1. Test Slide

2. Data Modes – Starting Out
Mike Richards G4WNC

3. 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)

4. 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)

5. 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)

6. 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)

7. 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)

8. 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)

9. 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 =
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)

10. 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)

11. 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)

12. 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)

13. 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)

14. 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)

15. 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)

16. 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)

17. 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)

18. 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)

19. 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)

20. 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)

21. 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)

22. 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)

23. 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)

24. 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)

25. 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)