JT65

JT65-HF -- an 'Odd' but Fun Digital ModeBy K8FB and WB9VGJ

What is JT65?

•A weak signal digital mode

•It is not a transmit-at-will or send-whatever-you-want mode

• It is highly structured (similar to FSK441 or ISCAT on VHF) and because the maximum number of characters you can send in freeform is 13 (that’s right, thirteen)

Why use JT65?

• Weak signal digital mode• Comparably - gets through better than CW or PSK31• When an HF band seems dead, you may still find JT65

activity• Low power mode - 20 watts works great• Compromise antennas work okay• Honest and accurate signal reports are sent and received• Existing SSB transceiver, PC, free software download,

sound card interface/ cable (e.g., SignaLink USB) • Standard frequency used on each band for JT65

What do you need?

•Radio

•Interface

•Software

Software

•Two most popular programs•JT65-HF

http://jt65-hf.com/downloads/

•WSJT-Xhttp://physics.princeton.edu/pulsar/K1JT/

SignaLink USB Interface

JT65 Transmit/Receive Mode

• Radio set to Data mode

• Upper sideband on all bands

• Be sure to use a wide filter setting in order to see the full width of the waterfall containing JT65 signals.

JT65 QSO Transmit/Receive Cycle

•JT65 works on a one-minute cycle•Transmits 47 seconds beginning 1 second into a new minute

•12 seconds idle•Receives 47 seconds•13 seconds idle

•Standard QSO takes six to seven minutes

JT65 Protocol

The JT65 protocol states that a transmission will begin at precisely 1 second into a new minute and end 46.811 seconds later. The protocol further defines that a frame will convey 72 bits of information with an additional 306 bits of error correction data (FEC) for a total of 378 bits. It is the structure of JT65, its timing, modulation method and heavy FEC that allows it to work so well at very low signal levels.

Within that frame of 72 data bits you may contain any one of the set of structured messages, a 13 character free form text message or (while different in the actual details of transmission, but close enough for now) any one of the 3 shorthand message types.

Normal QSO Sequence

• CQ WB9VGJ DM34

• WB9VGJ EA1EI IN63

• EA1EI WB9VGJ -6

• WB9VGJ EA1EI R-12

• EA1EI WB9VGJ RRR

• WB9VGJ EA1EI 73

• EA1EI WB9VGJ 73 (Optional)

Shorter Version - Common

• CQ WB9VGJ DM34

• WB9VGJ EA1EI IN63

• EA1EI WB9VGJ -6

• WB9VGJ EA1EI R-12

• EA1EI RR 73

• EA1EI WB9VGJ 73 (Optional)

Accurate time is important

The sequence of a contact depends on the computer clock being very accurate. We’re not talking within 30 seconds here. 2 seconds off is barely acceptable. 1 second off is usually OK. In reality, you’ll want it to be less than 0.5 seconds off. What that means for you is that the built-in Windows clock sync probably won’t be sufficient. You need to get good clock sync software. The most popular one is D4 (Dimension 4); Meinberg is the other major choice (links below). If you’re running Win7 or Vista, look at Meinberg first, but D4 will work if you run it as Admin and in XP compatibility mode. Either of them will keep your clock accurate to within a few hundredths of a second.

How to ensure accurate time

Use Dimension 4 utilityhttp://www.thinkman.com/dimension4/

Dimension 4

• Why Dimension 4?

• Simply put, Dimension 4 is the fastest and easiest way to synchronize your computer's clock if you're running a Windows-based operating system. Once Dimension 4 is installed, you'll most likely forget that it's even running. It's that automatic.

• Once installed, you can rest assured that at least one of your clocks has the correct time.

Dimension 4How's Dimension 4 work?

• Dimension 4 uses a low level internet protocol, called SNTP, to connect with special purpose Internet Time Servers that have been keeping the rest of the web on-time for the last 20+ years. These time servers typically have direct access to their very own time source, or they are connected directly to other Internet Time Servers that do.

• At an interval you specify, Dimension 4 connects to one of these Internet Time Servers, which you get to choose from an exhaustive list built directly into Dimension 4. The Time Server then sends the correct time back to your computer, where Dimension 4 uses sophisticated algorithms to correctly adjust your computer's clock to with-in a few milliseconds of the real time.

The JT65-HF Screen

Calculating Where Actual RF Tones Will Fall

•The right portion houses the spectrum display (waterfall display) and its controls. Across the spectrum display's top is a marker indicating offset in 100 and 50 hertz increments from the audio pass band's center point.

•The red marker indicates where your transmitted tones will fall.

Calculating Where Actual RF Tones Will Fall

• The center frequency of the JT65-HF audio pass band is 1270.46 Hz (or ~1270.5 Hz) and knowing this you can easily calculate where the actual RF tones will fall. Simply take the dial QRG, add 1270.5 then add the offset to find the lower absolute edge in RF. Add 200 Hz to that and you'll have a close figure for the upper bounds.

• A JT65a signal is not quite 200 Hz wide, but, for quick calculations it's close enough. The actual maximal width of JT65a is 174.9605 Hz.

Calculating Where Actual RF Tones Will Fall

For example; Frequency = 14076000 Hz, TXDF = 0.

Lower RF limit = 14076000 + 1270.5 +0 = 14,077,270.5 Hz and the upper limit is then 14,077,470.5 Hz.

It's important to understand where your actual RF tones fall in case you're ever operating near a band's edge, or simply to know what's happening... though it's not (usually) something you will have to think about.

JT65-HF Setuphttp://www.arrl.org/files/file/Get on the%20Air with HF Digital/jt65-hf-setup.pdf

Sound Card Adjustments

•Need to set up 2nd sound card

•Need to adjust volume of SignaLink sound card

•Need to specify primary sound card

•Good idea to rename SignaLink sound card

Effectiveness of Various ModesFrom How Much “Punch” Can You Get from Different Modes? QST, December 2013, pp 30 – 32

Two Maximum Range Factors:

1. Average transmitter power (assume 100W PEP)• CW 44W (off time and duration of dits and dahs)

• SSB 25W (-2.5 dB compared to CW)• RTTY 95W (+3.3 dB compared to CW)• PSK31 75W (+2.3 dB compared to CW)• JT65 100W (+3.5 dB compared to CW)

Effectiveness of Various Modes

Second Maximum Range Factor:

2. Receiver sensitivity for each mode •CW base reference of zero•SSB -14.7 dB compared to CW•RTTY -7.7 dB compared to CW•PSK31 +4.8 dB compared to CW•JT65 +21.2 dB compared to CW

Effectiveness of Various Modes

Total Mode Effectiveness (sum of output power and receiver sensitivity dB)

• CW base reference of zero• SSB -17 dB compared to CW• RTTY -4 dB compared to CW• PSK31 +9 dB compared to CW• JT65 +25 dB compared to CW (a little more than doubling the effective power of JT65 8 times)

Effectiveness of Various Modes

Relative Range Compared to CW distance of 1 unit(Assuming the transmission path is long enough)

• SSB 0.18 distance unit• RTTY 0.625 distance unit• PSK31 2.5 distance units• JT65 12 distance units

JT65 is the clear winner

Useful websites• PSK Reporter – see who is hearing your signals and whose

signals you are hearing

• https://www.pskreporter.info/pskmap.html

• Amateur Radio Ham Maidenhead Grid Square Locator Map –enter call sign or grid square to see where station is located

• http://www.levinecentral.com/ham/grid_square.php

• JT65 Frequencies

http://hflink.com/jt65/

HAMSpots.net for Digital Modes PSK Reporter spots and spotted by on left. Reported spots by others appear on right.

A QSO with EA1EI

Logging• JT65-HF automatically writes to two logging files:

� jt65h_log.adi – Short term ADIF file; logs your QSOs

�JT65hf-log.csv – Long term Common Separated Values file; logs all

traffic; can be opened with Microsoft Excel

• Use TQSL to automatically upload contacts from ADIF log file to LoTW

• Click on ‘Settings’ button in your QRZ logbook and then the ‘Download from LoTW’ button to import your LoTW log entries

• Import ADIF file directly to eQSL, Ham Radio Deluxe and other logging files

LoggingJust click on the ‘Log QSO’ button – specify power on

first contact to be logged

JTAlert – A Useful Extension for JT65-HF

• Visual and audible alerts for various things: CQ, Your Call, Wanted DXCC

Entity, Wanted State, Wanted CQ Zone, etc. • Can be used to log contacts to Ham Radio Deluxe logbook• Shows location of a station as above

AI5II - B4 = In QSO with AI5II, he sent me a report; I worked him beforeK0PT – B4 = K0PT in SC decoded; I worked him before

KC9RFO – IL = KC9RFO in IL is calling CQ Many other useful features

Number of Unique Call Signs per Band

Awards• QRZ awards

• Grid Squared Award for confirming contacts with 100 different grid squares

• United States Award for confirming contacts with all 50 states

• World Continents Award for confirming contacts with all 6 continents

• DX World Award for confirming contacts with 100 countries

• QRZ on-line awards are free – paper copies are sold

• Awards will appear on your QRZ page

• ARRL DXCC, WAC, WAS awards

• eQSL and other awards

Common Problems EncounteredThese problems can be show stoppers, but are easily overcome:

• Incorrect sound cards “enabled” or selected for playback and recording - defaults may not work

• Your PC’s clock must be set within a second or two of actual WWV time or you and others won’t decode correctly – use Dimension 4

• Incorrect Mode - USB mode is always used on each HF band• Overdriving of signal levels or too much power can cause

transmitted signal distortion or spurs (ALC needle should not move very much) – Turn down mic gain or TX level

• High power for extended period of time can ruin final transistors, as transmissions run for 48 seconds every other minute. Final failure can be an expensive proposition.

References• JT65 the Musical Mode (QST):

http://www.arrl.org/files/file/Get%20on%20the%20Air%20with%20HF%20Digital/FORD%20JT.pdf

• Ham Spots - DX Spotter Integrated with PSK Reporter: http://hamspots.net/

• The JT65 Communications Protocol -http://www.arrl.org/files/file/18JT65.pdf

• Getting Started in Digital Communications -http://www.arrl.org/files/file/Technology/tis/info/pdf/39233.pdf

• How Much “Punch” Can You Get From Different Modes -http://www.qsl.net/k4fk/presentations/Mode-sensitivity-2013-Dec-QST-Siwiak-Pontius-1.pdf

References• JT-65 HF -- An “Odd” but Fun Digital Mode -

http://www.eham.net/articles/25604• JT-65 Articles from CQ Magazine -

http://sparqi.blogspot.com/2011/08/jt65-articles-from-cq-magazine.html

• WJST Meteor Scatter Weak Signal Group -https://www.google.com/webhp?sourceid=chrome-instant&rlz=1C1AFAB_enUS530US530&ion=1&espv=2&ie=UTF-8#q=n4au+JT-65+Article

• Getting Started with JT65 on the HF Bands -https://www.dropbox.com/s/0o6k4m009d251ip/JT65HF-Intro-WB8IMY.ppsx?dl=0

References• JT-65 HF• https://www.dropbox.com/s/d7c1x1nmfx553bn/JT65-HF-

W4ZSC.pptx?dl=0• JT65-HF Setup and Operations Guide -

http://www.arrl.org/files/file/Get%20on%20the%20Air%20with%20HF%20Digital/jt65-hf-setup.pdf

• JTAlert Download - http://ham-apps-jtalert.software.informer.com/download/