PSK31 and WSPR May 2010 KWARC Nick Waterman VA3NNW & Don Fisher VE3ESE
PSK31 Introduction Still the fastest growing digital mode worldwide Needs: Some software (almost always free) Any computer with a sound card Any reasonably stable transceiver An antenna … and really not a lot else!
PSK31 Introduction Very narrow bandwidth, much narrower than RTTY, comparable with CW Gets through like CW (OR BETTER) at comparable power and S/N ratio Manages about 50 wpm
PSK31 Introduction Good for ragchews and nets, good for QRP and DX No error correction, so less good for error-free file transfer, mailboxes, etc. PSK31 category in ARRL Field Day (more points, more mults?)
PSK31 Error Rate Signal to Noise Ratio (dB) Error Rate PSK-31 RTTY 100W SSB ≈ 8W RTTY ≈ 1W PSK31 – You WILL NOT NEED a lot of power ! (Chart borrowed from YCARS, with thanks)
PSK31 Stands for... Phase Shift Keying, 31 Baud Specifically Binary Phase Shift Keying (So sometimes called BPSK31) 31.25 baud (so BPSK31.25 ?) There's also a QPSK31 (Quad Phase shift keying), uses 4 phases instead of 2, some error-correcting, but less common. There's also PSK63, PSK500, and some other variants, won't go into too much detail on these.
PSK31 History Developed by Peter Martinez (G3PLX) and introduced to the wider amateur radio community in December 1998. Martinez initially called his creation "varicode", because it uses variable length encodings (Huffman codes) to represent characters (more on that later) The slightly obscure 31.25bps bit rate was chosen as being a nice binary multiple of the sound card clock rate (8kHz/256)
PSK31 Waveform Unmodulated carrier: CW: BPSK (bad) BPSK (good) In phase 180º out Phase changes
PSK31 Encoding A “0” is sent as a 180º phase shift A “1” is sent as no phase shift 0110000011000 The “alphabet” is then designed to make sure that commonly-sent characters are made up of a small sequence of 1s and 0s, rare characters are longer (a little like CW) There are never too many long strings of 1s (difficult to tell how many 1s belong on a long carrier with no phase changes to sync off). The gap between chars is “00”. Long string of 0s when idling This alphabet is called Varicode
PSK31 - Operating Line out Sound card Line in Mic Audio out
PSK31 - Operating Line out Sound card Line in Audio out 100k1k Mic Bit of attenuation often helps. Some people do clever stuff with isolation transformers, capacitative DC blocking, opto-isolators, etc.
PSK31 - Operating Line out Sound card Line in Audio out 100k1k Mic PTT via VOX BUT BEWARE any other sound coming out of your computer (web page audio, MP3s, and even windows startup jingle) may be transmitted
PSK31 - Operating Line out Sound card Line in Audio out 100k1k Mic PTT via regular CAT cable (same one you use for rig control, programming memories etc)
PSK31 - Operating Line out Sound card Line in Audio out 100k1k Mic 22k 2N2222 1N4148 PTT Serial RTS PTT via serial port (RTS, DSR, or similar signal line)
PSK31 - Operating Mic Audio out Sound Card Interface West Mountain Radio RIGblaster (about 5 types) MFJ make a few MicroHAM RigExpert SignaLink Many more, inc many homebrew designs starting at about $10
PSK31 - Operating If you're feeling REALLY cheap, some people get away with simply putting their rig mic near their computer speaker and vice-versa! This provides good electrical isolation, but it's tricky to get the audio levels right, ambient noise can ruin your transmitting or receiving, and besides, PSK31 doesn't sound all that nice anyway!
PSK31 - Software SOFT- WARE! MixW - www.mixw.net MultiPSK - http://f6cte.free.fr/index_anglais.htm DigiPan - www.pavane.net/digipan/digipan.htm Fldigi - www.w1hkj.com/Fldigi.html Hamscope - www.qsl.net/hamscope WinPSK, Zakanaka (with Logger32) Plenty of others. Almost always FREE Usually includes multiple other digital modes (RTTY, Olivia, Hell, sometimes packet, SSTV) Often includes logging software, some level of CAT, rotor control
PSK31 - Software SOFT- WARE! This is what we'll be using for the demo MixW - www.mixw.net MultiPSK - http://f6cte.free.fr/index_anglais.htm DigiPan - www.pavane.net/digipan/digipan.htm Fldigi - www.w1hkj.com/Fldigi.html Hamscope - www.qsl.net/hamscope WinPSK, Zakanaka (with Logger32) Plenty of others. Almost always FREE Usually includes multiple other digital modes (RTTY, Olivia, Hell, sometimes packet, SSTV) Often includes logging software, some level of CAT, rotor control
PSK31 Audio Settings Windows audio mixer or equivalent Adjust “Line In” volume until the waterfall looks nice or until the stronger signals are using about 50% of the available range. Adjust “Line Out”, “Headphone”, or “Wave” (and make sure you're using the right one) until your rig ALC is barely deflecting and flat, and again about 50% power output is probably ideal Make sure you're not overdriving or clipping in either direction – will cause bad IMD (inter modulation distortion). Vol DOWN if you are. Compression OFF on your rig
PSK31 - Demo (White with two sugars please!) ;-)
WSPR Pronounced “Whisper” Weak Signal Propagation Reporter, by K1JT Definitely NOT for ragchews Not even really QSOs This mode effectively turns your PC+Rig into a beacon, but also monitors for, and reports, other people's WSPR beacons. Good use of your Rig when you're not using it! You can be heard WORLDWIDE on <1W, We've seen spots of 13,000km on 0.1W or less
WSPR - timing Time is divided into 2-minute slots (it helps to have your PC sync'ed over the net using NTP, any of the free atomic clock tools or just Windows time sync) You will occasionally transmit for a 2 min time- slot (actually 110.6s) You will usually receive in all other 2-minute time-slots, and automatically report any “spots” to the wsprnet.org website, assuming you have “always on” internet.
WSPR - Encoding VERY slow data rate (1.4648 baud) – you take 2 minutes to transmit just your callsign, your 4-digit Maidenhead locator, and your power level. Tonnes of error-correction to ensure you can be heard at -28dB If you want to use a callsign with prefixes or suffixes, or a 6-digit locator, there are special ways to send it, and you end up taking 4mins instead of 2
WSPR - Encoding 4-FSK, tone separation 1.4648 Hz Occupied bandwidth: about 6 Hz Not going to go into all the details of the error-correcting codes, there's some complex coding theory there... … but for operating it really doesn't matter, the software is trivial to run, you just set it up and leave it running.
WSPR - Operating Line out Sound card Line in Audio out 100k1k Mic EXACTLY THE SAME AS PSK-31!* *(Just different software)
WSPR Software: http://www.physics.princeton.edu/pulsar/K1JT/ http://www.physics.princeton.edu/pulsar/K1JT/ Reports: http://wsprnet.org/ http://wsprnet.org/olddb?findcall=VE3IC&findreporter=VE3IC http://wsprnet.org/ http://wsprnet.org/olddb?findcall=VE3IC&findreporter=VE3IC Who's on the air? http://wsprnet.org/drupal/wsprnet/activity http://wsprnet.org/drupal/wsprnet/activity