JT65a
A
MINIMALIST’S
ERROR FREE
HAM RADIO PROTOCOL
OVH - July 2013 -- by Terry WA5NTI
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WELCOME TO THE WONDERFUL WORLD OF
JT65-HF
JT65-HF is a amateur radio digital mode written by W6CQZ. It is
an extremely efficient weak-signal mode – it is possible to decode
signals you simply cannot hear with your ears in audio and can
barely see on your waterfall display.
JT65-HF is so labeled because it sends 65 discrete audio tones,
spread out over 175Hz of bandwidth. The “JT” part comes from
the original creator’s name, Joe Taylor (K1JT) - the 1993 winner of
the Nobel Prize in Physics, and the author of the excellent HSMS
and EME software known as WSJT.
OVH - July 2013 -- by Terry WA5NTI
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FOR FURTHER, MORE IN-DEPTH, STUDY
THE FOLLOWING INTERNET LINKS SHOULD HELP
Download JT65-HF:
http://iz4czl.ucoz.com/index/0-28
JT-Alert add-on software with visual and audio alerts
http://ham-apps.com/
SP time sync (lets you synchronize your computer's clock with any Internet
atomic clock (time server)
http://www.spdialer.com/
-------------------------------------------------------------------------------------------http://hamspots.net/wsjt/
"cluster"-type spots for JT65-HF and other digital modes
http://groups.google.com/group/jt65-hf
JT65-HF group discussions (on Google groups)
http://www.meinberg.de/english/sw/ntp.htm
Meinberg time sync
OVH - July 2013 -- by Terry WA5NTI
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JT65 is a tightly structured protocol with a severely limited set of
structured messages and a limited 'free text' message type limited
to 13 characters in length.
In any one minute period you may send any one of the structured
message types, 13 characters of text or any one of the 3 shorthand
messages.
Nothing more, nothing less !
JT65 is not a free form data transmission protocol like most other
modes we use. Each transmitted 'frame' is of a fixed length,
starting and ending at a predefined time. By using this
restrictive timing arrangement and a fixed frame length it
becomes possible to achieve some “signal gain” by knowing
when and where to look for signals.
A properly executed QSO takes exactly six (6) minutes to
complete.
OVH - July 2013 -- by Terry WA5NTI
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Transmissions begin at precisely 1 second into a new minute
and end precisely 46.811 seconds later.
A transmitted message (frame) will convey 72 bits of user
information with an additional 306 bits of error correction data
(FEC) for a total of 378 bits.
That’s more FEC data being transmitted in each frame
than it is user payload data !
Its timing, modulation method and heavy FEC that allows it to
work so well at very low signal levels.
Within that frame of data 72 data bits you may have any one of
the set of structured messages, a 13 character free form text
message, or any one of the 3 shorthand messages.
OVH - July 2013 -- by Terry WA5NTI
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The six (6) Structured messages are as follows.
1)
2)
3)
4)
5)
6)
CQ CALLSIGN GRID
CALLSIGN CALLSIGN GRID
CALLSIGN CALLSIGN -##
CALLSIGN CALLSIGN R-##
CALLSIGN CALLSIGN RRR
CALLSIGN CALLSIGN 73
With structured messages the text is not sent character by
character, but, instead, the software uses a mathematical formula
to 'translate' a call sign or grid into a unique numerical value that
takes less bit space to convey than a character by character
transmission format.
Structured messages can appear to exceed the 13 character limit.
OVH - July 2013 -- by Terry WA5NTI
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User Data (the math details):
A structured message actually consists of 3 'fields' with the lengths of 28 bits, 28
bits and 15 bits for a total of 71 bits. The 72nd bit is used as a marker and when set
(1) indicates the message is 13 character text or, if unset (0) the 71 bits contain a
structured message.
An amateur call sign consists of a one or two character prefix, at least one of which
must be a letter, followed by a digit and a suffix of one to three letters. Within these
rules, the number of possible call signs is equal to 37×36×10×27×27×27, or
somewhat over 262 million. (The numbers 27 and 37 arise because in the first and
last three positions a character may be absent, or a letter, or perhaps a digit.)
Since 2^28 is more than 268 million, 28 bits are enough to encode any standard call
sign uniquely. Similarly, the number of 4 digit Maidenhead grid locators on Earth is
180x180 = 32,400, which is less than 2^15=32,768; so a grid locator requires 15
bits in a message.” This implies that any pair of call signs [that fits the encoding
rule] and a grid can be sent in 28+28+15=71 bits.
OVH - July 2013 -- by Terry WA5NTI
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WHAT
you need:
HF Transceiver
Computer with:
JT65-HF.exe software
JT-ALERT.exe software
SP TimeSync.exe software
PC to Soundcard interface **
** See note about soundcard on next slide
OVH - July 2013 -- by Terry WA5NTI
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** Special note about Soundcards:
JT65-HF does NOT require a 'high quality' sound device as
is suggested for applications like SDR (Software defined
radio) usage.
A high quality sound card (better SNR, better linearity,
better ADC accuracy, better sample rate accuracy) may
make a decode that a cheaper card will miss at the extreme
lower limits of possibility, but …overall, the expense of
purchasing such a card will hardly be worth the returns.
In general almost any sound card will work with JT65-HF.
OVH - July 2013 -- by Terry WA5NTI
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WHERE
TO LISTEN
1838
3576
7076
~10138
14076
18102
21076
24917
28076
50076
50276
to
to
to
to
to
to
to
to
to
to
to
JT65a-HF freq
USB
1840
160
3578
80
7078
40
~10140
30
14078
20
18104
17
21078
15
24919
12
28078
10
50078
6
50278
6
OVH - July 2013 -- by Terry WA5NTI
meters
meters
meters
meters
meters
meters
meters
meters
meters
meters
meters
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The Process:
This is typical of most digital modes.
•
•
•
•
•
•
•
•
•
Audio tones are picked up by the radio (operating in Upper Sideband).
Audio tones are sent from radio to the PC’s sound card (via line-in).
The PC interprets the tones and prints text messages on the PC’s screen.
You respond by typing on keyboard or clicking on mouse.
The PC translates keyboard text to audio tones on it’s soundcard.
The PC sends the audio tones (via line-out) to the transceiver (MIC in).
The transceiver transmits the tones over the air.
Your QSO partner hears the tones and sends them to his computer.
Your QSO partner sees the text you typed and prepares to respond.
OVH - July 2013 -- by Terry WA5NTI
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The proper sequence of a JT65 QSO ( on HF ).
I See
Assume I (WA5NTI) see VE3ODZ calling CQ and I engage in a QSO.
It would go something like the following;
( I SEE )
( I DO )
CQ VE3ODZ FN03
1 – VE3ODZ is calling <1> CQ
VE3ODZ WA5NTI CM87
call sign and grid
2 – I answer (((1))) VE3ODZ with my
3 – VE3ODZ answers <2> my call with a report
WA5NTI VE3ODZ -13
(((-13)))
VE3ODZ WA5NTI R-08
(((R))) and send his (((-08)))
WA5NTI VE3ODZ RRR
(((RRR)))
VE3ODZ WA5NTI 73
WA5NTI VE3ODZ 73
I Send
4 – I acknowledge (((2))) my report
5 – VE3ODZ acknowledges <3> my report
6 – I end (((3))) the QSO with a 73
7 – VE3ODZ ends <4> the QSO with a 73
That's it. The 'perfect' JT65 QSO.
Call signs exchanged, locations (grids) exchanged, signal reports exchanged and
confirmed with R- and RRR and lastly QSO ended with the 73 messages.
OVH - July 2013 -- by Terry WA5NTI
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This is the First
screen you see
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This is the Waterfall
area
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This is the Text-Decode
area
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This is the Sound Card
control area
(left and right channel select)
(left and right volume levels)
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This is the Sound Card
“identification” area
(If your PC has more than one sound
card, this area tells you which one
the software is using)
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This is the Transceiver’s
Operating Frequency
(Dial Frequency)
If CIV / CAT control
is activated.
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“odd” vs. “even” indicator
This is the previous minute
(the 16 th minute - is “even” number)
Note the minute indicator
(the 17 th minute - is “odd” number)
OVH - July 2013 -- by Terry WA5NTI
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These settings control
The Waterfall
This shows the text to be
transmitted at
time = t 0
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Free Style Text
entry area
(max 13 characters)
Automatically
Generated
Text
Transmit audio delta (f)
Receive audio delta (f)
from zero ( 0 )
center of waterfall
OVH - July 2013 -- by Terry WA5NTI
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Tx / Rx
Event Sequence
Control Buttons
Decode Window width
(within the 2 kHz waterfall)
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1
If You Call CQ
1) Call CQ,
2) Respond w/signal report,
3) “Roger” “Report”
1,2,3
The
“Push Button”
QSO
2
If You Answer a CQ
1) Answer their QC,
2) Send Signal Report,
3
OVH - July 2013 -- by Terry WA5NTI
3) Say 73
23
Beginning of minute (a 49 sec Rx frame)
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AN
ESSENTIAL
free add-on product
is
JT-Alert
by VK3AMA.
JT-Alert is distinct from JT65-HF, but works closely with it.
It looks at the decodes made by JT65-HF and then displays info and
makes sounds when it detects things like someone calling CQ, or
your callsign being sent by someone (such as an answer to your CQ),
or a wanted state.
It can also detect that you've worked someone before on the band
you're on and optionally ignore any alert that may have been
generated. It is a very very helpful tool that is worth installing.
OVH - July 2013 -- by Terry WA5NTI
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Starting the JT-ALERT
companion
application
Mouse-Over to see band
popup display
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Decode Phase begins at time = 49 sec.
NOTE: no Rx text printed yet.
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This is the
relationship between
the waterfall
and
the decoded data.
OVH - July 2013 -- by Terry WA5NTI
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QUESTION
When I send someone their RST
(signal report)
Where do it get it ?
ANSWER
The JT65-HF software
shows your partner’s
signal report
These signal report numbers
will automatically show
up as his/her RST in your
transmitted text.
OVH - July 2013 -- by Terry WA5NTI
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NOTE;
You can NOT even
see this decoded
signal.
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-OKNext we will start looking at
some real live-captured data
and walk through
a real sequential JT65HF
QSO
OVH - July 2013 -- by Terry WA5NTI
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Here we see AB0YM calling KB7N
Note that AB0YM is in Grid Square CN97
Here we see AA4DD giving AG0A a “-06” signal report
OVH - July 2013 -- by Terry WA5NTI
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Here we see K5USF (who is in grid square DM62)
calling CQ
Note that my software used method “B” to decode
this line
Here we see UA6BRD calling CQ
Note that my software used method “K” to decode
this line
OVH - July 2013 -- by Terry WA5NTI
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These numbers report the number
of “sync” vectors/pulses
detected in their transmission
These numbers represent the delta-t
between your sound card’s clock
rate and their sound card’s clock rate
OVH - July 2013 -- by Terry WA5NTI
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This Demonstrates
THE POWER
of
JT-ALERT
(helps you get QAS, QAC, DXCC …)
OVH - July 2013 -- by Terry WA5NTI
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Now to click on
“Call CQ”
OVH - July 2013 -- by Terry WA5NTI
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1
Note that we are 2
in an “odd”
numbered
minute
START HERE
Clicking on “Call CQ” button
puts a dashed line
around the button
3
Also NOTE:
Pushing “Call CQ”
did NOT immediately start
transmitting.
4
Because we are in an “odd” minute,
the software will start transmitting
at the top of the next “even” minute.
OVH - July 2013 -- by Terry WA5NTI
5 This is the text that
you will transmit
at the top of
the NEXT minute
37
Tx began at the top of minute
we are now 37 sec into the
transmission
Tx DF is the delta
in frequency from
the zero (center)
of the waterfall
OVH - July 2013 -- by Terry WA5NTI
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OK
Now we are going to
answer someone’s CQ and
do a complete QSO
OVH - July 2013 -- by Terry WA5NTI
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Tx is enabled, but 3
will NOT start until
top of the next “odd”
minute
I see YO2LGK
1
calling CQ.
To formulate a response,
I just double-click on
the YO2LGK line-item
in the Rx Window
2
YO2LGK’s callsign and
signal report are automatically
generated
OVH - July 2013 -- by Terry WA5NTI
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Here we see that YO2LGK
has answered our call and given us a “R”
on the signal report we sent.
Also note that YO2LGK is sending us
a “-04” db signal report.
When I double-clicked on his line-item,
the system generated the “RRR” indicating
that both ends of the QSO have “rogered”
the signal reports - so, it’s a valid QSO !
OVH - July 2013 -- by Terry WA5NTI
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Here we see that YI2LGK has received
the “RRR” and has now sent
“73”
When I double-click on his “73” line-item
the system generates “73” to be sent back to him.
The QSO is now complete.
OVH - July 2013 -- by Terry WA5NTI
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The sending of “73” is now complete,
the system is back in “Rx” mode, and
“Tx OFF” is the final status.
Now all I need to do is click on the
“Log QSO” button to record the
completed QSO.
OVH - July 2013 -- by Terry WA5NTI
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Click here to “log”
the QSO
Last chance
to change
things
before you
log the
QSO
This is the JT65HF logging window.
It shows you what information will be entered into your log.
If you are using DXLab like I do - the info goes into that log.
If you are not using any logging package then this
information goes into a JT65HF ADIF file for you.
OVH - July 2013 -- by Terry WA5NTI
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If JT65HF is successful logging the QSO,
this screen appears indicating the success
of the operation.
OVH - July 2013 -- by Terry WA5NTI
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Now we want to ask the JT-ALERT system to check our log.
It will scan the log, finding the new QSO and update
your “Progress Matrix” to show you where you stand
as you work your way toward DXCC, WAS, WAZ ....
Click here to
start the update.
OVH - July 2013 -- by Terry WA5NTI
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You can either “Scan All” or only scan for
specific results - I want to see my DXCC status
now that I have worked YI2LGK on the
10 MHz (30M) band.
OVH - July 2013 -- by Terry WA5NTI
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This window shows progress, as the log file is scanned.
OVH - July 2013 -- by Terry WA5NTI
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And, here is the scan results showing a new DXCC
count for my 30M standing.
OVH - July 2013 -- by Terry WA5NTI
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One Final Note
about
QRM
OVH - July 2013 -- by Terry WA5NTI
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A Special Note About QRM Immunity
( The Resilience of JT65a )
“Just for fun this morning, I had a couple of QSOs through the S9 +20db
QRM from and over the horizon radar station.
This racket (on 30m) probably emanates from Northern Australia...
Anyway, I was astonished that I could copy stations through this.
I hope that we spoiled their war games at least in some small measure.
73 Julian VK4CMV”
OVH - July 2013 -- by Terry WA5NTI
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THE
END
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Configuration
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JT-ALERT
settings
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Click here with the mouse to change
the configuration of settings
This is a binary switch
turning sound on/off
Click here with the mouse to change
the alerts you want the system
to look for
OVH - July 2013 -- by Terry WA5NTI
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This shows I still need
QSOs with CT, ND, and
West VA to have WAS
OVH - July 2013 -- by Terry WA5NTI
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You can ask for help
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You can
customize
these colors
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THE
END
(OF CONFIGURATION)
SECTION
73
( questions ? )
OVH - July 2013 -- by Terry WA5NTI
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These are the log fields
if using the JT-ALERT logging.
I interface to DXXLabs
OVH - July 2013 -- by Terry WA5NTI
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The most popular JT65A frequency is in the 20 Meter band:
The JT65 frequency 20metres is 14076.0 kHz USB VFO.
The JT65a sync frequency is 14077.27 kHz.
The JT65 signal frequency is about 14077.3 to 14077.7 kHz.
The JT65A frequency 30metres is 10139.0 kHz USB VFO.
The JT65a sync frequency is 10140.27 kHz
The JT65 signal frequency is about 10140.3 to 10140.7 kHz*.
*Note: This transmit signal is within the 10140-10150kHz
automatic digital sub-band.
OVH - July 2013 -- by Terry WA5NTI
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International JT65A frequency 40metres is 7039.0 kHz USB VFO.
The International JT65A sync frequency is 7040.27 kHz
The JT65A signal frequency is about 7040.3 to 7040.7 kHz.
The JT65A frequency 40meters (USA) is 7076.0 kHz USB VFO.
The JT65A sync frequency (USA) is 7077.27 kHz
The JT65A signal frequency is about 7077.3 to 7077.7 kHz.
OVH - July 2013 -- by Terry WA5NTI
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The JT65A frequency 17metres is 18102.0 kHz USB VFO.
The JT65A sync frequency is 18103.27 kHz
The JT65A signal frequency is about 18103.3 to 18103.7 kHz.
The JT65A alternate frequency 17meters is 18098.0 kHz USB VFO.
The JT65A frequency 12metres is 24917.0 kHz USB VFO.
The JT65A sync frequency is 24918.27 kHz
Note: before date 9/2011, the old JT65A frequency was 24920 kHz
(changed to avoid QRM)
OVH - July 2013 -- by Terry WA5NTI
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IMPORTANT INFORMATION
ABOUT ALL JT65A FREQUENCIES
•
•
•
•
•
•
•
•
•
JT65A operators use USB VFO FREQUENCY for spots.
JT65A signal is about 1.3+kHz higher than the VFO frequency.
The JT65A Passband is about 355Hz. Bandwidth is about 200Hz.
JT65A may be used in the 500Hz bandwidth segments of bandplans.
Normal operation of JT65A is a sync audio frequency of 1270.5Hz.
Sync tone is the reference mouse-click frequency for JT65.
JT65A signal bandwidth extends about 200Hz above 1270.5Hz sync.
The lowest tone of the JT65 signal is normally 1270Hz.
The system allows approximately +/-600Hz auto-tuning on receive.
OVH - July 2013 -- by Terry WA5NTI
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Special Notes on Good Operating Procedure:
1. Operators should be careful of frequency selection, accurate clock,
and calibration.
2. Always listen and observe the waterfall spectrum of signals on the
frequency before transmitting, and during activity.
3. JT65A is a weak signal digital QSO mode.
4. Always use very low power on HF to avoid QRM to other
JT65 signals and other modes.
5. 20Watts ERP is typical for normal activity and DXing in the
40metre to 10metre bands.
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6. Normal activity of JT65A is in the "weak signal" part of the
ham bands, near the PSK, MFSK, and Olivia 500 frequencies.
7. JT65A should not be used in parts of the ham bands where faster
digital modes are in use.
8. The long tone carrier duration of JT65 transmissions has potential
to cause severe interference to other modes.
9. Do not use JT65 in 10144kHz-10150kHz because
JT65A is NOT COMPATIBLE with MFSK, FSK, HELL, OLIVIA,
CONTESTIA, ALE400, or RTTY and can cause severe interference
to fast time-sharing modes such as PACKET, PACTOR, ALE,
PSKmail, and APRS.
OVH - July 2013 -- by Terry WA5NTI
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THE
END
73
( questions ? )
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