1. Sound starts after calling up the next slide

2. Ham Radio Friedrichshafen June 21-23, 2019
WSJT-X: FT8 and Beyond
Joe Taylor K1JT
Ham Radio Friedrichshafen June 21-23, 2019

3. Weak-Signal Communication Software
WSJT – 2001 – VHF+: meteor scatter, EME; HF: QRP DXing
MAP65 – 2006 – Wideband EME: multi-decode, adaptive polarization
WSPR – 2008 – QRP propagation probe
WSJT-X – 2012 – All bands, many modes LF MF HF VHF UHF SHF
2019: ~25,000 active users, world-wide

4. FT8: Introduced July 2017 Designed for multi-hop E-skip on 6m
Short structured messages
Timed T/R sequences, 15 s
Works at S/N = -21 dB and below
Highly effective for HF, VHF DXing
 Fast minimal QSOs
Not for casual chats or rag-chewing!

5. FT8: Introduced July 2017 Designed for multi-hop E-skip on 6m
Steve Franke, K9AN
FT8: Introduced July 2017
… and Bill Somerville, G4WJS
Designed for multi-hop E-skip on 6m
Short structured messages
Timed T/R sequences, 15 s
Works at S/N = -21 dB and below
Highly effective for HF, VHF DXing
 Fast minimal QSOs
Not for casual chats or rag-chewing!

6. Modes used, 2017-2019 (ClubLog) 78 million QSOs FT8 CW Phone JT65, JT9
RTTY
PSK31
2017
2018
2019

7. PSK Reporter: FT8 Usage Spots per hour: 300,000 – 900,000
Active monitors in any hour
Midweek: ~ 2000
Weekend: ~ 5000
Active transmitters in any hour
– Midweek: 2000 – 5000
– Weekend: 3500 – 7500
DXCCs reported by top spotter:
in 24 hours: ~150
in 7 days: ~200

8. FT8 Digital Protocol Simple user messages
Compression to 77 information bits
Error detection: 14-bit CRC
Error correction: LDPC (174,91) code
Synchronization: three 7x7 Costas arrays
Modulation: 8-GFSK, 6.25 baud, BW=50 Hz
Tx duration: 79/6.25 = s

9. Weak-signal minimal QSOs, using structured messages
CQ K1ABC FN42
K1ABC DL9XYZ JO31 DL9XYZ K1ABC -17
K1ABC DL9XYZ R-13 DL9XYZ K1ABC RRR
K1ABC DL9XYZ 73

10. Structured Messages 77-bit Payload
Calls and locator or signal report:
K1ABC DL9XYZ JO31
Bits: = 77
Free text, up to 13 characters:
TNX
BOB 73 GL
Bits: 71
+ 6 = 77

11. Structured Messages 77-bit Payload
Calls and locator or signal report:
K1ABC DL9XYZ JO31
Bits: = 77
Message type
Free text, up to 13 characters:
TNX BOB 73 GL
Bits: = 77

12. Message Types K1ABC DL9XYZ JO31 Free text Nonstandard callsign
NA VHF contest
EU VHF contest
ARRL RTTY Roundup
ARRL Field Day
DXpedition (“Fox & Hound”) mode
Telemetry: arbitrary 71 bits …

13. WSJT-X  PSK Reporter https://pskreporter.info/pskmap

14. PSK Reporter: FT8 - all bands
monitors

15. FT m

16. FT m

17. FT m

18. FT m

19. FT m

20. FT m

21. FT m

22. FT m

23. FT m

24. FT8 - 6 m

25. 6 m: 2019 June 13, 17:20 UTC

26. 6 m: 2018 June 17, 00:35 UTC

27. 6 m: 2018 June 17, 14:21 UTC

28. Q: Who is hearing me?

29. 6 m: 2018 June 20, 20:31 UTC

30. 6 m: 2018 June 20, 2018, 20:35 UTC F4FGC IK2GSO VE2EBK G8HGN G3YDY
IW4AOI G0PQO PA0RDY N6PE AI4FR IZ5DKJ KF7F S57RR
ON8DM IK5GQK HB9AMO IK5YJY ON8KW OO9A EA8DBM

31. 6 m: 2018 June 20, 23:06 UTC

32. 2018 June 21, 22:08 UTC NA to East Asia!

33. FT8 DXpedition Mode One “Fox”, many “Hounds”
Works with weak signals, poor propagation
Development: collaboration with KH1/KH7Z group
Used by many DXpeditions
QSO rate up to ~400/hour

34. Fox uses up to 5 “slots”
Fox
Hounds

35. FT8 in WSJT-X Rig control for nearly all modern radios
“Meeting place” (~3 kHz) on each band
Decodes all signals in passband
State-of-the-art decoders: 50% copy at
S/N = −21 dB, sometimes to −24 dB
No “partial copy”; false decodes are rare
Accurate frequency calibration of your radio

36. Summary Comments on FT8 Error-free communication (minimal QSOs)
Fills your log quickly (it’s addictive)!
Good for chasing DXCCs, states, grids, …
Good for QRP, compromise antennas
Rapid popularity growth on HF and VHF
Derivative programs: JTDX, MSHV, JS8Call, …

37. Essential Collaborators
Steve Frank, K9AN
Protocol details
Waveform design
Decoder algorithms, optimization
Performance measurement
Bill Somerville, G4WJS
Overall program structure
Platform independence
Rig control

38. Recent Developments … Improved waveforms: GFSK
Decoder extensions and optimizations
Signal subtraction, multi-pass decoding
Use available channel coherence
Belief Propagation and Ordered Statistics
Improved speed
Test in standard ITU propagation models
FT4: Designed for contesting

39. GFSK Smoothed frequency transitions

40. WSJT-X FT8:FSK
WSJT-X FT8: GFSK

41. Spectra: RTTY, FT8, FT4

42. FT4: Digital Contesting Mode
“Faster, better, cheaper” (than RTTY ?)
Message types: same as FT8
77-bit payload, LDPC (174,91) code
Tx duration 5.04 s
Modulation: 4-GFSK, baud
Decodes at S/N = dB
Bandwidth 80 Hz, steep skirts

43. Spectra: FT8, FT4

44. FT4 Practice Contest: May 9 60 QSOs / hour

45. FT8 Decode Probability Propagation models 1 AWGN 0.0,0.0 MidQ 0.1,0.5
MidM 0.5,1.0
MidD 1.0,2.0
0.8
NVISD 1.0,7.0
LowM 1.5,2.0
HighM 10.0,3.0
Decode Probability
LowD 10.0,6.0
0.6
HighD 30.0,7.0
0.4
Propagation models
0.2
–25
–20
–15
–10 –5
SNR (dB)

46. FT4 Decode Probability Propagation models 1 AWGN 0.0,0.0 MidQ 0.1,0.5
MidM 0.5,1.0
MidD 1.0,2.0
0.8
NVISD 1.0,7.0
LowM 1.5,2.0
HighM 10.0,3.0
Decode Probability
LowD 10.0,6.0
0.6
HighD 30.0,7.0
0.4
Propagation models
0.2
–25
–20
–15
–10 –5
SNR (dB)

47. Weak-Signal S/N Limits
Mode (B = 2500 Hz)
SSB ~ +10 dB
RTTY -5
MSK144 -8
CW, “ear-and-brain” ~ -10 FT4
-17 }
Sweet
FT8
-21
Spot ?
JT4
-23
JT65
-25
JT9
-27
QRA64
WSPR
-31

48. Digi-mode Ethics How much power ? How much spectrum ?
How much automation ?
Robotic QSOs = “Real” QSOs ?
Should software be Open Source ?

49. Have you worked a robot ? A41ZZ A45XR CN2MA ES6DO EW8W HA1RB HA7TM
IK4LZH
KA1AQP
KW4SP
OG0C
OO6O
OO7B SV5DKL
RA9H W1KE
SQ9IWA
???
SV1EDY

50. See you on the air, with WSJT-X !

51. © Joe Taylor © Presentation Management Dokumentationsarchiv Funk
Tonaufzeichnung Christoph Hubner und Post production: Jakob Mohl