1. System Fusion by Yaesu
Roger Reini, KD8CSE

2. Overview Digital communications in amateur radio and the case for C4FM
Yaesu’s implementation of C4FM: System Fusion

3. History of Digital Modes in Land Mobile
1980’s: first digital LMR radios appear, using GMSK (GFSK) technique
Now, GMSK is out of favor, and C4FM (4-level Frequency Shift Keying) is dominant
2003: first GMSK transceiver released for amateur radio market
2004: Icom’s D-STAR released; it also uses GMSK
2011: Motorola LMR’s Digital Mobile Radio released, using C4FM; DMR- MARC demonstrated it for Amateur Radio at Dayton

4. Types of Digital Communication Systems
Modulation: GMSK, π/4 DPQSK, C4DM (4-level FSK)
Communication type: FDMA (Frequency Domain Multiple Access), TDMA (Time Domain Multiple Access)
Protocol

5. GMSK Simple, used in earlier cell phone systems
Performance exceeded by other systems
D-STAR uses GMSK

6. π/4 DPQSK (4-minute pi DPQSK)
High-grade modulation method, produces low distortion
Requires linearity (like SSB transceivers) and complicated circuitry to implement
Not commonly used in LMR

7. C4FM Modulation
At same bandwidth, C4FM circuit can be simplified and the Bit Error Rate approved
Main modulation method in LMR these days
Yaesu using this as the basis for SystemFusion in the amateur market

8. FDMA vs TDMA FDMA circuitry is simpler than TDMA
TDMA reduces transmission time by one-half or more, reducing power consumption

9. Is C4FM compatible with D-STAR?
No, it’s not; different modulation techniques (GMSK vs C4FM)
Is this a problem in the amateur radio world?
Not really; an example of the experimentation that amateur radio is known for

10. Is C4FM Digital always the superior mode?
No, it isn’t; there will be instances when analog is superior
We amateurs know that different modes have different advantages and that some are preferred in certain circumstances
C4FM is another mode available to amateurs, increasing our capabilities; it’s another tool in our toolbox

11. Yaesu’s implementation: System Fusion
Three C4FM modes, using 12.5 kHz bandwidth:
V/D Mode – Voice/Data simultaneous communication, half for voice, half for data and error correction
Voice FR (full rate) Mode – all bandwidth used for voice, top audio quality
Data FR Mode – all bandwidth used for data
Analog FM – 25 kHz; used when signals too weak for digital

12. AMS (Automatic Mode Select)
Transceiver recognizes the incoming mode (C4FM digital or analog FM) and switches over to match that mode
No need to remember to manually switch the mode on the transceiver
Enables mixed-mode communication on compatible repeaters
If a SystemFusion repeater is installed, you’re not locked out if you don’t have a SystemFusion transceiver

13. New Functions Gained with C4FM
Digital GM (Group Monitor) Function – see where group members are located
Snapshot Function – transmit images taken with camera microphone
Smart Navigation Functions
Simultaneous Voice and Data transmissions allows APRS-type position data to be sent while transmitting
Backtrack navigation – allows one to return to a preset point (useful for hiking)

14. Equipment that is C4FM capable
Repeater DR-1 144/430 dual band C4FM/FM repeater
HT FT1DR 144/430 dual band C4FM/FM 5W transceiver
Mobile FTM-400DR 144/430 dual band C4FM/FM 50W transceiver

15. For More Information Yaesu – www.yaesu.com; link to System Fusion page
FT1DR 2m/70cm HT
FTM-400DR 2m/70cm mobile
DR-1X digital 2m/70cm repeater