JT65 is one of the more specialist data modes that I’ve played with, but I must admit, it’s quite addictive.
As with modes such as PSK31 and WSPR, you interface your HF rig to a computer, and send out text encoded by your computer over the amateur bands. With JT65, you’re restricted to very small messages, with a limit of 13 characters per message.
Here is a typical conversation over JT65:
|“CQ M6PSK JO01”||CQ call from M6PSK|
|“M6PSK M0PSX -08”||M0PSX replies with a signal report|
|“M0PSX M6PSK -12”||M6PSK responds with a signal report|
|“M6PSK M0PSX RRR”||M0PSX says Reception Report Received|
|“M0PSX M6PSK 73”||M6PSK says Best regards|
|“M6PSK M0PSX 73”||M0PSX says Best regards|
Each message of up to 13 characters is sent over the course of 50 seconds, starting at the top of each minute, so the above conversation would take six minutes. One person sends on the odd minute, and the second person sends on the even minute.
You’ll see from the above screenshot that there is a “waterfall” (as with PSK31) that shows multiple QSOs. It’s a case of tuning in to a JT65 frequency, waiting for one-minute transmit cycle to complete, and looking for a CQ message to reply to.
JT65 handles very weak signals, just like WSPR, so will get through where voice and PSK31 won’t. You can also use the great online PSK Reporter website to see where your JT65 CQ calls are reaching, making it great for checking your antenna’s performance.
Setting up for JT65
This is one of the more tricky modes to set up for, and this won’t be a full “how to” guide, as there are plenty of those online already. This is just a summary, plus some notes on what I’ve discovered so far.
First off, you need to connect your PC to your HF rig. As with WSPR and PSK31, you’ll need some kind of TNC (Terminal Node Controller) to interface between rig and soundcard
Then, you’ll need some software:
- JT65-HF by W6CQZ – The main application for JT65 (Also available here: JT 65 at Sourceforge)
- JT65 Alert – A handy application that helps manage your JT65 QSOs
The software is rather tricky to get set up, and sorting the handshaking between rig and PC was something of a trial-and-error affair. Once it’s working though, using the software is fairly straightforward.
One key thing I learnt along the way is that your computer’s clock has to be spot on. Computer’s onboard clocks are notorious for drifting off, and you need your clock to to be accurate to the precise second, or things don’t work. I found the application Dimension 4 really helps here, as it runs in the background and keeps your clock in-sync by resetting the time to one of the online atomic clock servers every 20 minutes. Very helpful.
That’s the basics. If there’s any interest, I’m happy to expend this article, but hopefully this tells you what JT65 is all about, and gives you enough to get started.