Saturday, September 7, 2013

Working JT9/JT65

In my working with digital modes, I have started with JT9/JT65. I've found them to be rather relaxing modes, you can easily do something else while you are talking, and just get back to the conversation every two minutes. I'm hoping to give a bit of an idea of how these two modes work, and what should be done to improve communications on the subject.
The basic premise behind any of the WSJT modes, of which both JT9 and JT65 are a part of, is that a low power signal consisting of tones is sent for a period of just under a minute. When the message is received, it is then decoded, and the operator has a few seconds to choose a message to send back to the original user. One person is talking on Even, the other on Odd minutes. It is extremely important to keep your clock synchronized as well. The message length is only a few characters, enough to include a very short message. Most conversations go something like this:


Basically, the message first passes location, in the form of grid squares. Next it passes signal reports, which is how strong the signal is above the noise floor. Finally, it passes an acknowledgement of  the received signal. 6 total messages, thus most JT9/JT65 messages are 6 minutes long.

The difference between JT9/JT65 is also of some worth. Basically, JT65 is intended to do EME messages, sending a message to bounce off of the moon. It is optimized for VHF, uses about 300 Hz of bandwidth, and sounds somewhat musical if listening to it. JT9 is optimized for HF, is newer than JT65, uses only 30-40 Hz of bandwidth, and has a slightly higher gain than JT9. There are fewer people who use JT9 than JT65, but that is slowly changing. JT9 sounds more like a buzzing sound.

These modes can be a lot of fun, and are good to do when reading a book, for instance. They are also a fantastic way to get new countries. In my brief time using them, I've got 13 worked states, and 8 worked countries, and I haven't spent a whole lot of time working these modes. Many of these are states/countries I haven't worked before too.


  1. You are partially correct about JT65. It WAS intended for EME/WS communication...but was quickly adapted for use on HF.

  2. John, as Ben noted, "It is optimized for VHF". This is 100% correct. Users found it was also capable with great success to be used on HF frequencies as well. This came after Joe Taylor designed it for 6m VHF EME experiments.

    If I knew your call John, I would like to meet for a QSO on 20m JT65a. Would love to have you in the logs. Ben, your welcome as well.

    Handing out Saskatchewan for eCanada Awards! (Right in the Middle of No Where, Saskatchewan!).