JT65A Digital Mode for High Frequency

JT65A is a weak-signal digital mode that allows you to pull great DX out from under the noise on the high frequency spectrum. The JT65A communications protocol was conceived and first implemented by Joe Taylor, K1JT. Joe, a Professor Emeritus of physics at Princeton University, shares a Nobel Prize with Russell Alan Hulse (ex-WB2LAV) for the discovery of the first pulsar in a binary system as well as the first confirmation of the existence of gravitational radiation in the amount and with the properties first predicted by Albert Einstein. Joe has contributed to the amateur radio community in much the same way, changing the playing field for weak-signal operation.

JT65A is actually a "sub-mode" of Joe's original JT65 protocol, which he designed to optimize EME contacts on the HF and VHF bands. JT65 includes error-correcting features that make it very robust, even with signals much too weak to be heard. It was later realized that this protocol, with some adaptation, would also be very usable for terrestrial HF communications.

The JT65A discussed in this guide is a submode within a suite of applications collectively referred to as WSJT . The WSJT software has been available for several years (2001) and was initially designed by Joe Taylor, K1JT. This amazing piece of software has evolved to the point that there is now a team, rather than one individual, that are developing the software. That team consists of Joe K1JT , DL3LST, KK7KA, ON/G4KLX., N5HY, VA3DB, and James Courtier-Dutton . This team is to be commended for their contributions to the advancement of amateur radio communications.

These non-bozos have already written a document that serves as a useful guide. I have read it several times, it takes several readings for this bozo to understand just a little. If you would like to read the smart people's guide, you can find it at People's guide

The first HF terrestrial use of JT65 appears to have been a JT65B QSO on August 14 2006 between Victor UA0LGY and Tetsu JE5FLM. The recent explosion of HF activity began after VE3FGU , and several of his friends, started experimenting with the JT65B on March 23 , 2007 and JT65A on March 24. 2007.

On March 28th, several members of the digitalradio reflector: Yahoo digital radio reflector group noted some unknown digital signals on 20M and on March 30th concluded that they were JT65A signals . The experiments of Mike VE3FGU, Tetsu JE5FLM, David WD4KPD, Marshall W9RVG, Seli TF3AO, and others, quickly exploded in to the hottest HF mode for weak signal DXing and experimentation.

Here is a list of common JT65A frequencies:

FrequencyAmateur BandNote
1.805 MHz USB 160 meters
1.838 MHz USB 160 meters
3.576 MHz USB 80 meters
7.040 MHz USB 40 meters
7.036 MHz USB 40 meters International
7.039 MHz USB
40 meters Typicaly Europe
7.076 MHz USB 40 meters USA
10.139 MHz USB 30 meters Note 1 and 2
14.076 MHz USB 20 meters
18.102 MHz USB 17 meters
21.076 MHz USB 15 meters
24.920 MHz USB 12 meters Note 3
28.076 MHz USB 10 meters
  1. Note 1: Do not use 10145-10150kHz because JT65A is NOT COMPATIBLE with PSK31, MFSK, or RTTY and the other fast time-sharing modes such as PACTOR, ALE, PSKmail, and APRS.
  2. Note 2: It is becoming a standard practice on 30m to actually use 101378 kHz as the window frequency (USB), to play 'nice' with WSPR stations. This, of course, is an issue with certain countries/regions where digital operation is not allowed below 10140 kHz. However, most JT65A appears to be shifting to 101378 for a window (dial) frequency. This issue with the frequency problem between IARU regions needs to be resolved. I will update this when new information is available.
  3. Note 3: Per discussion amongst the JT65A crowd on the reflectors: There is discussion about moving the 12-meter window frequency, USB to 24927. THIS IS A PENDING ISSUE: Those amateur radio operations in Region 3 must operate at 24920 to 24929. Discussion is currently underway to resolve an issue with using 24920 kHz (PSK-31 since 1999). I will update this list as soon as a new consensus is reached. (last updated October 1, 2011)

An article series on using the original JT65-HF software appeared in CQ Amateur Radio's October and November 2010 issues.
jt65a 1

To download the introduction and interface PC please clik: Introduction-1 & Introudction-2, Handbook and Interface Schematic
To download the software and user manual please click: JT65A & manual.

Source :

  • https://en.wikipedia.org/wiki/WSJT_%28Amateur_radio_software%29
  • http://nw7us.us/jt65a.html

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