WSJT (Amateur radio software)
Encyclopedia
WSJT is a computer program used for weak-signal
radio communication between amateur radio
operators
. The program was initially written by Joe Taylor, K1JT, but is now open source and is developed by a small team. The digital signal processing
techniques in WSJT make it substantially easier for amateur radio operators to employ esoteric propagation
modes, such as high speed meteor scatter and moonbounce
.
. This licensing change required substantial rewrites and took several months to complete. Although Joe Taylor was the original developer (and still acts as maintainer), several programmers are currently involved in writing the software. Currently, the program is written in Python
and C
, with several utilities written in Fortran
.
WSJT versions up through 7.06 r1933 (referred to as colloquially as WSJT7) and earlier were aggregations of previous versions, and as such WSJT7 contained 16 different modes (FSK441, JT6M, JT65 variants A - C, JT2, JT4 variants A - G, WSPR, and a preview of JT64A). As of version 8.0 (referred to as colloquially as WSJT8) the available modes changed completely such that WSJT8 now offers 5 different modes (JTMS, ISCAT, JT64A, JT8, and Echo) -- none of which are back-compatible with WSJT7 or earlier releases. This backwards-incompatibility includes JT64A, such that the preview release of JT64A in WSJT7 cannot communicate with the stable release of JT64A in WSJT8.
techniques; however, the communication modes rely upon different ionospheric propagation
modes and may be used on many different bands.
by the trails of meteors entering the Earth's atmosphere. The bursts of signal created by such trails are commonly referred to as “pings”, due to their characteristic sound. Such pings may be as short as a tenth of a second and carry enough information to complete at least one stage of a contact
. FSK441 employs multi-frequency shift keying using four tones, at a data rate of 441 baud
. Because of the choice of character codes in the protocol, it is self-synchronizing
and does not require an explicit synchronization tone. FSK441 is generally used on the 2-meter
and 70-centimeter
amateur bands. Contacts
may be made at almost any time (that is, a meteor shower
is not required to be in progress) at distances of up to 1400 miles (2250 km).
. The mode also employs multiple frequency-shift keying, but at 44 tones. One of the tones is a synchronization tone, leaving 43 tones to carry data (one tone per character in the character set, which includes alphanumeric
s and some punctuation
). The symbol rate
is 21.53 baud; the actual data rate as encoded for transmit is 14.4 characters per second. The mode is known for sounding "a bit like piccolo
music".
, or "moonbounce") paths. It can decode signals many decibels below the noise floor
, and can often allow amateurs to successfully exchange contact information without signals being audible to the human ear. Like the other modes, multiple-frequency shift keying is employed; unlike the other modes, messages are transmitted as atomic units after being compressed
and then encoded with a process known as forward error correction
(or "FEC"). The FEC adds redundancy to the data, such that all of a message may be successfully recovered even if some bit
s are not received by the receiver. (The particular code used for JT65 is Reed-Solomon.) Because of this FEC process, messages are either decoded correctly or not decoded at all, with very high probability. After messages are encoded, they are transmitted using MFSK with 65 tones.
Operators have also begun using the JT65 mode for contacts on the HF
bands, often using QRP
(very low transmit power); while the mode was not originally intended for such use, its popularity has resulted in several new features being added to WSJT in order to facilitate HF operation.
An article series on using JT65-HF appeared in CQ Amateur Radio's October & November 2010 issues.
Signal (electrical engineering)
In the fields of communications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
radio communication between amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators
Amateur radio operator
An amateur radio operator is an individual who typically uses equipment at an amateur radio station to engage in two-way personal communications with other similar individuals on radio frequencies assigned to the amateur radio service. Amateur radio operators have been granted an amateur radio...
. The program was initially written by Joe Taylor, K1JT, but is now open source and is developed by a small team. The digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
techniques in WSJT make it substantially easier for amateur radio operators to employ esoteric propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
modes, such as high speed meteor scatter and moonbounce
EME (communications)
Earth-Moon-Earth, also known as moon bounce, is a radio communications technique which relies on the propagation of radio waves from an Earth-based transmitter directed via reflection from the surface of the Moon back to an Earth-based receiver....
.
History
WSJT was originally released in 2001 and has undergone several major revisions. Communication modes have been both added and removed from the software over the course of its development. Since 2005, the software has been released as open source software under the GNU General Public LicenseGNU General Public License
The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU Project....
. This licensing change required substantial rewrites and took several months to complete. Although Joe Taylor was the original developer (and still acts as maintainer), several programmers are currently involved in writing the software. Currently, the program is written in Python
Python (programming language)
Python is a general-purpose, high-level programming language whose design philosophy emphasizes code readability. Python claims to "[combine] remarkable power with very clear syntax", and its standard library is large and comprehensive...
and C
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
, with several utilities written in Fortran
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
.
WSJT versions up through 7.06 r1933 (referred to as colloquially as WSJT7) and earlier were aggregations of previous versions, and as such WSJT7 contained 16 different modes (FSK441, JT6M, JT65 variants A - C, JT2, JT4 variants A - G, WSPR, and a preview of JT64A). As of version 8.0 (referred to as colloquially as WSJT8) the available modes changed completely such that WSJT8 now offers 5 different modes (JTMS, ISCAT, JT64A, JT8, and Echo) -- none of which are back-compatible with WSJT7 or earlier releases. This backwards-incompatibility includes JT64A, such that the preview release of JT64A in WSJT7 cannot communicate with the stable release of JT64A in WSJT8.
Communication modes provided
The software carries a general emphasis on weak-signal operation and advanced DSPDigital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
techniques; however, the communication modes rely upon different ionospheric propagation
Radio propagation
Radio propagation is the behavior of radio waves when they are transmitted, or propagated from one point on the Earth to another, or into various parts of the atmosphere...
modes and may be used on many different bands.
FSK441
FSK441, introduced in 2001 as the first communications mode included with WSJT, is designed to support communication using streaks of radio-reflecting ions created in the ionosphereIonosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
by the trails of meteors entering the Earth's atmosphere. The bursts of signal created by such trails are commonly referred to as “pings”, due to their characteristic sound. Such pings may be as short as a tenth of a second and carry enough information to complete at least one stage of a contact
Amateur radio contact
An amateur radio contact, more commonly referred to as simply a "contact", is an exchange of information between two amateur radio stations. The exchange usually consists of an initial call, a response by another amateur radio operator at an amateur radio station, and possibly a signal report. A...
. FSK441 employs multi-frequency shift keying using four tones, at a data rate of 441 baud
Baud
In telecommunications and electronics, baud is synonymous to symbols per second or pulses per second. It is the unit of symbol rate, also known as baud rate or modulation rate; the number of distinct symbol changes made to the transmission medium per second in a digitally modulated signal or a...
. Because of the choice of character codes in the protocol, it is self-synchronizing
Self-synchronizing code
In telecommunications, a self-synchronizing code is a line code in which the symbol stream formed by a portion of one code word, or by the overlapped portion of any two adjacent code words, is not a valid code word...
and does not require an explicit synchronization tone. FSK441 is generally used on the 2-meter
2 meters
The 2-meter amateur radio band is a portion of the VHF radio spectrum, comprising frequencies stretching from 144.000 MHz to 148.000 MHz in International Telecommunication Union region Regions 2 and 3 and from 144.000 MHz to 146.000 MHz in ITU Region 1...
and 70-centimeter
70 centimeters
The 70-centimeter amateur radio band is a portion of the UHF radio spectrum. This band is used by amateurs engaged in emergency communications where portable and mobile radios are frequently used. Many such radios have dual-band capabilities, operating on both the 70-centimeter and 2-meter bands.-...
amateur bands. Contacts
Amateur radio contact
An amateur radio contact, more commonly referred to as simply a "contact", is an exchange of information between two amateur radio stations. The exchange usually consists of an initial call, a response by another amateur radio operator at an amateur radio station, and possibly a signal report. A...
may be made at almost any time (that is, a meteor shower
Meteor shower
A meteor shower is a celestial event in which a number of meteors are observed to radiate from one point in the night sky. These meteors are caused by streams of cosmic debris called meteoroids entering Earth's atmosphere at extremely high speeds on parallel trajectories. Most meteors are smaller...
is not required to be in progress) at distances of up to 1400 miles (2250 km).
JT6M
JT6M, introduced in late 2002, is intended for meteor scatter and other ionospheric scattering of signals, and is especially optimized for the 6-meter band6 meters
The 6-meter band is a portion of the VHF radio spectrum allocated to amateur radio use. Although located in the lower portion of the VHF band, it nonetheless occasionally displays propagation mechanisms characteristic of the HF bands. This normally occurs close to sunspot maximum, when solar...
. The mode also employs multiple frequency-shift keying, but at 44 tones. One of the tones is a synchronization tone, leaving 43 tones to carry data (one tone per character in the character set, which includes alphanumeric
Alphanumeric
Alphanumeric is a combination of alphabetic and numeric characters, and is used to describe the collection of Latin letters and Arabic digits or a text constructed from this collection. There are either 36 or 62 alphanumeric characters. The alphanumeric character set consists of the numbers 0 to...
s and some punctuation
Punctuation
Punctuation marks are symbols that indicate the structure and organization of written language, as well as intonation and pauses to be observed when reading aloud.In written English, punctuation is vital to disambiguate the meaning of sentences...
). The symbol rate
Symbol rate
In digital communications, symbol rate is the number of symbol changes made to the transmission medium per second using a digitally modulated signal or a line code. The Symbol rate is measured in baud or symbols/second. In the case of a line code, the symbol rate is the pulse rate in pulses/second...
is 21.53 baud; the actual data rate as encoded for transmit is 14.4 characters per second. The mode is known for sounding "a bit like piccolo
Piccolo
The piccolo is a half-size flute, and a member of the woodwind family of musical instruments. The piccolo has the same fingerings as its larger sibling, the standard transverse flute, but the sound it produces is an octave higher than written...
music".
JT65
JT65, developed and released in late 2003, is intended for extremely weak but slowly-varying signals, such as those found on troposcatter or Earth-Moon-Earth (EMEEME (communications)
Earth-Moon-Earth, also known as moon bounce, is a radio communications technique which relies on the propagation of radio waves from an Earth-based transmitter directed via reflection from the surface of the Moon back to an Earth-based receiver....
, or "moonbounce") paths. It can decode signals many decibels below the noise floor
Noise floor
In signal theory, the noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where the noise is defined as any signal other than the one being monitored....
, and can often allow amateurs to successfully exchange contact information without signals being audible to the human ear. Like the other modes, multiple-frequency shift keying is employed; unlike the other modes, messages are transmitted as atomic units after being compressed
Data compression
In computer science and information theory, data compression, source coding or bit-rate reduction is the process of encoding information using fewer bits than the original representation would use....
and then encoded with a process known as forward error correction
Forward error correction
In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels....
(or "FEC"). The FEC adds redundancy to the data, such that all of a message may be successfully recovered even if some bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
s are not received by the receiver. (The particular code used for JT65 is Reed-Solomon.) Because of this FEC process, messages are either decoded correctly or not decoded at all, with very high probability. After messages are encoded, they are transmitted using MFSK with 65 tones.
Operators have also begun using the JT65 mode for contacts on the HF
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
bands, often using QRP
QRP operation
In amateur radio, QRP operation means transmitting at reduced power levels while aiming to maximize one's effective range while doing so. The term QRP derives from the standard Q code used in radio communications, where "QRP" and "QRP?" are used to request, "Reduce power," and ask "Should I reduce...
(very low transmit power); while the mode was not originally intended for such use, its popularity has resulted in several new features being added to WSJT in order to facilitate HF operation.
Alternative Software for JT65
There are alternative software packages available for JT65 including MultiPSK (a commercial package developed by F6CTE), and JT65-HF (a freeware package developed by W6CQZ). The JT65-HF software may be obtained from Sourceforge.An article series on using JT65-HF appeared in CQ Amateur Radio's October & November 2010 issues.
External links
- Official WSJT website
- Official WSJT open source project information
- Get ready for 2m EME communications. A step by step beginners guide.
- K3UK's "Bozo's Guide to HF JT65A": a tutorial on how to properly operate WSJT for JT65 use on the HF bands
- WSJT manuals (in different languages available)
- N0UK's web-based chat for coordinating terrestrial JT65 skeds: chat site where operators may coordinate with each other in order to arrange "skeds", or scheduled contacts
- W6DTW blog article on using JT65A for extreme DX on HF bands
- W6DTW blog article on the resurgence in popularity of JT65A on HF
- JT65 frequency and JT65A frequencies for HF band DX information page; 30 metres, 20 metres, etc.
- JT65A and JT65-HF Introduction with PDF articles download and frequencies