Radio
Terminology
(A-M)
A
ACC : (ACCessory)
Access code : one or more numbers and/or symbols that are keyed in
with a telephone key pad to activate a repeater function e.g. autopatch, link
etc.
Adjacent-channel interference : when a receiver
is tuned to a specific frequency and interference is received on a nearby
frequency.
AF : (Audio Frequency)
AFC : (Automatic Frequency Control) automatically
compensate frequency drift.
AFSK : (Audio Frequency Shift Keying)
AGC : (Automatic Gain Control) automatically
optimize receiver amplifier gain.
ALC : (Automatic Limiting Control) limits RF
drive level to power amplifier during transmit to prevent distortion.
Alternating current (ac) :
electrical current
that flows first in one direction in a wire and then in the other. The applied
voltage is also changing polarity. This direction reversal continues at a rate
that depends on the frequency of the ac.
AM (amplitude modulation) : a method of combining
an information signal and an RF (radio frequency) carrier. In double-sideband
voice AM transmission, we use the voice information to vary (modulate) the
amplitude of an RF carrier. Short-wave broadcast stations use this type of AM,
as do stations in the Standard Broadcast Band (535-1710 kHz). Few amateurs use
double-sideband voice AM, but a variation, known as single sideband, is very
popular.
Amateur auxiliary : a voluntary organization,
administered by the ARRL. The primary objectives are to foster amateur
self-regulation and compliance with the rules.
Amateur operator : a
person holding a written authorization to be the control operator of an amateur
station.
Amateur service : a radio communication service
for the purpose of self-training, intercommunication and technical
investigations carried out by amateurs, that is, duly authorized persons
interested in radio technique solely with a personal aim and without pecuniary
interest.
Amateur station :
a station licensed in the
amateur service, including the necessary equipment, used for amateur
communication.
Amateur Teleprinting Over Radio (AMTOR) : AMTOR
provides error-correcting capabilities. See Automatic Repeat Request and Forward
Error Correction.
American National Standard Code for Information
Interchange (ASCII) : a seven-bit digital code used in computer and radio
teletype applications.
Ammeter :
a test instrument that measures
current.
Ampere (A) :
the basic unit of electrical
current. Current is a measure of the electron flow through a circuit. If we
could count electrons, we would find that there are 6.24 x 10^18 electrons
moving past a point in one second, we have a current of one ampere. We
abbreviate amperes as amps.
AMSAT : (AMateur SATellite)
AMTOR : (AMateur Teleprinting Over Radio)
ANF : (Automatic Notch Filter)
ANL : (Automatic Noise Limiter) eliminates
impulse and static noise peaks.
ANT : (ANTenna)
Antenna :
a device that picks up or sends out
radio frequency energy.
Antenna ground system : term used for a RF
reference potential for some types of antennas. Most unbalanced or asymmetrical
antennas need a good RF ground.
Antenna impedance : the impedance of an antenna
at its resonance. Although an antenna's impedance fluctuates with frequency of
operation, an antenna should be 50 Ω for most transceivers.
Antenna matching : when
the antenna's impedance at resonance is at optimum performance for your
transmitter output circuit.
Antenna separation : the physical spacing between transmit and receive
antennas, when separate antennas are used.
Antenna switch :
a switch used to connect one
transmitter, receiver, or transceiver to several different antennas.
Antenna tuner :
a device that matches the antenna
system input impedance to the transmitter, receiver, or transceiver output
impedance.
APC : (Automatic Power Control) current limiting
of power amplifier to prevent damage to finals in high SWR conditions.
APRS (Amateur Packet Reporting System) :
a system which supports
plotting of station positions on screen maps.
ARES : (Amateur Radio Emergency Service) ARES is
a public-service organization of the ARRL.
ARRL : (American Radio Relay League) the national
association for amateur radio in the US.
ASCII : (American National Standard Code for
Information Interchange)
ASL (above sea level) : a method of measuring antenna height.
Athermal effects of RF radiation : biological
effects of RF radiation not directly related to heating effects in exposed body
tissue. While research is ongoing, no conclusive evidence has been found to
demonstrate that such fields cause serious health effects at low-level energy
exposure.
ATT : (ATTenuator) a network designed to reduce
the amplitude of a signal.
ATV : (Amateur Television) FSTV, SSTV
Audio rectification : interference to
electronic devices caused by a strong RF field that is rectified and amplified
in the device.
Audio-frequency shift keying (AFSK) : a method
of transmitting radioteletype information by switching between two audio tones
fed into an FM transmitter microphone input. This is the RTTY mode most often
used on VHF and UHF.
Automatic Repeat Request (ARQ) : one of two
AMTOR communication modes. In ARQ, also called Mode A, the two stations are
constantly confirming each other's transmissions. If information is lost, it is
repeated until the receiving station confirms reception.
Autopatch; auto patch: a device that interfaces a
repeater to the telephone system to permit repeater users to make
telephone calls. Often just called a "patch."
Average power : power measured on a standard
power meter.
Azimuthal-equidistant projection map : a map
made with its center at one geographic location and the rest of the continents
projected from that point. Also called a great-circle map, this map is the most
useful type for determining where to point a directional antenna to communicate
with a specific location.
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B
Backscatter : form of ionospheric
propagation via the E and F layers allowing stations to hear other stations
within the skip zones.
Balanced line : feed line with two
conductors having equal but opposite voltages, with neither conductor at ground
potential.
Balanced modulator : a mixer
circuit used in a single-sideband suppressed-carrier transmitter to combine a
voice signal and the RF carrier-oscillator signal. The balanced modulator
isolates the input signals from each other and the output, so that only the sum
and the difference of the two input signals reach the output. The original
carrier-oscillator signal or the pure audio signal do not reach the output. A
modulated RF signal contains some information to be transmitted.
Balun : contraction for balanced to
unbalanced. A device to couple a balanced load to an unbalanced source, or vice
versa.
Band (amateur radio frequency band) : the range of
contiguous frequencies over which amateurs may communicate.
Band-opening : a condition that results in
greater-than-normal communication range on the VHF and UHF bands.
Band-pass filter :
a circuit that
allows signals to go through it only if they are within a certain range of
frequencies. It attenuates signals above and below this range.
Band-plan; band plan : a voluntary system of frequency allocations in each
amateur radio band.
Band spread :
a receiver quality used to describe
how far apart stations on different nearby frequencies will seem to be. We
usually express band spread as the number of kilohertz that the frequency
changes per turning-knob rotation. Band spread and frequency resolution are
related. The amount of band spread determines how easily signals can be tuned.
Bandwidth :
the width of a frequency band outside
of which the mean power is attenuated at least 26 dB below the mean power of the
total emission, including allowances for transmitter drift and Doppler shift.
Bandwidth describes the range of frequencies that a radio transmission occupies.
Bank: memory bank.
Battery :
a device that converts chemical energy
into electrical energy.
Baudot : a five-bit digital code used in
teleprinter application.
BCI : (BroadCast Interference)
Beacon
or beacon station : An amateur station transmitting
communications for the purposes of observation of propagation and reception or
other related experimental activities.
Beam antenna :
a directional antenna. A beam
antenna must be rotated to provide coverage in different directions.
Beat-frequency oscillator (BFO) :
a receiver
circuit that provides a signal to the detector. The BFO signal mixes with the
incoming signal to produce an audio tone for CW reception. A BFO is needed to
copy CW and SSB signals.
Bleeder resistor :
a large-value resistor
connected to the filter capacitor in a power supply to discharge the filter
capacitors when the supply is switched off.
Block diagram :
a drawing using boxes to
represent sections of a complicated device or process. The block diagram shows
the connections between sections.
BNC : (Bayonet Neill-Concelman) a type of antenna
connector.
BPF : (Band Pass Filter)
Break : the word used to interrupt a
conversation on a repeater to indicate that there is an
emergency.
Broadcasting :
transmissions intended to be
received by the general public, either direct or relayed.
Busy lockout : inhibits transmit on a frequency
in use.
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C
Callsign; call sign : sequence of
letters and numbers used to identify amateur radio operators and issued by the
FCC.
CAP : (Civil Air Patrol) volunteer
affiliate of the United States Air Force.
Capacitance : a measure of the
ability of a capacitor to store energy in an electric field.
Capacitor : an electronic component
composed of two or more conductive plates separated by an insulating material. A
capacitor stores energy in an electric field.
Carrier : your un-modulated (no speech) transmitter
signal.
Carrier frequency offset : (=
Carrier Shift) distance betweens mark and space of the carrier for RTTY or
similar communications.
CAS (carrier activated switch) : see
COR
Cathode-ray tube (CRT) : a vacuum
tube with a phosphor coding on the inside of the face. CRTs are used in
oscilloscopes and as the "picture tube" in television receivers and
computer monitors.
Cavity resonator : a sharply tuned circuit using the
physical dimensional resonance of one or more tuned cavities.
CBR : (Cross Band Repeater) a
repeater which receives incoming signals and re-transmits them in different
bands - e.g. receives 144 MHz bands and re-transmits 430 (440) MHz bands.
CCW : (Counter ClockWise)
Centi : the metric prefix for 10^-2,
or divide by 100.
CH : (CHannel)
Channel: the pair of frequencies (input and
output) used by a repeater.
Channel spacing : the frequency spacing between adjacent frequency
allocations - may be 50, 30, 25, 15 or 12.5kHz, depending upon the convention in
use in the area of the repeater.
Chassis ground :
the common connection for all
parts of a circuit that connect to the negative side of the power supply.
Chirp :
a slight shift in the transmitter
frequency each time you key the transmitter.
CI-V : (Icom computer Control Interface) allows
multiple radio control simultaneously.
Closed repeater : a repeater whose access is limited to a select group
(see also open repeater).
Closed, or complete circuit :
an electrical
circuit with an uninterrupted path for the current to follow. Turning a switch
on, for example, closes or completes the circuit, allowing current to flow.
Coaxial cable :
coax (pronounced kó-aks). A type
of feed line with one conductor inside the other.
Co-channel interference : the interference resulting when a repeater
receives signals from a distant repeater on the same frequency pair.
Coil : a conductor wound into a series of
loops. See also inductor.
Color code :
a system in which numerical values
are assigned to various colors. Colored stripes are painted on the body of
resistors and sometimes other components to show their value.
Conductor :
a material that has a loose grip on
its electrons, so an electrical current can pass through it.
Connected :
the condition in which two
packet-radio stations are sending information to each other. Each is
acknowledging when the data has been received correctly.
Continuous wave (CW) :
Morse code telegraphy.
Controller : the control system within a repeater which may include
turning the repeater on-off, timing transmissions, sending the identification
signal, controlling the autopatch and CTCSS encoder/decoder.
Control operator : an amateur operator designated
by the licensee of a station to be responsible for the transmissions of an
amateur station.
Control point :
the locations at which the
control operator function is performed.
Controlled environment :
any area in which an RF
signal may cause radiation exposure to people who are aware of the radiated
electric and magnetic fields and who can exercise some control over their
exposure to these fields. The FCC generally considers amateur operators and
their families to be in a controlled RF exposure environment to determine the
maximum permissible exposure levels.
Conversion :
number of IF circuits in the
receiver.
COR (carrier-operated relay) : a device that causes the repeater to
transmit in response to a received signal.
Core : the material used in the center of
an inductor coil, where magnetic fields is concentrated.
Courtesy tone: a tone or beep
transmitted by a repeater to indicate that it is okay for the next station to
begin transmitting. The courtesy tone is designated to allow a pause between
transmissions on a repeater, so other stations can call. It is also indicates
that the time-out timer has been reset.
Coverage: the geographic area within which
the repeater provides communication.
CPU :
(Central Processing Unit)
CQ :
"calling any station" : the
general call when requesting a conversation with anyone.
Critical angle : if radio waves leave an
antenna at an angle greater than the critical angle for that frequency they will
pass through the ionosphere instead of returning to Earth.
Critical frequency : the highest frequency at
which a vertically incident radio wave will return from the ionosphere. Above
the critical frequency radio signals pass through the ionosphere instead of
returning to Earth.
Cross-band : the process of transmitting on one band and receiving on
another.
Crystal oscillator :
a device that uses a quartz
crystal to keep the frequency of a transmitter constant.
Crystal-controlled transmitter :
a simple type of
transmitter that consists of a crystal oscillator followed by driver and power
amplifier stages.
CTCSS (Continuous Tone-Coded Squelch System) : This is a sub-audible
tone transmitted by your radio in addition to your voice signal. When it is
equipped with a CTCSS decoder, a repeater will not function unless it hears the
CTCSS tone and the "carrier" signal from your transmitter. Different
CTCSS tones are in use for different repeaters or areas. These may be applied to
input or output frequencies, or both. CTCSS tones are used to minimize the
effects of co-channel interference due to band-openings causing reception of
distant signals. Also called a PL tone.
Cubical quad antenna :
an antenna built with its
elements in the shape of four-sided loops.
Current :
a flow of electrons in an electrical
circuit.
CW (Morse code) :
a communications mode
transmitted by on/off keying of a radio frequency signal. Another name for
international Morse code.
CW filter :
used to narrow IF passband to improve
reception in crowded band conditions.
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D
D region : the lowest region of the ionosphere.
The D region contributes very little to short-wave radio propagation. It acts
mainly to absorb energy from radio waves as they pass through it. This absorption
has significant effect on signals below about 7.5 MHz during daylight.
Data : computer-based communications
modes, such as packet radio which can be used to transmit and receive
computer files, or digital information.
Data communications :
transfer of
data between two or more locations.
dBd : unit of RF power as compared
to a dipole antenna.
dBi : unit of RF power as compared
to an isotropic antenna.
dBm : decibels measure, 1 mW with a
load impedance of 600 Ω (0 dBm = 1 mW)
DC : (direct
current)
DC ground : a
connection point directly to chassis or battery ground to prevent build-up of
hazardous DC voltages.
DE : the Morse code abbreviation for
"from" or "this is".
Deci : the metric prefix for 10^-1,
or divide by 10.
Decibel (dB) : the smallest change
in sound level that can be detected by the human ear. Power gains and losses are
also expressed in decibels.
Delta-loop antenna :
a variation of
the cubical quad with triangular elements.
Desense (desensitization) : the reduction of receiver sensitivity due
to overload from a nearby transmitter.
Detector :
the stage in a receiver in which the
modulation (voice or other information) is recovered from the RF signal.
Devation :
a measurement for a FM signal for the
maximum carrier frequency changes either side of the carrier frequency.
Deviation ratio : the ratio between the maximum
change in RF-carrier frequency and the highest modulating frequency used in an
FM transmitter.
Digipeater (digital repeater) : a packet-radio
station used to retransmit signals that are specifically addressed to be
retransmitted by that station.
Digital communications :
computer-based
communications modes. This can include data modes like packet radio and
text-only modes like radio teletype (RTTY).
Dipole antenna :
see half-wave dipole. A
dipole need not be ½ wavelength long.
Direct current (dc) :
electrical current that
flows in one direction only.
Directional antenna : an antenna that
concentrates more of the transmitted energy in a particular direction. A
directional antenna must be turned to provide the best signal coverage in
various directions. Such antennas also receive signals better from the direction
they are pointed. Also called a beam antenna.
Directional watt meter :
(see wattmeter)
Director :
an element in front of the driven
element in a Yagi and some other directional antennas.
Distress call :
signals a life-threatening
situation. Most commonly referred to as a SOS or MAYDAY call.
Distress Frequency :
a frequency or channel
specific for use in distress calling. Radiotelephone distress frequencies are
2.182 MHz and 156.8 MHz. Survival craft use 243 MHz. Maritime distress
frequencies are the same, while general aviation frequencies are 121.5 MHz.
Double-pole, double-throw (DPDT) switch :
a
switch that has six contacts. The DPDT switch has two center contacts. The two
center contacts can be connected to one of two other contacts.
Double-pole, single-throw (DPST) switch :
a
switch that connects two contacts to another set of contacts. A DPST switch
turns two circuits on or off at the same time.
Downlink :
(see also Uplink) frequency that
repeaters or satellites transmit on to a user.
Driven element :
the part of an antenna that
connects directly to the feed line.
Dropping out: the situation, while using a repeater, when your signal
does not have enough strength to keep the repeater triggered.
DSP : (Digital Signal Processor) used to improve
the signal to noise ratio for clearer and more legible communications. Is
relatively new to the ham radio.
DTCS :
(Digital Tone Coded Squelch) a selective
call system.
DTMF : (Dual Tone Multi-Frequency) see Tone pad.
Dual-band antenna :
antenna designed for use on
two different Amateur Radio bands.
Dualwatch :
receiving two signals simultaneously.
Dummy antenna :
a station accessory that allows
you to test or adjust transmitting equipment without sending a signal out over
the air. Also called dummy load.
Dummy load :
a
station accessory that allows you to test or adjust transmitting equipment
without sending a signal out over the air. Also called
dummy antenna.
Duplex : a mode of communication in which you transmit on one
frequency and receive on another frequency (see also half and full duplex).
Duplexer : highly selective filter which allows a repeater's
transmitter and receiver to share one antenna.
Duty cycle :
a measure of the amount of time a
transmitter is operating at full output power during a single transmission. A
lower duty cycle means less RF radiation exposure for the same PEP
output.
DX :
distance, foreign countries.
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E
E region :
the second lowest ionospheric region,
the E region exists only during the day. Under certain conditions, it may
refract radio waves enough to return them to Earth.
Earth ground :
a circuit connection to a ground
rod driven into the earth or to a cold-water pipe made of copper that goes into
the ground.
Earth-Moon-Earth (EME) or moonbounce :
a method
of communicating with other stations by reflecting radio signals off the moon's
surface.
Earth station :
an amateur station located on, or
within 50 km of, the Earth's surface intended for communications with space
stations or with other Earth stations by means of one or more other objects in
space.
EBS :
(Emergency Broadcast System) a system where
first an attention tone is transmitted over all stations, followed by a second
tone with specific instruction regarding the receivable frequency in the
national emergency.
EEPROM :
(Electrically Erasable and Programmable
Read-only Memory)
Effective voltage : the value of a dc voltage
that will heat a resistive component to the same temperature as the ac voltage
that is being measured.
EIRP (effective radiated power referred to isotrope) : ERP plus 2.14
dB to correct for reference to isotrope.
Electric field :
an invisible force of nature. An
electric field exists in a region of space if an electrically charged object
placed in the region is subjected to an electrical force.
Electric field strength : the field resulting
from the electric charge distribution present on a radiating element. Electric
field strength is expressed in volts per meter (V/m).
Electromotive force (EMF) :
the force or pressure
that pushes current through a circuit.
Electron :
a tiny, negatively charged particle,
normally found in an area surrounding the nucleus of an atom. Moving electrons
make up an electrical current.
EME :
(Earth-Moon-Earth) moon bounce
communication.
Emergency :
a situation where there is danger to
lives or property.
Emergency communications : communications
involving the immediate safety of human life and immediate protection of
property when normal communication systems are not available.
Emergency traffic :
messages with life and death
urgency or request for medical help and supplies that leave an area shortly
after an emergency.
EMI :
(Electro-Magnetic Interference) often
called RFI (Radio Frequency Interference)
Emission :
the transmitted signal from an amateur
station.
Emission privilege :
permission to use a
particular emission type (such as Morse code or voice).
Emission types :
term for the different modes
authorized for use on the Amateur Radio bands. Examples are CW, SSB, RTTY, and
FM.
Energy :
the ability to do work : the ability to
exert a force to move some object.
Encryption :
transmitting in cryptic form so that
only certain people understand what has been sent.
ERP (effective radiated power) : radiated power, allowing for
transmitter output power, line losses and antenna gain.
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F
F region :
a combination of the two highest
ionospheric regions, the F1 and F2 regions. The F region refracts radio waves
and returns them to Earth. Its height varies greatly depending on the time of
day, season of the year, and the amount of sunspot activity.
Fading :
Signal reduction due to atmospherics.
False or deceptive signals :
transmissions that
are intended to mislead or confuse those who may receive the transmissions. For
example, distress calls transmitted when there is no actual emergency are false
and deceptive signals.
Far field of an antenna : that region of the
electromagnetic field surrounding an antenna where the field strength as a
function of angle (the antenna pattern) is essentially independent of the
distance from the antenna. In this region (also called the free-space region),
the field has a predominantly plane-wave character. That is, locally uniform
distributions of electric field strength and magnetic field strength are in a
plane perpendicular to the direction of propagation.
Feed line; feedline :
the wires or cables used to connect a
transmitter, receiver, or transceiver to an antenna. See transmission line.
Field strength meter : a simple test instrument
used to show the presence of RF energy and the relative strength of the RF
field.
Filter :
a circuit that will allow some signals
to pass through it but will greatly reduce the strength of others.
Flattopping : a distorted audio signal produced
by an SSB transmitter with the microphone gain set too high. The peaks of the
voice waveform are cut off in the transmitter because of overmodulation. Also
called clipping.
FM : see frequency modulation.
Forward Error Correction (FEC) : one of two
AMTOR communication modes. In the FEC mode, each character is sent twice. The
receiving station checks for errors in the mark/space ratio. If an error is
detected, a space is printed to show that an incorrect character was received.
Also called Mode B.
Fox hunt : a friendly Amateur Radio competition
to locate a hidden transmitter. Amateurs practice their direction-finding, which
can be useful in tracking down interference sources.
Frequency :
the number of complete cycles of an
alternating current that occur per second.
Frequency bands :
a group of frequencies where
amateur communications are authorized.
Frequency coordination :
allocating repeater
input and output frequencies to minimize interference between repeaters and to
other users of the band.
Frequency coordinator : an individual or group responsible for
assigning channels to new repeaters with minimal interference to existing
repeaters.
Frequency deviation : the amount the carrier
frequency in an FM transmitter changes as it is modulated.
Frequency discriminator :
a type of detector used
in some FM receivers.
Frequency modulated (FM phone) :
the type of
signals used to communicate by voice (phone) over most repeaters. FM is a method
of combining an RF carrier with an information signal, such as voice. The voice
information (data) changes the RF carrier frequency in the modulation process.
(See amplitude modulation). As you might suspect, we use voice or data to
vary the frequency of the transmitted signal. FM broadcast stations and most
professional communications (police, fire, taxi) use FM. VHF/UHF FM voice is the
most popular amateur mode.
Frequency modulation (FM) : a method of modulation, where the strength of
the signal is constant, but the frequency varies with the strength of the voice,
and the rate of change varies with the frequency of the voice.
Frequency privilege :
permission to use a
particular group of frequencies.
Frequency-shift keying (FSK) : a method of
transmitting radioteletype information by switching an RF carrier between two
separate frequencies. This is the RTTY mode most often used on HF.
Front-end overload :
interference to a receiver
caused by a strong signal that overpowers a receiver RF amplifier ("front
end"). See also receiver overload.
Front-to-back ratio : the energy radiated from
the front of a directive antenna divided by the energy radiated from the back of
the antenna.
FSTV :
(Fast Scan TV) graphics (and audio)
communication using TV broadcast signals, requires a wide bandwidth.
Full-break in (QSK) : with QSK, an amateur can
hear signals between code characters. This allows another amateur to break into
the communication without waiting for the transmitting station to finish.
Full duplex : a mode of communication in which you transmit on one
frequency while you simultaneously receive on another frequency.
Full quieting: a received signal that
contains no noise. Sometimes you'll hear hams use the term
"DFQ," which means "dead full quieting."
Full-wave bridge rectifier : a full-wave
rectifier circuit that uses four diodes and does not require a center-tapped
transformer.
Full-wave rectifier : a circuit basically
composed of two half-wave rectifiers. The full wave rectifier allows the full ac
waveform to pass through; one half of the cycle is reversed in polarity. This
circuit requires a center-tapped transformer.
Fuse :
a thin metal strip mounted in a holder.
When too much current passes through the fuse, the metal strip melts and opens
the circuit.
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G
Gain : an increase in the effective
power radiated by an antenna in a certain desired direction, or an increase in
received signal strength from a certain direction. This is at the expense of
power radiated in, or signal strength received from, other directions.
Gateway : a link or bridge between one communication
network and another. Can be repeater to satellite.
General-coverage receiver : a
receiver used to listen to a wide range of frequencies. Most general coverage
receivers tune from frequencies below the standard broadcast band to at least 30
MHz. These frequencies include the short-wave broadcast bands and the amateur
bands from 160 to 10 meters.
Geomagnetic disturbance : a
dramatic change in the Earth's magnetic field that occurs over a short time.
Giga : the metric prefix for 10^9 or
times 1,000,000,000.
Grace period : the time FCC allows
following the expiration of an amateur license to renew that license without
having to retake an examination. Those who hold an expired license may not
operate an amateur station until the license is reinstated.
Gray line : a band around the
Earth that separates daylight from darkness. It is a transition region between
day and night.
Great-circle path : either one of
two direct paths between two points on the surface of the Earth. One of the
great-circle paths is the shortest distance between those two points.
Great-circle paths can be visualized if you think of a globe with a rubber band
stretched around it, connecting the two points.
Ground connection : a connection
made to the earth for electrical safety. This connection can be made inside (to
a metal cold-water pipe) or outside (to a Ground rod).
Ground plane : a type of
omni-directional antenna.
Ground plane antenna : a vertical
antenna built with the central radiating element one-quarter-wavelength
long and several radials extending horizontally from the base. The radials are
slightly longer than one-quarter wave, and may droop toward the ground.
Ground rod : a copper or copper-clad
steel rod that is driven into the earth. A heavy copper wire from the ham shack
connects all station equipment to the ground rod.
Ground wave : electrical wave
directly traveling from transmitter.
Ground wave propagation : the method
by which radio waves travel along the earth's surface.
Grounding : electrical connection to
the earth.
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H
HAAT (height above average terrain) : a method of measuring antenna
height.
Half duplex : a mode of communication in which you transmit at one
time on one frequency and receive at another time on another frequency.
Half-wave dipole : a basic antenna used by radio
amateurs. It is consists of a length of wire or tubing, open and fed at the
center. The entire antenna is ½ wavelength long at the desired operating
frequency.
Half-wave rectifier : a circuit that allows
only half of the applied ac waveform to pass through it.
Half-wavelength dipole antenna : a fundamental
antenna one-half wavelength long at the desired operating frequency, and
connected to the feed line at the center. This is a popular amateur antenna.
Ham-bands-only receiver : a receiver
designed to cover only the bands used by amateurs. Usually refers to the bands
from 80 to 10 meters sometimes including 160 meters.
Hand-held: a portable transceiver small
enough to fit in the palm of your hand or clipped to your belt.
Sometimes called an H-T or handie-talkie.
Harmful interference : interference that
seriously degrades, obstructs or repeatedly interrupts a radio communication
service operating in accordance with the Radio Regulations.
Harmonics : signals from a transmitter or
oscillator occurring on whole-number multiples (2x, 3x, 4x, etc.) of the desired
operating frequency.
Health and welfare traffic : messages about the
well being of individuals in a disaster area. Such messages must wait for emergency
and priority traffic to clear, and results in advisories to
those outside the disaster area awaiting news from family and friends.
Helical resonator : a compact resonant filter circuit to block
multiple interfering signals.
Hertz (Hz) : an alternating-current frequency of
one cycle per second. The basic unit of frequency.
HF : (High Frequency) 3-30 MHz range signals
(normally, 1.9 MHZ band is also included).
High-pass filter : a filter designed to
pass high frequency signals, while blocking lower frequency signals.
Horizontal polarization : the antenna elements are horizontal (used at
vhf/uhf for weak signal CW/SSB operation).
Horizontally polarized wave : an
electromagnetic wave with its electric lines of force parallel to the ground.
HPF : (High Pass Filter)
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I
IC : (Integrated Circuit)
ID : (IDentification) the means by which a station identifies its call
sign by Morse code or speech.
IF : (Intermediate Frequency) internally
converted frequency for amplification and other signal processing.
IF shift : a function that electronically shifts
IF frequency from a center frequency.
Image response : a form of interference to
receive signals that is produced when a mixer responds to a signal frequency
equal to the LO - the IF when the desired signal frequency is equal to the LO +
the IF. Also when the mixer responds to a signal frequency equal to the LO + IF
when the desired signal frequency is the LO - IF.
IMD : (Inter-Modulation Distortion) distortion
within RF circuits made from upper and lower adjacent channel signals.
Impedance : the opposition to electric
current in a circuit. Impedance includes factors other than resistance, and
applies to alternating currents. Ideally, the characteristic impedance of a feed
line is the same as the transmitter output impedance and the antenna input
impedance.
Impedance-matching device : a device that matches
one impedance level to another. For example, it may match the impedance of an
antenna system to the impedance of a transmitter or receiver. Amateurs also call
such devices a transmatch, impedance matching network or antenna tuner.
Inductance : a measure of the ability of a coil
to store energy in a magnetic field.
Inductor : an electrical component usually
composed of a coil of wire wound on a central core. An inductor stores energy in
a magnetic field.
Input frequency : a repeater's receiving
frequency. To use a repeater, transmit on the input frequency and receive on the
output frequency.
Insulator : a material that maintains a tight
grip on its electrons, so that an electric current cannot pass through it
(within voltage limits).
Intermediate frequency (IF) : the output
frequency of a mixing stage in a super heterodyne receiver. The subsequent
stages in the receiver are tuned for maximum efficiency at the IF.
Intermod (intermodulation distortion or IMD) : interference that
results when strong signals from nearby transmitter(s) mix with the desired
signal in a radio receiver.
International Telecommunication Union (ITU) :
the international organization with the responsibility for dividing the range of
communications frequencies between the various services for the entire world.
Ionizing radiation : electromagnetic radiation
that has sufficient energy to knock electrons free from their atoms, producing
positive and negative ions. X-rays, gamma rays, and ultraviolet radiation are
examples of ionizing radiation.
Ionosphere : a region of electrically charged
(ionized) gases high in the atmosphere. The ionosphere bends radio waves as they
travel through it, returning them to Earth. Also see Sky-wave propagation.
Isolation : the difference in level (measured in dB) between a
transmitted and received signal due to filtering.
Isotrope : a theoretical antenna with zero dimensions and a spherical
radiation pattern. Gain is -2.14 dB from dipole.
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J
J antenna (J pole) : a
mechanically modified version of the zepp (Zeppelin) antenna. It consists
of a half-wavelength radiator fed by a quarter-wave matching stub. This antenna
does not require the ground plane that ¼-wave antennas do to work properly.
Junction diode : an electronic
component formed by placing a layer of N-type semiconductor material next to a
layer of P-type material. Diodes allow current to flow in one direction
only.
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K
K : the Morse code abbreviation for "any
station respond".
Kilo : the metric prefix for 10^3, or times 1,000
Kilohertz (kHz) : a unit of frequency measurement equal to 1,000
cycles per second (Hertz).
Ker-chunk : to key up a repeater without identifying.
Key pad : see Tone pad.
Key up - to turn on the repeater by transmitting on its input
frequency.
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L
LF : (Low Frequency) 30 - 300 kHz range signals.
Lightening protection :
there are several ways to
help prevent lightening damage to your equipment (and your house), among them
unplugging equipment, disconnecting antenna feed lines and using a lightening
arrestor.
Li-Ion :
(Lithium Ion) rechargeable battery which
has better capacity than Ni-C, Ni-MH, etc., no memory effect after repeated
non-full charge/discharge cycles.
Limiter :
a stage of an FM receiver that makes
the receiver less sensitive to amplitude variations and pulse noise.
Line-of-sight propagation :
the term used to
describe VHF and UHF propagation in a straight line directly from one station to
another.
Link/linking: many repeater systems have the
capability to interconnect receivers and transmitters on more
than one band. A 2-meter repeater, for example, may have a
repeater on the 440-MHz band. The repeaters can be tied together
(ie, all signals received on 2 meters or 440 MHz are
simultaneously retransmitted on 2 meters and 440 MHz, and vice
versa). When the repeaters are in this state, they are said to be
"linked." In this operating mode, users on one band
can't readily tell what band other users are actually coming in
on because the repeater equipment automatically carries the
incoming signals across both bands. Such repeaters may be linked
or unlinked by remote control, by users or by a designated
control operator, and may have coded courtesy tones (see above)
that indicate the status of the links. Complex systems may
provide links to operators on 29, 50,144, 222,440, 902 and 1270
MHz.
Local oscillator (LO) : a receiver circuit that
generates a stable, pure signal used to mix with the received RF to produce a
signal at the receiver intermediate frequency (IF).
Long-path communication : communication made by
pointing beam antennas in the directions indicated by the longer Great-circle
path between the stations. To work each other by long-path, an amateur in
Hawaii would point his antenna west and an amateur in Florida would aim east.
Lower sideband (LSB) :
the common single-sideband
operating mode on the 40, 80, and 160 meter amateur bands.
Low-pass filter (LPF) : a filter that allows signals
below the cutoff frequency to pass through and attenuates signals above the
cutoff frequency.
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M
Machine : a slang expression meaning a repeater system.
Magnetic field strength : this is the field
resulting from the currents on a radiating element. Magnetic field strength is
expressed in amperes per meter (A/m).
Magnetic mount, mag-mount: a mobile antenna
with a magnetic base that permits quick installation and removal
from a motor vehicle.
Magnetizing current : a small current that
flows in a transformer primary winding, even with no load connected to the
secondary.
Main lobe : the direction of maximum radiated
field strength from an antenna. Also called major lobe.
Malicious (harmful) interference : intentional, deliberate
obstruction of radio transmissions.
MARS : (Military Affiliate Radio Service)
Maximum average forward current : the highest
average forward current that can flow through a diode for a given junction
temperature.
Maximum Permissible Exposure (MPE) limits : the
electric field strength, magnetic field strength and plane-wave equivalent power
density associated with a radiated electromagnetic wave to which a person may be
exposed without harmful effect, and with an acceptable safety factor.
Maximum usable frequency (MUF) : the highest
frequency radio signal that will reach a particular destination using sky-wave
propagation, or skip. The MUF may vary for radio signals sent to different
destinations.
MAYDAY : from the French m'aidez (help me),
MAYDAY is used when calling for emergency assistance in voice modes.
Memory bank : a set of memory channels organized
into a group.
Memory effect : rechargeable batteries such as
Ni-Cd and Ni-MH types may be consistently getting less capacity as a result of
repeated non-full charged/discharged cycles. It is called this because
rechargeable batteries lose capacity as if they are "memorizing" the
wrong full capacity level at less than full charge. Li-Ion batteries are free
from this effect.
Mega : the metric prefix for 10^6, or times
1,000,000.
Megahertz (MHz) : a unit of frequency measurement equal to 1,000,000
cycles per second (Hertz).
Metric prefixes : a series of terms used in the
metric system of measurement. We use metric prefixes to describe a quantity as
compared to a basic unit. The metric prefixes indicate multiples of 10.
Metric system : a system of measurement developed
by scientists and used in most countries of the world. This system uses a set of
prefixes that are multiples of ten to indicate quantities larger or smaller than
the basic unit.
MF : (Medium Frequency) 300 kHz - 3 MHz range
signals.
MIC : (MICrophone)
Micro : the metric prefix for 10^-6, or divide by
1,000,000.
Microphone : a device that converts sound waves
into electrical energy.
Microwave : the region of the radio spectrum above 1 giga hertz (GHz).
Milli : the metric prefix for 10^-3, or divide by
1,000.
Mixer : a circuit that takes two or more input
signals, and produces an output that includes the sum and difference of those
signal frequencies.
Mobile device : a car radio transmitting device
designed to be mounted in a vehicle. A push-to-talk (PTT) switch generally
activates the transmitter.
Modem : short for modulator/demodulator.
A modem modulates a radio signal to transmit data and demodulates a receive
signal to recover transmitted data.
Modulate : to vary the amplitude, frequency, or
phase of a radio frequency signal.
Modulation : the process of varying an RF carrier
in some way (the amplitude or the frequency, for example) to add an information
signal to be transmitted.
Modulation index : the ratio between the
maximum carrier frequency deviation and the audio modulating frequency at a
given instant in an FM transmitter.
Monitor mode : one type of packet radio receiving
mode. In monitor mode, every transmitted on a packet frequency is displayed by
monitoring TNC. This occurs whether or not the transmissions are addressed to
the monitoring station.
Monitor oscilloscope : a test instrument
connected to an amateur transmitter and used to observe the shape of the
transmitted-signal waveform.
Morse code : see CW.
Multimeter : an electronic test instrument used
to measure current, voltage, and resistance in a circuit. Describes all meters
capable of making these measurements, such as the volt-ohm-milliammeter (VOM),
vacuum-tube voltmeter (VTVM) and field effect transistor VOM (FET VOM).
Multimode transceiver : transceiver capable of
SSB, CW, and FM operation.
TOP
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