Introduction to latest Digital Radio Modes such as DMR, DStar, YSF, C4FM, NXDN and Codec2 - MMDVM modem - Brandmeister Networks - SmartMic - DIY !

1. DIGITAL RADIO FOR VOICE
EVOLUTION OF RADIO COMMUNICATION SYSTEMS

2. WHY DIGITAL VOICE - LOUD CLAIMS FIRST ☺
• What would you say to nearly noise-free voice quality, clearer transmissions, and no
background interference?
• How would you like to allow multiple groupsto use one repeater on the same
frequencyat the same time?
• How would you like to reduce the transmission rate of your radio by one-half or more, extending
the battery lifelonger than ever before?
• How would you like to have your own personal repeater(hotspot) that can connect to any
other repeater across the world?
Trends in Digital Voice, W0AKO

3. EVOLUTION OF COMMUNICATION MODES
Telephone Telegraph Modem GSM 4G
Analog
Radio
CW RTTY Packet
Radio
Digital
Radio

4. Conventional Radio Architecture
Antenna
RF Amp Mixer
Local
Oscillator
Band Pass Filter IF Amp Demodulator AF Amp Audio
RF Amp Mixer
Local
Oscillator
Band Pass Filter IF Amp
Antenna
Analog<>Digital
Converter
DSP Processor
(SDR based) Digital Radio Architecture
RF Frontend
Audio
Analog<>Digital
Converter

5. DSP FOR DIGITAL RADIO
• Voice Coder for Compression of Voice Signals
• AMBE-2+ by DVSI is used in most DV systems (Patented)
• Codec2 developed by David Rowe VK5DGR used in FreeDV (Opensource Experimental)
• Packetizied Digital Modulation Schemes
• 4FSK, GMSK, C4FM
• Forward Error Correction – soft “decoding”
• Multiplex Access Schemes – strict timing management

6. CH.1
CH.2
TDMA CH.
SLOT 1 SLOT 2 SLOT 1 SLOT 2 SLOT 1 SLOT 2 SLOT 1 SLOT 2
TIME DIVISION MULTIPLEX ACCESS

7. ECONOMICS OF THE EVOLUTION
• SPECTRUM is a valuable “resource” now ☺
• 2 simultaneous channels in a single narrowband FM ch.
• Better Audio Quality @ Weaker Signal Strengths
• Ongoing debate on coverage improvement !
• ~40% improvement in Battery Efficiency
• Intermittent transmission in Timeslots
• IP based interconnectivity
• Everything in the network speaks the same language

8. DIGITAL RADIO MODES - COMPARISON
FEATURES / SYSTEM DMR DSTAR SYSTEM FUSION NXDN FREEDV
Developer / Promoter ETSI JARL / Icom Yaesu Kenwood VK5DGR + hams
Multiplex Method TDMA FDMA FDMA FDMA TDMA*
Modulation 4FSK GMSK C4FM 4FSK DQPSK
Vocoder AMBE+2 AMBE+2 AMBE+2 AMBE+2 Codec2
Transmission Bitrate 4.8kbps x 2 4.8kbps 9.6kbps 9.6kbps 1.4kbps

9. NETWORKED RADIO SYSTEMS
• Radio over IP networks
• Linking multiple repeaters across the world – DMR-MARC,
BrandMeister, etc.
• Enhanced Echolink-like functionality
• Worldwide Calling Channel !!
• Roaming
• Continous exchange with Repeater autoswitch on common
Talkgroups
• Remote IP based Programming
• Radios and Repeaters can be programmed over air / IP networks
• Data exchange modes
• SMS Messaging
• Location Beacons with GPS attachment – APRS gateway
http://hose.brandmeister.network – Listen Online!

10. Term Defintion
Timeslot (TS) A brief interval to which a DMR radio, especially a repeater, accepts data from
another radio. For DMR there are two (2) 30ms time slots.
Talkgroup
(TG)/ Reflector
Virtual Radio Channel, typically assigned by geography or language. Dynamic TG are
assigned to a channel on keying PTT for a time period. Static TGs are fixed on TS.
Color Code A number that is analogous to the PL or CTCSS tone used during analog FM Analog
Operation (defaults to value 1 mostly)
C-bridge A Server that bridges together regional DMR Networks / Brandmeister
DMR ID A unique number assigned to each radio on the DMR Network. Also known as
“Subscriber ID” or a “Radio ID”
BER Bit Error Rate – Ratio of bits successful decoded without error. Equivalent of SNR in
Analog communications.
CPS Short for Customer Programming Software, which is the software used to program a
DMR Radio.
NETWORK TERMS AND DEFINITIONS

11. DMR PORTABLE RADIOS
TYT MD-380
VHF or UHF Single band
~90 USD
Radioditty GD-77
VHF/UHF Dual band
~100 USD
Anytone AT-D868UV
VHF/UHF Dual band
~160 USD

12. DV HOTSPOTS
Shark openSPOT
Supports DMR/Dstar/SystemFusion
USB Powered, 20mW output on UHF
~190 Euro
DVMega
VHF/UHF Dual band
Pluggable on Raspberry PI
~120 GBP
DV4Mini
Supports DMR/Dstar/SystemFusion
USB Powered, 10mW on UHF or VHF
~ 130 USD - UHF
~150 USD - VHF
MMDVM / ZumSpot
VHF/UHF Dual band
Pluggable on Raspberry PI / Arduino Due
~80 - 100 USD

13. PI-STAR DIGITAL
VOICE DASHBOARD
• Software running on Raspberry PI
• Management of Digital Voice Modes
for MMDVM Modem
• Supports DMR, Dstar, YSF, P25, NXDN
• Live monitoring of RF / IP Gateways
• TG/TS/Call/Duration/Loss/BER reports

14. DIY / HOMEBREW…
Monitoring with RTL-SDR dongles using DSD decoder plugins
https://www.rtl-sdr.com/rtl-sdr-radio-scanner-tutorial-decoding-digital-voice-p25-with-dsd/

15. DIY / HOMEBREW…
Using FM Discriminator Output from Analog Radios for building Repeater / Hotspots
http://www.mountainwestdmr.org/styled-22/styled-3/files/notes-for-interfacing-the-
cdm-1250-uhf-radio-with-the-mmdvm-board.pdf

16. DIY / HOMEBREW…
SM1000 SmartMic - David Rowe VK5DGR / Rick Barnich KA8BMA (open design)
http://www.rowetel.com/sm1000.html