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

2. 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

3. 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

4. 2nd generation: BPsK31 enters the stage
Developed by SP9VRC and G3PLX in the 1990s
Quickly became the most popular digimode, overshadowing RTTY

5. 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???

6. 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 MT MT
Olivia
1000/32
1000/16
500/16
500/8
250/8
250/4
125/4
I could go on…and on…and on!

7. 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

8. How can you create a digimode station?

9. 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

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

11. …Or build it yourself
Example from

12. 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

13. A Closer Look at the Digimodes

14. 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

15. 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

16. PSK31 on winwarbler software

17. 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

18. JT65 – weak signal DX at its best
14.076, 7.076, 1.838, 3.576,
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

19. Jt65 on jt65-hf software

20. 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.

21. RTTY: the contester’s mode,
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

22. RTTY on MMTTY software

23. 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
vs. 5NN 5NN?

24. 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

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

26. 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

27. 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, s, 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

28. 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

29. Packet (9600 baud) on AEA pk-96

30. 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!

31. MT on Fldigi

32. MT63-2000 on Fldigi with emcomm form!

33. 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

34. 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

35. JT9 – narrow weak signal DX
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

36. 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!

37. For more information:

38. Questions?