OVH - July 2013 -- by Terry - WA5NTI 1 JT65a A MINIMALIST’S ERROR FREE HAM RADIO PROTOCOL

OVH - July 2013 -- by Terry - WA5NTI

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JT65aJT65aA

MINIMALIST’S

ERROR FREE

HAM RADIO PROTOCOL


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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.


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Download JT65-HF:http://iz4czl.ucoz.com/index/0-28

JT-Alert add-on software with visual and audio alertshttp://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

FOR FURTHER, MORE IN-DEPTH, STUDY

THE FOLLOWING INTERNET LINKS SHOULD HELP


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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 thisrestrictive 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.


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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 towork 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.


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The six (6) Structured messages are as follows.

1) CQ CALLSIGN GRID2) CALLSIGN CALLSIGN GRID3) CALLSIGN CALLSIGN -##4) CALLSIGN CALLSIGN R-##5) CALLSIGN CALLSIGN RRR6) 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.


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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.


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WHAT you need:

HF TransceiverComputer with:

JT65-HF.exe softwareJT-ALERT.exe software

SP TimeSync.exe software PC to Soundcard interface **

** See note about soundcard on next slide


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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.


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WHERE

TO LISTEN

1838 to 1840 160 meters3576 to 3578 80 meters7076 to 7078 40 meters

~10138 to ~10140 30 meters14076 to 14078 20 meters18102 to 18104 17 meters21076 to 21078 15 meters24917 to 24919 12 meters28076 to 28078 10 meters50076 to 50078 6 meters50276 to 50278 6 meters

JT65a-HF freqUSB


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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.


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The proper sequence of a JT65 QSO ( on HF ).

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 2 – I answer (((1))) VE3ODZ with mycall sign and grid

WA5NTI VE3ODZ -13 3 – VE3ODZ answers <2> my call with a report(((-13)))

VE3ODZ WA5NTI R-08 4 – I acknowledge (((2))) my report(((R))) and send his (((-08)))

WA5NTI VE3ODZ RRR 5 – VE3ODZ acknowledges <3> my report(((RRR)))

VE3ODZ WA5NTI 73 6 – I end (((3))) the QSO with a 73

WA5NTI VE3ODZ 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 andconfirmed with R- and RRR and lastly QSO ended with the 73 messages.

I See I Send


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This is the Firstscreen you see


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This is the Waterfallarea


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This is the Text-Decodearea


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This is the Sound Cardcontrol 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 soundcard, this area tells you which one

the software is using)


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This is the Transceiver’sOperating Frequency

(Dial Frequency)If CIV / CAT control

is activated.


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Note the minute indicator

(the 17 th minute - is “odd” number)

This is the previous minute

(the 16 th minute - is “even” number)

“odd” vs. “even” indicator


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These settings controlThe Waterfall

This shows the text to betransmitted at

time = t 0


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AutomaticallyGenerated

Text

Transmit audio delta (f)Receive audio delta (f)

from zero ( 0 )center of waterfall

Free Style Textentry area

(max 13 characters)


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Tx / RxEvent SequenceControl Buttons

Decode Window width(within the 2 kHz waterfall)


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1 , 2 , 3The

“Push Button”QSO

If You Call CQ1) Call CQ,

2) Respond w/signal report,3) “Roger” “Report”

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If You Answer a CQ1) Answer their QC,

2) Send Signal Report,

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3) Say 733


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Beginning of minute (a 49 sec Rx frame)


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AN

ESSENTIALfree 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.


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Starting the JT-ALERTcompanionapplication

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 therelationship between

the waterfalland

the decoded data.


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QUESTION

When I send someone their RST(signal report)

Where do it get it ?

ANSWER

The JT65-HF softwareshows your partner’s

signal report

These signal report numberswill automatically showup as his/her RST in your

transmitted text.


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NOTE;You can NOT even

see this decodedsignal.


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-OK-Next we will start looking atsome real live-captured data

and walk througha real sequential JT65HF

QSO


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Here we see AB0YM calling KB7NNote that AB0YM is in Grid Square CN97

Here we see AA4DD giving AG0A a “-06” signal report


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Here we see K5USF (who is in grid square DM62)calling CQ

Note that my software used method “B” to decodethis line

Here we see UA6BRD calling CQNote that my software used method “K” to decode

this line


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These numbers report the numberof “sync” vectors/pulses

detected in their transmission

These numbers represent the delta-tbetween your sound card’s clock

rate and their sound card’s clock rate


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This DemonstratesTHE POWER

ofJT-ALERT

(helps you get QAS, QAC, DXCC …)


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Now to click on

“Call CQ”


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START HEREClicking on “Call CQ” button

puts a dashed linearound the button

Note that we arein an “odd”numbered

minute

Because we are in an “odd” minute,the software will start transmitting

at the top of the next “even” minute.

Also NOTE:Pushing “Call CQ”

did NOT immediately starttransmitting.

This is the text thatyou will transmit

at the top of the NEXT minute

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3

4 5


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Tx began at the top of minutewe are now 37 sec into the

transmission

Tx DF is the deltain frequency fromthe zero (center)of the waterfall


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OK

Now we are going to answer someone’s CQ and

do a complete QSO


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I see YO2LGKcalling CQ.

To formulate a response,I just double-click on

the YO2LGK line-itemin the Rx Window

YO2LGK’s callsign andsignal report are automatically

generated

Tx is enabled, butwill NOT start untiltop of the next “odd”

minute

1

2

3


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Here we see that YO2LGKhas 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” indicatingthat both ends of the QSO have “rogered”the signal reports - so, it’s a valid QSO !


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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-itemthe system generates “73” to be sent back to him.

The QSO is now complete.


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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.


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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 thisinformation goes into a JT65HF ADIF file for you.

Click here to “log”the QSO Last chance

to changethings

before youlog theQSO


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If JT65HF is successful logging the QSO,this screen appears indicating the success

of the operation.


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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 updateyour “Progress Matrix” to show you where you standas you work your way toward DXCC, WAS, WAZ ....

Click here tostart the update.


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You can either “Scan All” or only scan forspecific results - I want to see my DXCC status

now that I have worked YI2LGK on the 10 MHz (30M) band.


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This window shows progress, as the log file is scanned.


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And, here is the scan results showing a new DXCCcount for my 30M standing.


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One Final Noteabout

QRM


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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”


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THEEND


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Configuration


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JT-ALERTsettings


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Click here with the mouse to changethe configuration of settings

Click here with the mouse to changethe alerts you want the system

to look for

This is a binary switchturning sound on/off


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This shows I still needQSOs with CT, ND, and West VA to have WAS


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You can ask for help


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You cancustomize

these colors


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THEEND

(OF CONFIGURATION)SECTION

73( questions ? )


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These are the log fieldsif using the JT-ALERT logging.

I interface to DXXLabs


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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 kHzThe JT65 signal frequency is about 10140.3 to 10140.7 kHz*.*Note: This transmit signal is within the 10140-10150kHz automatic digital sub-band.


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International JT65A frequency 40metres is 7039.0 kHz USB VFO.The International JT65A sync frequency is 7040.27 kHzThe 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 kHzThe JT65A signal frequency is about 7077.3 to 7077.7 kHz.


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The JT65A frequency 17metres is 18102.0 kHz USB VFO.The JT65A sync frequency is 18103.27 kHzThe 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 kHzNote: before date 9/2011, the old JT65A frequency was 24920 kHz (changed to avoid QRM)


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• 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.

IMPORTANT INFORMATIONABOUT ALL JT65A FREQUENCIES


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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.


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THEEND

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( questions ? )

Documents

OVH - July 2013 -- by Terry - WA5NTI 1 JT65a A MINIMALIST’S ERROR FREE HAM RADIO PROTOCOL