TETRA (Terrestrial Trunked Radio) is a set of standards developed by the European Telecommunications Standardization Institute (ETSI) that defines a mobile radio communications infrastructure. Originally designed for European use, it has become widely adopted across the globe, especially by public safety organizations, utility companies, and other professional users who require reliable voice and data communications.

TETRA was originally created for high-end users of Private Mobile Radio (PMR) and Public Access Mobile Radio (PAMR), such as law enforcement, fire departments, and utility services. These groups rely on fast, efficient communication for critical operations. TETRA serves as a modern digital solution to meet these needs, replacing outdated analog systems.

With roots in various communication technologies like mobile radio, digital cellular, paging, and wireless data, TETRA is designed to provide features that go beyond traditional radio systems, offering improved voice quality and faster data transmission. Its digital trunking capability allows for efficient use of radio spectrum and advanced features like encrypted communication and high data transfer rates.

Although TETRA was originally designed for use across Europe, its usefulness has led to global adoption. ETSI changed the name from Trans-European Trunked Radio to Terrestrial Trunked Radio to reflect its growing international use. Countries like Denmark, China, and even the United States are adopting TETRA systems, although the U.S. also relies on other standards, like APCO 25, for public safety communications.

In 2012, the FCC (Federal Communications Commission) modified its Part 90 rules to permit the use of TETRA in the 450-470 MHz and 809-824/854-869 MHz frequency bands, expanding TETRA's reach into the U.S. market. TETRA systems are now legal for amateur radio use in the U.S. and several other countries.

While TETRA was initially designed for public safety and industrial users, the availability of TETRA equipment on the secondary market has opened up new possibilities for amateur radio operators. Amateurs can now legally experiment with and operate TETRA systems in certain frequency bands.

In TETRA systems, two key identifiers are used to manage network access: the Mobile Country Code (MCC) and the Mobile Network Code (MNC).

• MCC (Mobile Country Code): A three-digit code that identifies the country in which a TETRA system operates. For example, the MCC for the United States is 310, while for the United Kingdom, it's 234. This code is vital for distinguishing between different national networks.

• MNC (Mobile Network Code): This is a two- or three-digit code used to identify the network operator within a country. The combination of MCC and MNC uniquely identifies the network and is essential for proper routing and user management in TETRA systems.

These codes are essential in ensuring proper access to the correct networks and are vital when using TETRA equipment in cross-border or international contexts.

TETRA’s introduction to the amateur radio community has allowed operators to explore new capabilities, such as:

• High-quality voice communications
• Data transmission at higher rates than typical analog systems
• Digital trunking, which improves the efficiency of spectrum usage

This makes TETRA an exciting option for amateur radio enthusiasts interested in experimenting with professional-grade communications systems.

As of 2012, the FCC's rule changes allow amateur operators to use TETRA equipment legally in specific frequency bands in the United States. This has opened the door for experimentation and development of TETRA systems in the amateur radio world. Other countries have similar regulations, allowing amateur radio operators to explore TETRA, provided they comply with local regulations.

TETRA’s availability for amateur radio use means that hobbyists now have access to robust and advanced communication technology initially designed for mission-critical operations.

Repeaters with Tetra capability can be listed on RepeaterBook. On the repeater's details page, the MCC and MNC can be listed.

• RepeaterBook TETRA Repeaters