For the most part, a liberal interpretation should be used for most
definitions. Remember, this glossary is intended to convey the basic terms
and concepts of radio to the newcomer. It is not intended to be an exhaustive
compilation of exact, technical content.
If anyone cares to offer up missing terms or can provide more lucid
descriptions, feel free to e-mail me with your suggestions.
- 9913
- Co-ax cable rated at 50 ohms. Its extremely low attenuation value makes it
an excellent candidate for long cable runs between antenna and scanner.
Price is moderately expensive and its diameter and stiffness make it
harder to manage.
Sometimes referred to as simply 'Belden' and might be labelled as RG-8A/U.
See ATTENUATE & CO-AX
- AC
- Alternating Current
Refers to the type of power a scanner needs. AC power is supplied by
normal household outlets rated at 120 volts. Some scanners come with an
adaptor which plugs into a household outlet but converts the current to
DC for scanner use.
See DC
- AFC
- Automatic Frequency Control
Feature used to automatically tune a frequency if it is detected as
being off-center to the transmission being received. Usually only
found on more costly models.
- AGC
- Automatic Gain Control
Feature used to automatically boost the amplification of signals being
received. As the received signal strength weakens, circuitry automatically
compensates by applying more gain to one or more frequency amplifiers thus
increasing signal strength. AGC is also used to weaken a signal if it
is detected as being excessively strong.
Most radios today contain this circuitry in the first stages of the
receiver to automatically compensate for varying signal strengths. If the
gain control can be adjusted by the user, it is usually referred to as RF
gain.
See DESENSITIZATION & RF GAIN
- Alpha-tag
- Feature allowing memory channels and other resources to be labelled with
user-specified alpha-numeric text. Usually found on more costly models.
- AM
- Amplitude Modulation
Type of signal modulation used by a transmitter and the receive mode that
must be used to hear this type of signal properly. AM signals are used on
the HF bands as well as for most commercial and military aircraft
communications. Some receivers come with narrow-AM modes for tighter signal
filtering.
See HF, MODULATE, NAM & RECEIVE MODE
- ANL
- Automatic Noise Limiter
See AUTOMATIC NOISE LIMITER
- APO
- Automatic Power Off
Feature used to automatically power-off the radio to conserve battery
power should the user forget to turn it off. Usually comes with several
selectable timeout values to choose from such as 10, 20 & 30 minutes.
See BATTERY SAVER
- ARINC
- Aeronautical Radio Inc
Private business which licenses several bands of frequencies and then
leases them and equipment for their use to airlines around the world.
- Attenuate
- Process whereby signal strength is reduced. May be intentional(attenuator)
or simply caused by the laws of physics(due to imperfect transmission).
If a cable is used to carry signals from a remote antenna to the receiver,
signal strength is attenuated by the cable. The longer the cable, the
more attenuation occurs. Higher frequencies are attenuated more than
lower ones.
See ATTENUATOR & CO-AX
- Attenuator
- Feature used to attenuate a received signal. The amount of reduction will
vary between models and is measured in decibels. Usually used to reduce
the likeliness of intermodulation.
See ATTENUATE, DB & INTERMODULATION
- Auto-Store
- Feature used to automatically store active frequencies into memory channels
during a search operation. Effectively a search operation that, instead of
stopping the search to hear the active transmission, simply stores the
active transmission frequency in a memory channel and then continues with
the search.
Some radios have "smart" auto-store in that they won't store the same
frequency multiple times. Radios with "dumb" auto-store simply write the
active frequency to memory without regard to whether it has already been
stored or not.
See SEARCH
- Automatic Noise Limiter
- Feature used to reduce noise components from AM mode signals. Usually
only found on more costly models.
Noise limiting effectively clips the audio signal from the amplifier
at a set level so that there is not a large difference between very
strong and very weak signals.
- Backlight
- Device used to illuminate the scanner LCD and/or keypad for night time
use. A handy feature found on most base models but for handhelds, it can
be a large drain on batteries.
- Band
- One of
- Pre-defined frequency range. Some manufacturers specify their scanner's
frequency coverage in terms of bands. Like the bands 30-50MHz and
50-54MHz and so on. Uniden likes to use the following "bands" :
25 - 26 HF Hi
26 - 29 CB
29 - 54 VHF Lo & Amateur Radio
54 - 72 TV Audio
72 - 76 Land Mobile
76 - 108 FM Broadcast
108 - 137 Commercial Aircraft
137 - 144 Military Land Mobile
144 - 148 Amateur Radio
148 - 174 VHF Hi & Government
174 - 216 TV Audio
216 - 225 VHF Hi
225 - 400 Military Aircraft
400 - 420 Government
420 - 450 Amateur Radio
450 - 470 UHF Standard
470 - 520 UHF "T"
520 - 550 TV Audio
760 - 806 UHF "T"
806 - 824 UHF Public Service
849 - 869 UHF Public Service & Land Mobile
894 - 1300 UHF Hi, Land Mobile & Amateur Radio
- Continuous set of logically related frequencies. Radio Shack likes to
use the following which is based on the FCC allocation services :
25 - 28 HF Hi & CB
28 - 30 Amateur Radio
30 - 50 VHF Lo
50 - 54 Amateur Radio
54 - 72 TV Audio
72 - 76 Land Mobile
76 - 88 TV Audio
88 - 108 FM Broadcast
108 - 137 Commercial Aircraft
137 - 144 Government
144 - 148 Amateur Radio
148 - 174 VHF Hi
174 - 216 TV Audio
216 - 222 VHF Hi
222 - 225 Amateur Radio
225 - 400 Military Aircraft
406 - 420 Government
420 - 450 Amateur Radio
450 - 470 UHF Standard
470 - 520 UHF "T"
520 - 760 TV Audio
760 - 806 UHF "T"
806 - 824 UHF Public Service
849 - 869 UHF Hi
894 - 956 UHF Hi
956 - 1240 Land Mobile/Private/Paging
1240 - 1300 Amateur Radio
- Section of scanner memory used to store settings for performing a
search. At the minimum these settings include the lower and upper
frequency search limits. They may also include attenuator setting,
receive mode, step size and alpha-tag.
See SEARCH
- Bandplan
- Map of the frequency spectrum with the step sizes and receive modes the
radio will use for any given frequency. Each country divides up the
radio frequency spectrum in to "chunks" or bands. Each band is assigned
a default step size(for frequency separation) and receive mode. Scanners
to be used in that country will typically have this bandplan programmed
into memory so that when a frequency is picked, the radio will
automatically set the proper receive mode and step size.
Some of the more costly models allow the user to override the default
bandplan receive mode and/or step size.
See RECEIVE MODE & STEP SIZE
- Bandscope
- Feature used to graphically display frequency activity. Usually found
on more costly models. User typically selects a center frequency and
the receiver then scans a set number of frequencies either side of
this for active transmissions. Any activity found is displayed as a
vertical bar on the LCD with the height of the bar indicative of the
associated signal strength.
- Bank
- A logical association of channels. A "good" scanner will have several
banks; typically 10 to 20. This allows the user to program a different
agency into each bank. It is then effective to scan only those banks
which contain the agencies that wish to be listened to.
Associated with the bank is the number of channels per bank. The more
the better but this should be dicatated by your location and the
number of frequencies used by a particular agency. The average figure
for today's models is around 30 channels/bank.
See CHANNEL & MEMORY
- Battery Saver
- Feature used to save battery power when no signal is being received by
powering down various circuit components. On some radios this is
automatic while others allow the user to configure it. Usually found on
more costly models.
Either way, the radio usually "goes to sleep" for a short period of
time and then "wakes itself" to check for a signal. If none is received
then it puts itself back to "sleep".
The ratio of the time it is awake to the time it is asleep is called the
duty cycle. Radios which have adjustable battery savers usually allow
you to control this duty cycle.
- Birdie
- Signal generated by the scanner circuitry and considered a form of RFI.
Since the scanner is composed of electrical components charged with
energy, it can radiate signals just like many other electrical devices.
Such signals sound like static since they occur at some frquency but have
no data modulated on them.
Better radios will incorporate various forms of shielding to keep
birdie signals from being picked up as valid radio transmissions.
See MODULATE & RFI
- BNC
- Type of connector used to attach a cable to some form of jack. BNC
connectors are typically used on the ends of antenna co-ax cables to
attach them to the scanner. The BNC connector is the most popular for
most electronic and radio equipment.
See CO-AX
- CTCSS
- Continuous Tone Coded Squelch System
One of approximately 41 sub-audible(can't be heard) tones transmitted with
a voice signal. A properly equipped receiver, set to one of these tones,
will only receive a transmission with a matching tone. This functionality
is used to help separate traffic from multiple agencies which must share a
single frequency.
CTCSS is marketted by Motorola as Private Line(PL) and by Ericson/GE as
Channel Guard(CG).
See SQUELCH
- CW
- Continuous Wave
Receive mode used to listen to International Morse Code signals. Usually
used in the HF and amateur radio bands.
See HF
- CG
- Channel Guard
See CTCSS
- Channel
- Single memory storage location used to hold a frequency. The number of
channels therefore dictates the maximum number of frequencies that can be
stored.
Associated with each memory channel can be settings such as attenuation,
delay, lockout, receive mode and step size. Some radios allow an alpha-tag
to be attached to a channel as well.
See ATTENUATE, DELAY, LOCKOUT, MEMORY,
RECEIVE MODE, SCAN & STEP SIZE
- Channel Count
- Feature found on some Uniden models. Used to indicate the number of
times a channel has been detected with an active transmission.
- Clock
- Time of day clock which can be used by itself or serve as a timekeeper
for various timers. Very few radios come with a clock.
See TIMER
- Cloning
- Feature that allows one radio to transfer all of its data to another
via a cable interface. This effectively makes a copy, or clone, of that
radio.
- Co-ax
- Shortended form of coaxial.
The cable used to carry signals from an antenna to a scanner. Most
people know this as the cable used to deliver broadcasts to their TV
from their cable company. Most co-ax is terminated in F-type connectors
but this can be easily changed to the BNC connection used by almost all
scanners.
See BNC, PL-259, RG-58, RG-6 & RG-8
- Communications Receiver
- A fancy name for a radio receiver. Similar to a scanner but also
different. Designed to receive signals like a scanner as well as
scan pre-programmed channels and perform searching. The biggest
differences are the addition of a VFO, rotary control, adjustable
step sizes and receive modes. They tend to scan and search at much
slower rates but usually cover the HF spectrum while scanners usually
do not.
Alinco, AOR, iCOM, Trident, Yupiteru, Welz make what can be called
communications receivers.
See ROTARY CONTROL, SCANNER & VFO
- Conversion
- Refers to the type of receive circuitry used by a scanner. Most models
use double or triple conversion. Triple conversion is more expensive
and is used to help eliminate images. The radio and the conversion it
uses will dictate the number of IFs it has.
See IF & IMAGE
- Data Skip
- Feature used to skip over a frequency which contains no modulated data or
some form of digital communications.
iCOM calls this feature Voice Scanning Control(VSC).
See MODULATE
- dB
- deciBel
Measurement of power relative to a known signal. Based on a logarithmic
scale, the decibel is usually used to compare the strength of two signals.
A difference in strength of 3dB is an effective factor of 2. That is,
twice or one-half(1/2) the strength compared to the reference signal.
6dB represents a factor of 4; four times or one-fourth(1/4). 10dB is
a factor of 10 and 20dB is a factor of 100.
See ATTENUATOR
- DC
- Direct Current
Refers to the type of power a scanner needs. DC power is usually supplied
by batteries or can be supplied from an adaptor which can be used in your
home or car.
See AC
- DCG
- Digital Channel Guard
See DCS
- DCS
- Digital Coded Squelch
One of approximately 30 sub-audible(can't be heard) digital signals
transmitted with a voice signal. A properly equipped receiver, set to one
of these signals, will only receive a transmission with a matching digital
signal. This functionality is used to help separate traffic from multiple
agencies which must share a single frequency.
DCS is marketted by Motorola as Digital Private Line(DPL) and by
Ericson/GE as Digital Channel Guard(DCG).
See SQUELCH
- Delay
- Feature used to wait a certain period of time(usually in seconds) after an
active transmission ceases before a scan or search operation continues.
Some radios have a fixed delay for all operations, some have a selectable
delay which can be toggled on or off while others allow you to specify
the delay time used.
See SCAN & SEARCH
- Demodulate
- Process used by a receiver to extract the data signal(usually human voice)
from the carrier frequency so that it can be amplified and sent to the
speaker to be heard. There are several forms of demodulation used
including AM, FM, WFM, SSB and CW.
To hear the intended data signal properly, the receiver must demodulate
the received transmission using the same mode that was used to transmit
it.
See MODULATE & RECEIVE MODE
- DES
- Digital Encrypted Speech
Very similar to DVP but much more affordable and therefore is the
primary encryption system used by federal agencies and law enforcement.
See DVP
- Desensitization
- Occurs when a reciever uses poor front-end filtering. When tuned to a
certain frequency, a strong nearby signal can "leak through" such filtering
making the receiver think the tuned frequency is stronger than it really
is.
To reduce this perceived excess signal, the AGC will automatically reduce
the gain to compensate which usually results in the tuned frequency being
received very poorly. This gives the illusion that the receiver has
poor performance in regards to sensitivity when this is not the case.
See AGC & FILTER
- Discone
- Type of antenna with omni-directional reception. Usually two to three
feet in height and designed for outside mounting. Designed to cover a
a wide range of frequencies; typically 25 - 1300MHz.
Consisting of a cental hub from which 8 - 10 radial elements project
downward at an angle, as well as 8 - 10 short elements radiating
horizontally. Some discones have a long element mounted on top of
the central hub for better reception in the lower VHF band.
- DPL
- Digital Private Line
See DCS
- DVP
- Digital Voice PProtection
Designed for Motorola for use by federal agencies and law enforcement.
Rarely used today due to high cost.
Audio signals are digitized using a complex code then transmitted.
Receiver's job is to unscramble the signal using the same code and convert
it back to analog. Such encoded signals sounds like noise.
See DES
- DX
- Abbreviation for distance.
Typically refers to the monitoring of signals whose origin is a large
distance from the receiver.
Monitoring DX signals is referred to as DXing while the person doing
such monitoring is referred to as a DXer.
- Dynamic range
- Receiver specification which measures the ability to receive very strong
signals without producing intermodulation. This figure is rarely seen
in manufacturer's specifications.
To keep the cost down, scanners/receivers are not usually designed to
have good dynamic range. But, as a rule of thumb, the more expensive
a receiver is, the more likely it is to have better dynamic range.
See INTERMOD
- Filter
- Refers to
- Active/Passive device used to block frequencies below a certain
cut-off frequency(hi-pass filter), block frequencies above a certain
cut-off frequency(lo-pass filter) or block frequencies below one lower
cut-off frequency and those above another higher cut-off frequency
(band-pass filter).
- Circuitry used in the initial receiver stages to screen out signals
other than the one on the currently displayed frequency. Each receive
mode usually has a different filter associated with it.
A perfect receiver would never allow the frequency being received to
be interfered with by strong signals or by adjacent frequency activity.
In the real world, filters can only do so much. Usually, the better
the filter, the more the receiver costs but the rewards are much less
interference.
See DEMODULATE, INTERMODULATION & RECEIVE MODE
- FM
- Frequency Modulation
Type of signal modulation used by a transmitter and the receive mode that
must be used to hear this type of signal properly. This mode is used for
most VHF & UHF transmissions. Sometimes referred to as NFM.
See MODULATE, NFM, RECEIVE MODE & WFM
- Frequency
- Measurement of how often an event occurs. In radio parlance, it is used
to indicate the number of cycles per second(Hertz) being used to transmit
the intended data signal(typically human voice).
Scanners can be programmed to scan known frequencies of specific agencies
as well as search for new, unknown frequencies.
See CHANNEL, HERTZ, MODULATE, SCAN &
SEARCH
- Frequency counter
- Device used to sweep a very wide range of frequencies(1 to 2GHz) in a very
short period of time(1 second) and display the strongest signal detected.
Usually used to detect an unknown operating frequency. The counter is
triggered at very close range to the transmitter at the moment it is
activated thereby revealing the frequency being used.
See FREQUENCY
- FRS
- Family Radio Service
Frequency band in which unlicensed radios are allowed to be used.
Typically for use by individuals.
Operates within 462.5625-462.7125MHz and 467.5625-467.7125MHz. Some
channels are shared with GMRS.
See GMRS
- GMRS
- General Mobile Radio Service
Frequency band in which licensed radios are allowed to be used. Typcially
by smaller business and for private use. Was originally the Class A
Citizen's Band service using AM mode in the 27MHz band.
Operates within 462.550-462.775MHz and 467.550-467.775MHz. Some channels
are shared with FRS.
See FRS
- Hertz
- Unit of measurement indicating the number of cycles per second a radio
wave is being transmitted. Radios transmit on specific frequencies which
are measured in hertz. Usually listed in kHz(kilohertz or 1,000 Hertz),
MHz(megahertz or 1 million Hertz) and GHz(gigahertz or 1 billion Hertz)
See FREQUENCY
- HF
- High Frequency
Those frequencies between 3MHz and 30MHz. Also referred to as the
shortwave band.
Typical receive modes for HF are AM, LSB & USB.
See AM, RECEIVE MODE & SSB
- HT
- Handheld Transceiver
Also Handie-Talkie
A handheld radio capable of transmitting as well as receiving. Mostly
referring to amateur radio models needing an FCC license to transmit.
Many can receive a broad range of frequencies.
- Hold
- Feature used to halt a scan or search operation as soon as the first
active transmission is detected. On some radios it is simply accomplished
by the user via a keypress, while on others it is a setting enabled by
the user and carried out by the radio itself.
See SCAN & SEARCH
- Hz
- Abbreviation for Hertz
See HERTZ
- IF
- Intermediate Frequency
Frequency used in the demodulation process to extract the data signal
from the carrier frequency. The number of IFs used will depend on the
radio itself and the type of conversion it uses. A double conversion
receiver will use two stages and two different IFs to extract the data
signal. Triple conversion uses three stages and three IFs.
The value of each IF is dependent on the design used by the manufacturer.
See CONVERSION, DEMODULATE & IMAGE
- Image
- A signal received on a frequency other than that on which it was
transmitted. This is a "false frequency" generated by the scanner itself
during the receive process. Makes it appear a new signal has been found
since this image usually shows up in a different frequency band. Exactly
where the image will show up varies by radio, the IF used and the
conversion scheme.
See CONVERSION, IF & INTERMODULATION
- Interface
- Usually refers to a computer connection found only on more costly models.
Can be used to simply upload/download memory data but may include control
over the scanner as well. This functionality allows unattended monitoring
sessions to be conducted with results logged for later viewing.
A similar interface is sometimes used for radio cloning.
See CLONING
- Intermodulation
- Process where multiple signals mix together. This may occur naturally
outside of the receiver or in the front-end of the receiver. Either way,
it results in the generation of a "false" frequency. The resultant audio of
this signal is usually a combination of the audio portions of each signal
involved. Sometimes only one of the original signals can be heard.
This typically occurs when the initial stages of the receiver are
"overpowered" by very strong, local signals. Radios with superior designs
have better filtering which are better at keeping multiple signals from
entering thereby helping to eliminate intermodulation.
Usually referred to as simply 'intermod'.
See ATTENUATOR, DYNAMIC RANGE & IMAGE
- Keylock
- Feature used to lock some or all of the keys, buttons and/or controls
thereby preventing accidental activation.
- LCD
- Liquid Crystal Display
Physical element allowing information and indicators such as freqeuncy,
receive mode, step size and channel to be displayed to the user.
- LF
- Low Frequency
Those frequencies between 30 and 300kHz.
- Linking
- Method allowing multiple banks/bands to be scanned/searched.
See BANK, BAND, SCAN & SEARCH
- Lockout
- Feature used to
- Keep a memory channel from being scanned
- Keep a frequency from being searched
Also referred to as 'Pass' or 'Skip' on some models.
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