Advanced Repeater Systems

Definitions

Amateur Radio- Radio Spectrum allocated for radio hobbyist referred to as "Amateur Radio Operators" and "Hams."  Spectrum from HF to Microwave.

Amplifier- An electronic circuit that increases the voltage and/or current and/or power of an Analog Signal

Analog- Communications or electronics circuits which utilize natural signals

Antenna- A Radio Frequency device that radiates and receives electromagnetic energy

BNC- A high performance RF connector with a quick connect and disconnect feature generally used on small (RG-58, RG-223...) diameters coax cables

CTCSS- Continuous Tone Coded Squelch (Trademark names Private Line®, PL®, Channel Guard®)  The CTCSS Tone is continuously transmitted with the modulated audio.  CTCSS tones are below 250 Hz and are considered sub-audible in FM communications.

CW- Continuous Wave, used to designate Morse Code transmissions, which doesn't make sense because the very act of sending Morse Code involves breaking up a Continuous Wave...  Hams still use CW to communicate.  Modulated CW (MCW) is often used on repeaters for identification.

D-Star®- Ham Digital Radios manufactured by ICOM which uses a 4800 bps GMSK waveform and a propriatary Vocoder, which some Hams consider unfriendly.  Nevertheless, D-Star works quite well and has a popular following throughout the world.

Decibels- Logarithmic ratio of voltage, current or power, expressed in dBs.

DCS- Digital Coded Squelch.  Similar to CTCSS DCS is continuously encoded low-speed data on the modulated carrier at a sub-audible rate.  At the end of the transmission, a 134 Hz tone is transmitted to turn off listening decoders to eliminate the squelch tail.

Digital- Communication via bits that represent either a high or low state
 
Diplexer- A device that separates frequency bands from a common source.  Generally used here to separate the VHF band from the UHF band (or 800 MHz band or others) so that a common transmission line can be used to feed multiple antennas from radios on different bands.

Duplex- Simultaneous operation of two different RF channels or frequencies

Duplexer- A device generally used to connect a receiver and transmitter to a common antenna while providing isolation to the receiver.  Usually used with a repeater but can also connect two transmitters or two receivers to a common antenna provided there is adequate frequency separation.  There are three types of duplexers: Bandpass, Bandreject and Bandpass-Bandreject.  Bandpass types are rarely used because they require wide frequency separation and have less isolation.  Bandreject types provide high isolation and low insertion loss, wide bandwidth and low cost, but offer limited protection from other signals.  Bandpass-Bandreject provide high isolation with a degree of bandpass characteristics but have limited bandwidth.

Echolink®- A ham radio internet based linking system which allows analog communications to link to other stations.  Similar to IRLP®

Ferro-Resonant Power Supply- A power supply that utilizes a saturated core power transformer which outputs squares wave that are rectified and filtered to produce a regulated direct current (DC).  The saturated core design is almost immune to powerline surges and spikes making these excellent supplies for repeater sites prone to lightning strikes.  However they have poor efficiency and make an audible "buzz."

FM- Frequency Modulation.  Audio or Data is impressed on an RF carrier by changing the frequency at the audio or data rate. 

Gain- Any device that provides signal amplification.  Usually expressed in decibels.  The gain can occur with active devices such as an electronic amplifier or a passive device such as an antenna that focuses electromagnetic energy in a particular direction.

GMSK- Gaussian Minimum Shift Keying.  A data transmission mode using two bits sent with sloped rise and fall times to minimize occupied spectrum.  D-Star® uses GMSK

Ham- Nickname for Amateur Radio and Operators

Ham Radio- Nickname for Amateur Radio

Hang Time- The time that a repeater transmitter stays on after an input signal drops, typically 0.5 to 5 seconds 

IRLP®- Internet Radio Linking Project, a ham radio internet linking system where analog transmissions are linked between ham radio stations.  Similar to Echolink®.

LID- A poor ham operator.  Term allegedly came from when early inexperienced CW operators would place a tobacco can LID of the keyer to help them copy code.  The experienced operators would call them LIDS.

MCW- Modulated (by turning a constant tone off and on) CW often used of FM repeaters for FCC identification

N Connector- A high performance RF connector.  The center conductor of the female is fragile and  easily damaged by an improperly installed male connector.  Often the male connector is not installed properly with the center pin either too long or too short and the shield not properly captivation which causes the connector to spin on the coax.  There is really no reason to use this connector below 500 MHz.

P-25- Open Digital Radio Standard that uses a C4FM waveform primarily used by Public Safety and Commercial radio systems.

PL-259- UHF connector.  Often given a bad rap by HAMS.  If properly installed it is provides good and reliable RF performance to 500 MHz.  Often improperly installed by not properly soldering the coax shield.

Rohn- Tower provider of the popular Rohn 25 and 45 series of towers.

RF- Radio Frequency.  Electromagnetic Waves in the approximate range of 3 kHz to 300 GHz.

Repeater- A device that receives on one channel and simultaneously retransmits the signal on another channel

Repeater Controller- A circuit that interfaces with a repeater, and controls the operation of the repeater

Reverse Burst- The shifting of the phase of the CTCSS tone for approximately 150mS after release of PTT meant to turn of the receiving station tone decoder before the carrier drops to eliminate the Squelch Tail.  DCS systems send a 134 Hz tone to quickly turn of DCS decoders.

Sets of Duplexers- More than one duplexer but more often a term improperly used by ham radio operators for a Duplexer who believe a filter cavity is a duplexer therefore you need a "Set of Duplexers" to make a duplexer.

STE- Squelch Tail Eliminator, generally a switched audio delay device that mutes the received audio just prior to the squelch tail.  CTCSS Reverse Burst is also a squelch tail eliminator providing that the CTCSS decoder responds to the phase shifted tone.

Spectrum- Frequency Domain

Spectrum Analyzer- Test Equipment that analyzes Radio Frequency Spectrum

Squelch Tail- Noise burst heard at the end on an FM transmission.  Often improperly used by hams to decribe a repeater hang time. 

VOX- Voice Operated Switch.  An electronic circuit that detects a voice and triggers an output generally used to key a transmitter

 

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