1. Digital Modes
RTTY, PSK31, Packet, Pactor, Clover, Hellschreiber, MFSK, G-TOR, MT-63, Throb, Q15X25

2. PSK 31
Cousin of RTTY
Excellent weak-signal performance
Not error free

3. History Created by Peter Martinez, G3PLX
At first, not very popular because special DSP hardware was needed.
Peter designed a version of PSK31 that needed nothing more than a common computer sound card.

4. History Simple piece of software that ran under Windows.
Software available free on Internet
Uses soundcard interface to the transceiver.

5. History PSK31 exploded in the HF digital community.
Most popular mode for casual QSO’s.
PSK63 appeared in 2003 and is used by contesters.

6. What is PSK31? PSK = Phase Shift Keying 31 = bit rate (31.25 baud)
===========================
Compare to CW
Simple binary code
Short pulses (Dits)
Long pulses (Dahs)
Communicate the whole English language by combining strings of dits and dahs.
Gaps separate characters and words.

7. Compared to RTTY PSK uses Varicode Still binary
Instead of on/off (CW), shift frequencies (FSK)
5 bits plus start and stop pulses.
PSK uses Varicode
Varying number of bits representing each character.
Shorter for often used characters
Longer for less often used characters

8. The letter “e” is used most often and gets a Varicode of 11, whereas, “E” gets a Varicode of 1110111
“z” gets very little use so it has a Varicode of ; “Z” gets
Gaps represented by “00”
Two zeros never get used in characters

9. A Digital Station What is needed? Transceiver – most already have one.
Modem – many have them in the form of a computer soundcard.
Software – converts binary data from computer to modulated audio tones.

10. A Digital Station
Interface – the connection between the computer soundcard and the transceiver.
Audio from soundcard to transceiver
Audio from transceiver to soundcard
PTT

11. Interface
Numerous available on the market
Rigblaster

12. Interface
RigExpert SD
Standard
Plus

13. Interface
Tigertronics SignaLink
SL-1+
USB

14. Interface
Buxcomm Rascal GLX

15. Interface
Homebrew

16. Interface NUE-PSK Digital Modem
A digital modem for PSK31 field operation ... without using a PC!
The NUE-PSK Digital Modem comes fully assembled and tested... just plug in your keyboard and SSB transceiver, and start operating!

17. How do we generate BPSK signal and transmit Varicode over the airwaves?
Use DSP capabilities of soundcard
Create audio signal that shifts phase angle 180 degrees in sync with bps data stream
“0” bit generates phase shift
“1” bit does not
Hence, Binary Phase-Shift Keying

18. When the BPSK audio signal is applied to an SSB transceiver we get BPSK modulated RF.
Only Hz wide, narrower than CW.
Concentrating RF into narrow bandwidth produces good reception.
Receiving station must sync with transmitting station (Software)
Phase transitions are mathematically predictable due to the structure of Varicode.

19. PSK31 Software Download off Internet:
Many are freeware or shareware with a requested donation.
Popular programs:
HRD/DM780 (IMHO, the best)
MixW
Digipan
MultiPSK
Others

20. PSK31 Setup
Receiving (You should be hearing a PSK warbling sound. If not, check your sound card volume)
Panoramic display – waterfall
With no IF or AF filtering the bandwidth on the waterfall is about 3000Hz.
Bandwidth of BPSK signal is 31Hz.
Many PSK signal can fit in that spectrum
Vertical lines of varying color/intensity will be seen on the waterfall
Bright = strong, faint = weaker

21. ACTIVITY Let’s get started… PSK31 activity found on:
160M 1807 kHz (USA)
1838 kHz (Europe)
80M 3580 kHz
40M 7070 kHz (USA)
7035 kHz (Europe)
7028 kHz (Japan)
30M kHz (Digital Only)
20M kHz – most activity
17M kHz
15M kHz
12M kHz
10M kHz
6M kHz (USA)
50250 kHz (Europe)
Let’s get started…

22. Park radio on frequency of your choice.
Frequency displayed is Suppressed Carrier Frequency (SCF)
USB – range is 2-3 kHz above SCF.
LSB – range is 2-3 kHz below SCF.
Example: Radio showing kHz USB
Receiving everything from to kHz.
Place cursor on vertical signal line and click.
Software selects and decodes the signal.
When you transmit, the software will generate a tone (warble) corresponding to the frequency of the selected tone.

23. Transmitting
Tone selected creates an RF signal on the correct frequency.
PSK31 is a % duty cycle mode.
Most operators run a 20-40% of maximum output.
Power level is adjusted by the level of the audio signal being fed to the input.
Most accepted procedure:
Set Power to max. (100W for most TRX)
Apply signal to audio input
Adjust level to 20-40% (20-40W)
Overdriving will cause splatter making your signal much wider than 31 Hz.

24. Overdriving Indications
ALC will show activity. There should be no ALC indications.
Goal is to stay in the linear portion of the operating curve.
Some radios will become non-linear at 50% max.
This is not as noticeable with SSB voice signals
Shows up as splatter in PSK31 mode.
Use IMD (Intermodulation Distortion) meter
Good signal shows IMD of <-20 db
Ideally, <-23
Overdriving can also burn out you final transistors

25. W8KRF PSK Station

26. Digital Signal Reporting
RSQ Reporting
Readability
Strength
Quality
Although not yet accepted in Region 2, it has been in Regions 1 & 3 and it is being used by some stations in the US.
It more accurately indicates the quality, as well as, strength of the PSK signal.
Go to for more informaiton.

27. Readability Strength Quality R5 95%+ Perfectly readable
R4 80% Practically no difficulty, occasional missed characters
R3 40% Considerable difficulty, many missed characters
R2 20% Occasional words distinguishable
R1 0% Undecipherable
Strength
S9 Very strong trace
S7 Strong trace
S5 Moderate trace
S3 Weak trace
S1 Barely perceptible trace
Quality
Q9 Clean signal – no visible unwanted sidebar pairs
Q7 One barely visible pair
Q5 One easily visible pair
Q3 Multiple visible pairs
Q1 Splatter over much of the spectrum

28. Resources
ARRL’s HF Digital Handbook, Third Edition by Steve Ford, WA8IMY
Websites:
(HRD)