Test Slide

Data Modes – Starting Out Mike Richards G4WNC

Mike Richards – Data Modes – Starting Out The Menu Data Modes - Why Bother? Data Modes Flow Chart Technical bits. What You Need Operating Summary & Questions 6th Sept 2012 Mike Richards – Data Modes – Starting Out (RSGB 2012)

Mike Richards - Introduction to Data Modes (RSGB 2012) Data Modes - Why Bother? Self Education A new dimension to your radio operating Efficient use of spectrum Great for QRP and DX You can do it for free! 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Mike Richards - Introduction to Data Modes (RSGB 2012) Data Modes - Overview Encoding Alphabet Conversion conversion Alphabet Conversion Error protection Alphabet Conversion Tone generation Alphabet Conversion R A D I O L N K Decoding Alphabet Conversion conversion Alphabet Conversion Error correction Alphabet Conversion Tone decoder 12th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Keyboard to Serial Data UNICODE(ASCII) 65 1 128 64 32 16 8 4 2 Serial data 1 1 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Mike Richards - Introduction to Data Modes (RSGB 2012) Data Modes - Alphabets Encoding Alphabet Conversion conversion Alphabet Conversion Error protection Alphabet Conversion Tone generation Alphabet Conversion R A D I O L N K Decoding Alphabet Conversion conversion Alphabet Conversion Error correction Alphabet Conversion Tone decoder 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Mike Richards - Introduction to Data Modes (RSGB 2012) Alphabets - 1 What alphabet? Code used to represent letters in text Why change the alphabet? RTTY Old system uses 5 bits for each character Adds a start bit and 1.5 – 2 stop bits Wraps-up each character 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Mike Richards - Introduction to Data Modes (RSGB 2012) Alphabets - 2 Why change the Alphabet? PSK31 Uses Varicode Common letters have short codes Less common have longer codes Space = 1, e = 11, o = 111, z = 111010101 Provides faster message speed on low speed links Ideal for typed QSOs and text messages 12th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Mike Richards - Introduction to Data Modes (RSGB 2012) Data Modes - Errors Encoding Alphabet Conversion conversion Alphabet Conversion Error protection Alphabet Conversion Tone generation Alphabet Conversion R A D I O L N K Decoding Alphabet Conversion conversion Alphabet Conversion Error correction Alphabet Conversion Tone decoder 12th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Dealing with errors – 1: SSB Ignore Rely on distant operator to work-out errors Repeat Say everything twice Short messages and confirm Bit at a time and confirm each transmission Use phonetics Add more information to get through 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Dealing with errors – 2: Data Modes Repeats Used in simple FEC – 3 characters at a time, delayed by 3 characters Automatic Repeat Request (ARQ) Send short bursts and await confirmation Forward Error Correction Add extra information 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Dealing with Errors – 3: Repeats Simple Forward Error Correction Original text H E L O Repeated text H E L O Transmitted text H ~ E L O ~ = Data padding Used for AMTOR FEC and NAVTEX marine safety system 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Dealing with Errors – 4: Automatic Repeat Request (ARQ) Send data in short bursts Wait for acknowledgement Repeat on request Originator Data 1 Data 2 Data 2 Data 3 Distant Stn ACK ARQ ACK ACK Very reliable Excellent with deep QSB Say everything once Only handles 1:1 connections Winmor, Pactor, Packet 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Dealing with Errors – 4 Forward Error Correction (FEC) Convolutional Coding Digital version of phonetics NASA Voyager algorithm 2 bits out for each 1 input Output pattern dependent on the 7 bits in the coder Used in MFSK16, ROS, WINMOR, V4Chat, QPSK31, JT65A Walsh functions Used in Olivia and MT63 Simple Convolutional Coder 1 1 1 1 10 01 01 10 00 11 11 00 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Data Modes – Modulation Systems Encoding Alphabet Conversion conversion Alphabet Conversion Error protection Alphabet Conversion Tone generation Alphabet Conversion R A D I O L N K Decoding Alphabet Conversion conversion Alphabet Conversion Error correction Alphabet Conversion Tone decoder 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Simple Modulation Systems - FSK Frequency Shift Keying (FSK) 1 Original Data +170Hz Carrier Frequency fc Audio Frequency Shift Keying (AFSK) 1445Hz Audio Tones 1275Hz RTTY 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Modulation Systems - MFSK Multi Frequency Shift Keying Used in many complex modes Uses multiple shifts typically 16 or 32 f8 f7 f6 f5 f4 f3 f2 f1 Time Olivia 12th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Simple Modulation Systems - PSK Phase Shift Keying (PSK) In PSK31 a logic 0 causes a phase reversal 1 Original Data 180 Carrier Phase 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Practical Systems – PSK31 Custom designed for keyboard QSOs Narrow bandwidth - just 31Hz Entire 20m activity in one speech channel! Perfect for normal typing speeds No error correction – keeps it simple Most popular mode Can always find activity 23rd Sept 2012 Mike Richards G4WNC- Introduction to Data Modes (RSGB 2012)

Practical Systems - RTTY Still survives! Fast and Simple Used extensively in contests 20m good starting band 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Data Modes Operation – Get Going What do you need: PC with a sound card Windows XP (or later), Linux, Mac Digital Modes Software FLDIGI or sim. SSB transceiver and Antenna Two screened leads for audio in and out Optional interface unit 12th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Data Modes – Connections Line out Mic in SSB Transceiver Computer Sound Card Line in Audio out Optional PTT Line out Mic in SSB Transceiver SignalLink Interface USB Line in Audio out PTT 12th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Data Modes – Operating Tips Listen first Start with PSK-31 – always activity on 20m Use low power – 5 watts is usually plenty Watch your modulation Keep to the band plans Use short CQ calls Give real RST reports Try conversing! 12th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)

Mike Richards - Introduction to Data Modes (RSGB 2012) Questions Have a go – it’s fun Any Questions? Don’t forget to pick-up a handout 6th Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012)