Rascal | R6 300 | Get Your Feet Wet with PSK31

Get Your Feet Wet with PSK31
Outline of Presentation
Get Your Feet Wet with PSK31
Clint Hurd - KK7UQ
Terry Dettman - WX7S - SGC
Presented at SEAPAC
Seaside, Oregon
June 14, 2003
Basics of Sound Card
Applications
• Audio frequency in 200 to 5000 Hz range
• Modulation of audio “carrier” using
software and sound card
• Transported via SSB radio
• Received by rig and converted back to
audio spectrum
• Decode done using software and sound card
Sound Card Applications - Basics
• Rig
– SSB in either USB or LSB
– Reasonable frequency stability
– Tight filters NOT needed in most cases
– Can NOT use ALC or Compression on
Transmit
– Must stay within TX bandwidth - typically
2200 Hz or less
• Interface
– Connects the Rig to the PC Soundcard
•
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Basics -Sound Card Applications
Basics - Interface Requirements
BPSK concept, demo & tour of Digipan
MFSK concept, demo & tour of MixW
Build your own interface
Review of commercial interfaces
Review of available software
Sound Card Applications - Basics
• Combo of Software, PC, Sound Card, SSB Rig &
Interface
• Software
– Spectrum display to 5 Hz resolution (step size)
– Bandpass filter for signal - 50 Hz
– Encode/Decode of signal
– Graphic User Interface (GUI)
• PC - Windows 95 or later, 100 MHz or faster
Sound Card Operating Modes
Basic Hardware Interface
Ham Rig
Computer
1 V p-p
SC Mic In
SC Spkr Out
Serial Out (RTS)
1 V p-p
+- 12V
Attenuator
Level Shifter
Spkr Out
10 mV p-p
Closure to Gnd
Mic In
PTT
Sound Card Modes - Interface Block Diagram
1
• Audio from Receiver to PC
– Signal level 5 Vp-p, typical signal is 1 Vp-p
– Audio frequency range from 200 to 4000 Hz, or whatever
the Rx passband will allow
– Cables need to be shielded
• Sound Card Accepts 5 Vp-p Before Saturating
– Software detects and warns against saturated signals at
around 1.5 V p-p
– Ways to control the maximum level to the sound card:
• RX RF/AF Gain
• PC Volume Control
• Interface Level Control
Sound Card Interface Requirements
• Audio from PC to Transmitter
– Sound Card output up to 5 Vp-p at max level
• PC slider set at mid level - output is about 1 Vp-p
– Rig expects microphone levels at about 2-10 millivolt p-p, so
signal must be attenuated in the interface
– Frequency range from 200 to 4000 Hz
• Max determined by Tx output bandwidth, typically 2200 Hz
– Audio drive levels determine power output - usually run rig at
25% to 50% of CW rating for clean signal, and cool TX
– System is operating in an RF environment:
• Shielded cables - lengths under 6 feet.
• Good grounding of all components - Rig, PC & Tuner
– Care taken to mute other audio sources during transmit
Sound Card Interface
Sound Card Interface Requirements
• SSB Rig Control
– TX On/Off
• Manual Switch - VOX - PTT via Serial Port Control
on PC
– TX Audio
• Input - Mic connector or Accessory Port
– TX Audio Drive Level Set by combination of:
• Audio level from PC
• Attenuation level control on Interface
• Mike Gain on Rig
– RX Audio to PC Provided by
• Line Out, Speaker/Headset Out, Accessory Port
3.5mm Stereo
Receptacle
w/ switches
1:1 600 ohm
Audio Transformer
Waterfall Drive
1k pot
Audio Taper
J2
To
Sound Card
Line In
X1
1
2
Tip
3
4
3.5mm Stereo
Receptacle
3
C1
R4 100
Tip
5
1
+
4
Ring
RTS
Gnd
7
5
Tip
R2
2.2k
Ring
2.5mm
Stereo
Receptacle
External Cable w/ DB9
female serial port
conn shown for ref.
U2
Dual Color
T 1 3/4 LED
Red - PTT
Yel - FSK
1.0 uF
5
J5
AT 20 Audio
Transducer
6
C5 .0047uF
Ret
3
SW1
PTT Control
(SPDT Ctr Off)
2
• Phase modulates an audio “carrier” at 31 baud
• Reverses phase 180 degrees (BPSK)
• Reduces signal level at phase shift time to
reduce spurious frequencies
• Uses variable length encoding - most used
characters are encoded into small word lengths
• Data rate consistent with that of a fast typist
• Adv: Narrow bandwidth, good performance
• Disadv: Poor performance on long path and
over the pole contacts (phase distortion)
Blu
Wht
D4
5
4
Up Auto
Ctr - PTT Off
Down - PTT On
To Xcvr
Grn
Ret Wht
PTT Org
To Xcvr
1N4148
4N33
Photo Darlington
Opto-Isolator
FSK Grn
1
Ret
All resistors
1/4W 5%
Org
Wht
Rig cable mating
connector and wire
colors shown for
ref.
kk7uq Interface Model II - Schematic Diagram
Binary Phase Shift Keying - BPSK31
From Xcvr
To Xcvr
1N4148
D3
5
4
1
2
Brn
Wht
Q1
2N3904
4N33
U1
LED 1
Ret
4 Mic Blu
SP 1
+
1
2
Red
2
3
R12
10 k
C4 10 uF
Yel
Tip
Sleeve
R10
2 meg
C3 10 uF
R9 4.7 k
J1
DTR
C2
R11
2.2 k
D1 1N4148
R1
2.2k
1
R8
4
D2 1N4148
Note: Return path for
audio to monitor amplifier
is made through the cable
shields to the ground
point at the PC.
7
R5 51
6
Primary
2
.0047uF
8 Aud.
Brn
Out
R6 51
Tx Drive
1k pot
Audio Taper
X2
3.5mm Stereo
Receptacle
J3 Ring
From Xcvr
Spkr Out
(Alternate)
Ring
1
1:1 600 ohm
Audio Transformer
R3 1.0 k
From
Sound Card
Spkr Out
3
Primary
2
5
R7
Ring
J4
Tip
6
RJ45
Receptacle
RJ45
Plug
Sound Card Interface Requirements
BPSK Signal Envelope
0
0
1
0
0
0
Varicode “Space” character = 1
where 0 is a Phase Reversal and 1 is no reversal
must have at least two 0 between characters
2
BPSK Excerpt of Varicode
SGC 2020-DSP Setup for Sound Card Modes
Note that lower case letters have shorter word lengths
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Digipan Screen with PSK Signals
Digipan Screen with PSK Signals
PSK31 Frequencies
Live Demo of
PSK31 with Digipan
3.580 USB
7.070 USB
10.139 USB
14.070 USB
18.095 USB
21.070 USB
24.9195 USB
28.120 USB
•
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Transceivers - SGC 2020-DSP
Interface - kk7uq Model II
Laptop Computers
Antenna - Light Bulb
3
Other Modes - MFSK16
Other Modes - PSK63
• Designed for contest work
• Faster than RTTY on data rate and exchange 100 wpm effective rate
• Better S/N than RTTY within 3db of PSK31
• Faster sync recovery than RTTY
• Much lower bandwidth than RTTY
• Full character set
• Look for signals 2.5 kHz higher than PSK31
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Multiple Frequency Shift Keying 16 Freqs.
Four bits per tone
250 Hz Wide
Uses Forward Error Correction (FEC)
Uses Varicode to optimize throughput
Data rate consistent with that of a fast typist
Adv: Very good performance on long path
contacts and over polar routes
• Disadv: Wider bandwidth, harder to tune,
needs stable TX/RX
Comparison of Digital Modes
MFSK16 Spectrogram
0
Freq Hz
300
Spectrogram of MFSK16 signal over 20 seconds
of transmission. Horizonal lines are at 1000 Hz
and 1300 Hz. Contains about 120 characters raw
rate, 60 characters effective rate (FEC used).
0
20
Time Sec
MixW Screen with MFSK Signals
WPM Rates for Various Modes
CW 20WPM
Feld Hell
BPSK31
RTTY 45.5Baud
MFSK
BPSK63
Time Sec Char/Sec WPM QSO/3KHz
324
1.64
19.81
12
170
3.12
37.76
9
125
4.25
51.36
30
117
4.54
54.87
9
110
4.83
58.36
9
62
8.50
102.70
25
Based on a typical 2 way QSO exchanging
English text. 531 characters, 107 words and
spaces. I.E. average 6 characters per word.
4
MixW Screen with MFSK Signals
Build Your Own Interface
kk7uq Interface Model II
Build Your Own Interface
•
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•
Mic Switch
Plug in Rig
Cable
Fully Isolated
Knob Level
Control
Built in Audio
Monitor
FSK Control
for RTTY
Built In VOX
Approx Cost
Sound Card Interface - Feature Comparisons
No
No
No
Yes
Yes
Yes
No
Yes
No
Yes
No
Yes
No
No
$20
$64
Ready to Go w/o Mic. Switching
BuxComm Rascal MkV
No
MFJ 1273B
No
Rigblaster Nomic
No
Tigertronics Signalink
No
Yes
No
Yes
Yes
Yes
No
No
Yes
No
No
No
No
No
No
No
No
Yes
No
No
No
No
No
No
Yes
$57
$70
$71
$67
Ready to Go with Mic. Switching
MFJ 1275
Yes No
MFJ 1279
Yes No
Yes Yes
Rigblaster Std
Rigblaster Plus
Yes Yes
Rigblaster Pro
Yes Yes
Yes
Yes
No
No
Yes
No
No
No
No
No
No
No
No
No
No
No
Yes
No
No
Yes
No
No
No
No
No
$110
$140
$121
$151
$311
Build it Yourself
BuxComm Rascal kit
kk7uq Model II
Interface Kit $55.00
Shielded Audio Cables $5.00
Rig Mic Connector $1.50
Box of Altoids $2.00
Total $63.50
Sound Card Interface Sources
BuxComm
Discovery Bay
MFJ
Tigertronics
West Mountain
www.packetradio.com/RASCALplus.htm
www.waypt.com/users/~discobay/
www.mfjenterprises.com/
www.tigertronics.com/
www.westmountainradio.com/
5
X
X
X
X
X
X
X
X
X
X
Log Supported
X
Name/Screen Pop
X
Hellschreiber
MFSK-8
CW
X
X
X
RTTY
X
X
X
MFSK-16
Digipan
Hamscope
IZ8BLY
MMTTY
Stream
WinPSK
WinWarbler
Zakanaka
PSK31-QPSK
PSK31 - BPSK
Sound Card Modes Software
X Internal
YPLOG
Internal
X Internal
Internal
X
http://www.digipan.net/
http://www.qsl.net/hamscope/
http://iz8bly.sysonline.it/
http://www.qsl.net/mmhamsoft/mmtty/
http://iz8bly.sysonline.it/
http://www.qsl.net/ae4jy/
http://www.qsl.net/winwarbler/
Logger http://www.qsl.net/kc4elo/
PSK mildlly
overdriven
occupies about
100+ Hz
PSK signal at 1450 is ok on drive level
but is creating spurs down every 300 Hz
probably has compression on or bad RF
feedback
PSK badly non linear,
occupies 1300 Hz and has
harmonic
and there is a
third harmonic
of the signal
Common Problems & Solutions
• Wide Signal
– Overdrive of audio on Tx, ALC or Compression on on Tx
• Hum on Signal
Signal at 1000 is
overdriven with multiples
of 31 Hz on either side of
center - about 185 Hz wide
– Needs shielding on cables
– Common mode noise, use transformers on both channels
– Ground all system components
• Harmonics of audio carrier
– ALC on, Compression on
– Transmitting outside of Tx bandpass
– Transmitting below 800 Hz audio offset
• Frequency offset between stations
– RIT is ON, or XIT is ON
– One of the transmitters has an offset
Common Problems & Solutions
• Signal Cutting In and Out
–
–
–
–
CPU too slow
Too many processes running on CPU and active processing
VOX is set too close to the signal level
Bad connection
• Strange signals mixed with a good psk signal
– Mute all sources on “Playback” except WAVE
• Sounds from the shack being transmitted, like typing
sounds, telephone ringing, etc.
– Mike is active
– Mike on PC is active (Mute it - see above)
6
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