Fundamentals of Repeaters
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Transcript of Fundamentals of Repeaters
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Fundamentals of Repeaters
Marc Tarplee, Ph.D. NCE
N4UFP
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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.
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Some History
Amateurs experimenting with VHF/UHF in the1930s discovered that propagation was generallylimited to line-of-sight.
The limited working range offset the advantages of
VHF gear for mobile/portable operation (smallantennas and light equipment)
In the 1950s, widespread availability of WWIIsurplus 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 wereintroduced.
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Basic Repeater Components
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Basic Repeater Block Diagram
DUPLEXER
RECEIVER
CARRIER
OPERATED
RELAY
TRANSMITTER
f1
f2
CARRIER
DETECT
PTT
AUDIO
ID TIMER
CW
ID
ID
XMIT
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Antenna
Repeater antennas are almost alwaysvertically polarized and have an
omnidirectional azimuth pattern. Generally the same antenna is used for
transmitting and receiving.
The antenna is mounted as high as possiblein order to have good line-of-sightcoverage.
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Duplexer Diagram
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Duplexer Operation
Received Signals
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Duplexer Operation
Transmitted Signals
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Receiver
A repeater receiver must have good sensitivity andexcellent selectivity, in order to have adequaterejection of the transmitted signal.
The receiver will have at least two outputs: Audio output
Carrier detect
The audio output can contain both audio signalsand out-of-band control tones.
A signal appears on the carrier detect line when anRF carrier breaks the receivers squelch. (arepeater 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 unnecessaryreceiver 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
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Important Upgrades
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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 carrieroperated relay is generally replaced by a repeater
controller
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Repeater Controller
A repeater controller provides (at least) thefollowing capabilitiesTelephone line interface
Voice ID and announcement capabilityLinking
Transmitter controls
Special supervisory tones (courtesy beep, etc.)
DTMF decoding
CTCSS decoding
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Types of External Control
Via telephoneThe repeater operation is controlled through
DTMF tone groups sent through a phone line. Via RF link
The repeater controller is accessed via aseparate simplex RF link (above 222.15 MHz)
On-the-AirDTMF tones sent into the repeater are used to
control its operation.
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Autopatch
An autopatch is a connection between an amateurrepeater 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 cellphones.
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Reverse Autopatch
A reverse autopatch is a connection from thePSTN 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 thecontroller.
Cell phones may also be used to provide a
line for autopatch. If the line will also beused to control the repeater, an older AMPS
cell phone is necessary.
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CTCSS
CTCSS is the continuous tone coded
squelch system
A repeater using CTCSS will cannot beaccessed 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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K4YTZ Repeater (Leroy)
DUPLEXER
RECEIVER
REPEATER
CONTROLLER
TRANSMITTER
147.03 MHz
146.43 MHz
CARRIER
DETECT
PTT
AUDIO
+
CTCSS
AUDIO
Line
Amp
AMPS
CELL PHONE
CABINET
TEMP SENSOR
OUTDOOR
TEMP SENSOR
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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 baselinking)
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Internet Repeater Linking
This type of linking uses VoIP (Voice overInternet Protocol) to connect repeaters via the
Internet.
The repeater is connected to the Internet via a PCrunning 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 primaryand secondary repeaters.
FCC rules require that this link operate above 222.15MHz
When the primary repeater is opened, its controllerroutes audio to the RF link transceiver and puts itinto transmit mode.
When the secondary repeaters RF link transceiverreceives a signal, this signal is sent to its controller,which retransmits the signal over the secondaryrepeater.
This type of linking is half-duplex (simplex)
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Remote Base Linking
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Useful DTMF Commands for the
K4YTZ RepeaterMacro Command / Message Macro Command / Message
* 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 K4YTZ repeater is a reflection onYCARS