An Overview of Digimodes for Ham Radio There’s a mode for everyone! Cathy James N5WVR

What are digimodes? Any method of coding signals based on digitizing information and sending it over RF Some consider CW a digital mode, but… For purposes of this presentation, it is not. As you are about to see, there are many digimodes currently used in amateur radio

1st generation: In the beginning was rtty First landline teleprinter built in 1849 Five-bit Baudot code created in 1874 First teleprinter tests over radio waves done in 1922 In commercial service by 1932 Primary means of news service communication in 1940s Converted from teleprinter hardware to computer software emulations in 1980s Still very popular in amateur radio contests

2nd generation: BPsK31 enters the stage Developed by SP9VRC and G3PLX in the 1990s Quickly became the most popular digimode, overshadowing RTTY

And digimodes quickly proliferated RTTY PSK SSTV Packet Pactor Hellschreiber MFSK MT63 Olivia JT65 JT9 Thor Throb DominoEX LENTUS COQUELET POCSAG AIS AUTEX ORBCOMM ARGOS HFDL ……are we done yet???

And digimodes quickly proliferated (2) Some modes form “families” of several closely-related modes Hellschreiber Feld-Hell FM-Hell MT-Hell PSK-Hell PSK BPSK31 BPSK63 BPSK125 BPSK250 QPSK31 QPSK63 QPSK125 QPSK250 MFSK MFSK8 MFSK16 MT63 MT63-500 MT63-1000 MT63-2000 Olivia 1000/32 1000/16 500/16 500/8 250/8 250/4 125/4 I could go on…and on…and on!

The good news Same hardware Multi-mode software Limited usage Almost all of these modes use the same sound card/cable rig arrangement Multi-mode software Free software is available that supports more than one mode Limited usage Only a few of these modes account for most digital usage on HF

How can you create a digimode station?

You’ll need: Radio transceiver A computer with a sound card Pretty much any modern rig that can operate on the frequencies you want to use Older radio may not be sufficiently frequency-stable This is not a good place to use “boat anchors” A computer with a sound card A cable to connect sound card to transceiver Some modern rigs connect directly over USB Computer software to handle coding & display

Interface options You can go fancy… Or something more basic…

…Or build it yourself Example from http://wa8lmf.net/ham/tonekeyer.htm

There are many software options Fldigi WinWarbler MultiPSK WSJT-X HamScope What you select will depend on the modes you want to use, which user interfaces you prefer, and support from the developers. You will probably end up with several installed on your shack PC. IZ8LY Ham Radio Deluxe MixW …and many more

A Closer Look at the Digimodes

What do they sound like? CW (for ref.) RTTY Feld-Hell PSK31 SSTV MFSK MT63 Olivia 8/500 Thor 8 Throb-4 DominoEX-8 JT65A AMTOR CLOVER Contestia FM-Hell Packet (1200) Pactor

PSK: the place to start 14.070, 7.071 PSK31 is one of the top-two most used digimodes You can find a PSK31 contact *somewhere* on HF almost any time on any date QRP is often enough power; 20 – 25 watts is usual max “Warbling” sound PSK is short for Phase Shifted Keying Similar to FSK, Frequency Shifted Keying Why “31”? PSK run at 31 baud (signals per second) is the same width as CW It can send characters at about the same rate that a fast typist can type them A large number of signals can fit into a narrow band

PSK31 on winwarbler software

Problems with psk31 Poor dynamic range Cannot copy weak signals next to strong signals Solution: Gentleman’s Agreement keeps power to about 25 watts Very slow if you are transmitting large files rather than live keyboard chats Solution: use wider, faster PSK modes! BPSK125 on VHF is ideal for rapid file transfer; used for emcomm BPSK125 is overkill for live chats, as no one can type that fast! Does not handle certain paths well, e.g. multipath or polar Solution: use a digimode that doesn’t depend on phase PSK31 PSK125

JT65 – weak signal DX at its best 14.076, 7.076, 1.838, 3.576, 10.139 JT65 is the “other” most-used digimode (besides PSK) You can find a JT65 contact *somewhere* on HF almost any time on any date QRP is often enough; 20 – 25 watts is usual max Significantly wider bandwidth than PSK31 JT is short for Joe Taylor, K1JT, Nobel prize winner Invented the JT modes based on new mathematical coding algorithms Originally developed for meteor paths on VHF Experimentation by hams showed that it worked very well on HF Quickly adopted for DXing by those with limited power and antennas If you have a marginal QTH, e.g. apartment, this is your mode! Amazing DX is possible

Jt65 on jt65-hf software

Problems with JT65 So popular that the sub-band can be wall-to-wall Requires extremely accurate timing (less than 1 second deviation from reference time) Solution: use software to sync computer clock with online reference clocks Extremely limited messages CQ N5WVR FN34 N5WVR K1JT FN20 K1JT N5WVR -5 N5WVR K1JT R-06 K1JT N5WVR 73 VERY slow, useless for chat Each line above requires 48 seconds to send Solution: None. For chatting, use a different mode.

RTTY: the contester’s mode 14.070-14.081, 7.070-7.081 RTTY is short for Radio Tele Type RTTY is seldom used outside of contests But it’s by far the most popular digimode for contesting The only digimode that has major contests dedicated to it Good luck finding an RTTY contact outside of a contest Usable at 50 watts, but benefits from more power The only digimode routinely used with amplifiers > 100 watts Significantly faster than PSK31

RTTY on MMTTY software

Problems with RTTY Seldom used outside of contests Solution: set up a sked for testing and experimenting Software configuration can be a pain Solution: set up a sked for testing and experimenting! Hard to tune, and tuning is critical There are only 5 bits in the BAUDOT code Only 32 characters available Must shift between LETTERS and FIGURES mode to handle both letters and numbers Upper-case only, no lower-case letters for special characters 599 599 vs. 5NN 5NN?

HellSchreiber: the visual text mode Completely different from any other digimode Very rare, but there is a club dedicated to it Look for nets or skeds Occasionally you’ll get lucky (e.g., Chile on 40 meters!) 25 watts is usually enough for good contacts Named for its inventor, Rudolph Hell Developed in the 1930s Works much like a continuous one-line FAX message Special fonts developed to maximize signal readability Feld-Hell FM-Hell

Feld hell on iz8bly software Slanted text indicates timing error; use Tools Menu to adjust correction factor

Problems with HELLSCHREIBER Many variant sub-modes FM-Hell, PSK-Hell, MT-Hell Solution: many are readable in Feld-Hell mode Few software programs support it Solution: Use IZ8BLY or MultiPSK Very rarely heard Solution: Use nets, or set up skeds Join the Feld Hell Club! Over 5000 members today https://sites.google.com/site/feldhellclub/Home

PACKET: vhf for mailboxes Packet was very popular in 1990’s 2-meter 1200 baud forwarding network was built across the country Disappeared when Internet became common Rebuilt regionally after 9/11 to handle emcomm Operates on VHF FM Can handle live chats, emails, or file transfer Requires actual hardware e.g. TNC/packet modem such as PK-232MBX Some may have used sound cards, but not recommended Packet Modems have built-in mailboxes for unattended operation Text appears in “bursts” of several characters at a time, unlike PSK which is slow and continuous

Problems with packet Slow Limited to 300 baud on HF Too slow to be useful; better modes exist Limited to 1200 baud on 2 meters Fast enough for mail transfer or slow chats Solution: Use on the 440 MHz band! 9600 baud will transfer files rapidly and reliably

Packet (9600 baud) on AEA pk-96

MT63: for really bad paths Designed for paths that experience fading and interference Complex scheme encodes text in matrix of 64 tones over time and frequency “Overkill method” offers error correction at the receiving end while still providing a 100 WPM rate Problem: Wide bandwidth (1 kHz standard, 500 Hz & 2 kHz optional) Solution: Use on VHF/UHF – can even go through an FM repeater! Fldigi has good support for MT63, including file transfers Strong potential for emcomm usage Soundcard mode, no TNC needed I would like to see MT63 get more use!

MT63-2000 on Fldigi

MT63-2000 on Fldigi with emcomm form!

MFSK16: chat mode for poor paths Multiple Frequency Shifting Key Seldom used, but very effective Deserves to be used more often I have found it will get through when PSK31 won’t 16 tones with Fast Fourier Transform (FFT) decode Uses Constant Phase Frequency Shift Keying Continuous Forward Error Correction (FEC) sends all data twice with an interleaving technique to reduce errors from impulse noise and static crashes. Signal width is similar to JT65A Text appears in “bursts” of several characters at a time, unlike PSK which is slow and continuous My best-ever DX chat QSO was MFSK16 to New Zealand

Olivia: fast chat mode for poor paths MFSK variant that is highly resistant to QSB (fading) and noise (QRM) Includes Forward Error Correction (FEC) Can work signals you cannot hear Created in 2005 by Pawel Jalocha (SP9VRC) Used in various widths, but all are much wider than PSK31 The wider the sub-mode, the higher the bandwidth and faster the transmission Very rare I have never made an Olivia contact Suggest making a sked with another user if you want to try it

JT9 – narrow weak signal DX 14.076 + 2 kHz JT9 is the “other” JT mode recommended by Joe Taylor for HF 5 watts is usual max! Bandwidth similar to PSK31 Amazing DX is possible – but not very popular May replace JT65A on HF someday, but right now QSOs hard to find Problem seems to be more inertia than any issues with the mode

Not enough modes for you? AMTOR is an expansion of RTTY that operates at 100 baud and include Forward Error Correction (FEC) CLOVER is a PSK mode which provides full duplex QSOs and adapts to conditions by constantly monitoring the received signal and shifting modulation scheme THROB is yet another new DSP sound card mode that uses FFT to decode a 5 tone signal; attempts to push DSP into the area where other methods fail because of sensitivity or propagation difficulties Enough! Make it stop!

For more information: https://www.nonstopsystems.com/radio/radio-sounds.html http://www.w1hkj.com/Modes

Questions?