Transcript Digital Communications

Digital Communications
 El
Paso Amateur Radio Club
 August 22, 2003
 Tom, WB5QLR
Repeat Offender – 8/9/00
Digital Modes
 RTTY
 PSK31
 PSK63
 MFSK
 WSJT
Computer Based
 Hardware
requirements
 SoundBlaster
compatible sound card
 PC capable of running Win95/98
 PTT switching mechanism
Computer Based
 Software
 Software
for mode of operation
 Might have multiple mode in same program
What is NOT Necessary
 Heavy
teletype
 TNC
 Special
tuning scopes
Main Point #1
 Digital
modes can be implemented
totally with:
 Computer
 Sound
Card
 Software
 Simple PTT circuit from serial port
Connections
 Receiver
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
Connections
 Computer
 Use
speaker in Transmitter audio
a resistor and 1:1 audio transformer
 Optional trimmer pot to control audio level
Audio Connection
Connections
 Computer
 Circuit
serial port to Transmitter PTT
includes:
1 resistor
 2 diodes
 1 transistor

 Optional
DPST to switch between 2 inputs
from serial port
PTT Connection
RigBlaster Interface
RigBlaster Interface - Back
RTTY
 Convention
is LSB
 Been 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 Frequencies
 3.580
MHz
 7.080 MHz
 10.140 MHz
 14.070 MHz
 18.100 MHz
 21.080 MHz
 28.120 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
MFSK
 Disadvantages
 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
– Meteor Scatter
 JT6M – Meteor Scatter for 6M
 JT44 – Tropo and EME
 EME Echo – Listening to your EME return
 FSK441
 Competitive
with 50 watts and 10-11
element beam
Bandpass Comparisons
Resources
 RTTY/PSK
 TrueTTY
software
- www.dxsoft.com
3KHz band pass
 On RTTY, both FSK and AFSK

 RigBlaster
Interface
 www.westmountainradio.com/RIGblaster.ht
m
Resources

PSK Home Page


PSK only software



www.aintel.bi.ehu.es/psk31.html
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/cgibin/pingtalk
Resources
 Articles
 QST
May, 1999 pg 41-44
 QST May, 2000 pg 42-45
 Book
 ARRL’s
HFDigital Handbook
Non Digital Resources
 Logging
 XMLog
software
- 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 #2
 Fun
 Easy
 On
air demonstration
 Slides and references at
www.striplingdata.com/w5es