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Reelfoot Amateur Radio Club. PSK31. A Basic Application. By James C. Hall WB4YDL. April 22, 2004. PSK31 Background. Developed by Peter Martinez, G3PLX The fastest growing digital mode worldwide Similar to RTTY – keyboard to keyboard QSO’s Bit rate is the same as bandwidth – 31.25 Hz

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psk31

Reelfoot Amateur Radio Club

PSK31

A Basic Application

By James C. Hall WB4YDL

April 22, 2004

psk31 background
PSK31 Background
  • Developed by Peter Martinez, G3PLX
  • The fastest growing digital mode worldwide
  • Similar to RTTY – keyboard to keyboard QSO’s
  • Bit rate is the same as bandwidth – 31.25 Hz
  • Well suited to sound card 8 kHz sampling
    • 8000 Hz ÷ 256
psk31 concepts
PSK31 Concepts

Frequency Shift Keying (FSK) used in RTTY where the ‘mark’ (1) and ‘space’ (0) are different frequencies

Mark

Space

psk31 concepts1
PSK31 Concepts

Phase Shift Keying (PSK) defines a zero (space) as a 180° phase reversal and a one (mark) as in phase with a reference frequency

psk31 concepts keeping the bandwidth narrow
PSK31 ConceptsKeeping the Bandwidth Narrow
  • The problem with phase reversal is broadband splatter
  • Solution: Gradually reduce the signal amplitude to zero at phase reversal
  • No need to reduce amplitude without phase reversal
psk31 concepts performance
RTTY uses ASCII

8 bits with start and stop bits for each character

PSK31 Brightness

For SSB, 100 watts in a 3 kHz bandwidth = 30 mwatts/Hz

For PSK31, 100 watts in a 31 Hz bandwidth = 3200 mw/Hz

This is > 100 times brighter (or 20 dB) than SSB

Much less power needed in PSK31 for the same S/N ratio

PSK31 is ideal for QRP with cross-country QSO’s common with 1 watt !

High S/N ratio = less bit error

PSK31 ConceptsPerformance
  • PSK31 use Varicode
    • Variable coding
    • Most common characters use the fewest bits
    • Average number of bits per character is about 6.5
    • Improves data rate for the same bandwidth
sound card digital modes
Sound Card Digital Modes

CW

PSK31

RTTY

PACKET

APRS

FSK411

JT44

EME

Connecting your Radio to your Computer

You can purchase an interface to connect your transceiver to your computer, OR you can make your own for a few $.

sound card digital modes1
Sound Card Digital Modes

CW

PSK31

RTTY

PACKET

APRS

FSK411

JT44

EME

Connecting your Radio to your Computer

The KK7UQ sound card interface kit packaged in an Altoids© tin

sound card digital modes2
Sound Card Digital Modes

CW

PSK31

RTTY

PACKET

APRS

FSK411

JT44

EME

Connecting your Radio to your Computer

Receive Audio Connection:

Connect an audio cable between the transceiver audio output and the soundcard LINE IN jack.

sound card digital modes3
Sound Card Digital Modes

CW

PSK31

RTTY

PACKET

APRS

FSK411

JT44

EME

Connecting your Radio to your Computer

Transmit Audio Connection:

Connect a shielded audio cable between the transceiver MIC input and the soundcard LINE OUT jack through a 40 db attenuator. If your transceiver has a LINE input, no attenuation is required. (eliminate the 2 resistors)

sound card digital modes4
Sound Card Digital Modes

CW

PSK31

RTTY

PACKET

APRS

FSK411

JT44

EME

Connecting your Radio to your Computer

T/R Connection:

PTT is controlled via the RTS and/or DTR outputs of the computer’s RS-232 serial port.

basic psk31 station
Basic PSK31 Station

Speaker Out

Computer

HF Transceiver

Line In

Sound Card

Line Out

Antenna

COM Port

PSK31

Application

Mic

Input

DTR or RTS of COM n

psk31 conclusions
PSK31 Conclusions

PSK31 is great for you if …

  • You want to try a new mode without a big investment
  • Enjoy digital modes
  • Enjoy ragchewing
  • Enjoy chasing DX
  • Enjoy software and computers
  • Enjoy QRP
  • Enjoy kit building
  • Have a marginal antenna, low power, or poor location
  • Want to stay on the cutting edge

73 de Jamie WB4YDL