The UK Amateur's Guide to NXDN

NXDN (Next Generation Digital Narrowband) is a digital radio protocol that began in the commercial Land Mobile Radio (LMR) space but has carved out a dedicated, high-fidelity niche in amateur radio. Developed jointly by JVCKenwood and Icom, it is favoured by hams who prioritise audio quality and narrow bandwidth over the sheer mass adoption seen in other digital modes.

What is NXDN?

NXDN is an open digital standard that uses FDMA (Frequency Division Multiple Access) technology. While older analogue radios use wide 25 kHz or 12.5 kHz channels, NXDN physically slices the spectrum into ultra-narrow 6.25 kHz channels.

How to Use It in the UK

Operating NXDN feels similar to DMR or D-STAR, but it relies on a specific network architecture.

• Get an ID: Just like DMR, you need a registered digital radio ID (CCS7 ID).
• Access the Network: Use local repeaters or personal MMDVM hotspots.
• Dial a Reflector: Program your radio to dial specific reflectors for wide-area communication.

Using NXDN in the amateur radio community

typically involves one of two paths: connecting through an existing repeater infrastructure or setting up a personal MMDVM (Multi-Mode Digital Voice Modem) hotspot.

Using NXDN via a Repeater

To use a repeater, you generally need to register for a valid NXDN ID (e.g., via RadioID.net) and program your radio to match the specific repeater's parameters.

Radio Configuration

You will need to program your radio with the repeater's frequency, the correct RAN (Radio Access Number—similar to a DCS code), and your assigned NXDN ID.

Talkgroups

• Repeaters are often linked to specific networks (like NXCore).
• You must set your radio’s "Contact" or "Talkgroup" to the one you intend to access.
• Consult the repeater owner’s website for their specific talkgroup list and channel requirements.
• Using an MMDVM HotspotAn MMDVM hotspot acts as a "personal repeater" that connects your radio to the internet.

Setup

You will need a device like a Raspberry Pi running software such as Pi-Star. You must configure the software to enable the NXDN mode.

Calibration

• NXDN uses a very narrow bandwidth (6.25 kHz).
• Because of this, it is highly sensitive to frequency offsets.
• It is common practice to use the hotspot’s calibration tool to adjust the modem frequency so your radio and the hotspot sync perfectly.

Operation

Once configured, you treat the hotspot much like a repeater. You send group calls to your desired talkgroup or reflector via your radio, and the hotspot bridges that traffic to the internet.

Finding Reflectors and Directories

NXDN reflectors are often accessed by sending a "Private Call" or a specific command to the reflector’s ID.

Dashboards

Most NXDN networks provide a web-based "Dashboard." These dashboards usually list active reflectors, talkgroups, and who is currently talking.

Resources

Websites like NXDNINFO.COM are primary resources for finding updated information, status, and links to various NXCore dashboards.Switching

Reflectors

On many systems, you can switch reflectors by initiating a "Private Call" on your radio to the specific 5-digit ID of the reflector you wish to connect to. Once you key up for a second, the server typically acknowledges the link via a voice announcement or by showing the status change on the dashboard.

Simplex (Direct) Operation

You can absolutely use NXDN for radio-to-radio communication without a repeater, commonly referred to as "simplex" mode. This bypasses all network infrastructure, making it a reliable method of communication during emergencies.

• Configuration: Both radios must be set to the same frequency, channel, and bandwidth (either 6.25 kHz or 12.5 kHz).
• RAN Codes: Similar to CTCSS tones in analogue, you can use a Radio Access Number (RAN) to filter traffic, or set it to 0 to act as an open "carrier squelch."
• Mixed Mode: Many radios support "Mixed Mode," allowing them to transmit in digital NXDN while still receiving both digital and analogue FM signals on the same frequency.

Available Radios & Pricing

Other Need-to-Know Information

• Programming Software (CPS): Programming commercial Kenwood or Icom NXDN radios is notoriously difficult for beginners. The software often costs extra, and the cables are proprietary. If you aren't tech-savvy, stick to the AnyTone AT-D890UV, which is designed with a much more amateur-friendly interface.
• Mixed Mode: Many NXDN radios feature "Mixed Mode," meaning they can listen to a single frequency and automatically decode it whether the incoming signal is analogue FM or digital NXDN.
• Ofcom Rules on Encryption: Commercial NXDN radios feature robust encryption capabilities (like AES-256). You must disable all encryption before transmitting on amateur bands. Encrypted ham radio communication is strictly prohibited under your Ofcom amateur radio licence.