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
1
0.1
0.01
RTTY
Error Rate
3
1  10
4
1  10
PSK-31
5
1  10
6
1  10
7
1  10
8
1  10
9
1  10
10
1  10
0
5
10
15
20
Signal to Noise Ratio (dB)
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
Phase changes
Phase changes
180º out
PSK31 Encoding

A “0” is sent as a 180º phase shift

A “1” is sent as no phase shift
0




1
1
0
0
0
0
1
1
0
0
0
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 Varicode Alphabet
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
1111101
11101011
10101101
10110101
1110111
11011011
11111101
101010101
1111111
111111101
101111101
11010111
10111011
11011101
10101011
11010101
111011101
10101111
1101111
1101101
101010111
110110101
101011101
101011101
101110101
101111011
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z
1011
1011111
101111
101101
11
111101
1011011
101011
1101
111101011
10111111
11011
111011
1111
111
111111
110111111
10101
10111
101
110111
1111011
1101011
11011111
1011101
111010101
SP
1
0
1
2
3
4
5
6
7
8
9
10110111
10111101
11101101
11111111
101110111
101011011
101101011
110101101
110101011
110110111
Worth
noting:
Really
Short
Also: Typing ALL IN
CAPS will actually slow
you down! ☺
!
"
#
$
%
&
'
(
)
*
+
,
.
/
:
;
<
=
>
?
@
[
\
]
^
_
.
/
{
|
}
~
111111111
101011111
111110101
111011011
1011010101
1010111011
101111111
11111011
11110111
101101111
111011111
1110101
110101
1010111
110101111
11110101
110111101
111101101
1010101
111010111
1010101111
1010111101
1010101101
111110111
111101111
111111011
1010111111
101101101
1011011111
1010110111
110111011
1010110101
1011010111
NUL
SOH
STX
ETX
EOT
ENQ
ACK
BEL
BS
HT
LF
VT
FF
CR
SO
SI
DLE
DC1
DC2
DC3
DC4
NAK
SYN
ETB
CAN
EM
SUB
ESC
FS
GS
RS
US
DEL
1010101011
1011011011
1011101101
1101110111
1011101011
1101011111
1011101111
1011111101
1011111111
11101111
11101
1101101111
1011011101
11111
1101110101
1110101011
1011110111
1011110101
1110101101
1110101111
1101011011
1101101011
1101101101
1101010111
1101111011
1101111101
1110110111
1101010101
1101011101
1110111011
1011111011
1101111111
1110110101
PSK31 - Operating
Mic
Line out
Sound card
Line in
Audio out
PSK31 - Operating
Mic
Line out
Sound card
Line in
100k
Audio out
1k
Bit of attenuation often helps.
Some people do clever stuff
with isolation transformers,
capacitative DC blocking,
opto-isolators, etc.
PSK31 - Operating
Mic
Line out
Sound card
Line in
100k
Audio out
1k
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
Mic
Line out
Sound card
Line in
100k
Audio out
1k
PTT via regular CAT cable
(same one you use for rig
control, programming
memories etc)
PSK31 - Operating
2N2222
22k
PTT
Serial
RTS
1N4148
Mic
Line out
Sound card
Line in
100k
Audio out
1k
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




SOFTWARE!






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
This is what
we'll be using
for the demo




SOFTWARE!






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 Frequencies
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

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1.83815 MHz
3.58015 MHz
7.035 MHz
10.13715 MHz
14.07015 MHz
18.10015 MHz
21.070 MHz
24.920 MHz
28.07015MHz
50.290 MHz
7.07015MHz
21.08015MHz
28.12015 MHz
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 timeslot (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
Mic
Line out
Sound card
Line in
100k
Audio out
1k
EXACTLY THE
SAME AS PSK-31!*
*(Just different software)
WSPR


Software:
http://www.physics.princeton.edu/pulsar/K1JT/
Reports:
http://wsprnet.org/
http://wsprnet.org/olddb?findcall=VE3IC&findreporter=VE3IC

Who's on the air?
http://wsprnet.org/drupal/wsprnet/activity
WSPR - Demo
QUESTIONS?
THANKS!

This presentation is at:
http://noseynick.net/va3nnw/PSK-talk/