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Glosary of Radio Amateurs Terms

Glossay of Terms

Scanner/Receiver Glossary

by: Miguel A. Martinez


In an attempt to help newcomers learn the lingo, I have created this glossary page. It lists the majority of terms you are likely to find when looking over scanner/receiver descriptions and specifications.

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.

Thank you and enjoy!

Miguel A. Martinez
Viper
miguel_mart@hotmail.com
Radio Amateurs Page.


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
  1. 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

  2. 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

  3. 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
  1. 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).
  2. 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
  1. Keep a memory channel from being scanned
  2. Keep a frequency from being searched
Also referred to as 'Pass' or 'Skip' on some models.


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Email: miguel_mart@hotmail.com