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

Digital Communication Email, 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.

Digital Communication A = 01000001 (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.

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.

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

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

Software FLDigi: http://sourceforge.net/projects/fldigi/files/fldigi/ FSQCall: http://www.qsl.net/zl1bpu/MFSK/FSQweb.htm (NW8L/KA4CDN FSQCall V0.24.6, US Edition) JT65-HF: http://sourceforge.net/projects/jt65hfhb9hqxedi/?source= directory RMS Express: http://www.winlink.org/RMSExpress (rms_express_install_1-3-7-0.zip link at bottom of page) (Other software Ham Radio Deluxe, MultiPSK, MixW)

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

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.

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

CW – Morse Code “Carrier Wave” Single frequency turned on & off CW (10 WPM) “Carrier Wave” Single frequency turned on & off http://lcwo.net http://aa9pw.com/morsecode 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

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

PSK31 Phase Shift Keying "31" is the symbol rate, 31.25 baud Variable length character code – varicode "31" is the symbol rate, 31.25 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

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”

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

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

FSQ Fast & Simple QSO Automatic ID Chat File Transfer FSQ (6 baud) Fast & Simple QSO Automatic ID Chat File Transfer Remote/Unattended Operation Where: 3.594 MHz 7.104 MHz 10.144 MHz 14.104 MHz Bandwidth: 300 Hz The noted frequencies are “calling frequencies”. This is not the type of mode where you tune around looking for someone.

Demonstration