Slide 2 Test Slide Slide 3 Data Modes Starting Out Mike Richards
G4WNC Slide 4 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) 3 Slide 5 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) 4 Slide 6 Data Modes -
Overview 12th Sept 2012 Mike Richards - Introduction to Data Modes
(RSGB 2012) 5 Encoding Decoding Slide 7 A UNICODE(ASCII) 65
Keyboard 00100001 1286432168421 Serial data 01000001 Keyboard to
Serial Data 6th Sept 20126 Mike Richards - Introduction to Data
Modes (RSGB 2012) Slide 8 Data Modes - Alphabets 6th Sept 2012 Mike
Richards - Introduction to Data Modes (RSGB 2012) 7 Encoding
Decoding Slide 9 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) 8 Slide 10 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) 9 Slide 11 Data Modes - Errors 12th Sept
2012 Mike Richards - Introduction to Data Modes (RSGB 2012) 10
Encoding Decoding Slide 12 Dealing with errors 1: SSB 6th Sept 2012
Mike Richards - Introduction to Data Modes (RSGB 2012) 11 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
Slide 13 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) 12 Slide 14
Dealing with Errors 3: Repeats HELLO 6th Sept 2012 Mike Richards -
Introduction to Data Modes (RSGB 2012) 13 Original text Repeated
text Transmitted text HELLO H~E~LHLEOL~L~O~ ~ = Data padding Used
for AMTOR FEC and NAVTEX marine safety system Simple Forward Error
Correction Slide 15 Dealing with Errors 4: Automatic Repeat Request
(ARQ) 6th Sept 2012 Mike Richards - Introduction to Data Modes
(RSGB 2012) 14 Originator Distant Stn Data 1Data 2 ACK ARQ Data
2Data 3 Send data in short bursts Wait for acknowledgement Repeat
on request Very reliable Excellent with deep QSB Say everything
once Only handles 1:1 connections Winmor, Pactor, Packet Slide 16
Dealing with Errors 4 Forward Error Correction (FEC) 6th Sept 2012
Mike Richards - Introduction to Data Modes (RSGB 2012) 15
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 00100111
00100011 1001 Simple Convolutional Coder Slide 17 Data Modes
Modulation Systems 6th Sept 2012 Mike Richards - Introduction to
Data Modes (RSGB 2012) 16 Encoding Decoding Slide 18 Simple
Modulation Systems - FSK 6th Sept 2012 Mike Richards - Introduction
to Data Modes (RSGB 2012) 17 Frequency Shift Keying (FSK) +170Hz
Carrier Frequency 1275Hz 1445Hz Audio Tones Audio Frequency Shift
Keying (AFSK) fc Original Data 0 1 RTTY Slide 19 Modulation Systems
- MFSK 12th Sept 2012 Mike Richards - Introduction to Data Modes
(RSGB 2012) 18 Olivia Multi Frequency Shift Keying Used in many
complex modes Uses multiple shifts typically 16 or 32 Time f1 f2 f3
f4 f5 f6 f7 f8 Slide 20 Simple Modulation Systems - PSK 6th Sept
2012 Mike Richards - Introduction to Data Modes (RSGB 2012) 19
Phase Shift Keying (PSK) 0 180 Carrier Phase Original Data 0 1 In
PSK31 a logic 0 causes a phase reversal Slide 21 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) 20 Slide 22 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) 21 Slide 23 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) 22 Slide 24 Data Modes Connections 12th
Sept 2012 Mike Richards - Introduction to Data Modes (RSGB 2012) 23
Computer Sound Card Line out Mic in SSB Transceiver Line in Audio
out Optional PTT SignalLink Interface Line out Mic in SSB
Transceiver Line in Audio out USB PTT Slide 25 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) 24 Slide 26 Questions Have a go its fun Any Questions? Dont
forget to pick-up a handout 6th Sept 2012 Mike Richards -
Introduction to Data Modes (RSGB 2012) 25
