Download - PSK31 A Basic Application By James C. Hall WB4YDL Reelfoot Amateur Radio Club April 22, 2004
PSK31PSK31A Basic ApplicationA Basic Application
By James C. Hall WB4YDL
Reelfoot Amateur Radio ClubReelfoot Amateur Radio Club
April 22, 2004
PSK31 BackgroundPSK31 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 ConceptsPSK31 Concepts
Frequency Shift Keying (FSK) used in RTTY where the ‘mark’ (1) and ‘space’ (0) are
different frequencies
Space
Mark
PSK31 ConceptsPSK31 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 ConceptsPSK31 ConceptsKeeping the Bandwidth NarrowKeeping 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 ConceptsPSK31 ConceptsPerformancePerformance
• 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 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 ModesSound Card Digital Modes
Connecting your Radio to your ComputerCW
PSK31
RTTY
PACKET
APRS
FSK411
JT44
EME
You can purchase an interface to connect your transceiver to your computer, OR you can make your own for a few $.
Sound Card Digital ModesSound Card Digital Modes
Connecting your Radio to your ComputerCW
PSK31
RTTY
PACKET
APRS
FSK411
JT44
EME
The KK7UQ sound card interface kit packaged in an Altoids© tin
Sound Card Digital ModesSound Card Digital Modes
Connecting your Radio to your Computer
Receive Audio Connection:
CW
PSK31
RTTY
PACKET
APRS
FSK411
JT44
EME
Connect an audio cable between the transceiver audio output and the soundcard LINE IN jack.
Sound Card Digital ModesSound Card Digital ModesConnecting your Radio to your
ComputerTransmit Audio Connection:
CW
PSK31
RTTY
PACKET
APRS
FSK411
JT44
EME
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 ModesSound Card Digital ModesConnecting your Radio to your Computer
T/R Connection:CW
PSK31
RTTY
PACKET
APRS
FSK411
JT44
EME
PTT is controlled via the RTS and/or DTR outputs of the PTT is controlled via the RTS and/or DTR outputs of the computer’s RS-232 serial port.computer’s RS-232 serial port.
Basic PSK31 StationBasic PSK31 Station
HF Transceiver
Computer
Sound Card
COM Port
PSK31 Application
Speaker Out
Line In
Line Out
Mic Input
DTR or RTS of COM n
Antenna
PSK31 ConclusionsPSK31 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