WSJT-X
New Codes, Modes and Tools for
Weak-Signal Communication

Joe Taylor
K1JT
EME ConferenceVeniceAug 21, 2016

“JT” Weak-Signal Software• WSJT – 2001 – VHF-and-up (meteorscatter, EME, ionoscatter, etc…)• MAP65 – 2006 – Wideband EME(multi-decode, adaptive polarization)• WSPR – 2008 – Quasi-beacon mode
(QRP propagation probe)• WSJT-X – 2012 – All bands, many modes
New VHF/UHF/SHF features> 4000 users, world-wideCodes ? Modes ??
• “Code” – symbols to represent information– Character-by-character: Morse (CW), baudot,ASCII, FSK441, …
– Block structured: Reed-Solomon, Convolutional,Turbo, LDPC, QRA, …

• “Mode” – signaling method and protocol:
coding, modulation, symbol rate, block size, …
– SSB, CW, FSK441, JT65, JT4, JT9, JTMSK, …

Block-Structured Messages
Standard minimal QSO
CQ K1ABC FN42
K1ABC W9XYZ EN37
W9XYZ K1ABC –22

K1ABC W9XYZ R–19
W9XYZ K1ABC RRR
K1ABC W9XYZ 73

Minimal QSO with EME “shorthands”
CQ K1ABC FN42
K1ABC W9XYZ EN37
W9XYZ K1ABC FN42 OOORORRR73

Relevant VHF+ Propagation Types
Fading rate, depth• Tropospheric scatter• Multi-hop (weak) sporadic-E• EME (VHF, UHF, microwave …)• Ionospheric scatter• Aircraft scatter• Meteor scatter}}slow
shallow

fastdeepModes in WSJT-X
Scatter  “Fast”

EME, QRP  “Slow”• ISCAT• JT9 E-H
• (JTMSK)• MSK144• JT65• JT4• JT9• QRA64• WSPREchoWhy so many modes?
• Different propagation types• Code design and parameter optimizationfor each purpose– Fading depth– Fading rate (Doppler spread)– Frequency stability, sync requirements• Also important: learning as we go …

Mode design: Tunable parameters
•••••
••

Block message structureCompression  Source encoding
Error control coding type and rate
Information transmission rate
Modulation type
Symbol rate  Bandwidth
Synchronization method

Structured Messages:
Design choice for ECC Modes
Information block size: 72 bits
Calls and locator:

KA1ABC WB9XYZ EN37
28+ 28 + 15 + 1 = 72

Free text:

TNX BOB 73 GL
71+ 1 = 72

Selected Mode Parameters
ModeBlockCode(k,n)

QModulation

SymbolSync
Message
Rate
Fraction Length
(Hz)
(s)

JT4

206,72

24-FSK

4.375

0.50

47.1

JT9206,728

9-FSK

1.736

0.19

49.0

JT65

63,1264

65-FSK

2.692

0.50

46.8

QRA64

63,1264

64-FSK

1.736

0.25

48.4

JT9H fast

206,72

8

9-FSK

200

0.19

0.425

JTMSK

198,72

2

MSK

2000

0.150.117

JTMSK sh24,122

MSK

2000

0.31

0.018

MSK144

128,72

2

MSK

2000

0.110.072

MSK144 sh

32,162MSK

2000

0.200.020

WSJT-X: Recent Advances• Platform independence (Windows,Linux, OS X, …)• Rig control for nearly all radios• Accurate frequency calibration• Franke-Taylor decoder for JT65
• Other decoder improvements• Added modes: WSPR, fast/wide JT9,JT4, (JTMSK), MSK144, QRA64

Franke-Taylor Decoder for JT65
• Published in QEX for May-June 2016
(link on WSJT web site)• Soft-decision algorithm• Performs better than Kötter-Vardy(patented KVASD no longer used)• As implemented in WSJT-X, includes
multi-pass decoding• Fully open source, GPL v3 licenseFranke-Taylor Decoder
2 kHz177 Hz

21 JT65A signals, all decoded !

New VHF+ Features in WSJT-X• Transverter offsets• Automatic EME Doppler tracking• JPL/NASA planetary ephemeris(Moon position and Doppler tracking)• Enhanced Echo mode
• MSK144, QRA64 modes• Auto-sequencing for fast modes… Brief guided tour, mostly EME …

WSJT-X Configuration
8 tabs

VHF+ items

RigControl

Frequency Settings
Calibration
parameters

Frequencies
by Mode &Band
Transverteroffsets

TS-2000X
Frequency
Calibration∆𝑓 = 𝐴 + 𝐵𝑓

Save/Restore Configurations

AutomaticDopplertracking

Echo Mode: G3WDG, 10 GHzDoppler rate:~70 Hz/min

Predicted Widthw = 135 Hz

Single-pulse Echow = 136 Hz

Doppler steering via Rig Control

w = 56 Hz

Doppler steering via transverter LOw = 57 Hz

Close to libration minimum

w = 4 Hz

Echo Mode: K1JT, 144 MHz

w = 2.6 Hz

Comic relief: JTMSK self-echoes

Logging, Reporting, UDP Server

Activate
PSK Reporter

PSK Reporter: 6 m, JT modesJT modes, 50 MHz

EME modes• 50 MHz:JT65A QRA64• 144, 222, 432 MHz: JT65B QRA64• 1296 MHz:JT65C QRA64• 2.3+ GHz (depends on Doppler spread) JT65C, JT4F, JT9F, QRA64
Don’t forget: In some ways,
 EME is easier at higher frequencies!

VK7MO: 10 GHz, 76 cm dish

VK7MO: 10 GHz, JT65C

VK7MO: 10 GHz, JT9F

G3WDG: 10 GHz, JT65CWSJT-X
G3WDG
received at
OK1KIR

10 GHzH
GF
JT9E

QRA64• Details in next talk:

IV3NWV• Q-ary (63,12) repeat-accumulate code
• Operationally similar to JT65
• Three 7×7 Costas arrays for sync
• Thousands of simulation tests• Many QSOs, HF through 10 GHz

QRA64: Better than JT65!
• Better code:+1.0 to +1.5 dB• Better sync scheme:+1.9 dB• Additional +0.5, +1.1, +2.3, +4.2 dB
using a priori information• No callsign database• Very low undetected error rate (UER)Standard minimal QSO
CQ K1ABC FN42
K1ABC W9XYZ EN37

W9XYZ K1ABC –22
K1ABC W9XYZ R–19
W9XYZ K1ABC RRR
K1ABC W9XYZ 73

Underline  a priori “known”

QRA64: Measured Sensitivity
Thresholds for 50% decode probability
Full 72-bit message:
Locator or report:
Sync only:–28.1 dB–30.4 dB–32.6 dB

Scatter Modes: Quick Overview• Ionospheric scatter (6m, 4m)
JT9G,H• Meteor scatter (6m, 4m, 2m, …) JTMSK 800 – 2100 km, any time!
MSK144• Aircraft scatter (10 GHz)(up to ~800 km)

ISCAT, JT9H

Meteor Scatter: Message duration
FSK441: 122 ms (18 char msg)
JTMSK: 117 or 17.5 ms
MSK144: 72 or 20 ms

MSK144 short messages
CQ K1ABC FN42
K1ABC W9XYZ EN37
W9XYZ K1ABC +06<K1ABC W9XYZ> R–03
<W9XYZ K1ABC> RRR<K1ABC W9XYZ> 73MSK144

Copy at
S/N = –4,–5 dB

Still to Come …
WSJT-X Version 1.7• Updated User Guide• WSJT-X v1.7-rc2• v1.7 General Release

MAP64• Inclusion of QRA64Operating Advice• Meteor scatter:
MSK144• Other scatter modes: MSK144,
Fast JT9, ISCAT• EME at VHF/UHF:• EME (w > 50 Hz):

QRA64
JT4, JT9

Special Acknowledgments
WSJT-X has many contributors!
Special thanks for recent efforts to:

G4WJS:K9AN:
IV3NWV:KI7MT:

Rig control, program structure
FT decoder, MSK144
QRA64 internals
Software developers kit

VE1SKY, G3WDG, VK7MO, OK1KIR: Tests