Digital CommunicationsEl Paso Amateur Radio ClubAugust 22, 2003Tom, WB5QLR

Repeat Offender – 8/9/00

Digital ModesRTTYPSK31PSK63MFSKWSJT

Computer BasedHardware requirements

SoundBlaster compatible sound card PC capable of running Win95/98 PTT switching mechanism

Computer BasedSoftware

Software for mode of operation Might have multiple mode in same program

What is NOT NecessaryHeavy teletypeTNCSpecial tuning scopes

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

Audio Connection

ConnectionsComputer serial port to Transmitter PTT

Circuit includes: 1 resistor 2 diodes 1 transistor

Optional DPST to switch between 2 inputs from serial port

PTT Connection

RigBlaster Interface

RigBlaster Interface - Back

RTTYConvention is LSBBeen around for a long time

RTTY

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 Tuning – Old Style

PSK Tuning – New Style

PSK Tuning – New Style

PSK Frequencies3.580 MHz7.080 MHz10.140 MHz14.070 MHz18.100 MHz21.080 MHz28.120 MHz

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

Bandpass Comparisons

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

ResourcesArticles

QST May, 1999 pg 41-44QST May, 2000 pg 42-45

Book ARRL’s HFDigital Handbook

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

Main Point #2FunEasyOn air demonstrationSlides and references at

www.striplingdata.com/w5es