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Senior Project Electrical Engineering -
2006W2UC Amateur Radio Repeater for Union
CollegeRobin StevensonAdvisor Prof. Hedrick
What is a Repeater?
The basic operation of a repeater can be broken
down into four basic components the receiver,
transmitter, duplexer, and control system. The
receiver and transmitter are the main RF
components of the repeater. The receivers
purpose is to convert incoming signals into
audio. The transmitter takes the converted audio
signal and transforms it back into an RF signal
before sending it out. The presence of the
duplexer between the receiver input and
transmitter output allow the two devices to share
the same antenna. Quite simply, the duplexer is
a set of very sharp filters that isolate the
received and transmitted signals from one
another. Finally, the controllers main purpose
is to turn the transmitter on and off when the
receiver detects a properly coded radio signal.
A repeater is an automated radio station that
retransmits signals it receives. Repeaters can
bridge geographic areas (as seen in the above
figure) and extend the range of mobile radios. A
handy talkie with a one mile range could transmit
to a repeater and communicate with someone 15-30
miles away.
Control System Block Diagram
Tone Encoder/Decoder
Audio Mute Circuit
Audio and Tone From Discriminator Output
HPF
Audio
To Microphone Input
LPF
Tone
Tone Detect
Microcontroller
To Microcontroller
From Tone Detect