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PSK31

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

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  1. Reelfoot Amateur Radio Club PSK31 A Basic Application By James C. Hall WB4YDL April 22, 2004

  2. 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

  3. PSK31 Concepts Frequency Shift Keying (FSK) used in RTTY where the ‘mark’ (1) and ‘space’ (0) are different frequencies Mark Space

  4. 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

  5. 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

  6. 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

  7. 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 $.

  8. 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

  9. 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.

  10. 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)

  11. 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.

  12. 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

  13. 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

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