Also known as: radio access number, RAN, NXDN RAN
A Radio Access Number (RAN) is a 6-bit code, 0 through 63, carried in every NXDN frame that identifies which system a transmission belongs to, so a repeater or radio accepts only its own traffic on a shared channel.1 It is NXDN’s equivalent of the P25 Network Access Code and the DMR color code: a small per-frame code that keeps co-channel systems from keying each other’s repeaters or unmuting each other’s radios.
How it works
NXDN is a narrowband (6.25 kHz and 12.5 kHz) FDMA digital protocol. The RAN travels in the frame’s Lich/signalling fields, so it is present on voice frames and on the control channel of trunked NXDN systems. A repeater is programmed with one RAN and will only repeat frames carrying it; radios mute anything else. With 64 possible values, planners give overlapping repeaters on the same frequency different RANs — the same interference-avoidance role that CTCSS tones play on analog channels and that the color code plays in DMR.
The RAN is only an access filter. It does not by itself uniquely identify a system over a wide area, and it says nothing about talkgroup or radio identity — those are separate fields, with full network identity coming from the system signalling on the control channel. The RAN is just the first, fastest check.
In practice
- On a conventional NXDN channel the RAN is set once per repeater; on a trunked NXDN system it is carried on the control channel and every voice channel, constant across the system.
- Adjacent repeaters sharing an output frequency use different RANs to coexist, the same frequency-reuse discipline as CTCSS tones or DMR color codes.
- With 64 values the RAN is easy to observe directly; a monitor reports whatever value arrives rather than needing to be told it in advance.
Relevance to SDR
For a monitor the RAN labels which system a decoded NXDN frame belongs to and helps separate two systems sharing a frequency. GopherTrunk reads the RAN from each frame it decodes and reports it; a receiver observes whatever value is present rather than being pre-programmed with it. As with the P25 NAC and DMR color code, the RAN is metadata, not encryption — matching it grants access to signalling and clear voice but does nothing against keyed traffic. NXDN is marketed as IDAS (Icom) and NEXEDGE (Kenwood), both of which use the RAN identically.