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AC (Alternating Current)
DC (Direct Current)

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The standard offsets for HF/VHF/UHF/SHF are:

29 MHz   100 kHz (-)147 MHz   600 kHz (+)1.2 GHz 12 MHz (-)
50 MHz   500 kHz (-)222 MHz   1.6 MHz (-)2.4 GHz 20 MHz (-)
145 MHz 600 kHz (-)440 MHz   5.0 MHz (-)** 
146 MHz 600 kHz (+or-)900 MHz 25.0 MHz (-) 

** Plus Offset In Some areas - notably Northern California.

When a repeater receives below the transmit frequency it is termed a minus offset. A repeater that transmits on 147.13 MHz and receives on 147.73 has a plus offset. Repeater input frequencies are given as either + or - signs to indicate whether the user's transmit frequency is above or below the repeater transmit frequency. Repeaters that have outputs in the lower part of the 146 MHz portion are often plus offsets while those operating in the upper portion of 146 MHz are minus offsets. See your repeater guides. Most of the new rigs default to the accepted offsets.

Code Squelch System

Digital Coded Squelch (DCS) Frequency's

DCS (Digital Coded Squelch) is digital data or code word that is transmitted with the voice audio. This data is sub-audible with most of it's energy below 300Hz. However is does have a wide bandwidth from 2 to 300 Hz. Unlike CTCSS (Continuous Tone Coded Squelch System) which uses continuous tones below 300 Hz., DCS uses digital data or code words. Each code word is unique and all code words may be used on the same channel without interference. At the end of the radio transmission and about 1/2 second before the transmitter un-keys, the radio will encode a 134 Hz tone that serves as a turn off code. The FM deviation level of DCS data should be in the range of 500 to 800 Hz.

Unlike CTCSS, DCS signal spectrum occupies considerable more bandwidth. A poor low frequency response in the transmitter or receiver may not seriously distort a single frequency tone signal but may seriously degrade a wide band signal containing multiple frequency components. The distortion risk is especially high if the frequency response delays the wide band frequency components.

DCS is operated at a low baud rate (134.4 bits per second) and because DCS may have extended periods of all ones and zeros almost all components in the transmitter and receiver chain must be coupled down to at lease 2 Hz or lower. This requirement means that certain transmitters and receivers must be modified before they are capable of DCS operation. Phase modulators, in particular, need special consideration because they theoretically are incapable of being directly modulated by dc, unlike direct FM modulation methods. Low frequency response is the primary requirement for DCS systems.

You will fined that it is extremely important for the receiver and transmitter to be on frequency to achieve maximum performance of the DCS function. Errors in the transmitter and receiver frequencies show up a the discriminator output as a step function. Because of the long time constant required for the low frequency response, a step function can block the decoder momentarily. With DCS, error correction is necessary. But if too many errors occur, you may experience some blocking out of the decoder. Errors can occur because of unwanted low frequency energy. The DCS decoders can be effected by voice energy that falls below 300 Hz. Some radios do not remove this energy before transmission and can cause voice blocking of the decoder. A sub audio filter that removes this low frequency energy before the audio is re-transmitted is necessary for reliable DCS operation.

Before you start modifying your radio to operate DCS, make sure your service monitor is DCS capable. Some older monitors require modifications to obtain the low frequency audio response needed for DCS operation. If in doubt, contact the manufacturer.

The following is a table of standard DCS codes

051023077  152103  311129  466
052025078  155104  315130  503
053026079  156105325131  506
054031080  162106331132  516
055032081  165107332133  523
056036082  172 108343134  526
057043083  174109346135  532
058047084  205110351136  546
059051085  212111356137  565
060053086  223112364138  606
061054087  225113365139  612
062065088  226114371140  624
063071089  243115411141  627
064072090  244116412142  631
065073091  245117413143  632
066074092  246118423144  654
067114093  251119431145  662
068115094  252120432146  664
069116095 255121  445147  703
070122096 261122446148  712
071125097  263123452149  723
072131098  265124454 150  731
073132099  266125455151  732
074134100  271126462152  734
075143101  274127464153  743
076145102  306128465154 754

Continuous Tone Coded Squelch System (CTCSS) Private Line (PL) Frequency's

CTCSS (Continuous Tone Coded Squelch System)

CTCSS (Continuous Tone Controlled Squelch System) a sub audible tone in the range of 67 to 254 Hz. The FM deviation level of CTCSS tones should be in the range of 500 to 800 Hz. These tones are encoded with the voice audio at all times during the transmission. Any one or more of the 50 tones can be used to gain access to the repeater. CTCSS decode and encode is provided as a standard feature on all of our controllers, using state of the art devices. All standard and non standard EIA CTCSS tones can be decoded or encoded. You may select 1, 2, 3 or up to all 50 CTCSS decode tones to operate the repeater. You can even use CTCSS tones and DCS codes on the same channel. We have also divided the CTCSS decode into six independent tone panels. This allows you to assign a different group of tones for different functions. These tone panels have the following functions:

Tone panel #1, Repeater operation (audio) only.
Tone panel #2, User commands.
Tone panel #3, System Commands (commands for programming the controller). This tone panel will also allow access of user commands.
Tone panel #4, Auxiliary output audio. Used when linking multiple controllers together.
Tone panel #5, Telephone audio. Used to access, dial and pass audio to the telephone interconnect.

Tone panel #6, Dial Click. Used for dial click commands, see S-Command 49.

The CTCSS encode deviation level can be adjusted up and down remotely over the air or telephone interconnect. The received or incoming CTCSS tones may be passed to the repeater transmitter, or filtered (removed with a high pass filter, with no tone going out to the repeater transmitter). Under normal conditions, you will filter out in incoming tone and re-encoding a new CT

CTCSS tone either on the same or a selected different frequency.

The following is a table of standard & non-standard CTCSS tones used in our controllers.

(Hz)EIA  Ham(Hz)EIA  Ham(Hz)EIA  Ham
67.0L1   01110.92Z   15179.96B   29
71.9L2   02114.82A  16186.27Z   30
74.4WA 03118.82B   17192.87A   31
77.0L3   04123.03Z   18203.5M1   32
79.7SP   05127.33A   19206.58Z
82.5L4   06131.83B   20210.7M2   33
85.4YA  07136.54Z   21218.1M3   34
88.5L4A 08141.34A   22225.7M4   35
91.5ZZ   09146.24B   23229.19Z
94.8L5   10151.45Z   24233.6M5   36
97.4ZB   11156.75A   25241.8M6   37
100.01Z   12162.25B   26250.3M7   38
103.51A   13167.96Z   27254.1OZ
107.21B   14173.86A   28  

CB Frequency Table

The American Citizens Band is channelized in the frequency range 26.965 to 27.405 MHz. There are no legal radio channels on which to operate that are above or below these channels.


Some channels are set aside either by the FCC or by custom for specific purposes or type of communication. There are radio control or "RC" channels in between some CB channels.

  • Channel 9 is the CB Emergency Channel. It may or may not be monitored. Many police agencies used to monitor channel 9 but that is not nearly as common as it used to be. REACT membership dropped to less tha 4500 persons nationwide and has not monitored CB in many areas for years.
  • Channel s 17, 18, and 19 are often occupied by truckers and travelers. very good channels to leave on the CB as you travel down the highway.

The reliable local range for a legal CB radio is from one to five miles. These radio frequencies are subject to ionisphereic skip so it is possible to hear stations that are many hundreds of miles away. You may legally talk to stations within a 150 mile radious of your station. It is not legal to talk "skip" on a CB radio.

Family Radio Service Frequencies (FRS) UHF

































Business DOTs VHF Frequencies

Red dot 151.625 MHz

Purple dot 151.955 MHz

151.700 MHz

151.760 MHz

Business DOTs & Star UHF Frequencies

Brown dot 464.500 MHzBrown dot 469.500 MHz
Yellow dot 464.550 MHzYellow dot 469.550 MHz
J dot 462.7625 MHzJ dot 467.7625 MHz
K dot 462.8125 MHzK dot 467.8125 MHz
Silver star 462.850 MHzSilver star 467.850 MHz
Gold star 462.875 MHzGold star 467.875 MHz
Red star 462.900 MHzRed star 467.900 MHz
Blue star 462.925 MHzBlue star 467.925 MHz

Multiple Use Radio Service (MURS) VHF Frequencies

151.820 MHz
151.880 MHz
151.940 MHz
Blue dot 154.570 MHz
Green dot 154.600 MHz
VHF, UHF & Repeater Definitions
am (amplitude modulation)
a radio transmission mode in which the strength of the speech signal controls the strength of the transmitter signal. This normally resuilts in two sidebands containing the modulation energy.
ASL (above sea level)
a method of measuring antenna height
antenna separation
the physical spacing between transmit and receive antennas, when separate antennas are used
a condition that results in greater-than-normal communication range on the VHF and UHF bands
a voluntary system of frequency allocations in each amateur radio band
This is the term generally referred to as your home base or base station. The location of your radio transceiver at home.
the word used to interrupt a conversation on a repeater , often to indicate that there is an emergency
Call sign:
The official FCC assigned call sign that you use in your GMRS system.
COR (carrier-operated relay)
a device that causes the repeater to transmit in response to a received signal
your unmodulated (no speech) transmitter signal
cavity resonator
a sharply tuned circuit using the physical dimensional resonance of one or more tuned cavities
the pair of frequencies (input and output) used by a repeater
channel spacing
the frequency spacing between adjacent frequency allocations - may be 50, 30, 25, 15 or 12.5kHz, depending upon the convention in use in the area of the repeater
closed repeater
a repeater whose access is limited to a select group (see also open repeater)
co-channel interference
the interference resulting when a repeater receives signals from a distant repeater on the same frequency pair
the control system within a repeater which may include turning the repeater on-off, timing transmissions, sending the identification signal, controlling the autopatch & CTCSS encoder/decoder
control operator
the amateur radio operator who is designated to control the repeater
courtesy tone
an audible indication that the repeater user may go ahead and transmit
the geographic area within which the repeater provides communications
the process of transmitting on one band and receiving on another
desense (desensitization)
the reduction of receiver sensitivity due to overload from a nearby transmitter
dropping out
the situation, while using a repeater, when your signal does not have enough strength to keep the repeater triggered.
a mode of communication in which you transmit on one frequency and receive on another frequency (see also half and full duplex)
highly selective filter which allows a repeater's transmitter and receiver to share one antenna
EIRP (effective radiated power referred to isotrope)
ERP plus 2.14 dB to correct for reference to isotrope
ERP (effective radiated power)
radiated power, allowing for transmitter output power, line losses and antenna gain
frequency coordinator
an individual or group responsible for assigning channels to new repeaters with minimal interference to existing repeaters
frequency modulation
a method of modulation, where the strength of the signal is constant, but the frequency varies with the strength of the voice, and the rate of change varies with the frequency of the voice
full duplex
a mode of communication in which you transmit on one frequency while you simultaneously receive on another frequency
full quieting
a received signal that contains no noise
HAAT (height above average terrain)
a method of measuring antenna height
An acronym for Handie-Talkie
half duplex
a mode of communication in which you transmit at one time on one frequency and receive at another time on another frequency
a portable transceiver small enough to fit in the hand, clipped to your belt, or in your shirt pocket
slang for your name (not recommended)
helical resonator
a compact resonant filter circuit to block multiple interfering signals
horizontal polarization
the antenna elements are horizontal (used at vhf/uhf for weak signal CW/SSB operation)
Hz (Hertz)
a unit of frequency measurement equal to one cycle per second
ID (identification)
the means by which a station identifies its call sign by Morse code or speech
input (frequency)
the frequency of the repeater's receiver
intermod (intermodulation distortion or IMD)
interference that results when strong signals from nearby transmitter (s) mix with the desired signal in a radio receiver
the difference in level (measured in dB) between a transmitted and received signal due to filtering
a theoretical antenna with zero dimensions and a spherical radiation pattern. Gain is -2.14 dB from dipole
the action of deliberate illegal interference with a repeater operation
kHz (kilohertz)
a unit of frequency measurement equal to 1,000 cycles per second (Hertz)
to key up a repeater without identifying
key up
to turn on the repeater by transmitting on its input frequency
MHz (megahertz)
a unit of frequency measurement equal to 1,000,000 cycles per second (Hertz)
a slang expression meaning a repeater system
magnetic mount (mag-mount)
an antenna with a magnetic base that permits quick installation and removal from a metallic surface, including an automobile body
modem (modulator-demodulator)
an interface device for use between computers. See TNC
negative offset
the repeater input frequency is lower than the output frequency
NiCd (or NicCad)
a nickel cadmium battery that may be recharged many times; often used in handheld transceivers
new technology nickel metal hydride battery that has advantages over NiCd, but is more expensive
odd split
unconventional frequency separation between input and output frequencies.
open repeater
a repeater whose access is not limited
indicates the end of a contact
output frequency
the frequency of the repeater's transmitter (and your receiver)
Carrying radio with you, or refers to a hand held radio.
positive offset
the repeater input frequency is higher than the output frequency
PrivateThis system is also found with groups, as wall as clubs, businesses, families, and other organizations. Outside persons should request permission to use this system, and may sometimes be required to pay monthly or yearly dues to help maintain the system.
ptt (push to talk)
the use of the microphone button or control line to key the transmitter on
radio direction finding (RDF)
the art and science of locating a transmitter
the vertical spacing of television scanning lines. Used also as slang for channel spacing
an automatic relay station, generally in a high location, which is used to increase the range of mobile and handheld FM transmitter/receivers
repeater directory
a repeater list for a particular area (RAC publishes one for Canada and neighbouring states)
rubber duck(y)
slang term for the flexible rubber-covered antenna supplied with handheld radios
sked (schedule)
a prearranged (scheduled) contact between two stations
separation (split)
the difference, in kHz, between the repeater's transmit & receive frequencies. Conventional separations by amateur band are: 29 MHz - 100 kHz; 50 MHz - 1 MHz; 144 MHz - 600 kHz; 220 MHz - 1.6 MHz; 440 MHz - 5 MHz; 902 MHz - 13 MHz; 1270 MHz - 12 MHz.
a mode of communication in which you take turns to transmit and receive on the same frequency. A frequency set aside for non-repeater use.
a circuit within a radio that keeps the speaker silenced (squelched) until the signal level exceeds a certain point, set by the squelch control. Normally you set the squelch to just block out noise & allow signals to pass.
the brief signal transmitted by a repeater transmitter after someone stops talking.
Talk Around:
Same as communicating direct except you are doing so on a repeater output frequency.
to cause the repeater, or a repeater function, to turn off because you have transmitted too long
a device which measures the length of each transmission & causes the repeater, or a repeater function, to turn off, after a transmission has exceeded the preset time.
translator (linear translator)
a device used to directly convert and retransmit a block of received frequencies
uhf (ultra high frequency)
the region of the radio spectrum between 300 and 1000 MHz or 1 GHz
vhf (very high frequency)
the region of the radio spectrum between 30 and 300 megahertz (MHz)
vertical polarization
the antenna elements are vertical (used at vhf/uhf for FM and repeater operation)
The measure of output power for a radio transmitter.
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This site was last updated Tuesday, April 18, 2023 06:43:40 PM By: Ryan Smith