Introduction to Repeaters

1
Introduction to Repeaters

• Ron Milione, Ph.D. CETma
• W2TAP
• w2tap_at_arrl.org
• ron.p.milione.ctr_at_us.army.mil

2
What is a repeater?

• A repeater is a device that performs 3 basic
  functions
• It receives and demodulates an RF signal.
• It regenerates the audio information.
• It modulates and retransmits the audio on a new
  RF carrier.

3
Some History

• Amateurs experimenting with VHF/UHF in the 1930s
  discovered that propagation was generally limited
  to line-of-sight.
• The limited working range offset the advantages
  of VHF gear for mobile/portable operation (small
  antennas and light equipment)
• In the 1950s, widespread availability of WWII
  surplus electronics led to the creation of the
  first repeaters on the West Coast.
• The repeaters were AM and used frequencies on the
  2 meter band.
• By the 1970s, standard offsets and FM were
  introduced.

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Basic Repeater Components
5
Basic Repeater Block Diagram
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Antenna

• Repeater antennas are almost always vertically
  polarized and have an omnidirectional azimuth
  pattern.
• Generally the same antenna is used for
  transmitting and receiving.
• The antenna is mounted as high as possible in
  order to have good line-of-sight coverage.

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Duplexer

• A duplexer is a special type of filter that
  allows a single antenna to transmit and receive
  simultaneously on two closely spaced frequencies.
• A typical duplexer consists of two pairs of
  resonant cavities.
• Two pass the transmit signal from the transmitter
  to the antenna while rejecting the received
  power.
• The other two pass the receive signal from the
  antenna to the receiver while rejecting
  transmitted power.
• Typical rejection is better than 70 dB, while
  attenuating the desired signal less than 2 dB

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Duplexer Diagram
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Duplexer OperationReceived Signals
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Duplexer OperationTransmitted Signals
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Receiver

• A repeater receiver must have good sensitivity
  and excellent selectivity, in order to have
  adequate rejection of the transmitted signal.
• The receiver will have at least two outputs
• Audio output
• Carrier detect
• The audio output can contain both audio signals
  and out-of-band control tones.
• A signal appears on the carrier detect line when
  an RF carrier breaks the receivers squelch. (a
  repeater use requests service)

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Carrier Operated Relay

• The carrier operated relay turns on the
  transmitter in response to
• a carrier detect signal
• an ID transmit signal

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Transmitter

• The transmitter should meet the following
  criteria
• High spectral purity (to avoid unnecessary
  receiver interference)
• Highest possible output power (for greatest
  coverage)

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ID Timer

• The ID timer performs basic ID housekeeping
  tasks
• Generating appropriate IDs
• Tracking time between ID transmissions

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Repeater Simulation
16
Important Upgrades
17
External Control

• The control operator (repeater trustee or his
  designee) needs to be able to control the
  operation of the repeater transmitter, in the
  event of
• Electrical malfunction
• Inappropriate use of the repeater
• To implement the external control function as
  well as some other desirable features, the
  carrier operated relay is generally replaced by a
  repeater controller

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Repeater Controller

• A repeater controller provides (at least) the
  following capabilities
• Telephone line interface
• Voice ID and announcement capability
• Linking
• Transmitter controls
• Special supervisory tones (courtesy beep, etc.)
• DTMF decoding
• CTCSS decoding

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Types of External Control

• Via telephone
• The repeater operation is controlled through DTMF
  tone groups sent through a phone line.
• Via RF link
• The repeater controller is accessed via a
  separate simplex RF link (above 222.15 MHz)
• On-the-Air
• DTMF tones sent into the repeater are used to
  control its operation.

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Autopatch

• An autopatch is a connection between an amateur
  repeater and the PSTN that permits a repeater
  user to make a phone call from his/her radio,
  provided that the radio has DTMF capability.
• The call made through the autopatch is subject to
  all the restrictions of an amateur transmission.
• The popularity and utility of of autopatch has
  declined significantly with the advent of cell
  phones.

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Reverse Autopatch

• A reverse autopatch is a connection from the PSTN
  to an amateur station through a repeater.
• The call is originated by the PSTN subscriber,
  not the mobile amateur.
• The originator of the call should be an amateur
  the call will be carried on amateur frequencies
• Once again, the restrictions on amateur
  transmissions apply to these communications.

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Implementing Autopatch

• All modern repeater controllers have an autopatch
  capability. All that is required is a connection
  between the phone line and the controller.
• Cell phones may also be used to provide a line
  for autopatch. If the line will also be used to
  control the repeater, an older AMPS cell phone is
  necessary.

23
CTCSS

• CTCSS is the continuous tone coded squelch
  system
• A repeater using CTCSS will cannot be accessed
  unless a user transmits a subaudible tone with
  his audio information.

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CTCSS Tones
67.0 69.3 71.9 74.4
77.0 79.7 82.5 85.4
88.5 91.5 94.8 97.4
100 103.5 107.2 110.9
114.8 118.8 123.0 127.3
131.8 136.5 141.3 146.2
151.4 156.7 162.2 167.9
173.8 179.9 186.2 192.8
203.5 206.5 210.7 218.1
225.7 229.1 233.6 241.8
250.3 254.1
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W2VL Repeater Block Diagram
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Repeater Linking
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Repeater Linking

• Repeaters may be linked to increase the coverage
  available to the users.
• Linking methods
• Internet ilink, etc.
• Telephone line
• VHF/UHF link between repeaters (remote base
  linking)

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Internet Repeater Linking

• This type of linking uses VoIP (Voice over
  Internet Protocol) to connect repeaters via the
  Internet.
• The repeater is connected to the Internet via a
  PC running software such as Ilink, Echolink,
  IRLP/Speak Freely
• The software provides A/D conversion and
  compression for the audio and transceiver
  control.
• The repeater may be accessed from the Internet by
  users who have VoIP capability

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Telephone Linking

• Uses a dial-up link to connect two repeaters.
• Primary repeaters controller makes an autopatch
  call to the secondary repeater.
• The secondary repeaters controller answers the
  call and goes into reverse autopatch mode.
• This type of linking is full duplex

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Remote Base Linking

• A separate RF link is installed between the
  primary and secondary repeaters.
• FCC rules require that this link operate above
  222.15 MHz
• When the primary repeater is opened, its
  controller routes audio to the RF link
  transceiver and puts it into transmit mode.
• When the secondary repeaters RF link transceiver
  receives a signal, this signal is sent to its
  controller, which retransmits the signal over the
  secondary repeater.
• This type of linking is half-duplex (simplex)

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Remote Base Linking
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Some Notes on Repeater Operation

• All transmission over a repeater should be in
  accordance with FCC Rules.
• Amateurs have no right to operate on a
  repeater. The repeater or his/her designee grants
  operating privileges to amateurs.
• Wait for the courtesy tone!!!!
• The repeater should not be tied up by long
  conversations use a simplex frequency for a
  long QSO.

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Useful DTMF Commands for the a Repeater as an
example
Macro Command / Message Macro Command / Message
ltautodialgt Patch Autodial 410 Morning Net
Patch Down 411 Evening Net
026 Time (male voice) 420 Skywarn Net
027 Time (female voice) 425 Meeting Week
029 Date 426 Meeting Tonight
400 Repeater Off 427 Breakfast
401 Repeater On 430 Outside Temperature
406 Patch Disable 431 Rack Temperature
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Closing Comments

• FM Repeater operation is often the first type a
  new amateur attempts, and is the main mode for
  many amateurs
• All repeater users should be polite, courteous
  and helpful to newcomers/visitors
• The W2VL repeater is flagship repeater of LIMARC
• 146.850- W2VL 1288.00-
• 147.375 W2KPQ 224.820-
• 449.125- W2KPQ
• PL for all is 136.5