Digital Modes

1. Digital Modes K4LRG

2. Themes of This Presentation • General Information: Why do digital? • Technical: some highly technical discussion • Practical: How to get started? • Focus: on sound-card modes (no TNC) • Focus: on newer modes (not RTTY or Packet)

3. Why Digital? • Fun of Experimentation • Use of computers along with ham radio • Excitement of being on a cutting edge • As technical as you want to get • Relevant to emergency response

5. How BPSK31 Works ASCII Character Varicode Encoder (Huffman Code) Binary Phase- Reversals Balanced Modulator Transmit Side Ensures Reversals Even during Idle Carrier Varicode Decoder (Huffman Code) ASCII Character Extract Tone at Baud Rate Receive Side Synchronization Signal No Error-Correction

6. Varicode

7. More than 2 phases: QAM From Binary To Multi-PSK (WINMOR, PACTOR, DRM, Etc.)

12. EasyPal Example

13. From: WINMOR@yahoogroups.com on behalf of kn6kb [rmuething@cfl.rr.com]Sent: Tuesday, October 27, 2009 12:46 PMTo: WINMOR@yahoogroups.comSubject: [WINMOR] Re: Anyone seeing 8car 16PSK mode?WINMOR's PSK16 mode is about 50% higher throughput than the 8PSK mode (3 user bits/symbol vs 2). This requires a "good" signal but a "good" signal is more than just high S/N.PSK is drastically affected by multipath (two or more "copies" of the signal arriving at the antenna via different paths) and 16PSK is more susceptable to this than 8PSK or 4PSK. WINMOR will attempt to go to 16 PSK if there are sufficient ACKs on 8PSK. If the shift to 16PSK does not yield a high enough ACK percentage it will ratched back to 8PSK and "raise the bar" for the next attempt to go to 16PSK. So if you see the system working at 8PSK and the signal is strong but has heavy multipath (fuzzy symbol groups) 16PSK is probably not possible or at least probalby not faster (NET after repeats) than 8PSK.We have seen and measured many successful 16 PSK session both over the air and through the HF simulator but normally not with poor multipath propagation condtions.Part of the beta effort is to fine tune the gear shift (mode shifting) algorithm to yield the fastest net throughput for the channel conditions.Rick KN6KB

14. HF Timing - Long Path DX • Can interfere with PSK detection • Up to 60 ms difference between short and long paths • BPSK31 operates at 31.25 BPS, or 1 bit per 32 ms

17. Weak Olivia Example

19. How Olivia 1000/32 Works 31.25 MFSK Tones per Second – 32 different tones 5 7-Bit ASCII Letters* Into 64-bit vectors … Transmit Side 64 tones sent in sequence from set of 32 (32 = 2^5) 64 tones At 31.25 tones/sec = 2.048 seconds per 5 letter block Coded by Walch-Hadamard Transform One 32-bit tone Encodes each 5-bit column Inverse Walch-Hadamard Transform Pick Highest Amplitude Tone FFT Receive Side 5 7-Bit ASCII Letters* Two-layer “1-out-of-N” FEC code: 1) Highest amplitude tone out of 32 2) Greatest amplitude vector of W-H transform (Viterbi decoder?) Populate 64-bit vectors a column at a time Picking greatest amplitude vector each column * Scrambled to minimize false lock with pseudo-random sequence ()xE257E6D0291574EC

20. How to calculate Olivia bit-rate Spectrum of one pure tone Tone modulated by fmod 32-Tones modulated by fmod 2 x fmod width freq freq freq fc fc Bit rate – Frequency relationship 32 evenly-spread modulated tones define a bandwidth . . . . 1 0 1 0 2 bits ~ 1 cycle Bandwidth / # tones = bit-rate 1000/32 = 31.25 500/8 = 62.5

21. Olivia Modes • Unconnected • Unlike WL2K, WINMOR, Packet • Manually-controlled • RX-TX specified by sender • Message-asynchronous • Not specific to messages • Unlike WL2K, WINMOR • Symbol-synchronous • Groups of characters used to form blocks • Simplex • One way at a time • Chat Mode • Unformatted interchanges • With FEC • Two-level FEC

22. WINMOR • Connected • Automatically-controlled • RX-TX specified by protocol • Message-synchronous • Specific to messages • Symbol-synchronous • Groups of characters used to form blocks • Like Olivia • Simplex • One way at a time • Like Olivia • Non-Chat Mode • Formatted interchanges according to an ARQ protocol • With FEC • Multi-level FEC • Like Olivia

23. WINMOR Comparison of Some Popular Modes in ARQ Environments 1 • Assumptions: • 70% ARQ efficiency • (typical of Pactor) • Max RAW data rate • (good channel assumed) • 200 Hz guard band used in • bandwidth calculations. • (allows automatic connections) Net bits/sec/Hz of BW Target For WINMOR (After ARQ overhead) .5 0 MT63 PSK31 PCALE Pactor 2 Pactor3 Pactor 1 HF Packet

24. WL2K Example

25. Implementation DetailsWINMOR DSP Processing Diagram WINMOR

26. WINMOR “Virtual TNC” Screen Capture: 15 Carrier QPSK WINMOR QPSK Constellation (heavy fading) Each pixel = 1 symbol Connection State Frame Type Bytes Received “+” decoded OK “M” recovery after Summation (memory ARQ) 2KHz waterfall “-” no decode, poor ID match (not added to summation) “m” no decode, Good ID (added to summation)

27. How to Get Started • Computer • Windows XP or greater • Software for sound-card modes • MIXW (trial is free, full-function app is not) • FLDIGI (free) • DRM780 (free) • Sound Card Interface • Any • Find out sampling rate! • Some software allows adjustment to this rate, some do NOT • Getting it all set up (how to connect it all up) • Where to find digital modes on the bands

28. 14.069.05 The Basic Digital Setup External speaker PC HF Rig LINE IN RX cable SPEAKER OUT LINE OUT MIC IN TX cable = Isolating transformer Connecting up your rig

29. Computer Transceiver Receive Transmit COM Port PTT

30. Another Example: RigBlaster Plug & Play

32. Popular Band Places for Digital • BPSK31 • 1.838, 3.580, 7.035, 10.140, 14.070, 18.100 • USB • Olivia 500/8 • 1908.75, 3577.75, 7073.25, • USB, 750 Hz Cf

34. FCC Rules on Data • In its 2006 Omnibus R&O, the FCC revised the definition of data to include certain image emission types in order to permit amateur stations to transmit both image and data emission types in the same frequency segments. The … Commission proposed this change in response to a rulemaking petition filed by Miller in 2003: “The Commission agreed with commenters, including Miller, who argued that permitting images to be transmitted on data emission frequency segments would allow Amateur Radio to make the most of new software programs, thereby advancing Amateur Radio technology, which would be consistent with one of the purposes of Amateur Service, namely to contribute to the advancement of the radio art.” • The FCC stated that their rules “do not specifically limit the permissible bandwidth for RTTY and data emissions in the amateur HF bands.” Instead, the Commission continued, Section 97.307(f) limits specified RTTY or data emissions “to a symbol rate not to exceed 300 bauds (in the 80 to 12 meter bands) or 1200 bauds (in the 10 meter band); or for frequency-shift keying (FSK), to a maximum frequency shift of 1 kilohertz between mark and space.”

35. §97.309(a)(4) Technical Descriptions • http://www.arrl.org/FandES/field/regulations/techchar/ • This is a one-stop Web site for technical characteristics called for in FCC rules § 97.309(a)(4), which reads: • (4) An amateur station transmitting a RTTY or data emission using a digital code specified in this paragraph may use any technique whose technical characteristics have been documented publicly, such as CLOVER, G-TOR, or PacTOR, for the purpose of facilitating communications. • Documentation should be adequate to (a) recognize the technique or protocol when observed on the air, (b) determine call signs of stations in communication and read the content of the transmissions. Click on names of the techniques already documented: • CHIP64 (61,588 bytes, PDF file) • CLOVER • CLOVER-2000 • D-Star (225,010 bytes, PDF file) • Domino • FDMDV (PDF) • G-TOR • JT65 (114,422 bytes, PDF file) • MFSK • MT-63 • Olivia (Draft specification provided by the creator of Olivia, Pawel Jalocha, SP9VRC) • PACTOR • PACTOR-II • PACTOR-III • PSK31 • Q15X25 • RWOP • WINMOR (PDF) • WSPR (MEPT_JT)

36. Common Pitfalls • Driving the rig too hard • Driving the rig too long at high tone level • Using audio processing/filtering • Driving the software too hard • Not using macros • Not employing CAT control of rig

37. Where to Get Info • http://kk7uq.com/html/hamfest.htm • http://www.w1hkj.com/ • Mode-specific sites • Sites with samples of modes • Others’ Ham Group Presentations • Mode-specific Yahoo Groups

40. Good Luck! K4KRG DigiNet: Tuesday Night 7 PM, 3582+750, Olivia 500/8 Copies of Slides: AI4IN@arrl.net