New Directions in HF Digital Communications

1
New Directions in HF Digital Communications

• Johan Forrer, Ph.D
• KC7WW
• June 5, 1999
• (forrerj_at_peak.org)

2
HF Communications Modes

• PSK31
• C-BPSK
• MT63
• MTHELL
• Q15X25
• Digital Speech

3
Development Influences

• Understanding of Ionospheric Effects
• HF Channel Simulation
• Testing Evaluation
• DSP
• Flexibility in Algorithm Development
• Hardware Platforms

4
Ionospheric Effects on the HF Channel

• Watterson Model
• Single and Multiple Refractive Rays
• CCIR 520
• Flat fading
• Selective fading
• SHARC Simulator

5
PSK31

• DBPSK / QPSK at 31.25 Baud Keyboard
• RC pulses - 62.5 Hz
• FEC
• VARICODE on BPSK, Viterbi Decoder for QPSK
• M56K EVM, TI C50, SHARC, Win95, Linux

6
C-BPSK

• PSK at Various Pulse Rates 1 - 1000ms, Keyboard
• Cosine-Shaped Pulses 100 Hz
• FEC
• ET1 (16 bits)
• ET2 (24 bits)
• GRAB
• PC platform I/face.

7
MT63

• 63-Tone OFDM, 10 Baud Keyboard
• Low CF 1000 Hz
• FEC and Interleaving
• Walsh Code ECC
• M56K EVM

8
MTHELL

• Multiple Tone (9) Keyboard
• Raster Scan
• No FEC, Human Interpretation
• M56K EVM. Other variants/platforms available.

9
Q15X25

• 15-Tone QPSK
• OFDM 2200 Hz SSB
• AX25, CSMA Networking model
• KISS Interface
• M56K EVM, Linux Soundcard

10
Digital Voice over HF

• Experimental
• Developed by Charles Brain, G4GUO
• 36 Tone OFDM modem - SSB B/W
• AMBE based on DVSInc 1000 chip
• M56K EVM

11
Acknowledgements Resources on the Web

• PSK31/MT63/MTHELL/Q15X25
• http//det.bi.ehu.es/jtpjatae/ham.html
• http//wwwcip.informatik.uni-erlangen.de/user/hsre
  iser/hamradio/
• http//www.qsl.net/dl6iak/index.html
• http//www.tapr.org
• MT63/MTHELL
• http//www.qsl.net/zl1bpu/
• Digital Voice over HF
• http//www.chbrain.dircon.co.uk/
• Ionospheric Models / HF Channel
• http//www.peak.org/forrerj/