Feb 3, 2026 – What is a Repeater and their Purpose?

Good evening. This is W1UT and tonight’s training is about “Repeaters and their Purpose.”

So what is an Amateur Radio repeater? An amateur radio repeater is a device that receives a weak or low-level radio signal and retransmits it at a higher power level, so that the signal can cover longer distances. Retransmission happens on a different frequency normally within the same band. Installation of a repeater is usually located at high locations, such as mountain sites, to extend coverage. This can be done using analog or digital means. The Intertie system currently uses analog means for all repeaters.

A repeater consists of a separate receiver and transmitter often contained in a common box. Some repeaters that are part of the Intertie consist of two mobile radios. One acts as a receiver the other as the transmitter. Both types perform the same function although equipment designed as a repeater often has longer service life and can maintain 100% duty cycle transmissions without overheating.

A repeater system consists of more than just the repeater unit. Each repeater site needs a rack, power, a controller, a duplexer, low loss feedline and an antenna. The controller is a device that allows the repeater owner to remotely shut down the repeater. The controller is either touch tone controlled via a radio or some other control method. The controller provides the brains to control the repeater and any other radios, such as link radios, at the repeater site.

The antenna is the radiating and reception device usually located on a tower at the repeater site. It needs to be a rugged device capable of withstanding the harsh conditions found at mountain top sites. Most of the time the same antenna is used for simultaneous reception and transmission. The VHF receive frequency is usually 600 Khz above or below the transmit frequency. On UHF the RX/TX frequencies are usually 5 Mhz apart.

A single antenna is used to minimize the cost of purchasing and installing two antennas, one for transmission and the other for reception. Most antennas are either simple rugged dipoles or phased dipoles providing some gain. These antennas can be expensive so using one is cheaper than two. Use of a single antenna also minimizes the cost of extra feedline.

In order to use a single antenna and avoid overloading or destroying the receiver, a duplexer is installed in the feedline between the repeater and the feedline run to the antenna. The duplexer looks like a set of large cylindrical cans on VHF and smaller ones on UHF. A duplexer is an electronic device that allows bi-directional (duplex) communication over a single feedline thus isolating the receiver from the transmitter while permitting them to share a common antenna.

The feedline used at a repeater site is something called hard line or rigid feedline. It is a 50 ohm impedance feedline that has very low losses at VHF and UHF frequencies. It is quite expensive and can withstand extreme weather conditions for many years of service. This makes it ideal for use on mountain top sites.

Repeaters typically require special test equipment to tune the duplexers, check receiver sensitivity, adjust repeater controller audio volumes or what is called deviation levels, test power output, etc. Newer repeaters also require programming using a computer.

That is all for this week. Hopefully this was helpful for some of you newer hams. I will turn the time back to the net control station from W1UT.