Inside WSPR, JT65 and JT9 Weak-signal HF Modes

Transcription

1 Inside WSPR, JT65 and JT9 Weak-signal HF Modes Nick Massey VA7NRM NSARC - Inside WSPR, JT65 and JT9 1

2 Created by. Joseph H Taylor K1JT Nobel Prize (Physics) WSJT / WSJT-X Software 2010 Arecibo DXpedition NSARC - Inside WSPR, JT65 and JT9 2

3 WSPR Weak Signal Propagation Reporter Probe radio propagation paths Intended for low power beacon like transmissions Exploits accurate time (NTP, GPS, GNSS, Galileo) Transmits: Callsign, Maidenhead Locator, Tx Power Not intended for QSOs Software: WSPR (2.0, 2.1, 3.0 ), WSPR-X, WSJT-X WSPR-X: WSPR-15 mode for LF/MF, not suitable for HF NSARC - Inside WSPR, JT65 and JT9 3

4 WSPR 2.0 Screen NSARC - Inside WSPR, JT65 and JT9 4

5 WSPRNet 20m NSARC - Inside WSPR, JT65 and JT9 5

6 WSPRNet 20m (Local) NSARC - Inside WSPR, JT65 and JT9 6

7 WSPR Transmit Callsign Locator Tx Power 6 Characters 4 Characters 0-60 dbm Tx Clock Hz Source Encoder 50 bits FEC Encoder 162 bits Interleaver 162 bits Merge s/s 162 sym Modulator s/s 4 MFSK Tx sec Sync Stream 162 bits 324 bits Hz Spacing NSARC - Inside WSPR, JT65 and JT9 7

8 WSPR Callsign Encode K 1 J T V A 7 N R M K 1 J T V A 7 N R M # 0-9 = 0-9 # A# A# # A A A A-Z, Space = A# A# # A A A K 1 J T V A 7 N R M x36x10x27x27x27 x1 (35-0) x36 x10 x27 x27 x27 x1 = x36 x36x10x27x27 x x10x27x27x27 x1 x27x27x27 x1 x27x27 x1 x27 x1 x1 (20-0) x10 x27 x27 x27 x1 (1-0) x27 x27 x27 x1 (19-10) x27 x27 x1 (29-10) x27 x1 (35-10) x1 = = = = = x36x10x27x27 x1 x10x27x27 x1 x27x27 x1 x27 x1 x Binary Hex 0xF04BE9E 0xD bits > 37x36x10x27x27x27 = NSARC - Inside WSPR, JT65 and JT9 8

9 WSPR Locator/Power Encode NSARC - Inside WSPR, JT65 and JT9 9

10 WSPR Convolutional Encoding Rate = ½ Constraint Length = bits + 31 padding Callsign Locator/Power XOR XOR x2 x bits NSARC - Inside WSPR, JT65 and JT9 10

11 WSPR Interleaving NSARC - Inside WSPR, JT65 and JT9 11

12 Autocorrelation JT65 Synchronisation Sequence (126 bits) NSARC - Inside WSPR, JT65 and JT9 12

13 WSPR Synchronisation WSPR Synchronisation Sequence (162 bits) NSARC - Inside WSPR, JT65 and JT9 13

14 WSPR Symbol Generation NSARC - Inside WSPR, JT65 and JT9 14

15 WSPR Modulation NSARC - Inside WSPR, JT65 and JT9 15

16 WSPR Transmit - Demo Callsign Locator Tx Power 6 Characters 4 Characters 0-60 dbm Tx Clock Hz Source Encoder 50 bits FEC Encoder 162 bits Interleaver 162 bits Merge s/s 162 sym Modulator s/s 4 MFSK Tx sec Sync Stream 162 bits 324 bits Hz Spacing 162 symbols x sec = secs NSARC - Inside WSPR, JT65 and JT9 16

17 WSPR Receive NSARC - Inside WSPR, JT65 and JT9 17

18 WSPR FEC Decoder = 1 trillion trillion trillion trillion possibilities! Viterbi decoder too complex Use Sequential Decoder Fano (Phil Karn KA9Q) Jelinek Rate ½ Constraint Length 3 e.g > NSARC - Inside WSPR, JT65 and JT9 18

19 JT65 and JT9 Intended for QSOs JT65 originally designed for EME and Meteor-Scatter JT65 has found favour at HF JT9 designed for LF, MF and HF (< 10% B/W of JT65) Exploits accurate time (NTP, GPS, GNSS, Galileo) Type 1 Message: Your Callsign, My Callsign, Info Supports Prefixes and Suffixes Info: Maidenhead Locator / Tx Power / Signal Report Free Text Message: <= 13 Characters Shorthand Message: RO, RRR, and 73 NSARC - Inside WSPR, JT65 and JT9 19

20 JT65 and JT9 Usually used at Low Powers (<= 5W) Exploits accurate time (NTP, GPS, GNSS, Galileo) Message starts on 1 minute boundaries Message lasts or secs Error correction means very few errors Software: WSJT and WSJT-X NSARC - Inside WSPR, JT65 and JT9 20

21 WSJT-X JT9 & JT65 Screen NSARC - Inside WSPR, JT65 and JT9 21

22 JT HF QSO NSARC - Inside WSPR, JT65 and JT9 22

23 JT9 Transmit NSARC - Inside WSPR, JT65 and JT9 23

24 JT9 / JT65 Encode Standard Message Callsign Callsign Locator Type 28 bits 28 bits 15 bits 1 bit = 72 bits Spare Values used for: Spare Values used for: CQ, DX, QRZ Signal Report, 73 Callsign Prefix/Suffix Free Text Message 13 Characters Character Set = 43 Characters (0-42) Type A# A# A# A# A# A# A# A# A# A# A# A# A# x42x42x42x42x42x42x42x42x42x42x42x42 x1 x42x42x42x42x42x42x42x42x42x42x42 x1 1 bit x42 x42 x42x42 x1 x42 x42 x1 71 bits + Type bit = 72 bits x1 NSARC - Inside WSPR, JT65 and JT9 24

25 JT9 Convolutional Encoding Locator 72 bits + 31 padding Callsign Callsign XOR XOR x2 0 0 x2 x bits NSARC - Inside WSPR, JT65 and JT9 25

26 JT9 Interleaving Input Output p = 0; for (i = 0; i >= 255, i++) { j = reversebits(i); if (j < 206) { Output(p) = Input(j); p++ } } NSARC - Inside WSPR, JT65 and JT9 26

27 JT9 / JT65 Gray Codes NSARC - Inside WSPR, JT65 and JT9 27

28 JT9 Synchronisation Sequence JT9 Synchronisation Sequence (85 bits with 69 0 s) NSARC - Inside WSPR, JT65 and JT9 28

29 JT9 Modulation 9 MFSK NSARC - Inside WSPR, JT65 and JT9 29

30 JT9 Receive NSARC - Inside WSPR, JT65 and JT9 30

31 JT65 Transmit NSARC - Inside WSPR, JT65 and JT9 31

32 JT65 RS(63, 12) FEC Code 72 bits Reed Solomon Encoder RS(63, 12) sym -> 63 sym 63 NSARC - Inside WSPR, JT65 and JT9 32

33 JT65 Interleaving NSARC - Inside WSPR, JT65 and JT9 33

34 JT65 Synchronisation Sequence JT65 Synchronisation Sequence (126 bits) NSARC - Inside WSPR, JT65 and JT9 34

35 JT65 Receive NSARC - Inside WSPR, JT65 and JT9 35

36 JT65 FEC Decoder Soft-Decision Decoder For each decoded symbol which is most likely, second most likely, third most likely etc. Patented Kotter-Vardy (KV) Decoder Licenced for Amateur Radio use only 2016 Open-Source (Franke-Taylor) (FT) Decoder QEX May/June 2016 Deep Search Decoder Uses a-priori list of known stations / locations Controversial! NSARC - Inside WSPR, JT65 and JT9 36

37 JT65 FEC Decoder BM - Hard Decision FT - Soft Decision DS - Deep Search 0-0Hz Doppler Hz Doppler Hz Doppler NSARC - Inside WSPR, JT65 and JT9 37

38 JT9 & JT65 Sample NSARC - Inside WSPR, JT65 and JT9 38