Work the World with WSJT-X, Part 2:
Codes, Modes, and Cooperative
Software Development
Here’s how the weak-signal digital protocols in WSJT-X work,and an overview of how their software is developed.
Joe Taylor, K1JT, Steve Franke,
K9AN, and Bill Somerville, G4WJSPart 1 of this two-part article covered
topics that highlight the capabilities of
weak-signal communication program
WSJT-X.1 This software package provides tools for a wide range of Amateur Radio activities including
low-power DXing, meteor scatter,
moonbounce, and precise frequency
measurement — all of them possible
with relatively modest station equipment. Based on modern communication and information theory, the
WSJT-X protocols and software canboost your signal’s effective reach by
the rough equivalent of 10 – 15 dB ofadded signal strength.

We have found that many other hams
would like to have a deeper understanding of how these weak-signal
protocols work, and how they weredeveloped. We hope this article satisfies that desire.

Digital Communication
Fundamentals
Digital communication conveys digital
information from an originating source
to one or more destinations. Here thedigital information is modulated onto a
carrier and transferred over a radio
channel. The basic unit of transmitted
data is a channel symbol. The symbols
represent numbers, in turn comprisedof bits. The modulator may transmit m
information bits in each symbol, using
This concluding Part 2 outlines some
2m different waveforms to represent
digital communication theory fundasymbol values from 0 up to 2m – 1.
The different waveforms
might have distinct ampliDigital communication conveys digital tudes,
phases, frequeninformation from an originating
cies, or shapes. The
source to one or more destinations.
WSJT-X waveforms are
made of sinusoids withconstant amplitude. The
mentals, including examples to make
MSK144 protocol uses Offset Quadrathe discussion accessible to most ama- ture Phase-Shift Keying (OQPSK)
teurs. We compare the eight weak-sig- with waveforms shaped to maintain anal protocols in WSJT-X and explain
constant envelope. All other modes use
how their impressive performance isfrequency-shift keying (FSK), with aachieved. Finally, we describe thedifferent tone frequency to represent
tools and informal cooperative praceach allowed symbol value. Binary
tices used for creating the WSJT-X
modulation (m = 1) implies transmitsoftware. We think it’s important thatting one bit at a time. Modulation
dedicated enthusiasts devote theirschemes with larger m are used to analgorithmic and programming skills
advantage in all but one of the WSJT-X
and interests to the good of the hobby. modes.

Important benefits can be gained byadding controlled redundancy to a digital message so that transmission errors
can be recognized and corrected. Simple repetition of each symbol is a trivial form of redundancy. But much
more powerful redundancy can bearranged by mapping each sequence ofk message symbols in a controlled way
into a unique and longer sequence ofn symbols called a codeword. This
technique is called forward error correction (FEC). The WSJT-X protocols
use block codes in which the values ofn and k are fixed, and labeled as (n,k)
codes. An integer parameter q can beused to define the range of available
symbol values for a code, analogous
to the m we used for modulation
schemes. Parameter Q = 2q is thenreferred to as the alphabet size of thecode. The code symbol values range
from 0 up to Q – 1, and each codeword
conveys kq message bits. The amountof redundancy is characterized by theratio n/k, and its reciprocal k/n is thecode rate. The mathematics underlying design of such k-to-n mapping
schemes and their corresponding n-tok reverse transformations forms amajor branch of modern communication theory.
Reception of transmitted symbols
requires accurate synchronization oftime and frequency between transmitting and receiving stations. To makethis possible with typical amateur station equipment, each WSJT-X protocol
includes a unique synchronizing pat-

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November 2017   1

tern: a sequence of known symbols
interspersed with those carrying message information. The software
demodulation algorithm starts by looking for the known pattern, thereby
determining any frequency and timeoffset, as well as the locations ofboundaries between received symbols.
Specifically, the JT65 mode uses a(63,12) code with q = 6 and thus
Q = 2q = 64. Its code rate is k/n = 0.19,
and its modulation uses m = 6 and thus
2m = 64 tone frequency-shift keying,
with one additional tone used forsynchronization.
Let’s divide the process of transmission and reception into a sequence ofindependent steps (see Figure 1). The
steps correspond roughly to identifiable blocks of the WSJT-X sourcecode. Steps 1 – 5 take place at thetransmitting station, and steps 6 – 9 at
the receiving end.
1) Generate a message.
2) Compress message to k symbols ofq bits per symbol.
3) Add error-correcting redundancy to
produce codeword of n symbols.
4) Add synchronizing pattern andmodulate onto a carrier.
5) Transmit modulated waveform overa radio channel.

User message

Source encode6) Receive, synchronize, and demodulate to yield n symbols, some of whichmight be in error.
7) Decode n received symbols torecover k error-free message symbols.
8) Decompress k symbols to recoveroriginal message in human-readable
form.
9) Deliver message to receiving user.
The most crucial are steps 3 and 7.
Step 7 likely requires the most computational resources.
When developing a protocol, we want
to choose an efficient code that maximizes the probability of recoveringtransmitted messages even when thereceived codeword is corrupted. It’s
also important to consider likely types
of fading, Doppler spread, and interference that may occur on the targeted
propagation paths. We need an efficient decoding algorithm that can be
executed in reasonable computing time
and will ensure that false decodes arerare.
The WSJT-X Protocols
Message Structure
Steps 2 and 8 involve lossless compression and decompression of data.
This process is called source encoding
the message. WSJT-X protocols JT4,
JT9, JT65, QRA64, and MSK144 alluse structured messages that source-

FEC encode

Modulation

Transmission
channelMessage to user

Source decode

FEC decode

Demodulation
QS1711-Taylor01

Figure 1 — Block diagram showing steps in a typical digital communication system.

2   November 2017

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encode human-readable information
for basic contacts into packets ofexactly kq = 72 bits. The packets contain two 28-bit fields normally used forcall signs and a 15-bit field for a grid
locator, signal report, acknowledgment, or 73. One additional bit is used
to flag packets encoding arbitraryalphanumeric text, up to 13 characters.
Special cases allow efficient encodingof other information, such as add-on
call sign prefixes (ZA/KA2ABC) or
suffixes (G8XYZ/P). The aim is tocompress the most common messages
used for minimal contacts into fixedlength 72-bit packets. FT8 uses similarsource encoding, but provides additional flexibility and room for growthby adding three extra bits that can beused to define up to 14 enhanced message types.
Why 28 bits for a call sign, and 15 fora grid locator? A standard amateur callsign consists of a one- or two-character
prefix, at least one of which must be aletter, followed by a digit and a suffix
of one to three letters. Within theserules, the number of possible call signs
equals 37 × 36 × 10 × 27 × 27 × 27, orsomewhat over 262 million. The numbers 27 and 37 arise because in thefirst and last three positions a charactermay be absent, or a letter, or perhaps adigit. Because 228 is greater than 268
million, 28 bits are enough. Similarly,
the number of four-digit Maidenhead
grid locators on Earth is 180 × 180 =
32,400, which is less than 215, so a grid
locator can be encoded uniquely with
15 bits.
More than six million of the possible
28-bit values are not needed for standard call signs. A few of these slots
have been assigned to special message
components, such as CQ, DE, and
QRZ. CQ may be followed by three
digits to indicate a desired call-backfrequency. In the meteor-scatter mode
MSK144, if KA2ABC transmits on
say 50.260, and sends the message“CQ 290 KA2ABC FN20,” it meanswww.arrl.org  that he or she will listen on 50.290 and
respond there to any replies. A numerical signal report of the form ±xx orR±xx can be sent in place of a grid
locator. As originally defined in JT65
mode, the numerical signal report values “xx” lie in the range –30 to–01 dB. Recent program versions
accommodate reports between –50 and+49 dB for all modes except JT65. A
country prefix or portable suffix may
be attached to one of the call signs.
When this compound call sign featureis used, the additional information issent in place of the grid locator, or byusing some of the six million available
slots mentioned above.

Figure 2 — Simulated signals for an unmodulated carrier, a 25 WPM CW signal, and the WSJTX slow modes WSPR, JT9, JT4, FT8, QRA64A, and JT65. The slow modes are shown in their“A” submode, in increasing order of occupied bandwidth. All signals have S/N of –10 dB in a
2,500 Hz reference bandwidth. The vertical extent of the waterfall corresponds to 50 seconds.
Two successive FT8 transmissions are shown.

use by Phil Karn, KA9Q.2,3 These areamong the best-known types of errorcorrecting codes, and they have beenstudied thoroughly for over half a cenOur compression algorithm supports
tury. Our latest modes use state-of-themessages starting with CQ AA
art codes that are close to the forefront
through CQ ZZ. Such messages areof this research field. MSK144 andFT8 use low-density parity checkWe want to choose an efficient code that(LDPC) codes and
QRA64 a Q-ary
maximizes the probability of recovering
repeat-accumulatetransmitted messages even when the(QRA) code, a parreceived codeword is corrupted.
ticular type of nonbinary LDPC code.
Full technicalencoded by sending the pseudo-callspecifications for each mode can besigns E9AA through E9ZZ in place of found in the WSJT-X User Guide andthe first call sign of a standard mesour openly available source code.4, 5
sage. Upon reception, these calls are
Protocol Details for Slow Modes
converted back to the form CQ AA
Figure 2 shows an example of eachthrough CQ ZZ. This allows users toslow mode on the WSJT-X waterfall
send directed CQ messages, such as
display. This also includes an unmoduCQ DX, CQ EU, or CQ VT.
lated carrier and a 25 WPM CW sigError-Correcting Codes
nal. The signals were generated with a
Different codes, modulation schemes,
key-down signal-to-noise ratio ofand synchronizing patterns have been
–10 dB in a 2,500 Hz reference bandadopted for each protocol in WSJT-X.
width. Among the WSJT-X modes,
The goal has been to optimize each
WSPR has the narrowest occupiedmode’s effectiveness for a particular
bandwidth, 5.9 Hz, and JT65 has thetype of propagation. To some extent,
widest at 177.6 Hz. JT4, JT9, JT65,
the final code choices also reflect ourand QRA64 use 1-minute timed
own incomplete but growing familiarsequences of transmission and recepity with historical developments intion, synchronized approximately with
communication theory. JT65 uses aUTC. FT8 uses 15-second sequences,Reed-Solomon code, and JT4, JT9, and and WSPR uses 2 minutes.
WSPR all use a robust convolutional
Some design parameters of the slow
code, first implemented for ham radiomodes are summarized in Table 1. The
type of FEC is denoted by LDPC for
low-density parity check, C for convolutional, RS for Reed-Solomon, and
QRA for Q-ary repeat-accumulate.
Chosen keying rates make the lengthof a transmission approximately
13 seconds for FT8 and 48 seconds forthe other modes. For JT4, JT9, JT65,
and QRA64, this leaves plenty of timeat the end of a transmission for a message to be decoded and the receiving
operator to decide how to reply, before
the start of the next minute. With
15-second T/R sequences, FT8 ismuch more tightly constrained. An
optional auto-sequencing featureallows the software to generate suitable messages in response to received
information. Exact values for keying
rates were chosen so that at 12,000
samples per second the number of digital samples per channel symbol is an
integer with no prime factor greaterthan 7. This advantageous choicemakes some of the digital signal processing algorithms more efficient.
In the following, modes are describedin chronological order of their development: JT65 was first introduced in
2003, JT4 in 2007, WSPR in 2008,
JT9 in 2012, QRA64 in 2016, and FT8
in 2017.
JT65 — A detailed description of theJT65 protocol was published in QEX.6
Half of its channel symbols are used
for synchronization, using a pseudo-

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Table 1: Parameters of the Slow WSJT-X Protocols
Bandwidths (BW) are for the narrowest submodes. S/N threshold is referenced to a 2,500 Hz bandwidth
at a 50% probability for decoding of an unfading signal.
Mode

FEC typeqm
Modulation(n,k)			Keying rate, BW, Hz
baud		

Sync energy
TX duration, s		S/N threshold,
dB

FT8
JT4
JT9
JT65
QRA64
WSPR

LDPC(174,87)
C(206,72)
C(206,72)
RS(63,12)
QRA(63,12)
C(162,50)

6.250
4.375
1.736
2.692
1.736
1.465

0.27
0.50
0.19
0.50
0.25
0.50

–20
–23
–27
–25
–26
–28

13
12
1 3#
6 6#
66
12

8-FSK
4-FSK
9-FSK
65-FSK
64-FSK
4-FSK

50.0
17.5
15.6
177.6
111.1
5.9

12.6
47.1
49.0
46.8
48.4
110.6

#Modulation includes one additional tone used for synchronization.

random pattern at the lowest tone frequency. The other symbols carry
encoded information using 2m = 64different tones. Special features (usedonly for Earth-Moon-Earth — EME)
can convey the EME-style “OOO” signal report and short messages interpreted as RO, RRR, and 73. EME
submodes JT65B and JT65C use tone
spacings two and four times larger
than JT65A. JT65 has become very
popular for low-power DXing at MF
and HF, as well as for EME on VHF
and higher bands.
JT4 — Each channel symbol carries
one information bit (the most significant bit) and one synchronizing bit.
Thus, 50% of the transmitted energy isdevoted to synchronization. Submodes
JT4A through JT4G have tone spacings at increasing multiples 1, 2, 4, 9,
18, 36, and 72 times the keying rate of
4.375 baud. The wider submodes areuseful on propagation paths with large
Doppler spread. For example, JT4F isfrequently used for EME communication on the 10 GHz band.
WSPR — Designed as a propagation
probe rather than for making two-way
contacts, it differs from other WSJT-X
slow modes by using message lengths
k = 50 bits and 2-minute T/Rsequences. Message packets normally
include a 28-bit call sign, a 15-bit grid
locator, and seven bits to convey transmitter power in dBm. Alternative formats can convey a compound call sign
4   November 2017

and/or a six-digit grid locator, using a
two-transmission sequence. Typical
WSPR usage was described in QST.7
JT9 — Eight tone frequencies are used
to convey message information, andone additional tone is used for synchronization. The slow submodes
JT9A-H have tone spacings at multiples 1, 2, 4, 8, 16, 32, and 64 times the
1.736-baud keying rate. JT9A (often
called simply JT9) uses less than 10%of the bandwidth of JT65, and forsteady, undistorted signals is about
2 dB more sensitive than JT65. For
these reasons, JT9 is popular for lowpower DXing on crowded HF bands.
QRA64 — An experimental mode

intended for EME and other extreme
weak-signal paths. Its internal code8
was designed by Nico Palermo,
IV3NWV. Synchronization is accomplished by using three 7 × 7 Costas
arrays.9 Submodes QRA64A-E use
tone spacings 1, 2, 4, 8, and 16 times
the 1.736-baud keying rate. Early tests
have shown QRA64A to be very effective for weak-signal work at MF and
HF, and for EME on the VHF andUHF bands. The wider submodes
QRA64C-E work extremely well for
EME on microwave bands up to
24 GHz.
FT8 — Designed especially for propagation conditions, such as multi-hop

Figure 3 — Screenshot of the PSK Reporter website using decoded FT8 transmissions to show
summertime multi-hop sporadic-E paths on 50 MHz around 1500 UTC on July 28, 2017.

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Table 2: Parameters of the Fast WSJT-X Protocols
MSK144-Sh is the optional short-message format in the MSK144 protocol.
Mode

FEC type (n,k)

qm

Mod

ISCAT-A
ISCAT-B
JT9E
JT9F
JT9G
JT9H
MSK144
MSK144-Sh——
C(206,72)
C(206,72)
C(206,72)
C(206,72)
LDPC(128,80)
LDPC(32,16)

—
—
1 3#
1 3#
1 3#
1 3#
11
11

42-FSK
42-FSK
9-FSK
9-FSK
9-FSK
9-FSK
OQPSK
OQPSK

Keying rate, baud

BW, HzSync energy

Message duration, s

21.5
43.1
25
50
100
200
2,000
2,000

905
1809
225
450
900
1800
2400
2400

0.17
0.17
0.19
0.19
0.19
0.19
0.11
0.20

1.176
0.588
3.400
1.700
0.850
0.425
0.072
0.020

#Modulation includes one additional tone used for synchronization.

baud, so the frame duration is 72 ms.
Compared to FSK441, the mode
widely used for digital meteor-scatter
since its introduction11 in
2001, MSK144 has the
The WSJT-X fast modes takeadvantages of strong
error correction, an effecadvantage of brief propagation
tive character transmisenhancements that bring a signal upsion rate about 1.7 times
to useful levels for a very short time.
faster, and significantly
better sensitivity.
MSK144 has rapidly
become the dominant mode for amaISCAT has proven especially usefulteur meteor-scatter contacts.
for making aircraft-scatter contacts on
the microwave bands.
Decoders and Sensitivities
JT9 Fast — Submodes JT9E-H differ
Together with additional details pubfrom their slow counterparts by using
lished in the WSJT-X User Guide andmuch faster keying rates. Otherwise
the open source code, Tables 1 and 2
the coding, modulation, and synchroand the preceding paragraphs define
nization schemes are the same as forthe various protocols supported in
the slow JT9 modes. JT9 fast modes
WSJT-X. For these protocols to be usehave proven useful for such propagaful, each one needs an efficienttion types as ionospheric scatter anddecoder. The algorithms we have
Protocol Details for Fast Modes weak double-hop sporadic E on theimplemented use soft-decision decod6-meter
band.
ing, and to the best of our knowledge,
The WSJT-X fast modes take advanthey are the most sensitive practicaltage of brief propagation enhanceMSK144 — FEC is implemented byalgorithm for each code. For JT4, JT9,
ments that bring a signal up to usefulaugmenting the 72 message bits withand WSPR, we use the Fano algolevels for a very short time. Keying
an eight-bit CRC calculated from therates and occupied bandwidths aremessage bits. The resulting 80-bit aug- rithm, as implemented by KA9Q (seeNote 3), and for JT65 we use themuch larger than for the slow modes,
mented message is mapped to aFranke-Taylor algorithm, recently pubbecause we want full messages to be
128-bit codeword using a (128, 80)
lished in QEX.12 There is a fullconveyed in a very short time. Table 2
LDPC code designed by K9AN spelists the essential parameter values forcifically for this purpose. Two eight-bit description of the QRA64 decoder,written by IV3NWV (see Note 8), andthese modes. The last column gives the synchronizing sequences are added to
we expect to publish details of thetime required to transmit a message
make a message frame 144 bits long.
MSK144 and FT8 decoders soon.
once. In these modes, the transmitted
Modulation is Offset Quadrature
information is repeated for the fullPhase-Shift Keying (OQPSK) at 2,000 Usage patterns of FT8, JT9, JT65, andduration of a T/R sequence.

sporadic E at 50 MHz — circumstances where signals are weak andfading, openings short, and quick completion of reliable, confirmable contacts is particularly desirable. Timedsequences for transmission and reception are 15 seconds rather than 1 minute. Shorter transmissions mean that
FT8 is about 6 dB less sensitive (forsteady signals) than it would be if its
duration was commensurate with theother slow modes. Message packets
include 75 information bits and a
12-bit cyclic redundancy check (CRC)that helps to ensure a very low false
decode rate. Modulation uses eighttone FSK at 6.25 baud, and synchronization uses three 7 × 7 Costas arrays.
As suggested by a snapshot from thePSK Reporter 10 website (see Figure3), FT8 has become popular very
quickly after its introduction in earlysummer of 2017.

ISCAT — Messages are free-form, up
to 28 characters in length. The protocol uses no FEC other than repetition.

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November 2017   5

WSPR makes it advantageous for the
decoders to focus not just on a single
frequency, but on a frequency range
covering several kilohertz. Our decoders are organized to scan a range of
frequencies up to 5 kHz, if the receiving hardware supports it, finding all
signals in the specified mode anddecoding and displaying the results.
For FT8, JT65, and WSPR, the present
decoders go one step further, taking
advantage of the fact that when a signal with strong FEC has been decoded,
we can calculate its transmitted waveform exactly. An amplitude-scaled version of that waveform can be
subtracted from the received data andthe decoder executed on the remainder,
thereby possibly decoding weaker, previously hidden signals. This approachhas proved very effective. In thesemodes, WSJT-X frequently decodes
weak signals lying within 1 or 2 Hz ofmuch stronger ones.
The various WSJT-X modes have better sensitivity than traditional modes
such as CW for three main reasons:
They use efficient modulation schemes
tailored to the targeted types of propagation; they use detection bandwidths
matched to the protocol keying rate,
and they benefit from coding gain provided by each specific error-correcting
code. Table 1 shows detection bandwidths for the slow modes range fromabout 1.5 Hz – 6 Hz. Noise power is
proportional to bandwidth, so each of
the slow modes has an advantage of
10 dB or more when compared to thetypical 50 Hz “ear-and-brain” bandwidth of the very best weak-signal
human CW operators.
The MSK144 decoder cannot use suchnarrow bandwidths because the signal
is roughly 2.4 kHz wide. However, it
can use coherent detection. Meteorscatter signals generally maintain signal coherence over the duration of aping. Our MSK144 decoder measuresa received signal frequency and phasewith enough accuracy to maintain6   November 2017

coherence over half a dozen or more of
the protocol’s 72 ms frames. So, theout-of-phase noise power can berejected and we gain 3 dB over noncoherent detection for single-frame
decodes, and up to 7 dB for sevenframe averages.
Summary
Additional details of the software engineering and development effort, as
well as a description of the computing
hardware and platforms, is available
on the QST-in-Depth web page at
www.arrl.org/qst-in-depth.
We hope that our description of thecapabilities of WSJT-X and its development process will inspire others to join
in and contribute to future developments in digital communication techniques for Amateur Radio. We
ourselves have many ideas that have
not yet reached fruition, but may do soin the future.
Many people have contributed to thedevelopment and success of WSJT-X.
We particularly wish to thank Greg
Beam, KI7MT, whose JTSDK software development kit has helped many
WSJT-X users build the program forthemselves, from the source code; andDr. C.W. Suckling, G3WDG; Roger
G. Sturtevant, VE1SKY; Rex Moncur,
VK7MO, and Roger B. Rehr, W3SZ,
for comments that helped us to
improve an early draft of this article.
Notes

1 Joe Taylor, K1JT, Steve Franke, K9AN, and Bill

Somerville, G4WJS, “Work the World with
WSJT-X, Part 1,” QST Oct. 2017, pp. 30-36.
2For more details about convolutional codes,
see https://en.wikipedia.org/wiki/
Convolutional_code#History.
3Phil Karn, KA9Q, www.ka9q.net/papers/cnc_
coding.html.
4www.physics.princeton.edu/pulsar/K1JT/
wsjtx-doc/wsjtx-main-1.7.1-devel.html
5physics.princeton.edu/pulsar/k1jt
6Joe Taylor, K1JT, “The JT65 Communications
Protocol,” QEX, Sept./Oct. 2005, p. 3.
7Joe Taylor, K1JT, and Bruce Walker, W1BW,“WSPRing Around the World,” QST Nov. 2010,
p. 30.
8Nico Palermo, IV3NWV, “Q-ary Repeat-Accumulate Codes for Weak Signals Communications,” microtelecom.it/qracodes/
QRACodes-Rev10.pdf.
9https://en.wikipedia.org/wiki/Costas_array

ARRL, the national association for Amateur Radio®

10Philip Gladstone, N1DQ, https://pskreporter.

info/pskmap.

11Joe Taylor, K1JT, “WSJT: New Software for

VHF Meteor-Scatter Communication,” QST,
Dec. 2001, pp. 36 – 41.
12Steven J. Franke, K9AN, and Joseph H. Taylor,
K1JT, “Open Source Soft-Decision Decoder
for the JT65 (63,12) Reed-Solomon Code,”
QEX, May/Jun. 2016, pp. 8 – 17.

Joe Taylor was first licensed as KN2ITP in
1954, and has since held call signs K2ITP,WA1LXQ, W1HFV, VK2BJX, and K1JT. He
was Professor of Astronomy at the Universityof Massachusetts from 1969 to 1981, andsince then Professor of Physics at Princeton
University, serving there also as Dean of theFaculty for 6 years. He was awarded theNobel Prize in Physics in 1993 for discoveryof the first orbiting pulsar, leading to observations that established the existence of gravitational waves. After retirement, he has been
busy developing and enhancing digital protocols for weak-signal communication by Amateur Radio, including JT65 and WSPR. He
chases DX from 160 meters through themicrowave bands. You can reach Joe at
joe@princeton.edu.
Steve Franke, K9AN, holds an Amateur Extra
class license. He was first licensed in 1971
and has previously held call signs WN9IIQ
and WB9IIQ. An early and abiding fascination
with radio science led to his current positionas Professor of Electrical and Computer
Engineering at the University of Illinois in
Urbana-Champaign. Steve is a member of
ARRL and a Fellow of the IEEE. You canreach Steve at s.j.franke@icloud.com.
Bill Somerville, G4WJS, read Chemistry at
the University of Bristol in the UK, graduating
in 1978 with a Bachelor of Science degree.
Since graduating, he has worked in computer
software and hardware in a variety of industries including defense, software vendors,
and financial services, more recently as afreelance consultant providing systems programming and related services to mid- tolarge-size software tool vendors. Bill has
been an active radio amateur since 1981,
holding the calls G6IJU and G4WJS. He
enjoys HF and VHF bands, contest operating,and DX chasing using CW, phone, and data
modes. He is a keen walker and swimmer. Bill
participates in open-source software projects
for Amateur Radio, with WSJT-X being thelargest contribution. Bill is happy to provide
input, drawing on his extensive software engineering experience, to help those with otherimportant domain skills provide robust, professional standard, software-based AmateurRadio communication tools. You can reachBill at bill.8@classdesign.com.

For updates to this article,
see the QST Feedback page at
www.arrl.org/feedback.

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