How a Repeater Works

An amateur radio repeater is an electronic device that receives a weak or low-level amateur radio signal and retransmits it at a higher level or higher power, so that the signal can cover longer distances without degradation. Many repeaters are located on hilltops or on tall buildings as the higher location increases their coverage area, sometimes referred to as the radio horizon, or “footprint”. Amateur radio repeaters are similar in concept to those used by public safety entities (police, fire department, etc.), businesses, government, military, and more. Amateur radio repeaters may even use commercially packaged repeater systems that have been adjusted to operate within amateur radio frequency bands, but more often amateur repeaters are assembled from receivers, transmitters, controllers, power supplies, antennas, and other components, from various sources.

There are some basic terms that need to be understood as they will be required for setting any equipment you have.

  • Input frequency:   This is the frequency on which the repeater receives signal – this is the frequency on which your equipment should transmit to access the repeater.
  • Output frequency:   This is the frequency on which the repeater transmits – this is the frequency on which you should listen.
  • Offset:   The repeater offset is the difference between the output and input frequencies. A repeater that transmits on 145.700 MHz and listens on 145.100 MHz has an offset of 145.700 – 145.100 = -600 kHz.
  • CTCSS tone:   CTCSS is the form of repeater access tone that is used these days on most repeaters. The different tones are denoted by letter and the correct tone must be used for each repeater. Sometimes repeaters transmit a Morse letter after the end of a transmission to indicate the tome it requires.

Information about these will be needed when setting any transceiver for repeater operation. The input and output and the offset are obviously related, so these will need to be entered. Also the CTCSS tone needed is also required. Transceivers can be programmed manually and they have the ability to store a number of channels and their associated CTCSS tones. Today it is normally possible to programm the transceiver using a computer. This is generally a lot easier and may be achieved using a spread-sheet style layout for an easy view of all the different stored channels.

Here are some local repeaters in Oklahoma City from RepeaterBook.