Digital Communications El Paso Amateur Radio Club August 22, 2003 Tom, WB5QLR
Dec 26, 2015
Computer BasedHardware requirements
SoundBlaster compatible sound card PC capable of running Win95/98 PTT switching mechanism
Main Point #1Digital modes can be implemented
totally with: Computer Sound Card Software Simple PTT circuit from serial port
ConnectionsReceiver audio out into Computer line in
Preferable if audio out is independent of AF gain
Could also run through a 1:1 audio transformer to help isolate grounds
ConnectionsComputer speaker in Transmitter audio
Use a resistor and 1:1 audio transformer Optional trimmer pot to control audio level
ConnectionsComputer serial port to Transmitter PTT
Circuit includes: 1 resistor 2 diodes 1 transistor
Optional DPST to switch between 2 inputs from serial port
PSK and sound Convention is USB Most around 14.070 MHz and up Phase shifted Variable code – combination of Baudot and
Morse Band width is 31.25 cycles wide Efficiency ranks with CW Implemented completely with sound card and
software
PSK 63 100 wpm character transmission speed for
contest exchanges and macro transmission versus RTTY at 60 wpm
Only 1/5 the bandwidth of RTTY - capable of displaying 24 signals simultaneously on a waterfall or spectrum display
Capable of color thumbnail portrait transmission in less than 2 minutes
Faster sync recovery than RTTY, resulting in fewer errors
PSK 63 Requires much less power than RTTY for the
same communications performance Identical to PSK31 except for a wider
bandwidth of 63 Hz Improved polar path performance compared
to PSK31 Works with any soundcard-equipped
Windows computer and SSB transceiver High-speed transmission of macros and brag
files
MFSK – Mutiple Frequency Shift Keying A Weak signal digital mode Advantages
High rejection of pulse and broadband noise due to narrow receiver bandwidth per tone
Low baud rate for sensitivity and multi-path rejection - data bit rate higher than symbol baud rate
Constant transmitter power Tolerance of ionospheric effects such as doppler,
fading and multi-path
MFSKDisadvantages
Narrow spacing and narrow bandwidth of the individual tone detectors
Drift can be a problem and accurate tuning is essential.
WSJT – Weak Signal by W1JT
Four Modes FSK441 – Meteor Scatter JT6M – Meteor Scatter for 6M JT44 – Tropo and EME EME Echo – Listening to your EME return
Competitive with 50 watts and 10-11 element beam
ResourcesRTTY/PSK software
TrueTTY - www.dxsoft.com 3KHz band pass On RTTY, both FSK and AFSK
RigBlaster Interface www.westmountainradio.com/
RIGblaster.htm
Resources PSK Home Page
www.aintel.bi.ehu.es/psk31.html
PSK only software DigiPan – www.digipan.net WinPSKse - www.winpskse.com
Other Sites Great overview - www.qsl.net/kk7lk/psk31.htm Interface details - www.w5bbr.com/psk31.html
Resources MSFK
http://www.qsl.net/zl1bpu/MFSK/ Software – Stream -
http://iz8bly.sysonline.it/Stream/index.htm WSJT
http://pulsar.princeton.edu/~joe/K1JT/ http://www.qsl.net/wa5ufh/WSJTGROUP/WSJTG
ROUP.htm Ping Jockey -
http://www.pingjockey.net/cgi-bin/pingtalk
Non Digital ResourcesLogging software
XMLog - www.xmlog.com Multiple logs books Easy reference to notes
Logger - www.qsl.net/kc4elo/ Little higher level Includes PSK
Contesting Software – www.writelog.com Includes RTTY and PSK