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9 A B C D E F G H I K L M N O P Q R S T U V W
Alpha-Numeric Index
9
- 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' (in fact, 9913 comes from the part number as a Belden product) and might be labeled as RG-8A/U.
A
- 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
- AF Gain
- Audio Frequency Gain
A fancy way to say 'Volume'
- 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 labeled 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/selectivity.
In AM signals, the data to be transmitted is conveyed by varying the amplitude (power) of the modulated wave. One of the biggest drawbacks with AM signals is the ease with which they can be interferred with from both natural and man-made sources.
See HF, MODULATE, NAM, RECEIVE MODE, & SELECTIVITY
- ANL
- 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.
Frequencies used are generally HF (in USB) and VHF (128.825 - 132.000). UHF frequencies are becoming more popular as trunked systems in the mid-800MHz range.
- 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 interference from 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 (ANL)
- 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.
B
- 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 BAND, 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 display 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.
- 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 frequency 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.
- 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 a majority of electronic and radio equipment these days.
See CO-AX
C
- 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. It can be used by the scanner user to selectively listen to such agencies or to block interference due to images or intermodulation.
CTCSS is marketted by Motorola as Private Line (PL) and by GE/Ericsson as Channel Guard (CG).
See IMAGE, INTERMODULATION & SQUELCH
- CW
- Continuous Wave
Receive mode used to listen to International Morse Code signals. Usually used in the HF and amateur radio bands and only found on more costly models.
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. Some examples include the Alinco DJ-X10, AOR AR3000/A and iCOM IC-R1
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.
- 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, and 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. Today's 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.
D
- Data Skip
- Feature used to skip over a frequency and/or mute the audio of a signal 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 GE/Ericsson 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.
- 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.
- Discone
- Type of antenna with omni-directional reception. Usually two to three feet in height and designed for outdoor 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.
A newer creation is the double discone which looks like a discone with a mirror set of radials projecting updward at an angle thereby allowing it even better signal reception.
- Discriminator
- In its simplest sense, the discriminator signal represents the content of a transmission (usually human voice) AFTER it has been removed from the carrier frequency it was transmitted on but BEFORE it is sent to the audio amplifier.
Such a signal is usually very clean (because it is in its raw form before it is sent to the audio amplifier which can both add and magnify noise components) thus making it an ideal signal to decode by electronic means.
As such, a discriminator usually refers to a discriminator tap which is the act of attaching a wire to the discriminator point so that it can be brought outside of the radio and the signal it carries decoded by another device.
Discriminator signals of interest tend to be digital forms of data such as CTCSS, DCS, DTMF, trunking control channels, satellite signals, pagers, etc.
This type of signal is sometimes refered to as a base band signal.
- 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 or a continuous burst of static.
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.
Typically used on HF signals which have the ability to travel great distances by bouncing off ever-changing layers of the upper atmosphere.
See HF
- 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 INTERMODULATION
E
- EDACS
- Enhanced Digital Access Communication System
A type of trunking system developed by Ericsson.
See TRUNKING
F
- 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 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.
- 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.
In FM signals, the data to be transmitted is conveyed by varying the frequency of the modulated wave. This mode of transmission is used for most VHF/UHF communications since it is less prone to interference and fading (compared to AM).
See AM, 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.
- 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
G
- 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
H
- 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).
Originally frequencies were measured in cycles per second but this was later replaced by Hertz to honor the early radio pioneer.
See FREQUENCY
- HF
- High Frequency
Those frequencies between 3MHz and 30MHz. Also referred to as the shortwave band. It is here that you will find the world broadcasters (like the BBC, VOA, etc), utility stations, pirates (broadcasting without a license), Citizen's Band (CB) and various amateur radio bands.
Typical receive modes for HF are AM & SSB.
See AM, RECEIVE MODE & SSB
- HT
- Handheld Transceiver
Also Handie-Talkie
A handheld radio capable of transmitting as well as receiving. Usually refers to amateur radio models needing an FCC license to transmit. Many can receive a broad range of frequencies and are thus a favorite of the typical scanner user.
- 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.
- Hz
- Abbreviation for Hertz
See HERTZ
I
- 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. Some receivers even use multiple IFs in the same stage; one for each type of possible modulation.
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 IFs used and the conversion scheme.
What usually happens, for instance, is that you'll hear a civil aircraft transmission (in the 118 - 137MHz range) in the VHF public safety band (153 - 156MHz).
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.
Some radios come with the interface built in while others can use after-market products to add such capabilities.
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 making it appear to be an image.
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, FILTER & IMAGE
K
- Keylock
- Feature used to lock some or all of the keys, buttons and/or controls of a radio thereby preventing accidental activation.
L
- LCD
- Liquid Crystal Display
Physical element allowing information and indicators such as frequency, 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 simultaneously.
- Lockout
- Feature used to
Also referred to as 'Pass' or 'Skip' on some models.
- Keep a memory channel from being scanned
- Keep a frequency from being searched
- 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 saves frequency bandwidth and was as well as needing less transmitter power.
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
- LTR
- Logic Trunked Radio
A type of trunking system developed by E.F. Johnson and later bought by Uniden.
See TRUNKING
- LW
- Long Wave
Refers to any frequency below 530kHz. Especially those in the 160 - 190kHz region.
M
- MF
- Medium Frequency
Those frequencies between 300 and 3000kHz (or 300kHz and 3MHz).
- MW
- 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.
- 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
N
- 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 or more narrow 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 & SELECTIVITY
- NB
- 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
- NiCd
- Shortened form of Nickel-Cadmium. May also be seen as 'nicad' or 'ni-cd'.
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.
NiCds 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 - 1100mAh.
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 NIMH
- NiMH
- Shortened form of Nickel-Metal Hydride.
A more recent development in rechargeable battery technology. NiMH cells provide around 25% more power than a comparable NiCd, cost about 1.5 - 2 times as much and about half the number of recharge cycles.
NiMH cells are much more finicky when it comes to being properly charged when compared to NiCds and need special chargers to prevent overcharging and keep charging temperatures within thermal limits.
See NICD
- 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.
O
- 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 (or burden) 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 4, 8 or 32 ohms).
P
- Pause
- Feature used to resume a scan or search operation if a received signal is active for more than a defined period of time.
- PL
- 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.
When attached to an equipment chasis, it is often referred to as an SO-239 connector.
- 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 lead to intermodulation within the receiver and poorly designed units can actually generate 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.
Q
- QTH
- An amateur radio abbreviation for geographic location. As in "What's your QTH?" or, in other words, where do you live?
R
- 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.
- 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.
- 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 can be much thicker than RG-6 making it less "manageable".
Cables of this type are typically labeled as RG-8/U or RG-8X
- 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 (usually human voice), the receiver must demodulate the received transmission using the same mode that was used to transmit it.
- 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.
S
- S-meter
- Feature usually found on more costly models. A meter or graphical display element giving a visual indication of the strength of the signal being received. Usually some form of bar graph with more elements indicating a stronger signal and calibrated in dB so the scale is not linear.
See DB
- 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, Sony 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.
- 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.
- 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
- SMA
- Type of cable connector used on cellular phones as well as some amateur radios.
- SO-239
- See PL-259
- 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 almost 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. Some receivers even allow the squelch to be controlled by audio detecters. Others allow memory channels to individually specify a numerical value representing the minimum signal strength needed to open the squelch.
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 to prevent interference. Receivers with many step sizes are more flexible and usually allow the user to select the step size to be used.
T
- 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.
- Trunking
- Usually refers to the type of communications protocol used on a Trunked Radio System (TRS).
See TRS
- 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. Since then, Uniden has made TrunkTrackers for RadioShack including the PRO-2050, PRO-2066, PRO-90 & PRO-91.
With the help of specialized software from Scan*Star, the Optoelectronics OptoCom is also able to track trunked radio systems.
Capabilities of first generation devices allow for tracking of Motorola 800MHz Trunked Radio Systems (TRS). Unfortunately, the unit can only track one TRS at a time and can not do trunking and conventional systems simultaneously.
The second generation of trunking receivers began with Uniden's BC245XLT which included the ability to track EDACS systems. This function was provided for the RadioShack PRO-94 & PRO-2052.
GRE entered the trunking scanner market in '99 with the introduction of the RadioShack PRO-92 and its mobile equivalent, the PRO-2067. These were later followed by the PRO-93, PRO-2053 and PRO-95.
Uniden rolled out the third generation of trunking radios with the very popular BC780XLT base/mobile which now included LTR tracking. These basic capabilities would later be found in the BCT-8, BC898T & BC246T.
The fourth generation of trunk tracking scanners was introduced with Uniden's BC250D handheld and BC785D base/mobile which could decode APCO P25 3600 baud digital TRS's with an optional decoder card (BCi25d).
RadioShack countered Uniden's BC250/785 with the arrival of the PRO-96 from GRE which was DSP-controlled and decoded both APCO P25 3600 and 9600 (Phase I/C4FM) digital systems. This was later followed by the PRO-2096 mobile.
Uniden then delivered the BC296D handheld and BC796D base/mobile which were officially called the 'TrunkTracker IV' generation which could handle 3600/9600 digital systems from the factory with no optional decoding card needed.
See TRUNKING
- TrunkTracker II
- Second generation of TrunkTracker by Uniden. The first model introduced with this technology was the BC245XLT which was released in July, 1997.
Capabilities of such models include the ability to track Motorola and EDACS trunked radio systems on both VHF and UHF systems. It is also possible to monitor multiple trunked and conventional systems simultaneously.
Uniden will build the PRO-2050 and PRO-94 for Radio Shack which will be based on the BC245XLT design (but will not allow trunked and conventional to be monitored simultaneously).
See TRUNKTRACKER
- TrunkTracker III
- Third generation of TrunkTracker by Uniden. The first model to use this technology was the BC780XLT which was released in late December 2000.
Uniden will build the PRO-2050 and PRO-94 for Radio Shack which will be based on the BC245XLT design.
Capabilities of this generation model are the same as the second generation but with the added ability to track LTR systems.
See TRUNKTRACKER
- TrunkTracker IV
- The fourth generation of TrunkTracker by Uniden. The first model to use this technology was the BC250D handheld and later followed by the base/mobile BC785D base/mobile.
This generation was charactirized by the ability to decode and track digital APCO P25 trunked systems using an optional decoding card.
These two radios were later replaced by the BC296D and BC796D which provided the same capabilities but without the optional decoder card.
See TRUNKTRACKER
- TRS
- Trunked Radio System
A radio system which uses a trunking communications protocol.
Such a system consists of multiple, physical frequencies which are controlled by a central computer 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, GE/Ericsson (EDACS) and E.F. Johnson/Uniden (LTR).
See EDACS, LTR & TrunkTracker
U
- 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 saves frequency bandwidth and was as well as needing less transmitter power.
USB frequencies are typically found in the HF band as well as on those frequencies used by amateur radio.
See AM, DEMODULATE, LSB, RECEIVE MODE & SSB
V
- 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 3 and 30kHz.
- VSC
- Voice Scanning Control
See Data Skip
W
- 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.
Newer radios are using the SAME technology which allows alert codes to be detected which are unique to each county. This allows NOAA to more accurately alert only the effected regions instead of alerting everyone in the listening area.
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 (88 - 108Mhz) and TV audio signals.
See FM, MODULATE & RECEIVE MODE
- WX
- 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.
Some radios only come with those frequencies programmed for the US while others include both US and Canada.
See WEATHER ALERT
| Copyright © 2005 by Richard J. Wells |
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