1. Digital Communication
RexburgHams.org/Training
Rigby Region Training
September 15, 2016
Todd Smith N7TMS
Digital Communication

2. Digital Communication
, files, keyboard-to-keyboard (chat)
Others?
It’s digital if the information is exchanged as individual characters encoded as digital bits.
Everything traverses the Internet as digital, even audio has to be converted to digital signals before being sent across the Internet.

3. Digital Communication
A = (ASCII)
A = di – dah (CW)
Everything traverses the Internet as digital, even audio has to be converted to digital signals before being sent across the Internet.
ASCII (American Standard Code for Information Interchange) is the most common format for text files in computers and on the Internet.

4. Emergency Communication Benefits
Long lists of information
Complex vocabulary
Formal traffic
Faster than voice communication
There is also an element of privacy because special software is required to “decode” the message.
It still should not be used to transmit names of casualties.

5. Equipment - Minimum
Radio (Even a HT)
Computer
Microphone
Speaker

6. Equipment – Full Station
Multimode Radio
Computer
SignaLink (~$105)
Interface Cable
Radio
Any HF Radio
Yaesu 857 or 891
Computer
Desktop (windows, Mac, Linux)
Laptop
Raspberry Pi
SignaLink

7. Software FLDigi: http://sourceforge.net/projects/fldigi/files/fldigi/
FSQCall: (NW8L/KA4CDN FSQCall V0.24.6, US Edition)
JT65-HF: directory
RMS Express: (rms_express_install_ zip link at bottom of page)
(Other software Ham Radio Deluxe, MultiPSK, MixW)

8. FLDigi Waterfall: X-axis = frequency Y-axis = time
Intensity = strength of signal

9. Popular Modes RTTY PSK31 Olivia PACTOR JT65 FSQ
Some modes are old, like radio-teletype (RTTY), invented in the 1930’s.
Some modes are new, like FSQ, invented in the mid-2015’s.
FLDigi supports ALL of these modes except JT65.

10. Popular Modes RTTY PSK31 Olivia PACTOR JT65 FSQ
Most modes have several variations.

11. CW – Morse Code “Carrier Wave” Single frequency turned on & off
CW (10 WPM)
“Carrier Wave”
Single frequency turned on & off
MorseRunner
RufzXP
CW as a mode of communication is still very much alive and popular.
Doesn’t require software.
But if you have software, you don’t need a key.
Where: x.000 – x.050 MHz
Bandwidth: < 100 Hz

12. RTTY Each character encoded in 5 bits 5 bits = 2^5 = 32 characters
Radioteletype
One of the oldest modes, developed in 1930’s
Uses ASFK (Audio Frequency Shift Keying), LSB
Encodes data using Baudot (origin of Baud)
• Each character encoded in 5 bits
• Initial start bit and inter-character pause (stop bit) are used to synchronize the stations
• 5 bits = 32 characters (not enough for ALL upper- and lower-case letters and numbers and punctuation) o Uses two special codes to switch between characters sets = 62 characters
Mark (2125 Hz) and space (2295 Hz)
Difference = signal shift (most common shift = 170Hz)
The rate of shifting determines the character speed
• 60, 75, 100 WPM = 45, 56, 75 baud
Troubleshooting: Can’t decode?
• Mark/shift reversed
• Wrong baud rate
• Wrong side-band
Approximate bandwidth = 200 Hz
Where: x.075 MHz
Bandwidth: ~200 Hz

13. PSK31 Phase Shift Keying "31" is the symbol rate, 31.25 baud
Variable length character code – varicode
"31" is the symbol rate, baud
Variable length character code – varicode
• Uses shorter codes for more common characters.
• Uppercase characters utilize more bits (and more time) to send.
Vertical lines adjacent to PSK31 signal is over-modulation (demonstrate w/ high volume?)
Where: x.070 MHz
Bandwidth = ~50 Hz

14. Olivia Designed for “difficult” HF ConDX ~40 different formats
Combos of bandwidth & tones
ERC HF Digital net begins in this mode
Where: x.070 MHz
Bandwidth = “depends”

15. PACTOR Packet Teletype Over Radio Speed negotiation based on ConDX
Packet (Winlink)
Packet Teletype Over Radio
Speed negotiation based on ConDX
2 meter packet
Winlink & RMS Express
Where: “Data”
Bandwidth = ~350 Hz

16. JT65
JT65
Excels at getting an extremely weak signal through atmospheric noise and ionospheric distortion
Transmissions are time-synced
Where: x.076 MHz
Bandwidth = ~350 Hz

17. FSQ Fast & Simple QSO Automatic ID Chat File Transfer
FSQ (6 baud)
Fast & Simple QSO
Automatic ID
Chat
File Transfer
Remote/Unattended Operation
Where: MHz
7.104 MHz
MHz
MHz
Bandwidth: 300 Hz
The noted frequencies are “calling frequencies”.
This is not the type of mode where you tune around looking for someone.

18. Demonstration