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Glosary of Terms (Continued)

Long Wave

Refers to any frequency below 530kHz. Especially those in the 160 to 190kHz region.

LSB

Lower Sideband

Type of signal modulation used by a transmitter and the receive mode that must be used to hear this type of signal properly. Basically an AM signal that only uses a half, or one side, of the frequency wave to modulate the data signal. In this case, the lower side is used. Generically referred to as single sideband(SSB) and complements upper sideband(USB).

By using the two sides of the same frequency signal(upper and lower), two transmitters can use the same frequency without interferring with each other. This operation saves frequency bandwidth.

LSB frequencies are typically found in the HF band as well as on frequencies used by amateur radio.

See AM, DEMODULATE, RECEIVE MODE, SSB & USB

Medium Frequency

Those frequencies between 300 and 3000kHz(or 300kHz and 3MHz).

Medium Wave

Typically referred to as the AM broadcast band found on most car and home radios. Covers 530 to 1700kHz.

Memory

Usually refers to the total number of channels existing on a particular radio. Memory is usually divided up into banks to allow logical grouping. Each banks consists of some number of channels which varies from model to model. Each channel can hold a frequency and other possible settings.

See BANK & CHANNEL

Modulate

Process used by a transmitter to combine the data signal(usually human voice) with the carrier frequency so that it can be transmitted. There are several forms of modulation 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 DEMODULATE & RECEIVE MODE

NAM

Narrow AM

Special type of filter found only a very few radios. Use of this mode demodulates a normal AM signal but uses a tighter filter. If there are several signals very close together in frequency, use of this mode and its more restrictive filtering will help to block out adjacent signals providing better reception of the desired signal.

See AM, DEMODULATE & RECEIVE MODE

Noise Blanker

See NOISE BLANKER

NFM

Narrow FM

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. Usually referred to as simply FM.

See FM, MODULATE, RECEIVE MODE & WFM

Ni-Cad

Shortened form of Nickel-Cadmium. May also be seen as 'nicad', 'ni-cd', or 'NiCd'.

A rechargeable battery. Some scanners use a proprietary or custom battery pack from which they receive their power. Others can use regular AA rechargeable cells.

Once depleted, they can not be used until they have been recharged.

While the up-front cost is much more per cell, the ability to recharge the cell hundreds of times saves money in the long run. However, to see these savings, the cells must be treated properly. Doing so will usually permit 300-500 recharge cycles depending on the battery. Careless use can easily lower this to 100-200 cycles.

Ni-cads come in many flavors. There are basic cells which provide a minimun power rating of 600mAh and there are the high-capacity types which can provide 800 - 1000mAh.

Unlike AA cells which have a long shelf life, ni-cads discharge rather rapidly(usually about 30-45 days) when left unused. Care must be taken to see that they do not sit uncharged for too long lest they become unusable.

See NI-MH

Ni-Mh

Shortened form of Nickel-Metal Hydride.

A more recent development in rechargeable battery technology. Ni-Mh cells provide around 25% more power than a comparable Ni-Cad, cost about 1.5 - 2 times as much and only have half the number of recharge cycles.

Ni-Mh cells are much more finicky when it comes to being properly charged when compared to Ni-Cads.

See NI-CAD

Noise Blanker

Feature used to remove pulse-type noise from SSB and CW signals. Usually only found on more costly models.

Pulse-type noise is usually created by separated spark discharges like those used on automobile ignition systems.

Ohm

Unit of measurement. Used to indicate the resistance of an electronic component to energy flow and is also used to indicate the electrical load that one circuit can present to another.

Scanner specifications usually list two figures measured in ohms. One is the load presented to the antenna at the BNC connector(usually 50 ohms). The second is referenced to the speaker and/or earphone jack(usually 8 ohms).

Pause

Feature used to resume a scan or search operation if a received signal is active for more than a certain period of time.

Private Line

See CTCSS

PL-259

Type of connector used to attach a cable to some form of jack. PL-259 connectors are typically used on the ends of antenna co-ax cables to attach them to larger antennas like the discone.

See CO-AX & DISCONE

Pass

See LOCKOUT

Pre-amplifier

Device or circuitry used to amplify a signal before it is presented to the first stages of a receiver. Doing so can help to improve the reception of very weak signals which might otherwise be missed.

Too much amplification can produce intermodulation.

See INTERMODULATION

Priority

Feature used to sample one or more specified channels on a periodic basis so that transmissions on the these frequencies are not missed while performing other operations such as scanning and searching.

RFI

Radio Frequency Interference

Any signal which interferes with normal receive operations. RFI can be created by almost any electrical device including computers, TVs, radios, VCRs, microwaves, hair dryers, cable TV lines, power tools, and so on. All of these devices radiate energy which can interfere with the reception process of a radio receiver.

When a receiver comes across such a radiated signal, it might be detected as a valid transmission without modulated data. This process might interfere with the reception of programmed channel frequencies. It might also pose a source of frustration when searching for new signals since the receiver will stop on these errant transmissions.

RG-58

Co-ax cable rated at 50 ohms, its large attenuation(worse than RG-6) makes it acceptable for only very short runs(20ft or less) between antenna and scanner. Price is cheap.

See ATTENUATE, CO-AX & RG-6

RG-6

Co-ax cable usually used to carry cable transmissions to your TV. Rated at 75 ohms, its low attenuation(better than RG-58 but worse than RG-8) value makes it a good candidate for medium-length cable runs(50-100ft) between antenna and scanner. Price is very affordable.

See ATTENUATE, CO-AX & RG-8

RG-8

Co-ax cable rated at 50 ohms. Its very low attenuation(better than RG-6 but worse than 9913) value makes it a great candidate for longer length cable runs between antenna and scanner. Price is affordable but it is much thicker than RG-6 making it less "manageable".

Cables of this type are typically labelled as RG-8/U or RG-8X

See ATTENUATE, CO-AX & 9913

Receive Mode

Form of demodulation being used by the receiver. 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 AM, CW, DEMODULATE, FM, MODULATE, SSB & WFM

RF Gain

Feature used to boost the amplification of signals being recieved. As the received signal strength weakens, gain can be increased by the user which is supplied to one or more frequency amplifiers thus increasing signal strength. Usually found on more costly models.

If the gain control is automatically adjusted by the radio, it is referred to as automatic gain control(AGC).

See AGC

Rotary control

Control found on some radios which is used to change the frequency in the VFO and/or scroll through memory channels. This control is rotated clockwise or counter-clockwise and changes the VFO frequency(increases or decreases it by the step size) or memory channel(scrolls to the previous or next channel in memory) accordingly.

See CHANNEL, STEP SIZE & VFO

S-meter

Feature usually found on more costly models. A meter or graphical display element giving a visual depiction of the strength of the signal being received. Usually some form of bar graph with more elements indicating a stronger signal.

SNA

Type of cable connector used on cellular phones as well as some amateur radios.

Scan

Action whereby selected memory channel frequencies are sampled for active transmissions. If an active transmission is detected, the scanner pauses to receive the signal and provide the user with the demodulated data(usually human voice).

See SEARCH

Scanner

Radio receiver capable of tuning a wide range of frequencies. Similar to your car radio, it can tune a selected frequency and then extract the audio portion which is fed to an amplifier for you to hear it from the speaker. Unlike your car radio, a scanner can tune an enormous range of frequencies when compared to the small segment your car radio is restricted to.

Just like your car radio, you can save your favorite "stations" in memory channels but a scanner typically has hundreds of channels. Most scanners also allow you to search through the frequency spectrum for active signals just like the seek function on your car radio.

Radio Shack, RELM and Uniden make what can be called "true" scanners. Scanners differ from communications receivers in that they usually have no VFO and pre-defined receive modes and step sizes which can not be changed. They usually scan and search much faster too. They usually do not cover the HF spectrum.

See COMMUNICATIONS RECEIVER

Search

Action whereby successive frequencies are sampled for active transmissions. If an active transmission is detected, the scanner pauses to receive the signal and provide the user with the demodulated data(usually human voice).

This search is usually conducted between a user-specified lower and upper frequency limit. As each frequency is tested, the next frequency is chosen by adding the step size to the frequency just sampled. This continues until the upper frequency is reached at which point the process starts over at the lower frequency limit.

See SCAN STEP SIZE

Search-Skip

Feature used to skip a specified frequency during a search operation. Each manufacturer has its own pet name for this feature but they all work the same way. The functionality is quite similar to locking out a memory channel so that it is not scanned. In this case, a frequency is locked out, or skipped, so that it is not searched.

The frequencies that are to be skipped are typically kept in a separate part of memory. Some radios allow this memory to be viewed and edited. The number of frequencies this memory can hold varies widely from 10 to 1000 based on the model and manufacturer.

See LOCKOUT

Selectivity

Measure of a receiver's ability to block adjacent signals on either side of the frequency currently being received. If the receiver does not have good selectivity, the data from an adjacent signal can interfere with the data on the frequency being listened to causing distortion and general annoyance.

Receivers designed with better selectivity are typically more expensive.

Shortwave

See HF

Skip

See LOCKOUT

Squelch

Feature used to set the minimum signal strength level that will be received. Signals with strengths less than this level will not be heard.

The squelch is usually set to a minimum level to allow any strength signal to be heard. But there are some circumstances where a higher level is necessary for productive reception.

Receivers with CTCSS/DCS may control the squelch with tones/codes rather than by signal strength.

See CTCSS

Squelch-tail

Refers to the burst of static heard after a transmission ends. Well designed receivers will keep the duration of this static burst to a minumum. Those which last too long can be quite annoying.

See SQUELCH

SSB

Single Sideband

Type of signal modulation used by a transmitter and the receive mode that must be used to hear this type of signal properly. Basically an AM signal that only uses a half, or one side, of the frequency wave to modulate the data signal. Collectively referred to as single sideband, it consists of upper sideband(USB) and lower sideband(LSB).

By using the two sides of the same frequency signal(upper and lower), two transmitters can use the same frequency without interferring with each other. This operation saves frequency bandwidth.

SSB frequencies are typically found in the HF band as well as on frequencies used by amateur radio.

See AM, DEMODULATE, LSB, RECEIVE MODE & USB

Step size

Increment used to change the currently displayed frequency. This increment is usually measured in pre-defined quantities of Hertz or kiloHertz. Simple scanners will only use two or three step sizes. Higher priced radios can have as many as 20.

The wider the frequency coverage of the receiver, the more step sizes it should have. Each frequency band is typically assigned a step size for adequate channel spacing. Receivers with many step sizes are more flexible and usually allow the user to select the step size to be used.

See BANDPLAN, SEARCH & VFO

Timer

Feature used in conjunction with the radio's clock to instruct the radio to turn on or off at a selectable time. This makes the radio more flexible than the preset times of auto power-off as well as allowing it to be used as an alarm clock.

See APO & CLOCK

TrunkTracker

Radio receiver developed by Uniden allowing Motorola 800MHz analog trunked radio systems to be decoded thus allowing conversations to be followed.

The first TrunkTracker, the BC235XLT, was released in May, 1997. The second was the BC895XLT released in September, 1997.

See TRUNKING

Trunking

Multiple frequency, computer controlled radio system. One frequency is always used as a digital data channel allowing the base computer to coordinate control of the radios in the field. An available frequency is chosen by the computer each time the transmit key on the field radio is keyed. The computer instructs the field radios which frequency to use via the data channel.

Using this methodology, a single conversation can take place on multiple frequencies which effectively mimics frequency hopping. In a system used by many agencies, it can be near impossible to follow a single conversation with a conventional scanner.

Trunked radio systems are developed, installed and managed by Motorola and GE/Ericson.

See TRUNKTRACKER

UHF

Ultra-High Frequency

Those frequencies between 300MHz and 3GHz.

USB

Upper Sideband

Type of signal modulation used by a transmitter and the receive mode that must be used to hear this type of signal properly. Basically an AM signal that only uses a half, or one side, of the frequency wave to modulate the data signal. In this case, the upper side is used. Generically referred to as single sideband(SSB) and complements lower sideband(LSB).

By using the two sides of the same frequency signal(upper and lower), two transmitters can use the same frequency without interferring with each other. This operation saves frequency bandwidth.

USB frequencies are typically found in the HF band as well as on frequencies used by amateur radio.

See AM, DEMODULATE, LSB, RECEIVE MODE & SSB

VFO

Feature typically found on communications receivers. Designed to allow entry of a frequency as well as selection of a receive mode and step size. The rotary control can then be used to manually change the displayed frequency by the selected step size.

Some models come with more than one VFO.

See COMMUNICATION RECEIVER, RECEIVE MODE, ROTARY CONTROL & STEP SIZE

VHF

Very-High Frequency

Those frequencies between 30MHz and 300MHz.

VLF

Very-Low Frequency

Those frequencies between 10 and 30kHz.

Weather Alert

Feature designed to detect the severe weather broadcast signal sent out on the NOAA weather broadcasts. During severe weather, NOAA weather broadcasts will send out a special signal designed to alert receivers with this feature. If this signal is detected, the radio usually alerts the user and then receives the NOAA weather broadcast containing the severe weather alert notice.

See WX

WFM

Wide FM

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 FM broadcast and TV audio signals.

See FM, MODULATE, RECEIVE MODE & WFM

Feature designed to pick up NOAA weather broadcasts on the VHF band. Some scanners come pre-programmed with the NOAA weather frequencies which can then be scanned for active transmissions.

See WEATHER ALERT

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