How To Set Up A Ham Repeater

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A Beginners Guide to Repeaters, Questions and Answers... Past Kevin K. Custer W3KKC   (AKA "the repeater builder guy")

For the sake of the complete beginner I'm going to comprehend all the parts, fifty-fifty those which may seem obvious.

What is a Repeater?
A repeater, in concept, is not really a complicated device. A repeater is an automatically controlled transmitter and receiver that simply transmits what the receiver hears simultaneously. Imagine having a receiver on i channel, and a high ability transmitter on the other, and then holding the microphone of the transmitter in front of the speaker of the receiver. Now brand the operation fully automatic. Whatever user that can be heard past the receiver has the effectiveness of the high power transmiter at his command.

In general, repeater systems are normally located in places of high meridian (on alpine towers, on summit of mountains or alpine buildings) and are equipped with large and efficient antennas, extremely depression loss feedlines, and a transmitter and receiver that is very durable, rated for continuous duty, and congenital to be as immune equally possible to interference.

The finish result? People using a repeater become much greater range from their radio equipment than would be possible talking from radio to radio. This is how an private with a portable walkie-talkie (handheld) transceiver tin communicate with people many miles abroad with proficient clarity.

Repeaters are used in police, burn down and ambulance service communications (normally called "Public Safety" or "First Responder"), Commercial (Business) Communications, Federal, State and Local Government agencies, Emergency Communications, and by Amateur Radio Operators. Repeaters tin be powered by the regular commercial power lines, or they tin can be connected to multiple sources of power, including batteries and/or generators for when commercial power is lost. Repeaters can be congenital that are extremely power efficient and may run exclusively from batteries; recharged by solar, current of air or water power.

Here's a link to a solar-powered amateur repeater: http://www.polkcounty.org/ham/

What is "Simplex"? (other mutual terms are "Directly" or "Talk Around")
Simplex is indicate to point communications without the use of a repeater. Simplex operation utilizes the same frequency for receive and transmit, like a CB radio. I.Eastward. directly Portable to Portable or Mobile to Mobile. A lot of the people in the commercial 2-way radio earth call Simplex operation "Talk Around" because you are talking around the repeater, not through it.

Thne at that place are such things as Simplex Repeaters. These machines mind on the frequency for activity, when information technology detects a valid indicate it will brainstorm to tape that activeness for a pre-determined time; ordinarily 1 infinitesimal. A slang term for these is a "parrot repeater". After the activeness ceases or the fourth dimension has expired, the unit volition primal the transmitter and play back what it has recorded. This method of communications is somewhat cumbersome over a conventional repeater; considering you are forced to listen to what you said earlier in time and the channel usage is problematic as you lot never know when someone else is recording; however it should not be discounted as these types of systems tin can be very benign.

What is "Duplex"?
The simple explanation of duplex is communications utilizing two channels, with ane channel in each direction. If the signals period in both directions simultaneously the communication is "full-duplex" else it is "half-duplex". Repeaters operate full duplex and the performance is similar your telephone, where the incoming signal and the approachable signal operate at the same time. In dissimilarity, a handheld or mobile radio operates in half duplex mode considering just one person can talk at a time. Since the "repeater" listens and talks at the same fourth dimension in relaying your message, information technology operates in full duplex mode. Some amateur communications can be total duplex, several older mobile radios like the Motorola Micor and GE Mastr II could be modified (and were) to operate full duplex.

How does a Repeater work?
At offset glance, a repeater might appear complicated, merely if we take it autonomously, slice by piece, it's really non really so difficult to empathize. A basic repeater consists of several individual pieces that, when connected, form a functional system. Here's a simple block diagram of a repeater:

The collection of the antenna, the feedline, the duplexer, and the interconnecting cables is often called the "antenna system".

Antenna -
About repeaters employ only one antenna. The antenna simultaneously serves both the transmit and receive RF (Radio Frequency) signals that are going in to and out of the repeater. It'southward generally a high performance, durable, and very efficient antenna located as loftier on a tower or structure every bit nosotros tin go it. Antenna systems of this type can easily cost $500 or more, and that's not including the feedline. On the other hand, when properly installed and maintaned they can terminal from x to 25 years.

Feedline -
The feedline on almost repeaters isn't just a piece of standard coax cable, it's what's called Hardline. This stuff is more like a pipe with a centre usher than a cable. It'south hard to work with and very expensive. So why do nosotros use it? Performance! The signal loss is much lower in hardline than in standard cable, and so more power gets from the antenna to the receiver and weaker signals tin exist received. A hard rule is that once any percentage of a received indicate is lost that you can't get it dorsum - ever. Remember, the point at a repeater site doesn't just travel a few feet to an antenna similar in a mobile rig. Information technology may become hundreds of feet up the tower to the antenna. Just for fun check out the specs on a curlicue of coax some time and encounter how many dB of loss you'll get from 200 anxiety of cablevision, and recall 3 dB is 1/2 of your ability, and 10 dB is 90% of your ability. Hardline also tends to be more than durable than standard cable, which increases reliability and helps us minimize the fiscal expense, and the belfry climbs to replace it.

Duplexer -
This device serves a critical role in a repeater. To make a long story curt, the duplexer separates and isolates the incoming indicate from the approachable and vice versa. Even though the repeaters input and output frequencies are different, the duplexer is still needed. Why? Have yous always been in a identify where there's lots of RF action, and noticed the receive functioning of your handheld radio degrades to some caste? This is chosen desensitization, or desense, and it'south a bad thing on a repeater. The receiver gets noisy or gets desensitized to the point of total deafness from the potent RF signals existence radiated in its vicinity and confused near which signal it should receive. The result is poor receive quality, or in extreme cases, complete lack of receive capability. Proceed in mind that in this example, the radios are picking up radiated power from one some other and that'south enough to crusade trouble. Now imagine how much trouble at that place volition be if you not just take the transmitter and receiver shut together, only connect them to the same antenna! Transmitting only a few hundred kHz away in frequency would blow away the input to the receiver if the equipment was simply connected together with a Tee. That'south where the duplexer comes in; it prevents the receiver and transmitter from 'hearing' one another by the isolation it provides. And the more isolation the better.

A duplexer is a device that is referred to by several different names similar cavities or cans. A duplexer has the shape of tall canisters and is designed to pass a very, very narrow range of frequencies and to reject all others. There is some loss to the system considering of the duplexer (called the "insertion loss"), notwithstanding, the advantage of being able to utilize a unmarried antenna and a single feedline normally outweighs the drawbacks.

Receiver -
Receives the incoming signal. This receiver is generally a very sensitive and selective loftier performance ane which helps weaker stations to be heard better by the repeater. It's also where CTCSS (Continuous Tone Coded Squelch Organization) or "PL" decoding takes place. More on this later.

Transmitter -
Most machines have a transmitter composed of 2 parts: an 'exciter' and a power amplifier. The exciter created low level RF free energy on the proper frequency and then modulates it with the audio. The power amplifier stages just boosts the level then the signal will travel further. Transmitters come up in two types: intermittent duty and continuous duty. 1 that is rated for continuous duty is preferred.

The "Station" -
The term "Station" is used to describe a stationary two mode radio set; which includes the transmitter, receiver and sometimes the control circuitry. One example is the dispatch radio for a fire department. A 'Repeater Station' is a station designed to be used as a duplex repeater.

Controller -
This is the brain of the repeater. It handles station identification (through either CW or phonation), activates the transmitter at the advisable times, controls the autopatch, and sometimes does many other things. Some machines also have a DVR (Digital Vocalisation Recorder) for announcements and messages. The controller is a little reckoner that'southward programmed and optimized to command a repeater. The various models of controllers have unlike useful features similar speed-punch for telephone patches, a voice clock, facilities to control a remote base or linking, etc. The controller gives the repeater its 'personality'. Whenever yous're using a repeater, you're interacting with its controller. In the early days of repeaters the controller was a big chassis full of relays and timers. These days a controller is most oft a microcomputer based unit.

What is a Phone Patch or Autopatch? AKA "The Patch"
Many repeaters have a feature that allows yous to place a telephone telephone call from your radio. Telephone calls are generally restricted to the local calling area of the repeater to avoid long altitude charges to the repeater's sponsors. If in dubiousness, ask if the repeater has an open patch and how to access it. When using the patch it is common courtesy to denote your intentions, eastward.g. "This is N3XZY on the patch". This may assistance to prevent anyone from keying up while you are trying to use the function. In near areas when you lot are finished with the patch the accepted protocol is to denote it, e.thou. "This is N3XZY clear the patch".

DVR -
A DVR is a Digital Vocalization Recorder, or in modern terms a "phonation postal service" arrangement for the repeater. Usually information technology's an selection that is installed into the controller.

Repeater Operation -
Operating using a repeater isn't difficult. A proficient source of info is the ARRL Repeater Directory. It'due south an cheap book with repeater listings all over the US. It contains frequency, start and whether the repeater is + or - in shift (encounter "get-go" below), whether or not it requires a PL tone, and other features (like an autopatch, or repeater-to-repeater linking).

What is Offset?
In order to listen and transmit at the aforementioned time, repeaters apply 2 different frequencies. On the 2 meter ham ring these frequencies are 600 kHz apart. As a general rule in the The states, if the output frequency (transmit) of the repeater is below 147 MHz then the input frequency (listening) is 600 kHz lower. This is referred to as a negative first. If the output is 147 MHz or higher up and then the input is 600 kHz to a higher place. This is referred to as a positive offset. However in any given area the first rules can exist different.

Nearly all ham radios sold today set the offset in one case you accept chosen the operating frequency. As an example ane repeater output is 145.270 MHz. The input, or the frequency it listens on is 144.670 MHz (600 kHz below). If you accept your radio tuned to 145.270 MHz with the offset enabled, when y'all push the PTT switch (Push-To-Talk) your radio automatically transmits on 144.670 MHz. When you release the PTT to heed, the radio reverts dorsum to 145.270 MHz to listen on the repeater's output frequency.

Standard Repeater Input/Output Offsets
Ring	Offset
vi meters (50-54 MHz)	No real nationwide standard, it varies widely. Nearly common are -500 kHz, -600 kHz or -one.0 MHz
2 meters (144-148 MHz)	Up and down 600 kHz, depends on frequency
i.25 meters (222-224 MHz, also called "220")	Downwards 1.half dozen MHz
70 cm (440 MHz, also called "UHF")	Up or down 5 MHz, depends on local area usage
33 cm (900 MHz)	-25 MHz
23 cm (1200 MHz)	-20 MHz

Note: There are exceptions to the to a higher place and then bank check local repeater listings.

Why do Repeaters use an Get-go?
To utilise a repeater a user station must use a different transmit frequency than receive frequency. This is a form of duplex, or ii frequency operation. It is known as half-duplex as yous do not receive and transmit at the same time merely normally utilize the push-to-talk button on your microphone to switch betwixt the two.

Most repeater installations use the same antenna for transmit and receive. Without having an first the repeater would only hear itself when it was transmitting on the same frequency information technology was listening on. Even with the beginning, the two frequencies are close enough that antenna organization isolation is required. Again, this isolation is afforded by the duplexer.

What is Carrier Access, Tone Squelch, CTCSS or a PL Tone?
Carrier Access, or Carrier Squelch means that the repeater is looking for a carrier on the receiver frequency to open the squelch. A circuit called a Carrier Operated Switch (COS) or Carrier Operated Relay (COR) senses the squelch opening, and tells the repeater that in that location is a carrier on the input. The controller keys the transmitter, thereby repeating the signal.

Continuous Tone Coded Squelch System, or CTCSS, is a radio communications manufacture standard signaling scheme. It provides an electronic means of assuasive a repeater to respond only to stations that encode or send a very precise audio tone at a very low level superimosed on the transmitter along with the microphone sound. The CTCSS system is used to prevent the repeater receiver from responding to unwanted signals or interference (it's looking for both the carrier and the tone before the betoken is considered as valid). If a repeater is "in tone mode" that means it requires a CTCSS tone to activate the repeater. If it is in "Carrier mode" then it is ignoring the CTCSS decoder, if there is i. Modern repeater controllers offer a style to switch back and forth, even automatically, between the two modes. Originally there were 32 standard tones, now there are 37. Some manufacturers offer more, only near repeaters employ one of the original 32 so as to let the older radios to use the system. Aftermarket tone generators from several differnet manufacturers permit any station to be fix to transmit a CTCSS tone. The tones are in the 67-250 Hz range and are called sub-audible, considering they're beneath the normal voice audio range of 300-3000 Hz. This doesn't hateful you can't or won't hear them; they can be quite noticeable depending on the radio you're using.

PL, an acronym for Private Line, is Motorola'south proprietary name for CTCSS. General Electric uses the name "Channel Baby-sit" or CG for the same system. Other names, such equally Telephone call Guard, Quiet Channel or Quiet Tone are used past other manufacturers.

In days of old, repeaters that used PL were considered to be closed or private. This is no longer the case as tone operation has get more the dominion instead of the exception. Uninformed people use CTCSS to "solve" interference problems. It doesn't. It merely covers them upward, or hides them. The unwanted point is still on the repeater input, the tone decoder simply prevents the repeater from making it obvious.

Of class, everything these days is digital. A later system called Digital Coded Squelch (DCS) uses 85 different sub-aural digital fleck streams. Motorola uses the name Digital Individual Line, or DPL for this. Other manufacturers use unlike names. DPL is gaining in popularity since more radios now come with it equally a standard feature.

How do you call someone on an Amateur Repeater?
First, listen to make sure that the repeater is non already in use. Then listen some more. If you are a new ham that has never used a repater before it might pay to mind for a week or then and see what goes on, who seems to be the "regular users", and if you lot know any of them, mayhap from the local ham social club coming together.

When yous are satisfied that the repeater is not in use, begin with the callsign of the station you are trying to contact followed by your callsign. e.g. "W3ABC this is N3XYZ". If you lot don't establish contact with the station you are looking for, wait a minute or 2 and echo your call.

If you are just announcing your presence on the repeater it is helpful to others that may be listening if you identify the repeater yous are using. due east.g. "This is N3XYZ listening on 6-2-5". This allows people that are listening on radios that scan several repeaters to identify which repeater yous are using (and therefore which microphone to pick upward to respond you).

If the repeater y'all are using is a busy repeater yous may consider moving to a simplex frequency (transmit and receive on the same frequency), once y'all have made contact with the station you were calling. Repeaters are designed to facilitate communications between stations that normally wouldn't exist able to communicate because of terrain or ability limitations. If you lot can maintain your conversation without using the repeater, going "simplex" will get out the repeater free for other stations to use.

Repeater Etiquette
The showtime and near of import rule is Listen FIRST. Few things are more annoying than someone that "keys up" in the middle of some other conversation without first checking to make sure the repeater is free. Proverb that your book control was down as well low and you didn't hear any chat is no excuse - information technology just says that you didn't chack your ain station before y'all used it. If the repeater is in utilise, expect for a pause in the conversation and simply announce your callsign and await for one of the other stations to acknowledge your call.

When yous are using the repeater go out a couple of seconds between exchanges to allow other stations to join in or make a quick call. Most repeaters have a "Courtesy Tone" that will assist in determining how long to pause. The courtesy tone serves two purposes. Repeaters have a time out role that will shut down the transmitter if the repeater is held on for a preset length of time (normally iii or four minutes). This ensures that if someone'southward transmitter is stuck on for any reason, it won't hold the repeater's transmitter on indefinitely.

When a ham is talking and releases the push-to-talk switch on their radio, the controller in the repeater detects the loss of carrier and resets the time-out timer. Many of the modernistic computerized controllers let the possessor to program a "beep" to betoken that the timer is reset. This beep is called the courtesy beep, or the courtesy tone. If you await until y'all hear this beep (normally a couple of seconds) before yous respond, you lot tin be sure that you are pausing a suitable length of fourth dimension. Later on y'all hear the beep, the repeater'southward transmitter will stay on for a few more seconds before turning off. This is referred to as the "carrier filibuster", or the "hang in timer". The length of the delay will vary from repeater to repeater only the boilerplate is about 2 or 3 seconds. You don't have to wait for the transmitter to drop off the air before keying up once more, but you should make sure that you hear the courtesy tone earlier going ahead.

Notation: If yous don't wait for the beep the fourth dimension-out timer to may not reset. Some repeater clubs take a rule that if y'all time-out the repeater yous get to buy a circular of coffee at the side by side ham club meeting.

What is "Doubling" ?
When two stations effort to talk at the aforementioned time the signals mix in the repeater'due south receiver and results in a buzzing sound or squeal. When you are involved in a roundtable discussion with several other stations it is always best to laissez passer off to a specific person rather than leave it up it the air. eastward.g. "W3ABC to take it, this is N3XYZ" or "Do yous have any comments Fred?, this is N3XYZ". Failing to practice and so is an invitation to chaos and confusion.

It is for this very reason that when groups hold scheduled Nets (network of hams meeting on air at a predetermined time), they assign a Net Control station. The Internet Controls job is to make sure at that place is an orderly exchange and that all stations go a chance to speak. Listen to a local net and you will go an idea of the format and how the Cyberspace Control juggles the diverse stations and traffic. It's a job most anyone can handle, but as you volition notice, some are much better at it than others. And if you try your hand at being Net Control for a nighttime, yous will discover merely how difficult it can be! (and you will proceeds a lot of respect for those that take the knack to do information technology and make information technology audio easy). A well run net is both informative and entertaining!

What is a Command Operator?
The Role 97 of the FCC Rules requires all stations in the Amateur Service that are capable of operating unattended must exist monitored for proper operation while in the unattended manner. This monitoring function is accomplished by a control operator. The Command Op tin exist the licensee of the station or anyone he or she chooses. In many cases, he or she too ends upward existence the person that answers questions about the repeater.

What is White Noise?
White noise is a term used to describe a spectrum of broad ring noise generated in a receiver'south detector and sampled to command the receiver's squelch. When y'all open the squelch control and hear the rushing noise from the speaker, this is white noise. When the receiver is in carrier squelch mode the squelch excursion uses the presence of that dissonance to determine that the signal has gone abroad and information technology should mute the receiver speaker. When the receiver is in tone squelch mode it uses the abscence of the tone AND the presense of the noise to bespeak loss of signal. The "squelch tail" is that burst of white noise that you hear that starts when someone unkeys and ends when the squelch circuit actually mutes the receiver audio (some people mistakenly utilize the term to refer to the carrier delay mentioned higher up).

I hope this article has explained the Repeater in plenty detail that you sympathize what it is and how to use it. If there is whatever office of this article that seems vague or confusing, please write me and I'll do my best to explain it better.

Email Kevin: kuggie //at// kuggie //dot// com

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Text and HTML Copyright © September half dozen, 2003 by Kevin Thousand. Custer W3KKC
All Rights Reserved.

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