , and that certifies the as one having a much greater understanding of regulations, operating practices, and electronics than that of a class licensee; see also

amateur radio

Type of operation, distinguished from , , and radio, and implies that the is not paid for radio services; often synonymous with radio; see also and

amateur radio club

Organized group of people (also called amateur radio society) who have (at least) as a common interest, whether or not the individuals are (because, for example, they're related to a ham or know one); see also ham radio clubs and ARRL-affiliated club search

Amateur Radio Emergency Service Corps of trained volunteers organized to assist in public service and ; see also and

amateur radio satellite

placed in orbit to serve (at least) purposes; see also and

Amateur Radio Service

See

amateur radio society

See

amateur radio station

See

ammeter Instrument that measures electric by connecting it in series with the circuit, and is usually one of the functions found in a ; see also

DC ammeter

amp

• Short or abbreviation for
  There are 2 amps flowing through that
• Short for
  My amp is starting to get warm

ampere / amperes

See

amplifier

• Device or circuit that outputs a signal that is identical to, but increased in intensity of, its input signal, the ratio of its output to input strength referred to as the amplifier , expressed in ; see also
• See

amplitude modulation Method of combining an information signal (your , , packets, etc.) with an signal of constant (the ), so that the amplitude of the output signal varies with the information signal; see also and

AM waveform © HamRadioSchool.com

AM spectrum

AMSAT

organization (officially Radio Amateur Satellite Corporation) that designs, builds, arranges launches for, controls, and maintains satellites with payloads, including the series of satellites; see also

AMTOR

amateur teleprinting over radio : once fast-growing and pioneering transmission that was an improvement over by using , , and , but is rarely used today; see also and

analog / analogue

Type of circuit or signal whose operational levels vary continuously with time, such as that of an (op-amp); see also

analog-to-digital converter

Device or circuit that converts an signal to a digital one by creating a digital value that represents each amplitude; see also

analyzer

See

ANCS

assistant net control station : the or person who assists the with control responsibilities

Anderson connector

See

Andrew coax / Andrew cable / Andrew Heliax

See

ANF

automatic notch filter : circuit that, when enabled, performs the function of a by removing (filtering out) any continuous signal that might be present in the

angle modulation

Process of varying () the phase angle of a sinusoidal wave to transmit information, of which and are two types; see also

angle of radiation

Angle (often called takeoff angle), with respect to level , of the strongest or average field delivered from an ; see also

ANL

anode

Positive terminal or of a device or component, into which flows; see also (and )

ANT

antenna Device that converts electrical into and vice versa; a piece of equipment by which radio waves are transmitted and / or received; see also Some antenna types and Some antenna categories Criteria antennas

ham radio antenna

antenna symbol

antenna analyzer Device that measures and characteristics, such as , (), and ; see also

antenna analyzer

antenna array Multiple installed or configured so that the combination results in a unit that exhibits greater and than each might otherwise realize on its own; see also

antenna array

antenna coupler

See

antenna current

See

antenna efficiency

Ratio of the total power radiated by an with respect to the net power input to the antenna, equal to the ratio of the antenna's to its total (ohmic plus radiation) resistance, often expressed in or as a percentage; see also

antenna element

See

antenna farm Location dedicated to the placement of (usually many) and TV ; see also Geographical location, with established boundaries, in which structures with a common impact on aviation may be grouped, as defined by of the rules, ; see also ; of the same Part

antenna farm of JH4UYB

antenna feed

See

antenna gain

See

antenna match Device or circuit that modifies () the of the to that of the and / or by presenting a complex conjugate of the antenna impedance, and often achieved by an ; see also

antenna (gamma) match

antenna mount

Device used to connect or install an to a fixture, such as a , a building, or a vehicle, and includes such types as and

antenna party

Event in which gather to help another ham erect an , especially a or large

antenna pattern

See

antenna rotator / antenna rotor Device that changes the aim of a by rotating the assembly; see also

antenna rotator

antenna rotator controller / antenna rotator control unit / antenna rotor controller Electrical device that changes the aim of a by sending signals to a attached to the assembly

antenna rotator controller

antenna switch Device (also called coax switch and antenna selector) that allows connection between the and that for any one of several , or between an antenna and one of several transceivers

antenna switch

antenna system

Collection of components and interconnected devices that support the delivery and conversion of an electrical signal into an field, or reception of an RF field, for conversion into an electrical signal, often including but not limited to a , , (including , , and ), , , , , and associated (can also include a and an meter, but does not typically include an or )

antenna tower Self-supporting structure used to support one or more , and/or other equipment; see also

beam antenna atop an antenna tower

antenna trap

See

antenna tuner Device (also known as an antenna tuning unit or antenna coupler or feedline coupler or matchbox or transmatch) that the of the system with that of the to maximize transfer from the transmitter to the antenna; see also and

(manual) antenna tuner

antennae

Outdated plural for ; more than one antenna

anti-aliasing filter / anti-alias filter

circuit that prevents or reduces the (usually) undesirable effect known as aliasing, which is the construction of a false (an alias) signal from a sample of the original signal, usually the result of under-sampling; see also and

apparent power

See

appliance operator

• Typically derogatory term for an operator who possesses little desire to , tinker with, or repair equipment, or one who has little desire to increase understanding of internal radio equipment operation or radio theory; so-called because the person is content with operating a piece of equipment that has been purchased (appliance) to perform a specific function, with little desire to understand more about the equipment and the than what the examination had required
• operator who frequently relies on others to configure or repair equipment because of unfamiliarity with the controls or settings necessary to perform satisfactorily

APRS

: digital communication ( radio) for exchanging information among a large number of radio covering a relatively large area; see also and

AR

for the end, to indicate the end of a formal message; see also

ARC

arcing / electric arcing Electrical breakdown of one or more gases to produce a plasma discharge, caused by electric current flowing through air, which is normally non-conductive; at one time called voltaic arcing; see also Note: arcing can also occur in a vacuum, but vacuum arcing is due to a slightly different set of circumstances

arcing between wires

lightning, a form of arcing

ARDF

AREDN

ARES

ARISS

Amateur Radio on the International Space Station : program that allows radio on earth to communicate with astronauts aboard the for educational purposes; see also

ARL number

See

ARQ

automatic repeat request or automatic repeat query : technique for controlling transmission errors by requesting a re-transmission of the same data; see also

array

See

arrester / arrestor

See

ARRL American Radio Relay League : non-profit association of enthusiasts, and the primary representative organization of amateur radio to the US government; see also

ARRL radiogram number

Shorthand code (abbreviated ARL number) used in composing formal written ARRL radiograms, as part of the program; see also

ARRL Section Any one of the American and Canadian geographic areas, as defined and designated by the ; see also and

ARS

artificial ground Device or circuit that presents an reference or in the absence of an actual connection, to allow an to be above ground level (such as on a tower or multi-story apartment building), for example Device or circuit (also known as a virtual ground) that maintains a reference at a specific point in the circuit without being directly connected to the actual point; see also

artificial ground

ARTS

Auto-Range Transponder System : automatic polling and reporting system in which multiple communicate with each other through a (handshake) that helps one transceiver determine whether other similarly equipped transceivers are located, within a predefined physical proximity sufficient for reliable communication, found primarily in transceivers, but supported in Motorola, TYT, and other radio makes as well

ASCII

American Standard Code for Information Interchange : seven- or eight-bit code for representing text characters in computers, text-based communication equipment, and transmissions; see also

ASK amplitude-shift keying : low-rate transmission that combines with ; see also

astable multivibrator

Circuit whose signal continuously alternates between two states without an external clock (also known as an ) and can itself function as a clock circuit; see also

atmospheric noise

Radio noise that originates from natural atmospheric processes, primarily lightning discharges in thunderstorms; see also and

ATS automatic transfer switch : electrical device that automatically the path of electrical from one (typically ) to another (such as or generator) without manual intervention; see also

attenuation / attenuate

or reduction of signal strength; see also

ATU

ATV

amateur television : video and (, also known as fast-scan television) transmissions made on , usually on the , , and , in that order by popularity; see also and

audio

• Audible () sound, which is and by one , then and by another, to reproduce the audible sound
  A is well-suited for demodulating signals to generate the audio
• Sound quality or level (volume)
  Your audio is very loud, but has a lot of

audio check / audio report

for (report on) sound quality, such as loudness, understandability, , background (such as , , and ), echo, distance from the whether you're or , or are using sufficient ; see also and
This is KNØJI...may I please get an audio check?

audio frequency Non- vibration range audible to the human ear, encompassing roughly 20 to 20,000 Hz; see also

audio FSK

See

aurora Visible natural phenomenon resulting from the interaction between charged particles in the and the (primarily the ), where the earth's magnetic field has deflected the particles toward the regions surrounding its magnetic poles, the display near the north magnetic pole called Aurora Borealis (northern lights) and the one near the south magnetic pole called Aurora Australis (southern lights); see also Type of made possible by reflecting off the charged ceiling produced by an aurora (auroral ), resulting in a fluttery or raspy sounding signal, making possibly the best of communication applicable to this phenomenon; see also

Aurora Borealis

auroral-E / auroral E

Type of that occurs as are off the near the earth's magnetic poles, normally during the time of day as auroral activity begins to diminish

auto repeater

See

auto tuner / autotuner / automatic tuner Type of that requires little user-intervention to perform the functions; see also

auto tuner

automatic control

Type of control in which the is not physically at the and not actively manipulating the station controls, such as operation (when the operator begins actively manipulating the controls, the control type becomes )

automatic gain control

Self-controlling circuit that attempts to maintain a constant level of output by automatically adjusting the of the input signal; see also

automatic level control

Self-controlling circuit that attempts to maintain a constant level of output by automatically adjusting the of the to prevent it from overloading, thereby reducing and possible physical damage to the due to excessive

automatic link establishment

for (without assistance) initiating and sustaining communication, to provide a rapid but reliable contact between in spite of changing , reception , and congestion; see also and

automatic noise limiter / automatic noise-limiter / automatic noise limiting

Circuit that reduces wide-band (often ) impulse and peaks by limiting their amplitude (sets the level) according to the incoming signal strength; see also
Note: because the two are often confused, ANL filters the unwanted signal by limiting amplitude while NB filters it by attenuating the signal for the duration of the noise

automatic repeater shift

Technique that allows a to automatically set the shift () and for a manually tuned , with assumptions based on a local (national)

autopatch

Interface between a and the local telephone service (also known as a phone patch), allowing you to make regular phone calls from your radio by the use of tones; see also and
Note: one type of autopatch, known as autopatch (or simpatch) is implemented through a non-repeater connected to the local telephone service

AUXCOMM

Auxiliary Communications or Auxiliary Emergency Communications : intense, multiple-day training course by the Department of Homeland Security that augments local communication types that include, but is not limited to, ; see also

auxiliary remote base

See

auxiliary station

that controls another station over a ; see also and

AVC

automatic volume control : former name for

average power

• Also called mean power, the total amount of energy expended, dissipated, absorbed, transferred, or required in a given amount of time, or P = Δ E / Δ t; see also
• Quantity of in an circuit

AWG

American wire gauge
• American standard for diameter, size, thickness, or -carrying capability of wire and other materials; see also
• American designation (also abbreviated gauge) for the diameter, size, thickness, or -carrying capability of a particular electrical wire model, as in 12 AWG

AX.25

Amateur X.25 : designed for and used by to transmit and receive frames that contain (location information); see also
• (as it applies to APRS)

az-el / azel azimuth-elevation : description (also called altazimuth) of an or other equipment that is capable of aiming an not only radially but also up at an angle toward the sky, useful in activities such as , , and communication; see also

az-el rotator shown on a satellite antenna mount

azimuthal / azimuth Radial appearance of something as you look down at it from above; for example, an azimuthal of an is its transmission strength pattern as seen looking down on it from above the antenna; see also and and

an antenna's azimuthal radiation pattern

backlash current

See

backscatter / back scatter

off the , often received on a above the ; see also and

bacon frying

See

bad solder joint

See

bail-out bag / bail out bag

See

balanced feedline / balanced feed line / balanced line

Pair of electrical conductors, both of the same size, shape, and material (and therefore the same ) their entire lengths, whose chief advantage is rejection, and of which , , and twisted-pair are examples; see also and

balanced modulator

Circuit whose input is a signal and the signal, and whose output is (the two sidebands without the carrier); see also

balanced tuner / balanced-line tuner

Type of whose symmetrical output circuit presents conductors with identical impedances with respect to , meaning they appear as though they contain separate tuning circuits for each conductor, but are adjusted in parallel, to ensure equal impedance presentation; see also

balun Type of inserted between a (such as ) or (such as a ) and an (such as ) to either provide an () between the two, or to function as an () to prevent the feedline from radiating; see also and

current balun

balun cutaway

band One or more sets of continuous within the that have been allocated by the or for communication purposes by specific groups, such as , or specfic uses, such as ; see also the FCC Amateur Radio Frequency Band Allocation Chart [PDF] for all radio bands and

band allocation chart

band conditions

Atmospheric (weather, etc.), , , and other activity that in concert affect for a particular

band-pass filter / bandpass filter / band pass filter Circuit or device that out most or all signals of outside a particular , thereby allowing only signals within the to pass through the device, useful for and other applications that require receiving or transmitting within a relatively narrow frequency range; see also

band-pass filter graph

band plan

Voluntary allocation of a , usually specified for a particular geographical location, to avoid between incompatible ; see also and

band-reject filter / band-stop filter / band reject filter / bandstop filter Circuit or device that out most or all signals of within a particular , thereby allowing all signals except those within the to pass through the device, useful for the removal of an interfering frequency such as the signal; see also

band-reject filter graph

band segment

See

bandspread / / band-spread / band spread Mechanical or electrical fine-tuning control on older (, obsolete) and whose primary is very coarse for the size; see also Granularity (resolution) of required to select a single on a particular (how close together the seem to be)

vintage receiver with bandspread tuning control

bandstop filter / band-stop filter / band stop filter

See

bandwidth

• Absolute value difference between the highest and lowest you are using; see also
• Continuous range of being used by a particular transmission or piece of equipment
  Many transmissions are limited to a 12.5 kHz bandwidth
• Continuous range of frequencies allocated for use in a particular
  The section of the has a bandwidth of 60 kHz

barefoot

Slang for without an
I was able to Japan barefoot

base station that is typically too large to be normally carried around by hand or installed in a vehicle that is installed in a home or other fixed location, regardless of transceiver size or facility type; see also (also called fixed station) that is established in a permanent structure with equipment not intended for operation; see also

base station transceiver

baseband / base band

• components present in the signal (in other words, the original unmodulated signal); see also
• of an signal

battery electric energy consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy; see also and

batteries

battery symbol

battle box / battle-box

See

batwing antenna / bat-wing antenna Variation of the normal , in which the are shaped into a characteristic butterfly, bowtie, or bat-wing shape, often used to cover a large by ; see also

batwing antenna

baud

• Number of symbols transmitted per second, also known as symbol rate; see also
• Modulation rate of transmission, expressed in bits per second

Baudot code

Outdated 5-bit code for representing text characters in teletype and other text-based communication equipment; see also

bayonet

Common (with many light bulbs, data cables, CD packaging spindles, and camera lenses) fastening mechanism used by some connectors, such as , characterized by a push-and-turn attachment method; see also

BBHN

BBTD

BCI

broadcast interference : originating from a or and picked up by an because of or

BCL

• broadcast listening : hobby of listening to primarily for informational or entertainment purposes
• broadcast listener : outdated term for a person who participates in broadcast listening

beacon

• that transmits information about and , and can be used to test equipment, perform experiments, and observe and reception ability; see also
• used or automatically enabled during a time of distress or , to alert others (especially , military, or other emergency personnel); see also

beam antenna Type of that possesses high transmission and reception performance while exhibiting relatively large reduction; see also and

beam antenna

beamwidth / beam width Angle between the half-power (-3 ) points on the main lobe of an 's ; see also

antenna pattern showing approximately 34° beamwidth

beat frequency oscillator

Circuit or device in a that converts and signals to (see ); see also

BER

• bit error rate : number of received data stream bits per second unintentionally altered due to , , , or bit synchronization errors, often expressed as a percentage; see also
• bit error ratio : ratio of the number of received data stream bits unintentionally altered, to the total number of bits transmitted, often expressed as a percentage

beta

parameter (also known as common-emitter current gain, symbol β) defined as the change in collector with respect to base current, and is the parameter most commonly associated with transistor (ability to amplify a signal); see also and

Beverage antenna Type of very long and low directional receiving made primarily for and and is characterized by its large size, often extending for miles and has comprised some of the world's largest continuous antennas, but is not typically used for transmitting due to high compared with that of other antennas; see also

modern 160-meter Beverage antenna, about 280 m in length

diagram for a Beverage antenna about 6 feet above ground and at least 1 wavelength long

BFO

BFSK

binary frequency-shift keying : low-rate transmission in which the signal is shifted between two to convey the information, in which a 1 is identified by the frequency and a Ø is identified by the frequency; see also and

BiCMOS bipolar complementary metal-oxide-semiconductor : logic family that uses both and , to offer the high input of CMOS and the low output impedance of bipolar transistors; see also

BiCMOS internal schematic

bilateral agreement / bilateral arrangement / bilateral operating agreement

Set of rules agreed upon by two countries to authorize radio operation in one or both countries by a person who is not a citizen of ( to) one or both countries

bipolar junction transistor

characterized by low input , using emitter, base, and collector , and whose flow characteristics are determined by the contacts of different materials in the device; see also

bird

Slang for satellite, especially one used as a radio ; see and (unrelated to the BIRD satellite )

birdie / birdy

Slang for a phantom (false) chirping or that is produced by a being to a that is a multiple of the output frequency of one of its own , and can often be hidden by increasing the level

BJT

black hole

See

bleeder resistor that is connected in parallel with the output of a high- to discharge the energy stored in the supply's , improving output voltage when the supply is on, and to bleed off the remaining electric charge when the supply is off, to allow for safe handling; see also

schematic showing bleeder arrangement

blind zone

See

block diagram Drawing or other visual aid containing boxes, figures, or shapes to graphically display the high-level interconnection, interdependency, or interoperability between the or other major functional sections of a device; see also

transceiver block diagram

blocking dynamic range

Difference in between the and the level of an incoming signal that will result in of

BNC bayonet Neill-Concelman : model name for a common quick connect / disconnect 50 Ω or 75 Ω used in and applications; see also and

BNC connectors

boat anchor / boatanchor Slang for a heavy, old (, antique, obsolete) that's typically powered by () for its internal , which lends to its extra weight; see also

Hallicrafters boat anchor

Heathkit boat anchor

bonding

Practice of electrically connecting all exposed metallic items not normally designed to carry electric in a room, building, or system, as a protection from electric shock by ensuring they are at the same electric potential, particularly potential if possible; see also

boom Rigid crossbar, , or other member for supporting the weight, shape, and placement of the , , and other , along with any other component necessary for the design and function of the particular antenna, and can be either conductive or non-conductive, depending on element placement

vertical Yagi antenna showing its elements held in place by the boom

boom placement with respect to Yagi elements

booming

Slang for clear and very strong signal; action of sounding or better
This guy was booming from Ohio on

bootleg

Older slang that describes some sort of illegal (indicating intentional) activity involving radio; see also and
• bootleg : describes illegally modified equipment or illegal radio operation
• bootlegger : person who operates on an either without an amateur or uses a call sign not belonging to the operator
• bootlegging : operation on an without an amateur or operation of a radio station containing illegally modified equipment (once applied primarily to operation)

bottle

Older slang for
I'm using a three-bottle

bowtie / bow-tie

See

BPSK

binary phase-shift keying : low-rate transmission that uses to shift between two phase angles of an signal to convey the information, and at one bit per symbol is the simplest form of ; see also

braid / braided strap

See

brass pounder

Older slang for who uses a instead of a or to send

break

• Message announcement of great urgency, formerly (unfortunately still common) used to request entry into a current
  Break! Break! Break! This is an ; all will please clear this
  Note: the ARRL discourages using the word break except during an emergency (click Joining a Conversation in Process)
• Pause between

break-in / break in

Attempt to transmit during a brief pause between two separate transmissions by others (or another), and have that transmission be heard or detected by them

breakdown voltage

Minimum reverse applied to a or to cause the component to conduct in the reverse direction; see also

breaker

• See
• CB slang for an announcement by a transmitting operator who wants to start a conversation
• CB slang for a who wants to join a conversation in progress

breaking squelch / break squelch

Action of un-muting the while an incoming signal's strength exceeds the squelch threshold

breaking station

that is attempting to join () a conversation in progress

bridge circuit Electric circuit in which two circuit branches, typically in parallel with each other, are connected (bridged) by a third branch connected between the first two branches at some intermediate point along them, to measure a null (zero volts), which confirms an between the two branches; see also

bridge circuit

bridge rectifier

See

broadband butterfly terminated dipole antenna Adaptation of the , with its elements formed into two equal and opposing triangles, lending itself to improved stealth and slightly greater over that of a typical

Broadband-Hamnet

See

broadband noise

As it applies to (as opposed to audio), type of that has unusually large or that is experienced in many ranges over an unusually large spectrum

broadband terminated dipole antenna

Adaptation of the , with the added ability to deliver a signal effectively across a wide , some reportedly across much of the spectrum

broadcast

• Type of one-way communication that is meant to be transmitted to the general public, also known as broadcasting; see also
• Transmit to the general public; making a one-way communication intended for the general public

broadside / broad-side / broad side

Side of an object presenting the greatest amount of surface area, such as flat-facing sides of a , rather than its ends

BT

for end of paragraph, to indicate the end of a thought, idea, or thread, and the beginning of the subsequent one; see also
Note: the code for BT is exactly the same as that for an equal ('=') sign

BTH

See

bug Slang for a sideways-motion semi-automatic and non-electronic telegraph made for high-speed transmissions; see also and and

Vibroplex bug

bug-out bag / bug out bag

See

bullet connector

See

bureau

Short for

BURO

; see also

bus Electrical conductor (sometimes misspelled buss) that provides multiple electrical devices a common connection or pathway, and is often un-, but sufficiently heavy compared with the conductors that attach to it; see also ground bus : thick, heavy plate or bar (busbar) that provides a common connection point for the of multiple pieces of equipment, and that is typically with power bus : single, relatively large conductor (distribution block) that provides (sufficient at the intended ) distribution to multiple devices (some distribution blocks provide both positive and negative sides to devices)

ground bus

power distribution block with both a positive bus and a negative bus

business band

See

busted call

Slang for a entry that was entered incorrectly, usually during

busy lockout / busy channel lockout

feature, in which the ability to transmit is inhibited if a signal is detected on the currently selected , even if the is by a , in an effort to prevent accidental

BW

BZ / B sub Z Direction and strength of the component that is perpendicular to the ecliptic plane, with a southward orientation indicating an increased likelihood that incoming solar particles will cause disturbed conditions, such as

IMF diagram showing BX, BY, BZ components

C

• for (correct)
• signal or unstable signal, when added to an report; see also

CØG / C0G

See

C4FM

continuous 4-level frequency modulation : transmission standard created by using at two bits per to create its four states; see also

Cabrillo

Text file format standard for radio targeted for submission or simple record-keeping; see also

California kilowatt

Older slang for magnitude of transmitting that exceeds the

call sign / callsign

Unique combination of letters and decimal digits assigned to a for identification, in the format XXNYYY for the US, of which XX is one or two letters, N is a decimal digit, and YYY is one, two, or three letters; see also
• call sign rules on W5YI

call sign area / calling area / call sign region

Geographic area defined by the organization overseeing the of its , which in the US is identified by a single numeral, 0 through 9, in the of each of its licensees whose address is registered within that area

calling frequency

General (of which a is one) that is recognized across the US by a gentleman's agreement for incidental use, requesting non-urgent assistance, true , testing, and whose use in making casual or first-time is encouraged; see also , which includes some calling frequencies, and a chart of amateur calling frequencies [PDF]

candy store

Slang for a store or dealer that sells radio

cans

• Slang for
• Older slang for

CAP

Civil Air Patrol : Civillian auxiliary of the US Air Force made of volunteers focused on and operations from an aviation perspective, and much of which involves communication; see also and the main CAP website

capacitance

Property of a device that defines its ability to store electric energy in an electric field to resist changes in the across it, expressed in farads (symbol F); see also

capacitance hat Device (also known as a capacity hat or roof capacitor) that complements or counteracts the of a for an electrically shortened (typically ) by presenting a roof capacitance

capacitance hat

capacitive coupling

Also known as AC coupling, effect of two or more conductors not connected to each other being close enough to allow an present in one conductor to result in an AC voltage at the others, with respect to signal ; see also

capacitive reactance

Imaginary quantity of opposition to flow in a circuit () due to , that varies with and is expressed in ohms (symbol Ω) and defined as = 1 / ωC, in which C is the capacitance and ω is the frequency in radians (ω = 2πf, in which f is the frequency in Hz); see also

capacitive time constant

See

capacitive top-loading / capacitance loading

See

capacitor Electrical component (formerly condenser) that resists changes in the across it and stores energy in an electric field; usually contains two electric conductors separated by a non-conducting ; see also

assorted capacitors

capacitor symbols

capacity hat / capacity top hat / capacity top-hat

See

capture effect

Phenomenon of a demodulating the stronger of multiple received signals and completely suppressing the weaker ones; see also

car-to-car

See

card checker

Person who is authorized by the to verify that the made by a US toward an award (such as , , or ) are authentic, according to the collected by the candidate; see also and

Carolina Windom antenna Type of () that uses a portion of its as a , typically resulting in a lower angle of radiation than that of a plain Windom antenna

Carolina Windom antenna diagram

carrier

signal that is with an input signal, such as your , to enable the resulting signal to be transmitted through space; see also

carrier delay

• Amount of time (also called hang time and drop-out delay) a continues to transmit a signal after the sending has , typically in number of seconds
  The hang time on that repeater is pretty long
• Time period between the moment when the sending has and the has terminated its transmission, during which the repeater might transmit a or system information
  I heard somebody during the repeater's hang time

carrier squelch

Muting () of a 's (less often called noise squelch) when no signal is being received at the selected with at least the signal strength for which the squelch level is set; see also

CAT

Computer Aided Transceiver : standard created by (formerly Vertex) to provide a serial interface between a computer and a that supports the , to control functions such as , , , and setting memory

cathode

Negative terminal or of a device or component, from which flows; see also (and )

cathode-ray tube / cathode ray tube whose emits a stream (ray) of electrons (negatively charged particles) onto a phosphorescent screen to display images; see also

cathode-ray tube

cat's whisker / cat's whiskers / cat whisker / cats whisker Adaptation of the , in which the active spread out radially from a central point, rather than parallel to each other Type of , in which the looped are spread out by non-conductive spacing rods that resemble a cat's whiskers when viewed Thin conductor of the side of a , especially that of a crystal detector in a

cat's whiskers antenna

diode showing cat's whisker

cavity filter Type of that exhibits high and stability, used mostly in to prevent transmitting to, or receiving interference from, other nearby repeaters and sources, and are typically implemented as or type; see also

band-pass cavity filters

cavity filter diagram

CB

CBRS

See

CCD

CC&R / CC&Rs / CCRs

Covenants, Conditions, and Restrictions : set of rules that dictate the conditions under which you can occupy a home, which conditions might include the prohibition of, or limitations on, the installation of radio or other related equipment, and often enforced by a local ; see also

center-fed Zepp antenna / center fed Zepp antenna / centerfed Zepp antenna

See

center insulator Non-conductive support component to which the two and the of a are connected, but can be used for other antenna types as well

dipole center insulator

center tap

See

centi

Prefix, or units modifier, to indicate ÷ 100 or × 10^-2, and is often abbreviated c

CEPT

: agreement between the US and European nations to allow an American to operate legally within participating countries without a special or permit; see also and

certificated / certification / certified

Formerly type-accepted and type-acceptance, as it applies to a , indicates Certification or Declaration of Conformity for meeting certain requirements to legally transmit outside the (simply put, all radios, and some types of radio support equipment, such as , must be type-accepted or certificated for an to use them to legally transmit outside the amateur bands); see also

CFA

crossed field antenna : controversial type of compact-sized intended to exhibit the same as conventional antennas; see also

cfm

Short for confirm

channel / channelized

Organization of a or continuous set of that are accessible at a specific, pre-defined subset of those frequencies, known as channels, and often assigned alphanumeric designators (channel 13, channel A5, etc.); see also

characteristic impedance

Quantity of opposition to flow () in a dependent on the line's physical properties and geometry (its characteristics), but not its length; see also

charge controller Electric device that controls or limits the rate of electric through a , to prevent overcharging, and can protect against overvoltage, which can reduce battery performance and lifespan; see also

solar charge controller

charge-coupled device / charge coupled device

Electronic device that uses a combination of analog and digital circuitry to sample, convert, and store a numerous array of electric charges into digital signals, often used as an image detector in a digital camera; see also

chasing DX

See

chassis

Typically metallic enclosure or frame of an electrical instrument or other machine that forms the basic external shape (footprint) of the device, protects inside workings from unwanted intrusion, and shields the from potentially dangerous contact with internal components

chassis ground

Type of identified by connection between metallic frames or enclosures of various equipment, especially a , , , , and other associated devices; see also

Chebyshev filter Type of that exhibits a very sharp (steep roll-off) and a ripple in its ; see also

Chebyshev filter schematic

check

• Word count in the of a
• Last two digits of the first year in which a was , for during some
• for communication quality, as in , , or

check in / check-in / checking in

Act of participating in a by announcing your , and possibly other information, upon request by

checkpoint

Person who is authorized by to verify that the made by a toward an award (such as or CQ DX) are authentic; see also

cheerleading

Slang for the practice of advertising, promoting, or information about another radio 's and location to aid other stations in making many in a short period of time, which practice is generally prohibited during ; see also and

chicken band

Slang for

chicken net

Slang for a in which participants do little more than periodically (but is still useful for testing equipment, , skill, etc.)

chip / chipset

See

chirp / CHIRP chirp : small change in a 's each time the transmitter is , typically due to poor stability in the ; see also CHIRP : free, open-source software tool for an with , , and of your choice; see also the main CHIRP website

choke / filter choke that blocks higher- in a circuit; see also

assorted chokes

choke symbol

choke balun

See

chordal hop between two points by two or more successive through the before arriving at its destination, resulting in a signal that exhibits less loss than the same signal, had it traveled through the dense ground atmosphere twice; see also

red = chordal hop green = typical radio wave hop

circuit breaker Automatically operated electrical (often shortened breaker) that interrupts the flow of through a circuit when the current exceeds a specified rating for a particular amount of time, to protect the powered equipment in case of overload, and is typically re-usable after being ; see also and

typical household circuit breaker

circuit ground

See

circuit Q

See

circular polarization Continuously rotating alignment of a signal's around the axis of directed away from the , and a signal with such an alignment is said to be circularly polarized; see also

circulator Type of that routes signals from the to the , and from the antenna to the , while preventing the signals from passing directly from transmitter to receiver, to reduce or eliminate produced by another nearby transmitter; see also and

circulator

Citizens Band

Set of 40 , low-, -free, and short-distance (typically 5 miles or less from base to mobile or 2 miles or less from mobile to mobile) (also called CBRS, for Citizens Band Radio Service); see also
• CB on CFR Part 95
• chart of assigned CB frequencies [PDF]

city power

See

CL

(not technically a ) for closing station, to indicate the is going ; see also

clarifier

See

class

category or classification that defines the 's transmitting privileges, of which , , and can currently be earned, and Advanced and are still recognized; see also and
Note: to prevent confusion, the term course more appropriately refers to a classroom experience, even online

Class A amplifier

that is characterized by low , and therefore appropriate for amplifying signals, in spite of being relatively ; see also

Class AB amplifier

Type of that is much more than a because it operates on less than the full (greater than 180° and less than 360°) signal cycle; see also

Class C amplifier

Non- amplifier that is characterized by high , and therefore appropriate for amplifying signals, but not those of ; see also

Class D amplifier

Type of that uses switching technology to achieve high , thereby requiring less to operate, compared with that of other amplifier types; see also

Class X / Class-X

See

clear

• I hereby relinquish this frequency for others to use (does not indicate whether you actually intend to stop speaking), or to a lesser extent, I have finished speaking and am ; see also
  I'll be clear and this
• Description of a or that appears to be free of transmissions (available for use) at the moment
  Let's to a clear

climbing harness

See

clipping / clip-distortion

Form of defined by limits on a signal at a specific threshold, often caused by excessive , more applicable to than to ; see also

closed closed circuit : circuit that makes a complete flow path closed repeater : that is available for use only to a specific group or by sending an access code The 448.325 is a closed repeater

CLOVER / CLOVER-II / CLOVER-2000 / CLOVER 2000 / CLOVER-400

Series of transmission that were specifically designed for use on ; see also

cloud warmer / cloud-warmer / cloudwarmer

Older slang for

club

See

club trustee

See

CMC

CME

CMOS complementary metal-oxide-semiconductor : technology that makes use of material for constructing in most of today's , , static memory, and many other digital logic circuits that require high-speed switching with very low consumption; see also

CMOS chip

CMOS transistor symbols

coax

Short for

coaxial cable made of an inner conductor surrounded by an layer, which is then surrounded by a conducting , all of which share the same cylindrical axis (hence the term co-axial), and used most often as a radio , the purpose of the shield to prevent of unwanted signals to or from the wire; see also chart of coax cable loss and capacity [PDF] for selected

coaxial cable

coaxial capacitor Electrical component (part of a class of called a feed-through capacitor) made of an uninterrupted wire or other conductor completely surrounded by a material, which is then completely wrapped in a cyclindrical metal sleeve, such that all three pieces share a common axis along the length of the wire; the wire at the center typically used to conduct supply in a circuit, while the sleeve is connected to , thus out high- (such as alternator noise) in the DC path; see also Note: the geometry and function of gives the appearance of a coaxial capacitor, but the capacitance of coax used in feedlines typically range in pF, while that of coaxial capacitors typically range in µF

coaxial capacitor

coaxial capacitor symbol

coax switch

See

code

Short for

code plug / codeplug

Binary file that contains configuration information, plus , , , , , and other settings, for the proper operation of a particular model, and so-called because originally much of the settings (code) were hard-wired on a small device (plug) that you can insert into a compatible transceiver, to perform the configuration and programming

cold solder joint Poorly soldered union of two or more electrical conductors, often resulting in an unsound connection or intermittent contact, and can have a grainy appearance; see also

cold solder joint (right)

cold (grainy) solder joint

collinear antenna Multiple arranged such that their primary radiating are positioned along a common line, to form an antenna whose is greater than that of each section alone; see also

vertical, two-element collinear antenna

color code / color-code / colorcode

• Set of colored stripes or dots painted, marked, or otherwise applied to an electrical component, to represent its functional quantity value; see also
• Setting that represents a digital version of value for access, allegedly so-called because the settings were once set by physical color-coded

Colpitts oscillator circuit that achieves its generation by supplied through a divider, and is one of (at least) three oscillator circuits used in equipment, commonly in applications; see also

circuit employing a Colpitts oscillator

combiner Device or circuit (sometimes RF combiner) that brings together two or more signals (often of differing within the same ) into one signal, to be transmitted through an or forwarded to another circuit or for further processing (not to be confused with ); see also Note: a combiner can often be used as a splitter (sometimes RF splitter), to perform the reverse function

combiner / splitter

come back

please reply : request or demand for a response
Come back with your

come in

begin speaking now or can you hear me?; see also

come on in

please join our conversation : CB slang for invitation to begin transmitting during a conversation already in progress

commercial

Type of local communication for use in corporate, industrial, or educational environments, such as construction sites, warehouse stores, mass transit vehicles, and school buses; see also

common-mode current / common-mode signal

Electric behavior in a two-conductor or other such that the in one conductor is not perfectly equal and opposite that of the other conductor (also called antenna current, imbalance current, or secondary-mode current), resulting in energy produced by the difference in the currents, often the cause of radiation; see also ; the following articles are recommended for a better understanding of this concept, as well as :
• (good private article)
• How Common-Mode Currents are Created [PDF] (article)

common-mode choke

See

companding / companded / compander

technique (named from compressing - expanding) that involves compressing an signal prior to transmission, then expanding (decompressing) it at the to improve the of the signal; see also

comparator

See

complex number

Sum of a real number and the imaginary unit multiplied by another real number, as in a + jb, with a and b being real numbers and j being the imaginary unit; see also

compliance

Conformance by a owner in behalf of equipment and its to the safety limits of maximum human exposure to fields (determination of which is known as a compliance evaluation or exposure evaluation, and similar determination following equipment change known as re-evaluation); see also

compliance evaluation

See

compression

See

condenser

See

condenser microphone

See

conditions

See

conductance

Real component of , or quantity of allowance for flow in a circuit, expressed in siemens (symbol S) and is the reciprocal of in a purely resistive circuit; see also

connector

For (especially ) connectors, see and and

For power, see

For other types, see (serial port) () (, also called phono)

See also

contact

Verified communication between two radio ; see also and
I made a contact on last night

Contestia

Type of transmission () that is a derivation of but is twice as fast; see also and the main Contestia website

contesting

Competitive activity (also called radiosport) pursued by radio in seeking and as many as possible within the timeframe, , and specified by contest rules, also known as a type of ; see also
• main contesting calendar page
• contesting and radiosport home

contest-style / contest style

Slang for a relatively formal operating plan (typically in reference to a or station), in which operation is organized according to a specific schedule (date, time, , ) during the event; unlike or

control grid

See

control operator

Person (often abbreviated operator or simply op) who has access to the control functions of a and one designated by the station as the party responsible for station transmissions, whose grant appears in the , and whose license determines the transmitting privileges of an station; see also

control point

Location at which functions are performed

controlled

Any environment, area, or situation in which humans presumably have control over their exposure to , including primarily the household, its occupants, and surrounding property, to ensure their 6-minute exposure levels remain within the controlled limits; see also
• FCC controlled / uncontrolled compliance document and worksheet [PDF]
• abbreviated controlled / uncontrolled compliance chart

CONUS

continental United States : lower (contiguous) forty-eight states of the US

convention

See

coordinated universal time

See

cootie key

See

copper strap

See

copy

Understand and acknowledge, similar to ; see also
Copy / copy that (got it)
How copy? (how well did you get that?)
No copy (didn't hear it well enough to understand it)

core

See

corner frequency

See

corona ball / corona ring / corona cap High-, high-, or high- conductor, usually near the termination of a or connection with another conductor, employing a curved shape to prevent localized concentration of strong electric fields and therefore undesirable ; see also Note: the end of a whip or similar antenna might be equipped with a small ball that looks like a corona ball, but is typically installed to prevent stabbing people and other things with its sharp point

corona ball

corona rings

corona discharge Electrical discharge caused by the ionization of gases surrounding a conductor of high electric charge when the strength of the electric field around a high-, high-, or high- conductor is large enough to form a conductive region around the conductor, and presents significant energy losses, possible health hazards, and causes embrittlement of nearby insulators, but not strong enough to cause ; see also

corona discharge around a ring

coronal hole

Area in the sun's corona where the magnetic field is not strong enough to prevent a larger-than-normal quantity of charged solar particles (known as the ) from being ejected into space at high velocity, which, in turn can disturb communication when those particles reach the earth; see also

coronal mass ejection Massive burst of charged solar particles, which take 20 to 40 hours to reach earth after being discharged, disturbing and communication, and affecting other ; see also and a video

coronal mass ejection

COTA

Castles on the Air : award program for radio enthusiasts who set up transmitting (activators) in, on, or nearby historical buildings (medieval castles and fortresses in particular) or contact those who do so (chasers), in conjunction with the WCA program, to help draw attention to these sites; see also COTA-PA website

counterpoise

or network of suspended wires, cables (), or other conductive material or surface used as a substitute for earth ground in a system, functioning as one plate of a large , with the conductive layers of the earth acting as the other plate; see also

coupling

• Physical association or connection between two systems, to transfer energy or information between them; see also
• Electrical type or connection method
  The coupling between my and my is a

courtesy tone / courtesy beep

Audible tone or beep transmitted by a shortly after a sending has , indicating when another station can begin transmitting

CQ

calling any station, anywhere : general call to request with, or get the attention of, any listening , without regard to location; see also and
CQ CQ CQ...this is K-N-Ø-J-I

CQ <country name>

calling any station within <country name> only : general call to request with, or get the attention of, any listening within <country name>
CQ Japan...CQ Japan...this is K-N-Ø-J-I

CQDX / CQ DX

calling any station outside my country : general call to request with, or get the attention of, any listening outside the local area, especially outside one's own country or continent; see also

CQFD / CQ FD

calling any station participating in Field Day : general call to request with, or get the attention of, any listening that is participating in

CQ Zone Any one of 40 geographic areas of the world, as defined and named numerically by CQ Amateur Radio for the purpose of obtaining specific awards, such as ; see also CQ Zones of the World map

craft / the craft

Hobby, service, skill, education, endeavor, design, building, and/or art of participation, promotion, or activity

CRC

cyclic redundancy check : code used in a to detect an unintentional alteration of transmitted by comparing a computed check of the received data with the check that was received in the transmission; see also

cross-band / crossband

• Communication method in which a radio receives a signal on one (or ) and simultaneously retransmits the signal on a different band (or frequency), similar to the action performed by a ; see also
• Type of (often called a cross-band ) that can be configured to receive a signal on one and simultaneously retransmit the signal on a different band

cross-modulation / cross modulation

Undesirable result from the of one strong signal being transferred onto other signals being received, often resulting in hearing an unintended station in the background of the sound from the intended station

crosstalk / cross-talk

Typically undesirable presence of a signal in a circuit or medium, due to unintentional between the and the signal source; see also

CRT

crystal

• See
• See
• Short for
  I actually heard the game on the crystal last night

crystal ladder filter / crystal filter / crystal lattice filter Electronic that uses for its , resulting in narrow and steep ; see also

crystal ladder filter diagram

crystal oscillator / crystal resonator Electronic circuit that uses the mechanical vibrations of a to create an electrical signal with a very precise ; see also and Note: many conventional oscillator circuits use quartz crystals as their resonators, so the terms quartz crystal and crystal oscillator are often interchangeable

crystal oscillators

crystal oscillator symbol

equivalent circuit, showing R1 = motional resistance C1 = motional capacitance L1 = motional inductance C0 = shunt capacitance

crystal radio that uses a or as a and is completely by that arrive at its ; see also

crystal radio set

CSCE Certificate of Successful Completion of Examination : document that certifies the named person as having successfully passed a radio examination; see also

CSQ

CTCSS

continuous tone-coded squelch system : circuitry that adds a (formerly and sub-channel) tone to the signal prior to and subsequent transmission, to be received by a or other that requires the tone, so that it will accept the signal and all others; see also and
Note: CTCSS is also known by some proprietary names, such as
• Channel Guard by General Electric
• Private Line ('PL tone') by Motorola
• Quiet Channel by RCA
• Quiet Talk ('QT') by Kenwood
• CallGuard or ToneGuard by Johnson Corp.
• ToneLock by Zetron
• C. Tone by Icom

cubical quad antenna

See

current

Quantity of electric flow in a circuit, expressed in amperes (symbol A); see also

current balun Type of inserted as a (also called choke balun) to reduce or control undesirable between a and a ; so-called because it attempts to balance the output currents (make them equal and opposite) regardless of the load impedances

cutoff frequency (also known as the corner frequency) at which energy through a system or circuit begins to be from one frequency to another by 3 (output is -3 dB, or half the strength of the input signal); see also and below which a is unable to penetrate a layer of the by at an incidence angle required for transmission between two given points; see also

cutoff frequency for a filter response

cut out / cutting out

Slang for intermittent or signal continuity during transmission
I could hear most of what you said, but you were cutting out

CVE

Contact Volunteer Examiner : in charge of other VEs in a particular ; the main contact between the and the group of local examiners

CW

continuous wave : primary for International transmission, in which a steady (continuous) signal is essentially switched off and on; see also

D layer / D region

Lowest (closest to the surface of the earth) section of the , and one that absorbs signals of lower than about 7.5 MHz, resulting in difficult daytime long-distance communication on the , , , and ; see also

DAB

digital audio broadcasting : standard for digital using between 174 to 240 MHz and 1452 to 1492 MHz, adopted primarily by countries in Europe and Asia Pacific; see also

dark side of the moon

CB slang for a location (also called black hole) that is within the of a or other signal source
I'm moving into the dark side of the moon, so my signal will start degrading quickly

data

Short for , any of several communication formats, such as , , , , and , for transmitting and receiving digitized information over
Technicians are permitted to operate both data and on a portion of the

data emission

See

dB

DB-9 / DB9

See

dBc

Ratio of the amplitude of a signal with respect to the power amplitude of the signal, and expressed in ; see also

dBd

of an with respect to that of a antenna, expressed in , and is calculated to be approximately 2.15 dB greater than the gain of an ; see also

dBi

of an with respect to that of an , a hypothetical point source of , and expressed in ; see also

dBm

Ratio of the amplitude with respect to a reference power amplitude in milliwatts, and expressed in ; see also

dBu

amplitude with respect to that of a reference RMS voltage, expressed in ; see also

dBµ / dBµV/m

strength relative to one microvolt per meter, expressed in ; see also

DC

direct current : the unidirectional flow of electric charge () in a circuit; see also

DC resistance

See

DCS

digital-coded squelch : circuitry that adds a digitally encoded to the signal prior to and subsequent transmission, to be received by a or other that requires the tone, so that it will accept the signal and all others; see also and

DDS / DDFS

DE

this is or from; see also
KR5LYS DE KNØJI (KR5LYS, this is KNØJI)

DE-9 / DE9 Model name for a once-common serial port , often mistakenly called DB-9 (and also properly called D-sub or D-subminiature); see also

DE-9 connectors

de-emphasis / deemphasis

See

dead air / dead-air

Period of silence during a transmission by a (such as or ) that sends a signal, or moment between transmissions of a mode (such as ) that does not; see also

dead carrier

Slang for transmission of an un- signal (also called an open carrier, although an open carrier is often thought to be accidental while a dead carrier is typically a deliberate transmission, such as for testing, and deadkey by operators), which is simply a sine wave of a particular frequency, similar to
If you give me a dead carrier, I can give you a more accurate signal report

dead key / deadkey

CB slang for

dead zone

See

decibel

Ten times the base-10 logarithm of a value, which value is typically a ratio of two other values; 10log₁₀(P_out/P_in), for example; see also

decimation

Process of reducing the effective sample rate of a signal by removing samples; for example, a digital signal by three, then decimate it by four, to adjust its sampling rate by a factor of 3/4; see also

decimator

Device or circuit that uses an to perform the function of ; that is, reduces the sampling rate of a signal; see also

delta loop antenna / delta-loop antenna Variation of the , but with three sides per , each side (leg) being 1/3- long for a symmetrical delta loop

delta loop antenna

delta loop antenna diagram

delta match / delta matching system / delta matching network technique that matches a higher-impedance with a lower-impedance by connecting the to the in two places spaced a fraction of the intended each side of the element center

delta match

delta match diagram

demodulation / demodulate Process of extracting the original information signal, such as your , from within a signal (using a for an signal, for example); see also

demodulation steps of an AM signal

depletion-mode FET

that exhibits a flow between and drain when no gate is applied; see also

desensitization / desensing / desense / de-sense

Undesirable effect by an signal of a that is close to your expected (receive) frequency and strong enough to overload your circuitry, often because the transmitting source is too close to your receiver (you and your spouse are unable hear each other, even though you're in the same house), or is transmitting with too much , or the of your receiver is set too wide, overcoming your receiver's ability to reject the signal, resulting in and reduced receiver , as well as poor
Note: desensitization is very similar to , except that desensing usually results in a severe reduction in receiver sensitivity, whereas fundamental overload many times results in the receiver shutting down its ability to function at all

destinate / destinated

CB slang for having arrived at a particular location
I've destinated, so to you

detector

circuit (often called a , even though many mixers are not detectors) that recovers () information contained in a ; see also

detune / de-tune

In most senses of the word, opposite of , or action of deviating from a tuned state, also known as a
Your just detuned my

deviation In , maximum difference between the and the frequency; the amplitude of the modulating signal determines the amount of deviation, whose increase results in the FM signal occupying more ; see also

deviation and bandwidth © HamRadioSchool.com

deviation ratio

In , ratio of the maximum from the frequency to the highest signal frequency

DF / DF-ing

dielectric

Non-conducting (electrically ) material that separates the two conductors of a ; see also

differential-mode current / differential-mode signal

Electrical behavior in a two-conductor or other , such that the in one conductor is perfectly equal and opposite that of the other conductor, resulting in a complete lack of energy produced by the currents; see also

digipeater

Short for digital repeater (sometimes called packet repeater), dedicated to receiving, storing, then re-transmitting digital packets; see also

digital communication

Communication by transmission and reception of digitized information, called when using as the medium and formatted in an ; see also

digital decimator

See

digital mobile radio

Open standard for two digital voice signals on a 12.5 kHz , originally used by Professional Mobile Radio, but widely adopted by many manufacturers for , , and applications; see also

digital mode

See

digital radio

Communication by transmission and reception of digitized information over using an (also called ); see also

digital signal processing

Numerical manipulation of a signal to prepare it for transmission or to the from it; see also

digital signal processor

Specialized that from a signal by converting the signal from to digital and using methods; specifically, automatic of ; see also

digital synthesizer / digital synthesis

See

diode Electronic component (often employed as a ) that allows to flow in only one direction through it (the ordinary type also known as a silicon diode and junction diode), and whose two are called the and the , the cathode end being identified with a stripe; other types of diodes include the , the , the , the , and the ; see also

silicon diode

silicon diode symbol

DIP

dip meter Instrument that measures the of an circuit, also known as a grid dip meter and grid dip oscillator; see also

dip meter

diplexer Device that allows a single dual-band to operate on two different that support different , or two transceivers of different bands to operate on a single dual-band antenna, or two transceivers of different bands to operate two different antennas using the same (not to be confused with splitter or combiner, both of which normally function on the same band or set of frequencies, or ); see also

mis-labeled diplexer

dipole Type of that consists of two, usually bilaterally symmetrical, conductive , of which the is perhaps the simplest and most widely used radio antenna, and another common type being the dipole; see also

stick trapped dipole

dipole configurations

dipole center insulator

See

direct digital synthesizer / direct digital frequency synthesizer

Electronic circuit or device used for an arbitrary (method known as direct digital synthesis) from a single, fixed- reference clock, and whose lookup tables contain amplitude values that represent an output waveform, such as a sine wave; see also

direct FSK

Type of in which the digital signal is applied to the for a (typically ) signal; see also and

direct radio

See

direct sampling

Method of that involves placing an as close as possible to the incoming signal, reducing or eliminating the need for signal , essentially replacing the circuitry, the term direct indicating an attempt to digitize the incoming analog signal directly (without modification) before presenting the signal for further processing (, , , etc.)

direct-sequence spread-spectrum / direct sequence spread spectrum

Technique of communication that uses a high-speed binary bit stream to shift the phase of the transmitted signal ; see also

directed net

that is under the direction of a , meaning that all communication during the net is directed to and regulated by Net Control unless otherwise requested; see also

directionality

Slang for (or layman version of) , as it relates to an

direction-finding

Location of a radio (also called amateur radio direction-finding or DF-ing) by detecting the direction of its signal source, often used in and to locate sources of or jamming; see also

directional antenna Type of that radiates greater in one direction than in others, or has greater from one direction over others (); see also

directional antenna

directional wattmeter

See

directivity

Quality of an that describes its transmitting , receiving , and of converting into radiated power in a particular direction compared with the same in other directions; see also

director element

Shortest of a or other , and one that adds to the signal originating from the ; see also

disaster kit / disaster-kit

See

discone antenna Type of (version of biconical antenna) that consists of a disc on top and downwardly open cone underneath, both made from sheet metal or sets of rods, but separated from each other by an ; see also

discone antenna of rods

discone antenna of sheet metal

discriminator

Circuit used in many for () FM signals by converting signals to signals; see also

dish antenna

See

dissipator / dissipater

See

distortion

Undesirable modification of an or signal, which can result in ; see also

dither

Small amount of added to the input signal to allow more precise representation of the signal over time; see also

diversity reception / diversity operation / diversity combining

See

DIY

do-it-yourself : term (also known as homebrew) that refers to building your own radio gear, especially ; see also and

DMM

digital multimeter : that displays its readings digitally (that is, with decimal digits)

DMR

dogbone insulator / dog bone insulator / dog-bone insulator Non-conductive component that physically connects two or more items that should not be connected electrically, such as , , and structural braces, typically part of an system; see also

dogbone insulators

Doppler shift

Observed change in signal due to relative motion between a and the observer; see also

double

• Unintentional or of one radio with another, by transmitting at the same simultaneously, usually resulting in both parties sounding mostly unintelligible (note that this term applies more to transmissions on and than to transmissions on bands, in which case the result is usually more of a )
  I believe there was a double with your transmission
• Action of transmitting at the same time as another on the same
  You just doubled with somebody

double extended Zepp antenna

See

double-pole, double-throw

See

double-pole, single-throw

See

double-sideband / double sideband Form of in which both are present, but the signal has been suppressed, also known as DSB-SC (double-sideband, suppressed-carrier); see also

double-sideband without carrier

compare with full AM

double Zepp antenna Center-fed of two half-wave horizontal that attach to the through a quarter-wave vertical often constructed from , making the appearance of two back-to-back Note: the double Zepp seems to be identical to the , except in the doublet the quarter-wave vertical section is allegedly not supposed to radiate

double Zepp antenna diagram

doublet antenna Center-fed of two half-wave horizontal that attach to the through a vertical Note: the doublet antenna seems to be identical to the , except in the doublet the quarter-wave vertical section is allegedly not supposed to radiate Classification of , whose radiating are a pair of conductors that form an circuit, of which the is an example

doublet antenna diagram

down-conversion / down conversion / downconversion

• Process of modifying a signal by changing it to a lower , allowing for convenient signal manipulation by circuitry, one step in the process, and integral to
• Process of modifying a signal by changing it to a lower frequency , thereby extending the spectrum available to a

down-converter / down converter / downconverter

Device or circuit that performs the function by changing the of an operating signal to one of a lower frequency, often part of a ; see also

down in the mud

See

downlink / down link / down-link

See

DPDT

DPSK

differential phase-shift keying : low-rate transmission that uses to shift the phase angle of an signal to convey the information; see also

DPST

DR

dear : beloved or good, often used as a salutation or greeting, or to describe somebody who is beloved, as in dear friend; see also

drift

See

drive

• Quantity of applied to the input of an , and known as overdrive if the quantity exceeds the amplifier's specification or capability
  Your amp's drive is currently at 20 watts
• Quantity of signal strength (typically , also known as minimum drive, or ) applied to a circuit sufficient to enable its primary function, such as , , or
  The drive required for your array is 80 watts

driven element

Sometimes called the active element, the conductor in a or other that is electrically connected to the or by the ; see also

DRM

Digital Radio Mondiale : set of digital technologies designed to work on the currently used for broadcasting, particularly the bands, making more use of the bands (mondiale is Latin for worldwide); see also and the main DRM website

drop out / drop off / dropping out / dropoff / dropout

Slang for abrupt termination of or signal transmission
I could hear most of what you said, but you dropped out near the end

drop-out delay / dropout delay / drop out delay

See

dropout timer

See

DSB-SC / DSBSC

DSP

DSSS

D-STAR

Digital Smart Technologies for Amateur Radio : digital and specification made for ; see also

DTMF

dual-tone multi-frequency : telecommunication signaling technology (known as Touch-Tone in push-button telephones) used to send control commands to the destination device, such as an node or a ; see also

dual-band / dual band / dualband

See

dual in-line package Type of through-hole electronic component package for made with two parallel rows of connecting pins on opposite sides of the package; see also

DIP IC example

dual-watch / dual watch / dualwatch

feature that allows the listener to two different simultaneously

duck

Slang or short for

ducting

See

dummy antenna

• Circuit applied in place of an to simulate its while testing a with an instrument such as a signal generator, to prevent inaccurate receiver circuirty alignment
• See

dummy load Device (sometimes called a dummy antenna) usually made of a non- and a heat sink, used in place of an to simulate an electric and prevent the radiation of signals when testing a ; see also

dummy load

duplex

In communication, operation of transmitting and receiving on different , such as in normal operations; see also

duplexer

• Device that uses a to isolate the and on a while permitting them to share a common ; see also
• Mis-labeled

duty cycle / duty factor Ratio of the amount of time a periodic event is active (the on time) to the entire period (total on plus off time), often expressed as a percentage; see also

duty cycle

DX

distant or long distance : typically refers to a or located outside one's own country, and usually overseas, to Americans also refers to any station outside the continental US and Canada (in many American circles DX can refer to a station located in Hawaii or Alaska, yet not Canada or Mexico); see also and

DX QSL manager

See

DX window

specified by a voluntary that is reserved for , and should not be used for between within the forty-eight United States

DXCC

DX Century Club : award given to a who makes verifiable with 100 different countries; see also and

DXCC Entity / DXCC Zone / DXCC Country / DXCC List / DXCC Prefix

Location of an officially recognized by the with whom another station in a different entity can make a verifiable for and other radio purposes; see also

DXer / DX-er / DX'er

Slang for a radio (also called a DX chaser) who makes with distant radio (), on a regular basis as a hobby

DXing / DX-ing / DX'ing

Hobby of making with distant radio , particularly those located outside one's own country, also known as chasing DX; see also and

DXpedition / DX-pedition / DX'pedition

Journey (expedition) by one or more radio to a distant, exotic, remote, difficult, or sparsely inhabited location or , often to set up at locations that have few hams, in an effort to provide the opportunity for hams world-wide to make with a station in those locations; see also

dynamic range

Ratio of the largest to smallest signals by a , and expressed in ; see also

E region / E layer

Section of the responsible for that can reach up to approximately 1200 miles along the earth's surface normally covered in one ; see also

E-plane / E plane Flat geometric surface defined by the electric wave component of an in a particular direction, also known as the vertical plane or elevation plane of a , or the horizontal plane or plane of a horizontally polarized antenna; see also

E and H planes for a vertical antenna

E and H planes for a Yagi antenna

early-out / early

Slang for announcement or request to check into a then leave prior to its conclusion, to alert the that the operator should not be called upon at a later time in the net; similarly spoken as in-and-out, out after roll (for a ), and short-time
Could you please give me an early-out tonight?
This is KNØJI and I'm in-and-out
This is KNØJI, out after roll
This is KNØJI for short-time

earphones

See

earth ground

Type of identified by direct connection with the Earth; see also

earth-moon-earth

See

earth station

radio located on, or within 50 km of, the earth's surface and intended for communication with or other earth stations by means of one or more objects in space

EAS

EchoLink

Software-based system that radio around the world through your cell phone or other computing device using Voice over IP; see also and the official EchoLink website

Edison effect

See

effective isotropic radiated power

Quantity of (also called equivalent isotropic radiated power) required to transmit a signal in all directions equally, from a theoretical spherically radiating (total power radiated from an isotropic source, as observed by a distant , making EIRP = ERP × 1.64, or EIRP is ERP + 2.15 dB); see also

effective radiated power

Realized amount of output radiating from the in a particular direction when compared with a reference antenna, especially a ; see also and

efficiency

Measure of a system output compared with its input, expressed as a ratio or percentage; as it relates to electric , it is defined as the useful power output divided by the total power input to a circuit or device, and often represented by the symbol η; for example, the efficiency of an power can be calculated by dividing the RF output power by the input power; see also and

EFHW

half-wave

egg insulator Non-conductive component that physically connects two or more items that should not be connected electrically, such as , , and structural braces, but provides for the connection in such a way that, should the insulator become damaged or be destroyed, the conductors will maintain their structural connection after their electrical separation is compromised, typically part of an system; see also

egg insulator

EH antenna

Specially designed that produces electric (E) waves and magnetic (H) waves that travel both and perpendicular to each other, to improve , thereby allowing for a smaller construction while maintaining the performance of conventional antennas; see also a technical description of the EH antenna

EHAAT

See

EHF

extremely high frequency : overall range of 30 GHz to 300 GHz; see also and the RF spectrum

EIRP

electret

Stable material that produces an electrostatic field originating from a permanently embedded charge (unlike a magnet, which produces a magnetic field); see also

electret microphone

Type of electrostatic -based (sometimes called an electret condenser microphone as a result), that eliminates the need for a polarizing by using permanently charged material; see also

electric field

Physical influence originating from an electrically charged particle, surface, or changing / moving , and one that can exert a force on another electrically charged object; see also

electric shock / electrical shock

Physiological reaction or injury caused by flowing through body tissue, and can range in severity from a barely perceptible tingling sensation to electrocution; see also

electrical grid

Interconnected network (often shortened the grid) of that deliver electrical (sometimes called line voltage) from multiple to the many consumers that require it, and is the primary source of commercially available to homes, businesses, and facilities; see also

electrical service Distribution box and meter (often shortened service), typically located outside a building, for providing from the power company or to the building or facility; see also

electrical service drop

electrode

Wire or other electrical conductor that provides a path to an electric device or circuit, some conductors labeled according to path function, such as those for a (emitter, base, collector, , drain, gate, etc.) or ( and ); see also

electrolytic capacitor Type of polarized that is often used in circuits to the due to its ability to present a high for a given volume; see also

electrolytic capacitors

capacitor symbols

electromagnetic compatibility

Ability of an eletrical device or system to function acceptably in its electromagnetic environment, by limiting unintentional generation, , and reception of ; see also

electromagnetic interference

Undesirable disturbance of normal operation by the introduction of electromagnetic or ; see also and

electromagnetic radiation Form of energy consisting of electromagnetic waves, which are synchronized of and fields that at the speed of light and oscillate perpendicular to each other; see also

electromagnetic spectrum Range of all possible of ; see also

electromotive force

Electrical force (pressure, or ) that moves through a circuit, expressed in volts; see also

electron tube

Older term for

electrostatic discharge

Sudden flow of electricity (of which is an extreme example) between two or more electrically charged objects when the difference in charge overcomes the ability to prevent (by distance or type) the transfer of energy; see also

element

• Either or conductor section whose length, shape, and size help determine the of the antenna
• Numerical designation for a set of examination questions that are presented to a candidate, such that currently Element 2 represents the , Element 3 represents the license class, and Element 4 represents the license class; see also and FCC rules for exam element credit
• Dot or dash in
• See

elephant

Slang for a , especially a , that seems to receive farther than it could transmit a signal (think big ears, little mouth); see also

elevation

• Angle of incline from horizontal, with respect to level
• Appearance of something as you look at it from its side; for example, an elevation of an (often called its or takeoff angle) is its transmission strength pattern as seen looking at it from the side of the antenna; see also

ELF

extremely low frequency : overall range of 3 Hz to 30 Hz, which is lower than that considered part of the regular radio frequency range, and has been used to communicate with submarines due to its ability to penetrate deep seawater; see also and the RF spectrum

elliptic filter / elliptical filter Signal that produces a response with a very narrow (very sharp transition), coupled with equal ripples in the and sides; see also

elliptic filter response

elliptical polarization of in which the travel path of the electric field describes an ellipse in relation to the direction of travel; see also

blue = electric field path orange = side view of the electric field purple = resulting apparent ellipse

elmer

Slang for a (usually experienced) mentor or tutor who offers personal guidance, technical knowledge, assistance, and encouragement to radio , especially newcomers and potential hams; see also

ELT

emergency locator transmitter : device () that transmits a signal to indicate location or position during a time of or distress; see also

EMC

EMCOMM / EMCOM

emergency communication : communication of any type and by any means during a , a drill, or an actual ; see also and

EME

earth-moon-earth : communication technique that relies on the of signals from an earth-based to an earth-based by reflecting the signal off the surface of the moon, often referred to as moonbounce; see also and

emergency

of unusual or serious concern, alarm, or danger, often associated with a situation that has compromised, or poses an immediate risk to health, life, property, or environment; see also
• steps to take during an actual emergency

Emergency Alert System

Dual-purpose national (established through the ) public warning system that 1) directs a variety of wireless, cable, and broadcasters to provide the President of the United States the ability to address the nation within ten minutes and 2) coordinates with FEMA and NOAA's NWS to warn the public on a more local level about , such as imminent severe weather or other environmental conditions that affect public well-being; see also and the main EAS website

emergency traffic

See

Emergency War Powers

See

EMF

• electromagnetic field : physical influence, consisting of an and a , emanating from an electrically charged object; see also

EMI

emission

Transmitted field (one that is emitted from a location); see also and

EMP

electromagnetic pulse : short burst of (usually high-energy) that can be disruptive or damaging to electronic equipment, primarily due to the high amount of it can in them; see also and Noji's EMP page

emphasis

Modification of the amplitude-vs.- characteristics of a signal to reduce the adverse effects of , using a pre-emphasis network to increase (boost) the amplitude of higher frequencies with respect to that of lower frequencies, and a de-emphasis network to decrease the amplitude of higher audio frequencies with respect to that of lower frequencies; see also

encryption / encrypted

Encoding of a message, transmission, or its information, such that it can only be read or understood by a receiver that is capable of decoding, or authorized to decode, the message; see also

end-fed Type of design whose connects to one end of a , as in those of a , or even a configuration; see also

end-fed antenna

end-fed Zepp antenna / endfed Zepp antenna

See

entity

See

EOC

emergency operations center : central command and control facility responsible for implementing emergency preparedness and emergency management functions at an upper-management level during an or other ; see also

equivalent isotropic radiated power

See

equivalent radiated power

See

ERC

Emergency Response Communications : department of the LDS Church responsible for communication and its preparation and training; see also ERC and Lindon Bishops' Storehouse

ERP

E_S / Es

Abbreviation for

ES

(not technically a ) for and or also
ES

ESD

E-skip / E skip

See

ESR

equivalent series resistance : total effect of an electrical component or circuit (device) at a given , as though the resistance is in series with the device; see also

evaluation

See

event

See

exam session / examination session

Formal and official arrangement to assess a candidate for knowledge and qualification through an examination

excessive drive

Signal strength (typically or , known as ) applied to a circuit greater than the amount the circuit can tolerate, possibly resulting in (on ), malfunction, overload, or even permanent damage

excessive deviation

See

exchange

Predetermined trade of information transmitted and received during a to verify the for , and usually includes your , but often includes a sequence number, general location indicator, or

exciter

• Once-popular device or circuit of a that combines an with the to create its output signal
• Device or circuit that the of a or

exposure evaluation

See

extended double Zepp antenna Center-fed of two 5/8-wave horizontal that attach to the through a quarter-wave vertical often constructed from , making it a little longer than the

Extra

See

extraordinary wave

One of two types of (also known as an X-wave) that results from the interaction with the and the one that is polarized by the influence of earth's magnetic field; see also and

eyeball QSO

Slang for an in-person (face-to-face meeting) between without the use of
We had an eyeball QSO the other day

EZNEC / EZ-NEC

Variation of the design modeling and simulation software; see also and the main EZNEC website

F10.7 Index

See

F region / F layer

Highest section of the , and the one mainly responsible for the longest , which can reach up to approximately 2500 miles along the earth's surface normally covered in one ; see also

FAA

Federal Aviation Administration : agency of the federal government responsible for regulating every aspect of civil aviation, including the construction and operation of airports and air traffic management; see also

factory reset

See

fall arrest / fall arrester / fall arrestor Type of climbing harness designed to safely stop a climber who is already in process of falling, and one of the major forms of fall protection; see also

fall arrest climbing harness

fall protection

See

fan dipole antenna Type of (also called parallel fan dipole), in which multiple parallel radiating join at a common point on each side, or in which the radiating elements spread out radially from the common points, like with a antenna

fan dipole antenna

far-field / far field

View of a for an or other object capable of , as seen from a relative distance, to observe the overall behavior of the field; see also (or for a very technical description)

Faraday, Michael English scientist whose contributions to the fields of electromagnetism and electrochemistry led to the discovery of , which forms the basis of ; see also

Michael Faraday

fast Fourier transform

Digital process applied to in order to recover the information, essentially converting the digital signals from the time domain to the domain; see also

fast-scan television

See

FB

fine business : OK or alright; see also

FCC

Federal Communications Commission : agency of the US government that regulates communication in general; see also

FDM

FDMA

FEC

forward error correction : technique for controlling transmission errors during unreliable or communication; see also and

feeder

Short (primarily British) term for

feed line / feedline

Electrical wire or set of wires that transfers signals between your and your ; see also

feedline coupler / feed line coupler

See

feed point / feedpoint

Point in an system (sometimes antenna feed) where the meets the or other ; see also

feed-through capacitor / feedthrough capacitor

See

ferrite choke / ferrite bead Type of that uses a ferrite ceramic to suppress high in circuits; while ferrite chokes and ferrite beads are usually regarded as the same electrically, ferrite beads often refer to the ferrite ceramic core without the wire winding; see also

snap-on ferrite chokes

built-on ferrite choke

ferrite beads

FET

FFT

FHSS

Field Day

Annual twenty-four-hour period, usually the last full weekend in June, in which engage in a to collect as many verifiable with other hams as they could , to promote training for rapid deployment of equipment; see also and

field-effect transistor characterized by a high input , using , gate, and drain (the gate electrode creating an electric field to control the flow through the device), and whose general operating characteristics most resemble that of a vacuum tube; see also

field-effect transistor

FET symbols

field-programmable gate array Programmable designed to be configured by a customer after being manufactured, to create complex logic functions in a single integrated circuit; see also

FPGA

field strength meter / field-strength meter Electronic device that measures the intensity at a distance from a , once used to determine an antenna's and monitor relative output when making antenna and transmitter adjustments; see also

field strength meter

filament

Heating element of a

filter Circuit used to improve a signal (by removing from the signal, for example) or process a signal (between the and the in a , for example); see also Some filter types Some application-specific filters

graphs of various filter types

filter choke

See

filter skirt

See

final

• Slang for a concluding transmission before leaving the
  I'll be on your final
• Short for , especially the or used for
  After troubleshooting my , I had discovered that its finals were blown

final amplifier

Device or circuit placed in a where the output signal meets the , and can be little more than a in the of an or as large as a separate unit

finite impulse response

Type of whose impulse response is finite, in that it will eventually reach zero, resulting in a filter that is easier to design, and delays all components of the signal by the same amount; see also

FIR

fist

Older slang for a 's style
I can tell by his fist that he's new at operating
It's fun to an with a good fist

five-and-nine

See

five-by-five

See

five-by-nine

See

five-over-nine

See

fixed station / fixed-station

See

flash conversion ADC / flash ADC

Type of that uses a linear ladder and a comparator to measure the input voltage with respect to successive reference voltages; see also

flat braid

See

flat strap

See

flat-topping / flat topping

See

float voltage

at which a is maintained after being fully charged, to compensate for self-discharge, and which can vary significantly between battery types; see also

floating ground

Type of that is not electrically connected with the Earth, such that its electric can differ from that of ; see also

FM

• Nickname (also called FM broadcast and FM band) for the portion of the that is dedicated to , which in the US spans 87.8 MHz to 108.0 MHz, using 0.2 MHz spacing of odd tenths of one MHz; see also

FME for mobile equipment : model name for a common 50 Ω (primarily ) used for in applications; see also

FME connectors

foldback / fold back

Device (, , or of a ) output circuit that attempts to limit the amount of being drawn by the , to help protect the device from overload; see also

folded dipole antenna Type of half-wave typically constructed from one wavelength of wire forming a very thin loop, whose is approximately 300 Ω; see also

folded dipole antenna

folded dipole antenna diagram

formal traffic message

Urgent or important message specifically formatted with a (including the ), address (name and address of the intended recipient), text (actual message), and signature (identifies the originator); see also and

fox hunt / foxhunt / foxhunting / fox hunting Also called T-hunting, activity in which participants attempt to locate a hidden by means of , using a ; see also

FPGA

FPIS

frequency

Number of wave cycles that occur in one second, expressed in Hertz (symbol Hz), and can be approximated by the equation f = 300 ÷ λ, in which λ is the in meters and f is the frequency in MHz; see also the RF spectrum chart for frequency designations and

frequency coordinator

Volunteer person or group that is selected by local to recommend transmit / receive and other parameters for and stations; see also and

frequency counter Instrument that measures the precise of an input signal; see also

frequency counter

frequency deviation

See

frequency division multiple access

Method of accessing a particular channel of a transmission system that requires high-performance for reliable communication; see also

frequency-division multiplexing / frequency division multiplexing

Communication technique by which a is subdivided into a series of non-overlapping sub-bands, each of which is used to carry a separate (either or digital) signal, thereby giving the appearance of transmitting signals of multiple frequencies simultaneously on a single ; see also

frequency drift

Undesirable and arbitrary change in , often due to temperature variation and component aging, and expressed in Hz/s; see also

frequency-hopping spread-spectrum / frequency hopping spread spectrum

Technique of communication in which the of the transmitted signal is changed very rapidly according to a particular sequence that's also used by the receiving station; see also

frequency modulation Method of combining an information signal (your , , packets, etc.) with an signal of constant amplitude, so that the of the output signal varies with the information signal; see also and

AM and FM waveforms compared

frequency multiplier

See

frequency synthesis

Creation of multiple (synthesized frequencies) or from a single reference (often a -based) frequency signal, rather than from a continuously- circuit or multiple , the two primary methods being synthesis and ; see also

Fresnel zone Roughly ellipsoidal (football-shaped) region of space between a and a defined by potential object (obstruction) locations lying off the , resulting in possible constructive (aided by ) or destructive ( by ) patterns, as in , often resulting in and other irritating sound effects; see also

front end / front-end

Generic term for all the circuitry between the and the ; typically, all the components in the receiver that process the original incoming signal before it is converted to a lower ; see also

front end filter / front-end filter

Portion of a that provides a , to reduce strong, out-of-band signals and

front end overload / front-end overload

See

FRS

Family Radio Service : set of allocated by the under for , -free, and short-distance use, primarily in ; see also and a chart of assigned FRS/GMRS frequencies [PDF]

FSK frequency-shift keying : low-rate transmission in which the signal is transmitted through changes in a wave , of which and are the two major types, and with and being most applicable forms to (relatively) modern radio; see also

FSK441

frequency-shift keying, 441 baud : type of transmission () at 441 , designed to support communication using events; see also

FSTV

FT4

Franke-Taylor, 4-FSK : type of transmission (specifically, ) designed to support very communication by decoding signals many below the (low conditions) using , is less sensitive than or , but transmitting at 6-second intervals, which is 2.5 times faster than in completion; see also
• FT4 description

FT8

Franke-Taylor, 8-FSK : type of transmission (specifically, ) designed to support very communication by decoding signals many below the (low conditions) using , is less sensitive than or , but transmitting at 15-second intervals, which is four times faster in completion; see also

full break-in / full break in

operating (also called ) that allows a listening to between the very of a transmitting station's individual dots and dashes, making the communication resemble operation; likewise, allows the transmitting station to receive a transmission between sending code and characters; see also

full-duplex / full duplex

Communication method that allows sending and receiving transmissions simultaneously; see also

full gallon

See

full-quieting

Signal that's clean enough for the receiving to all perceptible , , and other , such that the transmitting station is understood clearly; see

full-wave bridge

that is constructed from a network of to perform the function; see also and

full-wave rectifier , such as a , that converts the entire input , instead of only a portion of it (see ), into ; see also

full-wave rectifier circuit

fundamental Lowest signal of a periodic ; see also Older slang for parent

fundamental and its overtones

fundamental overload

Undesirable effect by an signal that is strong enough to overload your circuitry (overcome your receiver's ability to reject it) by entering your receiver through its components rather than through the , possibly because the transmitting source is too close to your receiver or is transmitting with too much , resulting in of your or even shutting down
Note: fundamental overload is very similar to , except that desensing usually results in a severe reduction in receiver , whereas fundamental overload many times results in the receiver shutting down its ability to function at all

fuse Automatically operated electrical device, typically placed in series with a conductor that supplies to a circuit, that interrupts the flow of through the circuit when the current exceeds a specified rating for a particular amount of time, to protect the powered equipment in case of overload, and is typically not re-usable after being blown; see also and

glass tube fuses top = 'blown' bottom = 'good'

fuse symbols

Fusion

See

G5

Most severe level of measurable (labeled extreme), in terms

G5RV Shortened version of the and adaptation of the , , fed with and a through a length of open-wire (such as ), serving as one of its ; see also

G5RV antenna

G5RV antenna diagram

G5RV, Junior / G5RV Junior / G5RV, jr / G5RV jr

Version of the physically shortened for space restrictions, and typically limited to and higher

gain

• In general, ratio of the output to input signal (can be , , or ) strength change by a circuit or device, often measured in or similar unitless designation; see also
• Ratio of the quantified tendency of an to focus more of its radiated signal strength or reception ability in one direction than that in other directions, often expressed as a ratio of the radiated signal strength of the antena in the direction of maximum radiation to that of a (another way to look at it is the ratio of the amount of required by an with respect to the amount of power required by a particular to produce the same field strength at a point, expressed in , or the ratio of the amount of power required by a with respect to the amount of power required by a particular antenna to produce the same field strength at a point, expressed in ); see also and
• Quantified ability of a to produce an output signal ( or ) that is proportional to a weaker input signal; see also
• Quantified ability of an to increase signal strength () at its output, compared with that of its input, often measured in (or , depending on amplifier type); see also

gain antenna

Slang or nickname for an that exhibits a greater than 0 (typically much greater than zero, such as 6 dBd or 9 dBd), without regard to

gain compression Ratio of the amount of nonlinear ( due to ) with respect to its ideal linear gain, expressed in , and often associated with that have a wide (not to be confused with dynamic range compression, a desirable audio process); see also

graph showing gain compression

gallon

• Slang for 1000 watts (or often full gallon when referring to 1500 watts)
• Slang for 1 kW when referring to or 1.5 kW when referring to or other
My 's running a full gallon

gamma match / gamma matching system / gamma matching network technique that matches an to an by connecting the feedline to the antenna at both the center of the and at a fraction of the intended to one side of the element center, the series capacitance intended to cancel the of the matching network

gamma match

gamma match diagram

gassy tube

into which some air molecules have penetrated, possibly changing some of the tube characteristics; see also

gateway

radio that is used to connect other ham stations to the internet

gauge

See

Gaussian minimum-shift keying

Form of transmission in which the data stream is shaped with a Gaussian filter prior to modulation; see also

gear

• Slang or short for any kind of radio equipment
  I plan to some more gear at the next
• Slang or short for any kind of equipment
  Don't forget your snow gear on the way out

General

Current mid-level radio whose privileges cover most of all , and that certifies the as one having a much greater understanding of FCC regulations, operating practices, and electronics than that of a class licensee; see also

general coverage

Feature attributed to a that can accept and signals outside the , specifically (typically) 100 kHz to 30 MHz, often for

geomagnetic index / geomagnetic indices Semi-logarithmic quantification of disturbances in the earth's magnetic field, denoted primarily by the K-index (0 through 9), which can vary throughout the day (an indicator of the short-term stability of the earth's magnetic field), and often accompanied by the A-index (0 through 400), which is a daily average (an indicator of the long-term stability of the earth's magnetc field); because measurements of these values could vary between earthly locations, the planetary (meaning global) KP-index and are often provided instead; disturbances such as can affect radio communication greatly, with generally the higher the index the more HF communication is degraded; see also

solar activity report showing the current planetary (globally averaged) indices KP and AP in the upper portion of the left column

geomagnetic storm

Temporary disturbance in the earth's , resulting in both degraded high-latitude and , which can reflect signals; see also

geometrical horizon / geometric horizon

See

geostationary Appears to stay in one position, or does not appear to move, relative to the earth, referring to an object that is orbiting in a circle directly above the equator, applicable to and orbits; see also Note: a geostationary orbit is a special case of the geosynchronous orbit, in that not only is the orbiting object synchronized with the earth's rotation, but it's also orbiting 1) in a circle and 2) directly over the equator, making it appear motionless

geostationary illustration

get kit / get-kit

See

getter

Reactive material deposited in a to absorb or chemically combine with air molecules that penetrate the evacuated enclosure, to maintain the tube's vacuum; see also and

GFCI

GFI

giga

Prefix, or units modifier, to indicate × 1,000,000,000 or × 10⁹, and is abbreviated G

gin pole Rigid rod, or supported pole with a pulley system, to safely lift or hoist an , section, or other equipment into a position where it can be secured to a structure or another section below it; see also

gin pole

gin pole use diagram

glass-mount / glass mount / glassmount Type of made from (typically) two metal pieces that adhere to opposite sides of a glass window or other non-conductive surface, and connect to each other by , with one of the pieces forming the base of an antenna, typically for and applications

glass-mount antenna

glowbug Slang for a or made with ; see also and

glowbug

GMRS

General Mobile Radio Service : set of allocated by the under for , , and short-distance use, primarily in ; see also and a chart of assigned FRS/GMRS frequencies [PDF]

GMSK

GMT

See

go ahead

begin speaking now; see also

go-box / go box

• See
• See

go-kit / go kit / gokit Type of survival equipment package (also known as go-bag, 72-hour kit, jump-kit, ready-kit, bug-out bag, grab-n-go kit, get-kit, disaster-kit, bail-out bag, go box, and battle box, with the longer-term (as in several days) type more appropriately referred to as a survival kit) that can be quickly picked up and carried by an individual during a moment of or other crisis, and usable for at least 72 hours; see also

go-kit

goniometer Device that measures the angle between two distant objects with respect to a stationary position (similar to a protractor, but typically with moving parts) to aid in by use of , for example; see also

goniometer

GOTA Get on the Air : general invitation to radio to become active in the ; see also Get-On-The-Air : particular set up in conjunction with to allow inactive or non- individuals to participate in making , subject to ARRL rules [PDF]

GPS

global positioning system : government-sponsored and space-based navigation system that provides location and time information anywhere on or near the earth within of four or more GPS satellites, regardless of weather conditions; see also

grab-n-go / grab and go / grab-and-go / grab & go

See

grant

Issue, award, or bestowal of a or certificate, typically the result of proficiency demonstration or examination, such as a license grant

Gray code

Digital code (binary numeral system) in which the character preceding or following a particular character differs by only one bit, which facilitates error detection; see also

gray-line / gray line / grayline / grey-line

Type of by enhanced along the between daylight and darkness, which occurs around sunrise and sunset () when D-layer absorption (which absorbs HF signals of lower than 15 MHz) is weak, while and propagation remain strong; see also and

green stamp Slang for US dollar (USD) bill

green stamp

grid

• Portion of a that controls the flow of electrons internally from the to the (plate), or in other words, the flow of internally from the anode to the cathode, and usually includes a control grid, screen grid, and suppressor grid; see also
• Slang or short for
• Short for

grid current

See

grid dip meter / grid-dip meter / grid-dip-meter / grid dip oscillator

See

grid locator

Also called Maidenhead Locator and locator, world-wide system of letter-number designators assigned to a specific geographical area known as a , outlined by latitude and longitude boundaries; see also

grid power

See

grid square

Letter-number designator assigned to a specific geographical area measuring 2.5 minutes latitude by 5 minutes longitude, by the system; see also

ground Reference point in a circuit by which are measured, and often include , and ; common return path for electric in a circuit; see also and Physical connection to earth , often called earth ground, and not to be confused with , which ensures two points have the same potential, which can be earth ground potential

ground symbols

ground braid / grounding braid / flat braid Cable typically made of braided tinned copper or braided copper for , which ensures two points (such as equipment) being connected have the same electric , which ideally is potential

ground braid

ground-fault circuit interrupter / ground fault circuit interrupter Type of fast-acting (formerly GFI, ground-fault interrupter, and outside the US often known as RCD, residual-current device) designed to shut off electric in a circuit when it detects that more is flowing through one conductor than through its return path conductor, indicating a possible imbalance, which typically occurs if part of the current is flowing through an unintended path, such as water or human tissue; see also

American GFCI outlet

grounded-grid amplifier / grounded grid amplifier

Type of , with the (and sometimes the screen grid) of the tube connected to , which configuration provides a low input and simplifies design, while nearly eliminating the potential for self-, but suffers from relatively low ; see also

ground loop

Undesirable condition in which two points in a circuit that are supposed to be at the same (usually ) are actually at different potentials; see also

ground plane Type of named for the electrically conductive surface or network (of rods, wires, cones, screens, etc.) attached to the antenna to compensate for lack of direct connection to Electrically conductive surface (, car body, refrigerator, etc.) or network (of rods, wires, cones, screens, etc.) that serves as the ground part of a (typically ) ; see also Electrically conductive area of a printed circuit board or independent circuit that serves as the signal reference for the circuit

ground plane antenna

ground rod Metallic electrode installed in direct contact by relatively large surface-area with the (dirt), to provide a path to earth ground or electrical reference; see also

copper-clad ground rod

ground strap / grounding strap / copper strap Flat ribbon conductor made of copper (often called flat strap or copper strap) for equipment in your to minimize losses in your grounding system

flat copper strap

ground wave / ground-wave Type of (also called surface wave) that uses the area between the surface of the earth and the for signal transmission, and can often follow the curvature of the earth for some distance, thereby extending beyond the ; see also

grounding

• System of interconnected wires, , , and cabling that provides a stable electrical reference to (preferably earth ground); see also
• Practice of providing or ensuring a connection to potential (also called earthing in the UK)

guard

Slang for aircraft (121.5 MHz AM for civilian and 243.0 MHz AM for military) reserved for distress communication; see also

guide wire / guide-wire / guidewire

Misspelling or mis-pronunciation of

gummers

Slang or short for

Gunn diode Electronic (also known as a transferred electron device) that is uniquely distinguished from other kinds of because it presents a negative with a positive applied ; used primarily in high- applications such as speed guns, , and microwave ovens; see also

Gunn diodes

Gunn diode symbol

Gunn diode oscillator

Circuit that is dependent on the negative properties of a to produce ; see also

guy-wire / guy wire / guywire / guy-line Rope, cord, or other (typically flexible) cable used to support a or of a , to keep the structure in a particular position or prevent it from falling or from excessive motion, due to or other movement; see also and

guy-wires supporting an antenna mast

H-plane / H plane Flat geometric surface defined by the magnetic wave component of an in a particular direction, also known as the vertical plane or elevation plane of a horizontally , or the horizontal plane or plane of a polarized antenna; see also

E and H planes for a vertical antenna

E and H planes for a Yagi antenna

HAAT

height above average terrain : difference (also known as EHAAT, or effective height above average terrain) in altitude of an site and the altitude of the average surrounding landscape of interest, often used by engineers, but also used by those installing an to help determine repeater range; see also

half-duplex / half duplex

Communication method that allows sending and receiving transmissions one direction at a time, so that the listening is unable to transmit until after the end of the currently transmitting signal; see also

half-power bandwidth / half power bandwidth / halfpower bandwidth

See

half-power beamwidth

See

half-wave dipole / halfwave dipole Type of that consists of two identical, and usually bilaterally symmetrical, conductive that together are measured to be one-half- of the intended times the of the element material, and is the antenna that provides the reference for measurements

half-wave dipole antenna

half-wave dipole antenna diagram

half-wave rectifier

Circuit or device that converts () exactly half of the input , instead of the entire signal (see ), into ; see also

ham Slang for hobby, practice, or equipment associated with , originally a taunt expressed by professional operators (some assert the unsubstantiated claim that HAM might be an acronym); see also for an explanation on the possible origin of the word for yet another explanation I enjoy ham Richard owns a lot of ham Slang for hobbyist or practitioner My father was also a ham

HamCation

Specific and unusually large held annually in Orlando, Florida; see also and the main HamCation website

ham cave / hamcave

See

HamCon / Ham-Con

See

hamexpo

See

hamfest

Informal social gathering or convention (sometimes hamvention and hamexpo and Ham-Con) between people who are interested in radio, and can include exhibits, forums, and a ; see also and

ham-in-a-can / ham in a can Slang for a , including , , and , along with other support , that is built into a carrying case, such as an ammunition ("ammo") can, similar to a Slang for equipment that's been installed on, or attached to, a computer dedicated as a digital for communication using , , or other

ham-in-a-can

ham net / hamnet

See

ham police

See

ham radio

Nickname for

ham shack / hamshack

See

hamspeak / ham speak

Language, terminology, and slang used among radio , hobbyists, and enthusiasts

hamvention

See

handheld transceiver (also known as a handy-talkie or HT or handy-scratchy or simply handy) that is small enough to carry around in your hand; see also and

handheld transceiver

handle

• Older slang for first name
• CB slang for nickname

handy-talkie / handy-scratchy

See

hang time / hangtime

See

hard line / hardline / hard-line Type of that consists of a solid outer conductor instead of braid, resulting in very low , typically used in applications; see also

Heliax hardline

harmful interference

Serious degredation, obstruction, repeated interruption (also called willful interference if it is deliberate), or excessive that prevents proper operation at any time, especially during an or other critical moment (said to be harmful because a person's life could depend on your ability to communicate)

harmonic Integer multiple of a , such that the fundamental frequency is the first harmonic, twice the fundamental frequency is the second harmonic, etc. ( do not include the fundamental frequency); see also Older slang for child, particularly that of a

Hartley oscillator circuit that generates a using supplied through a , and is one of (at least) three primary oscillator circuits used in equipment, commonly in a circuit; see also

circuit employing a Hartley oscillator

hash

Short for and older slang for

headphones / head phones Pair of small speakers (sometimes earphones and cans) worn on or over the ears by a , can also be a single speaker instead of a pair; see also

headphones

headset / head set Combination of and used as a unit by a for two-way communication; see also

headset

heater

Nickname for

Heliax Brand name (often Andrew Heliax or Andrew cable) of a very low-, rugged, and relatively expensive , often characterized by a corrugated outer and a low-density foam (often abbreviated LDF in product names) or air

helical resonator Type of used typically in a to isolate or protect a particular signal from by other RF signals close in to that used by nearby repeaters or other (such as and telephone); see also and

VHF helical resonator

Hepburn map

Graphical image to aid in predicting the probability of for

heterodyne / heterodyning (combining) of two signals to shift them into a range that is easier to process, for purposes of and ; see also Audible rise and/or fall whine created by the of two mismatched signals that are attempting to combine into an

audible heterodyning example click to listen

HF

high frequency : overall range of 3 MHz to 30 MHz (although most also include the band when considering the HF spectrum); see also and the HF frequency designation in the RF spectrum

HF scatter

of signals as they are scattered into the through several different paths, often resulting in a wavering or sound

HI HI / HIHI

ha ha : laughter; see also

high-pass filter Circuit or device that out most or all signals with lower than a particular cut-off frequency, thereby allowing signals of all higher frequencies to pass through the device, useful for preventing from entering sensitive circuits and low-frequency signals from interfering with the intended signal, such as with the case of ; see also

high-pass filter

high-speed multimedia radio

Wireless high-speed network (mesh) over using commercial off-the-shelf hardware such as a WiFi router or equipment, for use in Amateur Radio Emergency Data Network (AREDN); see also
• main Broadband-Hamnet (BBHN) / HSMM-Mesh website
• main AREDN (successor to BBHN) website

Hilbert transform filter / Hilbert-transform filter

Type of often used to generate a signal; see also

hit the repeater / hitting the repeater

Slang for access the repeater or communicate with the repeater, in an effort to make use of a 's repeat and other functions (such as or )
I can you, but you're not hitting the repeater

HOA

homeowner association : corporation established by a real estate developer to market, manage, and sell homes and lots in a residential subdivision, which management can include enforcement of applicable that limit the installation of radio equipment; see also

hold the repeater / holding the repeater

Slang for keep the repeater open or maintain repeater access, in an effort to maintain continuous use of a 's repeat and other functions (such as or ); see also
I can you, but you're not holding the repeater

hole Lack of an electron at a position where one could exist in an atom or atomic lattice of a doped material; see also

hole left after an electron leaves an atom

hole-mount / hole mount

See

holiday-style / holiday style

Slang for a relatively relaxed operating plan (typically in reference to a or station), in which operation might be seccondary to the intended journey, or that making contacts is not the station's first priority (the station will operate as time permits, in between activities, for example); often synonymous with

homebrew / home brew

Slang for home-made; see also and and the DIY page

hop

Travel path of a from the to the , then down to a ( refers to the mode, while hop refers to the path of travel); see also and

horizon Perceived boundary between earth and sky from a given height visual horizon / visible horizon : also known as skyline, apparent line or circle that separates the earth from the sky, whose distance is approximately 8 percent greater than the geometrical horizon because of downward bending caused by atmospheric density variations; see also radio horizon : distance over which two can communicate by direct path (also known as line-of-sight propagation when applied to signals of frequencies higher than 30 MHz), approximately 15 percent greater than the geometrical horizon because of downward bending caused by atmospheric density variations; see also and geometrical horizon / true horizon : calculated boundary between a spherical body (such as a star, planet, or moon, but in most applications, a spherical earth) and its sky, assuming ideal (no atmosphere) conditions; see also

diagram showing geometrical horizon H to observer O of height h

diagram showing radio horizon compared with visual horizon

horizontal loop

See

horizontal polarization Alignment of a signal's parallel to the level surface of the earth (actually, perpendicular to the vector force of Earth's gravity), and a signal with such an alignment is said to be horizontally polarized; see also

hot

• Slang for wire or other conductor in a (particularly ) electrical system that has electric relative to ; see also
  The is inserted into the hot wire side of your
• Slang for over- that results in
  Your is running hot
• Slang for excessive amount of signal flowing in the cabinetry or housing; see also
  My housing is way too hot (notice the reference here is not to temperature)

hot-carrier diode / hot carrier diode

See

hot mic

Slang for that is turned on
I accidentally some rather personal comments while my was hot

house current / house power

See

household power

General-purpose household electrical that is supplied to a home, business, or facility; see also
Note: people in the UK tend to agree on the term mains power when referring to household electrical power, while we in the US are in general disagreement on what to call it, due primarily to the conflict between common modern usage and precise descriptive language, and so have come to use a variety of terms such as house current, AC power, utility power, city power, wall power, outlet power, line voltage, etc., for convenient reference

HPSDR

high-performance software-defined radio : open-source (GNU type) hardware and software project defining next-generation by a more modular approach (using a common bus); see also and the main OpenHPSDR website

HSMM

HT

hum

• Unwanted and often constant low- sound, characteristic of an unintended or within a circuit
• See

I/Q data / IQ / I and Q signal in-phase / quadrature : components of a signal that reflect changes in the amplitude and phase of a sine wave, used for or in analysis; see also

I/Q components of a modulated signal

I signal / I data

See

iambic keyer / iambic paddle Dual-paddle telegraph that requires a (typically sideways) squeezing action to produce tones, unlike a ; see also

iambic keyer

IARP

International Amateur Radio Permit : permit that allows a licensed of participating (North, South, Central American, plus Caribbean) countries to operate in any other participating country without an additional or permit; see also and
Note: operating an amateur in an IARP country using class or higher privileges ("Class 1") requires demonstration of proficiency

IARU

International Amateur Radio Union : international collection of national organizations that provides a forum to address common concerns and represents issues to the ; see also and IARU / ITU region map

IC

ID

• identification : in most cases, a
  The 's ID is K7UVA
• State or send a
  You need to ID every ten minutes and at the end of your transmission

IF

IIR

image

Communication (such as and ) used for transmitting pictures over , often for reporting severe weather information, location announcements, and individual identification; see also

image rejection

Ability for a to reject unwanted signals that result from ; see also

image response

Undesirable signal generated when a a with a received signal to produce an signal; in other words, the unwanted signal is a 'mirror image' of the receive signal in response to the mixing function; see also and

imbalance current

See

IMD

IMF

IMI

impedance

Quantity of opposition to flow in a circuit, expressed in ohms (symbol Ω) and defined as Z = R + jX, in which Z is the impedance, R is the real () , j is the imaginary unit, and X is the see also and

impedance matching

Practice of designing or adjusting the of a circuit or signal to maximize the amount of transferred to its , or minimize the amount of returned from its load, by presenting a complex conjugate of the load impedance, the failure to properly match a load to its source called an impedance mis-match; see also

IMRR

image response rejection ratio : ratio of signal strength produced by the received signal with respect to that produced by the , expressed in ; see also

in-and-out

See

incident

Situation, occurrence, or risk that poses a threat to health, life, property, or environment, and one that might require the services of an Incident Management Team or Incident Response Team; see also

Incident Commander

Highest-level leader in the National Incident Management System during a particular , and the person in charge of managing and coordinating all resources in conjunction with the incident; see also and

inductance

Property of a conductor that defines its ability to store electrical energy in a magnetic field to resist changes in the through it, expressed in henries (symbol H), and whose magnetic field can induce (create) a voltage in itself and one or more nearby conductors; see also

inductance index

Specification of , dependent upon its material , dimensions, and shape, expressed in per square turn

inductive coupling

Effect of two or more circuits not connected to each other being close enough that an through one can result in an AC across the others through ; see also

inductive reactance

Imaginary quantity of opposition to flow in a circuit () due to , that varies with and is expressed in ohms (symbol Ω) and defined as = ωL, in which L is the inductance and ω is the frequency in radians (ω = 2πf, in which f is the frequency in Hz); see also

inductive time constant

See

inductor Electrical component that resists changes in electric passing through it and stores energy in a magnetic field; these include air- , iron-core , and ; see also

assorted inductors

inductor symbols A = air-core B = ferrite choke C = iron-core

inductor core Centrally located section (sometimes called a ) of greatest magnetic field concentration, highly dependent on material type, of which soft iron, powdered metals, ferrite, air, and some special alloys are among the most common; see also

assorted inductor cores

inductor tap

See

infinite impulse response

Type of whose impulse response can be infinite, in that it might never reach zero, resulting in a filter that is generally easier to implement for a given set of requirements; see also

in-phase / in phase / inphase

• Description of two signals whose values or values reach their peak levels at the same time; see also
• See

input-offset voltage / input offset voltage

Differential input of an required to bring its open-loop output voltage to zero; see also

input frequency

Value of a 's at which it receives incoming signals to eventually re-transmit them on its ; see also

insertion loss

Signal introduced by the addition of an electric component, such as a , , meter, , or extension; see also

insulator

Material that does not conduct electric under working , such as plastics and glass; see also

integrated circuit

Device that combines several and other components into a single package (chip) or collection of packages (chipset), which can be digital (such as a ) or analog (such as a voltage ); see also

intercept point

See

interference

Anything that discrupts or modifies a signal; interruption or excessive in a radio transmission; see also and
Your radio is putting out a lot of interference

intermediate frequency

to which a signal is shifted as an intermediate step during transmission or reception to improve ; see also

intermodulation distortion

Undesirable signal (often abbreviated intermod and IMD) generated by the of two or more signals with different , arising from system nonlinearities, and resulting in and (IMI) with an excessively large (not to be confused with ); see also and

intermodulation interference

Undesirable effect (often abbreviated IMI) of (IMD)

international reply coupon

Post office coupon that at one time could be exchanged for postage stamps representing the minimum return postage for a card or letter to the country that issued the coupon, but is no longer issued by US post offices; see also

interplanetary magnetic field Portion of the solar magnetic field that is carried by the among the planets of the solar system (interplanetary space); see also

IMF interaction

interpolation

Process of mathematically increasing the sample rate of a signal (upsampling); for example, interpolate a digital signal by three, then it by four, to adjust its sampling rate by a factor of 3/4; see also

in the mud

See

intrinsic Meaning natural state, as it applies to , material or portion (region) of material that has not been doped, but exists in its extremely pure form, opposite of extrinsic; see also

PIN diode diagram showing intrinsic region i

inverted-L antenna / inverted L antenna / inverted ell antenna Type of whose section is bent over and made parallel to the ground

inverted-L antenna diagram

inverted-V antenna / inverted V antenna / inverted vee antenna Type of whose is the highest part of the structure, with sides slanted down toward the ground; see also

inverted-V antenna diagram

inverting

Type of non--specific that re-transmits a received signal at the same passband offset from the end of its as that of the received signal, but on the opposite end of the passband (roughly mirrored image of the received signal); see also and
Example: suppose that a linear transponder's receive passband is 432.000 MHz to 432.100 MHz, and its transmit passband is 146.000 MHz to 146.100 MHz. If it receives an signal on 432.008 MHz (therefore using a passband offset of 432.008 MHz − 432.000 MHz = 0.008 MHz), the transponder will re-transmit on (146.100 MHz − 0.008 MHz = ) 146.092 MHz, and in

ionizing radiation

, made of both energetic subatomic particles and high- (typically > 3 PHz), that possesses enough energy to ionize (free electrons from) the atoms and molecules of living tissue, which in turn can cause genetic damage; see also and

ionoscatter

See

ionosphere Region of the upper atmosphere that is ionized by solar radiation and influences to distant places on earth as a result, reaching its maximum height where the sun is overhead; see also

ionospheric layers

ionospheric scatter

Form of (sometimes called ionoscatter) in which are by the of the , allowing for communication between 25 MHz and 100 MHz as a result of irregularities or discontinuities in that atmospheric region

IOTA

Islands on the Air : list of islands or island groups designated and labeled by the Radio Society of Great Britain (RSGB, the British counterpart of the ) for and other radio-related purposes; see also

IP3

See

IRC

IRLP

Internet Radio Linking Project : system that radio around the world using Voice over IP by keying specific signals; see also and the main IRLP website

isolator

See

isotropic antenna

Theoretical used as a reference for antenna measurements, and has no gain in any direction; see also

isotropic radiator

Hypothetical point source of , used as a measurement reference for and other ; see also

ISS International Space Station : habitable facility in permanent , used for testing and experimentation of a huge variety of cases under (seeming) gravity-free, out-of-atmosphere, and other physical conditions unique to those in earth orbit; see also main ISS website

ITU

International Telecommunication Union : United Nations agency responsible for issues that concern information and communication technologies, and coordinates the shared global use of the spectrum; see also

ITU Region Any one of 3 major geographic world areas, as defined and named numerically by the ; see also and ITU Region map