NXDN

Key takeaways NXDN is a narrowband 4FSK FDMA standard developed by Icom and Kenwood. It comes in two widths: NXDN48 (6.25 kHz, 2400 symbols/s) and NXDN96 (12.5 kHz, 4800 symbols/s), both using the AMBE+2 vocoder. It supports conventional and trunked (Type-C) operation and is sold as NEXEDGE by Kenwood and IDAS by Icom. It’s common in business and industrial radio, with some public-safety use. Its signature is being very narrow — NXDN48 is one of the thinnest signals you’ll see on the waterfall. Its close ETSI cousin dPMR works almost identically.

After the 25 kHz bulk of TETRA, NXDN is the opposite extreme: one of the narrowest digital voice standards in regular use. Where TETRA spread its calls wide, NXDN squeezes them into a sliver of spectrum.

What NXDN is

NXDN grew out of a joint effort by Icom and Kenwood to define an open common air interface for narrowband digital radio. The result is FDMA — each call gets its own frequency, no time slots — using 4FSK, the same four-level frequency modulation you met in digital modulation for trunking and that P25 and DMR also use. Voice rides on the AMBE+2 vocoder.

Because the two vendors sell it under their own names, you’ll see NXDN behind several brands:

Brand	Vendor	Notes
NEXEDGE	Kenwood	Kenwood’s NXDN product line
IDAS	Icom	Icom’s NXDN product line
NXDN	(the standard)	The common air interface both implement

It’s the same protocol underneath — a NEXEDGE radio and an IDAS radio speak NXDN to each other.

NXDN48 and NXDN96

The standard defines two channel options, and the names come from the bit rate:

Variant	Channel width	Symbol rate	Spirit
NXDN48	6.25 kHz	2400 symbols/s	maximum spectrum efficiency
NXDN96	12.5 kHz	4800 symbols/s	higher throughput

NXDN48’s 6.25 kHz channel is the headline feature — it fits two channels into the space a single 12.5 kHz DMR or P25 channel uses, which is why it’s prized where spectrum is tight. NXDN96 trades that efficiency for a faster channel in a conventional 12.5 kHz slot. Both use the same 4FSK and AMBE+2; only the width and rate change.

NXDN48 at 6.25 kHz is one of the narrowest digital voice signals you'll encounter — about half the width of a DMR or P25 channel.

Conventional and trunked

NXDN runs in both styles you met earlier in conventional vs trunked:

Conventional — a fixed channel that a group always uses, common for small business and industrial fleets.
Trunked — NXDN’s trunking is called Type-C, with a control channel granting traffic channels just like the systems you’ve studied. GopherTrunk follows the control channel to track talkgroups and IDs.

Recognising it, and its cousin dPMR

The easiest tell is width. NXDN48’s 6.25 kHz channel is one of the thinnest signals on the waterfall — much narrower than DMR or P25. It is 4FSK like those systems, so width alone won’t fully distinguish it; the reliable answer comes from letting the decoder read the signaling once it locks.

NXDN has a very close European relative, dPMR, an ETSI standard that also does 6.25 kHz 4FSK FDMA. They are separate standards but so similar in footprint that they’re easy to confuse — we cover dPMR alongside D-STAR and System Fusion in dPMR, D-STAR & System Fusion.

Quick check: what is the most distinctive thing about NXDN48 on the air?

Recap

NXDN is a narrowband 4FSK FDMA standard from Icom and Kenwood, branded IDAS and NEXEDGE.
NXDN48 is 6.25 kHz (2400 symbols/s); NXDN96 is 12.5 kHz (4800 symbols/s); both use AMBE+2.
It runs conventional and trunked (Type-C), used mostly in business and industry with some public safety.
Its signature is being very narrow — though confirming it usually means letting the decoder read the signaling.
Its ETSI cousin dPMR is nearly identical in footprint.

Next, we turn to a North-American giant that’s still everywhere — Motorola’s analog trunking family: SmartNet / SmartZone & Type II.

Frequently asked questions

What is NXDN?

NXDN is a narrowband digital land-mobile-radio standard developed jointly by Icom and Kenwood. It uses 4FSK FDMA in very narrow channels — 6.25 kHz (NXDN48) or 12.5 kHz (NXDN96) — with the AMBE+2 vocoder. It comes in conventional and trunked forms and is branded NEXEDGE by Kenwood and IDAS by Icom.

What is the difference between NXDN48 and NXDN96?

They are the two channel options of the same standard. NXDN48 runs at 2400 symbols/s in a 6.25 kHz channel for maximum spectrum efficiency. NXDN96 runs at 4800 symbols/s in a 12.5 kHz channel for higher throughput. Both use the same 4FSK modulation and AMBE+2 voice; they differ in width and bit rate.

Who uses NXDN?

NXDN is common in business and industrial radio — utilities, transport, security, and similar — and appears in some public-safety and government deployments. Because it is very narrow, it suits operators who want to fit many channels into limited spectrum. You’ll meet it both conventionally and as Type-C trunked systems.

How do I recognise NXDN on the air?

Its defining trait is how narrow it is, especially NXDN48 at 6.25 kHz — a thin sliver on the waterfall, narrower than DMR or P25. It is 4FSK like those systems, so the surest identification comes from letting a decoder read the signaling once it locks the channel.