Working the World with WSJT-X (JT-65 & JT-9)
What are the WSJT modes of JT65 & JT9
 Both are digital modes optimized for extremely weak signal communications.
 JT65 uses a series of 64 tones for data plus a sync tone.
 JT9 uses a series of 8 tones for data plus a sync tone (modulation 9-FSK)
 Hardware requirements are a computer, computer to radio interface, and a
SSB transceiver that will operate on your frequency of choice.
Note: If you are set up to run the digital modes like FLDIGI & MMSSTV,
you most likely have everything that you need.
Weak Signal by Joe Taylor (WSJT)
In July, I had the privilege of meeting Joe at
the Symposium of Amateur Radio
Astronomers held at the National Radio
Astronomy Observatory in Green Bank,
West Virginia.
Joe Taylor discovered the first Pulsar in a
binary star system. He has used this to
make high-precision tests of general
relativity and in 1993, received a Nobel
Prize in Physics for this discovery
Joe Taylor, K1JT created the set of weak signal protocols used in the WSJT system
for EME. This has enabled stations using a single Yagi & 50 watts to work larger
stations off the moon. He then created the WSPR application used by thousands of
amateurs world wide as a realtime propagation indicator on HF. His most recent
accomplishment is WSJT-X, a system that enables stations running low power and
compromise antennas to make world wide contacts.
All of this is FREE!
Quotes from forums on the Web
We've all heard the old saying, oft repeated in these review pages (usually about
antennas), "if you can’t hear …them you can’t work them". Well...welcome to the
new world of WSJT, I can't hear them but I work them anyway. WB0FDJ
Joe is adding 3dB of gain every month. SP9TTG
WSJT, and the modes contained therein (JT65/WSPR/JT2/JT4/PSK441), are with little
doubt, the most cutting edge weak signal modes afforded to us as Amateurs. JT65 makes
it possible to work DX that I never thought was possible with a compromise antenna and a
QRP-only rig (FT-817ND) as my main/only radio. KB2HSH
Although Joe provides the software free of charge, it does not come without cost. His
program is so addictive that you will find yourself spending hours in the shack exploring
the fascinating world of weak signals. WB4ECR
JT65, and JT9 that followed, enabled me to make WAS in a month on the air, and DXCC
within a couple of months, all while running 5 watts QRP to a horrible end-fed antenna
stapled to trees.
WB4SON
What is the attraction of the Weak Signal Modes
such as JT-65, JT-9 and others?
• Large antennas are NOT required (a short whip on back of rig works)
• High power is not needed ( 2 to 5 watts will make lots of contacts)
• Narrow bandwidth (JT-65 is 200 Hz, JT-9 < 30 Hz)
• So just how does JT-65 & JT-9 stack up against the other modes …
*** Levels required to obtain an intelligible output
Where does JT65 & JT9 take place?
Static crash
Noise
RTTY
C
W
HDGC
WSJT
PSK31
Scanner
Wall Wart
Ionospheric SSB voice
Pinger
Why is JT65 so efficient at delving deep into
the noise floor?

65 tone Frequency Shift Keying- Much more efficient then on/off keying as in CW

Narrow bandwidth- 200 Hz for JT65 <30 Hz for JT9

JT65 message much more compact then a CW message
In CW – “W3SMF WA3USG FN10” takes 170 bits (bit=key down dot interval)
In JT65- 71 bits

Data is sent with an redundancy ratio of 5.25 to 1 and is repeated throughout the
message using a mathematical algorithm developed based on probability (Reed
Solomon Codes).

A sync pulse starts each transmit cycle as a definitive reference.

Data tones are on line long enough for the receiving computer to perform quasi
long term integration in order to detect them below the noise floor.

Transmit and receive cycle are both automatic and dependent upon computers
at each end being in sync within 2 seconds of each other.
An example of the results …
WSJT Modes – Structure of a QSO
Both JT65 & JT9 consist of the minimum information needed to complete a valid
QSO
The typical QSO takes about 6 minutes
Consists of a minimum of 6 T/R exchanges, each taking 1 (one) minute. This
is broken down into 50 seconds to send the data and 10 seconds for the other
station to decide on how he or she is going to respond.
1. Station 1 Calling CQ along with a location (eg: CQ WA3USG FN10
2. Station 2 answering along with a location (eg: WA3USG W3SMF FM19)
3. Station 1 responding with a signal report (eg: W3SMF WA3USG -07
4. Station 2 responding with a signal report (eg: WA3USG W3SMF -04)
5. Station 1 acknowledging reception of signal report (eg: W3SMF WA3USG RRR)
6. Station 2 acknowledging receipt & closing down QSO with a 73
(eg: W3SMF WA3USG 73)
The WSJT-X Screen
In Summary

Both Modes of WSJT (JT65 & JT9) are FUN!

Performance is amazing.

JT9 is a lot narrower then JT65 and goes a bit deeper into the noise …
use it! You can fit a lot more QSO’s into the 3 KHz allocated space!

Receive & Transmit stability is required.

There seems to always be activity on the WSJT recommended frequencies
(even when the band is “dead”).

It takes a bit of time & effort to set the software up and master it but anyone
here can do it. The effort is part of the challenge and adds to the
satisfaction of working great DX with just a few watts!