GMRS Repeaters

What is a repeater?

A repeater is a radio device that receives a radio signal on one frequency and retransmits it on another. Repeaters increase the effective range of low power radios by retransmitting the received signal at higher power.

For maximum effectiveness, repeater antennas are placed at the highest point in the nearby terrain. A repeater place on top of the highest hill will prevent the hill from being an obstacle.

Privacy

In GMRS, repeaters are operated by individuals. Those operators are responsible for ensuring that only licensed operators and their families have access to the repeaters. For this reason operators often configure their repeaters are configured to use CTCSS or DCS codes. These codes are shared only with authorized users. While getting the codes is not difficult, it does provide a simple barrier to unauthorized use.

Duplexers

A duplexer is a device that allows a repeater to  transmit on a frequency close to the receive frequency. Without a duplexer, the transmitter would overload the receiver. In addition, the duplexer allows both transmitter and receiver to share the same antenna, increasing consistency between transmitted and received signals. Duplexers usually are set for 600 kHz separation on 2 meters and 5 megahertz on 70 cm. By statute, GMRS repeaters use 5 megahertz.

What are CTCSS and DCS codes

CTCSS are sub-audible tones that get transmitted with the voice or data signals. The tones range from 67 hz to 250 hz. The can’t be detected by human ears, but are used by the repeater to “open” the transmitter. The exact frequency is configured in the repeater and connecting radio.

DCS codes are very similar, but use the sub-audible frequencies to transmit a three digit code. Like CTCSS, DCS codex are used to “open” the transmitter. Repeaters and radios must be configured to be the same.

To obtain codes for accessing repeaters in your area, request permission to use a repeater via the mygmrs.com website.