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PSK31 Lecture 2010-03-24 For PSK31PSK31 andand otherother soundsound cardcard digitaldigital radioradio modesmodes Alan J. Masson, GM3PSP / K6PSP Lothians Radio Society, 24 March 2010 SummarySummary PSK31PSK31 descriptiondescription OtherOther digitaldigital soundsound --cardcard modesmodes SoundSound clipsclips PSK31PSK31 InventedInvented inin 19981998 byby PeterPeter Martinez,Martinez, G3PLXG3PLX (also(also responsibleresponsible forfor introductionintroduction ofof AmTorAmTor )) RSGB RadCom December 1998. “A New Radio -Teletype Mode - Improving on RTTY ” WithoutWithout disadvantagesdisadvantages ofof somesome digitaldigital modes:modes: Avoids need for error correction / latency, which he believes make some modes unsuitable for live QSOs No need to send faster than can be typed by hand High frequency stability of modern transceivers allows use of much narrower bandwidth Powerful modern digital processors allow better coding PSK31PSK31 isis nownow thethe mostmost popularpopular digitaldigital modemode PSK31PSK31 TechnicalTechnical SummarySummary Symbol rate 31.25 baud (~ 50 wpm) - considered a reasonable typing speed - easily derived from common 8kHz sample rate used in many DSP systems Bandwidth 62.5 Hz Modulation Differential 2 -PSK (BPSK) Binary Phase -Shift Keying Average power 80% Protocol Asynchronous unconnected chat mode (!) Character set Varicode , ASCII user interface PSK31PSK31 UsesUses VaricodeVaricode CodingCoding VaricodeVaricode –– examplesexamples a 1011 A 1111101 b 1011111 B 11101011 c 10111 C 10101101 d 101101 D 10110101 e 11 E 1110111 i 1101 Space: 1 o 111 t 101 CODE DEFINITIONS: 0 = PSK phase reversal 0 10110111 1 = No phase change 1 10111101 Every character starts and ends 2 11101101 with a 1 3 11111111 Shorter codes for most common characters, like Morse Code 4 101110111 At least two 0s are inserted 5 101011011 5 101011011 between characters ( “letter gap ”) No character contains two 0s Complete 128 -character ASCII set with 10 bits PSK31PSK31 WaveformWaveform Raised Cosine waveform - smoothly changes from 0 to 1 like a cosine wave, avoiding square-wave switching-noise on phase- change being transmitted. This provides minimum bandwidth properties The amplitude changes are used to synchronize the receiver clock PSK31PSK31 ModulatorModulator (DSBSC) PSK31PSK31 DemodulatorDemodulator InterfacingInterfacing TransceiverTransceiver && ComputerComputer FixedFixed --levellevel audioaudio outputoutput fromfrom transceivertransceiver toto soundsound cardcard LineLine inputinput SoundSound cardcard LineLine outputoutput viavia levellevel --adjustadjust potpot toto microphonemicrophone input.input. SerialSerial portport viavia optoopto --isolatorisolator toto micmic PTTPTT (Use(Use ofof VOXVOX tendstends toto bebe unreliable)unreliable) VariousVarious interfaceinterface boxesboxes areare availableavailable toto organizeorganize thesethese interinter --connectionsconnections DIGIPANDIGIPAN IsolatingIsolating InterfaceInterface forfor PSK31PSK31 InterfacingInterfacing TransceiverTransceiver && ComputerComputer forfor PSK31PSK31 andand manymany otherother digitaldigital modesmodes SoftwareSoftware PackagePackage Fixed-level Rx audio out MIC in Sound Card Audio out Level Adjust Interface Box Opto-Isolator PTT in COM1 Port out ““PSKPSK ThisThis WeekendWeekend ”” QST Article, Jan 2010 Steve Ford WB8IMY Receive -only Audio input to computer via desk microphone Free Digipan software PSK31PSK31 SignalSignal onon WaterfallWaterfall DisplayDisplay SpectrumSpectrum ofof PSK31PSK31 SignalSignal ComparisonComparison ofof PSK31PSK31 andand FSKFSK OverOver --DrivenDriven PSK31PSK31 SignalSignal Unwanted Clean A GROSSLY over-driven signal can Sidebands Signal have multiple unwanted sidebands BPSKBPSK SignalSignal LevelLevel ControlControl • Audio signal level must be adjusted to operate in a completely linear manner • Overload of MIC pre-amp is most likely cause of non-linearity • This cannot be corrected using MIC Gain control • Transmitted signal should have IMD < -25 dB • IMD can be measured (Rx) in Digipan or using PSKMeter accessory in Tx mode FrequenciesFrequencies forfor PSK31PSK31 18381838 35803580 70357035 -- RegionsRegions 11 andand 33 70707070 -- RegionRegion 22 1013910139 1407014070 1810018100 2107021070 2492024920 2812028120 TheThe activityactivity ofof multiplemultiple stationsstations occupiesoccupies thethe bandwidthbandwidth ofof aa singlesingle SSBSSB channelchannel withwith thethe aboveabove carriercarrier frequenciesfrequencies RelatedRelated BPSKBPSK ModesModes PSK31PSK31 GeneralGeneral useuse (most(most common)common) QPSK31QPSK31 LowLow --signalsignal // errorerror correctioncorrection PSK63PSK63 HigherHigher --speedspeed PSK125FPSK125F HigherHigher speedspeed PSK250FPSK250F HigherHigher speedspeed FSK31FSK31 SimilarSimilar toto PSK31PSK31 PSK31PSK31 SoftwareSoftware Digipan V.2 PSK31, QPSK31, PSK63, FSK31, Pactor Rx - including Multichannel receive screen MixW PSK31, PSK63, QPSK, FSK31, RTTY, Packet, (Reg. fee) Pactor RX, AMTOR RX & FEC TX, MFSK/Graphics Color/BW, Olivia, Contestia , RTTY, Throb, MT63, Hell, FAX, SSTV Stream PSK31, PSK63, PSK125, PSK250, MFSK16/8 Hamscope PSK31, QPSK31, CW, RTTY, MFSK16, Packet PocketDigi PSK31, CW, RTTY – for programmable PDAs MMVARI PSK31, RTTY, MFSK16, FSK31 - linked to N1MM contest logging software PSK31PSK31 DemoDemo -- RxRx KenwoodKenwood TSTS --850850 inin USBUSB modemode FixedFixed --levellevel audioaudio intointo soundsound cardcard DigipanDigipan Ver.2Ver.2 -- multimodemultimode 14.07014.070 MHzMHz OtherOther DigitalDigital SoundSound --CardCard ModesModes -- thatthat II havehave usedused RTTYRTTY MFSK16MFSK16 MT63MT63 HellschreiberHellschreiber ThrobThrob AnalogAnalog SSTVSSTV -- ScottieScottie 11 DigitalDigital SSTVSSTV –– DIGTRXDIGTRX AllAll thesethese modesmodes useuse samesame basicbasic hardwarehardware ++ freefree softwaresoftware Frequencies:Frequencies: 1010 kHzkHz aboveabove PSK31PSK31 (not(not SSTV)SSTV) PSK31PSK31 andand PSK63PSK63 PSK31PSK31 demodemo (35(35 sec):sec): QPSK16QPSK16 demodemo (17(17 sec):sec): PSK63PSK63 demodemo (35(35 sec):sec): RTTYRTTY SoundSound --cardcard modesmodes useuse AFSKAFSK Software:Software: MMTTY,MMTTY, MMVARI,MMVARI, MixWMixW etcetc AudioAudio DemoDemo (25(25 sec):sec): MFSK16MFSK16 InventedInvented byby MurrayMurray GreenmanGreenman ,, ZL1BPUZL1BPU (1999)(1999) DevelopedDeveloped forfor WindowsWindows -- NinoNino PorcinoPorcino IZ8BLYIZ8BLY 1616 tonestones spacedspaced atat 15.62515.625 Hz;Hz; 44 char/secchar/sec FullFull --timetime ErrorError CorrectionCorrection (FEC)(FEC) DesignedDesigned forfor longlong --haulhaul DxDx conversationsconversations Software:Software: IZ8BLYIZ8BLY --Stream,Stream, HamscopeHamscope ;; MixWMixW MFSK16MFSK16 demodemo (32(32 sec):sec): MFSK8MFSK8 demodemo (55(55 sec):sec): FSK441FSK441 (by(by K1JT)K1JT) forfor meteormeteor --scatterscatter 44 tonestones atat 147147 cps;cps; 14701470 wpm;wpm; b/wb/w 22052205 HzHz MT63MT63 DevelopedDeveloped byby PawelPawel JalochaJalocha ,, SP9VRC,SP9VRC, 19981998 6464 tonestones spacedspaced atat 15.62515.625 Hz;Hz; 1010 char/secchar/sec PowerfulPowerful FECFEC DesignedDesigned asas aa chatchat mode,mode, esp.esp. multimulti --stationstation SoundsSounds likelike broadbroad --bandband noisenoise Software:Software: IZ8BLYIZ8BLY --MT63,MT63, MixWMixW SuperimposedSuperimposed CWCW ID:ID: MT63MT63 500500 HzHz demodemo (40(40 sec):sec): MT63MT63 10001000 HzHz demodemo (22(22 sec):sec): MT63MT63 20002000 HzHz demodemo (12(12 sec):sec): HellschreiberHellschreiber DerivedDerived fromfrom mechanicalmechanical systemsystem (Dr(Dr RudolfRudolf Hell,Hell, Germany,Germany, 1927)1927) DSPDSP systemsystem developeddeveloped byby G3PLXG3PLX inin 19971997 ColumnsColumns ofof 1414 dotsdots // 55 columnscolumns perper charactercharacter 2.52.5 characterscharacters // secsec (25(25 wpm)wpm) OnOn // OffOff keyingkeying ofof transmitter;transmitter; bandwidthbandwidth 350350 HzHz Software:Software: IZ8BLYIZ8BLY --Hell,Hell, MixWMixW FeldFeld HellHell demodemo (35(35 sec):sec): FMFM HellHell 105105 baudbaud demodemo (35(35 sec):sec): THROBTHROB InventedInvented byby LionelLionel Sear,Sear, G3PPTG3PPT inin 20002000 MFSKMFSK system;system; 99 tonestones 1,1, 22 oror 44 tonestones // secsec BandwidthBandwidth 100100 oror 200200 HzHz Software:Software: Throb,Throb, MixWMixW 11 ThrobThrob // secsec demodemo (60(60 sec):sec): 22 ThrobThrob // secsec demodemo (35(35 sec):sec): 44 ThrobThrob // secsec demodemo (19(19 sec):sec): SSTVSSTV AnalogAnalog SSTVSSTV –– ScottieScottie --11 demodemo (30(30 sec):sec): DigitalDigital SSTVSSTV –– DIGTRXDIGTRX demodemo (30(30 sec):sec): FurtherFurther ReadingReading RTTY/PSK31 for Radio Amateurs By Roger Cook G3LDI RSGB Includes free CD of amateur programs FurtherFurther ReadingReading Digital Modes for All Occasions By Murray Greenman , ZL1BPU RSGB, 2002 PSK31PSK31 DXCCDXCC butbut itit sayssays ““RTTYRTTY ”” !! PSK31PSK31 andand otherother soundsound cardcard digitaldigital radioradio modesmodes ANYANY QUESTIONS?QUESTIONS? Alan J. Masson, GM3PSP / K6PSP Lothians Radio Society, 24 March 2010.
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