Colour code
An access discriminator similar in purpose to analogue CTCSS. VKDMR repeaters and hotspots use Colour Code 1.
A practical technical guide
Digital radio, made understandable.
DMR combines an RF channel, two timeslots, digital identities, and network routing. Learn the pieces in the order your radio uses them, then see how RadNET connects into the VKDMR IPSC3 network.
12.5 kHz RF channel2 timeslots30 ms per slot
01 The signal
One RF carrier. Two independent paths.
DMR Tier II uses two-slot TDMA on a 12.5 kHz carrier. A repeater alternates between Slot 1 and Slot 2 in 30 millisecond bursts, allowing two conversations or data paths to share the channel.
0 msone 60 ms frame60 ms
Timeslot 130 ms
Timeslot 230 ms
Conversation AConversation B
Timeslot
The physical TDMA path: Slot 1 or Slot 2. It is capacity, not the destination of the call.
Talkgroup
A group address carried inside the digital call. It tells the network which audience should receive the audio.
Radio ID
Your unique digital identity. It is transmitted with each call and lets radios and dashboards resolve your callsign.
02 The RadNET decision
Why ARNSW chose DMR.
DMR gave RadNET a practical combination of spectrum efficiency, obtainable hardware, a published multi-vendor air interface, and immediate access to an established Australian amateur network. It was a system ARNSW could deploy, maintain, and continue improving with the amateur community.
Spectral efficiency
Two call paths in one 12.5 kHz carrierTwo 30 ms timeslots allow a Tier II repeater to support two independent paths without requiring a second RF channel pair.
Accessible hardware
A broad supply of capable radiosThe large commercial DMR market created a steady flow of reasonably priced new and used radios, repeaters, accessories, and service knowledge.
Amateur firmware
Community software on selected radiosCompatible models can run amateur-developed firmware such as OpenGD77, adding operating workflows designed around amateur use rather than fleet dispatch.
Explore OpenGD77Published protocol
An ETSI multi-vendor standardDMR's air interface is defined in the ETSI TS 102 361 series. That gives RadNET an interoperable standard instead of a single-vendor RF system.
Amateur-built core
IPSC3 can follow amateur prioritiesVKDMR's locally developed IPSC3 platform can evolve routing, roaming, hotspot behaviour, and diagnostics around real amateur-network operation.
Existing national network
RadNET did not have to become an islandVKDMR already connected repeaters, hotspots, clubs, and operators across Australia, giving RadNET an established community and national reach.
About the VKDMR network03 Choosing hardware
Pick the operating style before the radio.
For repeater operation, confirm DMR Tier II support, the correct amateur band, suitable Customer Programming Software (CPS), and an obtainable cable. Displays and feature lists matter less than a clean RF path and a codeplug you can maintain.
01Handheld
Portable DMR radio
The everyday choice for local repeater access, events, field work, and travel.
- Best for
- Portable operation and learning the network
- Know before buying
- Battery powered, compact, and usually lower power. Performance depends heavily on location and antenna efficiency.
02Mobile / base
Vehicle or shack radio
A stronger RF platform for regular driving, fixed stations, and fringe coverage areas.
- Best for
- External antennas and longer duty cycles
- Know before buying
- Normally powered from 13.8 V with a remote microphone or control head. Installation and antenna quality matter as much as output power.
03Commercial
Tier II fleet radio
Rugged hardware with disciplined channel operation and often excellent RF and audio performance.
- Best for
- Reliability and simple, repeatable controls
- Know before buying
- May have a small display, limited contact storage, or no front-panel programming. Confirm amateur-band coverage and CPS access before buying.
04Hotspot path
Radio plus hotspot
A low-power RF access point for locations without usable repeater coverage.
- Best for
- Home, travel, and controlled personal coverage
- Know before buying
- The hotspot is not the user radio. Simplex units provide one talkpath; duplex units can expose two independent timeslots.
04 Programming model
A DMR channel is more than a frequency.
The codeplug is the radio's operating database. Build it from identity to destination to RF channel, then organise those channels into zones you can navigate under real operating conditions.
- 1Radio IDYour registered identity
- 2Digital contactThe talkgroup or private ID
- 3ChannelFrequency + CC + slot + contact
- 4ZoneA usable group of channels
- 5Scan / roamOptional operating behaviour
Minimum channel record
- Repeater receive and transmit frequencies
- Colour Code 1 for VKDMR
- Timeslot 1 or 2
- Talkgroup contact and call type
- Admit criteria and transmit power
- A short, unambiguous display name
Reliable ruleRead the radio first.
Save a known-good backup before changing firmware, contacts, zones, or channel definitions.
05 VKDMR IPSC3
RF at the edge. Routing in the core.
Your radio reaches a repeater or hotspot over RF. IPSC3 then uses endpoint state, timeslot, talkgroup, and radio identity to route the call across the VKDMR network. The dashboard makes that path visible.
01Your radioDMR Tier II RF
02Access pointRepeater or hotspot
03IPSC3 coreState + routing
04DestinationsSelected network endpoints
VK call channel
The network's static VK calling and general-operation path. Use specialist groups when that audience is intended.
Parrot
Records and returns your audio so you can check level, clarity, timing, and whether your ID resolves correctly.
Talkgroup scan
On supported IPSC3 endpoints, scan mode follows active traffic and can route a reply to the last active group.
Person-to-person
IPSC3 can route a direct call toward the endpoint where the destination radio was recently seen.
Simplex hotspotOne effective talkpath
IPSC3 controls competing traffic while a dynamic group is active to avoid unexpected drag-back.
Duplex hotspotTwo independent timeslots
Closer to repeater slot behaviour, provided the hotspot and radio are programmed consistently.
06 Good operating
Give the network time to do its work.
Digital routing is fast, but not instantaneous. A deliberate operating rhythm gives repeaters, hotspots, announcements, and remote paths time to establish and release cleanly.
PTTpausespeak clearlyreleaselisten
07 First contact
From blank radio to a clean call.
Work through one known repeater before adding a state-wide codeplug. When the basic path works, expand in small, testable steps.
- 01
Get your identity
Register a DMR ID and program your own ID into the radio before transmitting.
- 02
Choose one repeater
Start with the frequencies and operating details for a single nearby RadNET repeater.
- 03
Build a small codeplug
Add only the contacts, channels, and zones you understand. Keep the first version simple.
- 04
Check the channel
Confirm RX/TX frequency, colour code, timeslot, talkgroup, admit criteria, and power.
- 05
Watch the dashboard
Key briefly and verify that IPSC3 sees the expected radio ID, endpoint, slot, and talkgroup.
- 06
Test your audio
Use Parrot on TG 9990 where available, then adjust microphone gain and operating technique.