So a little more about JS8Call, as I mentioned in the previous post the JS8Call software is derived from WSJT-X which most radio amateurs have used, most likely extensively. On top of the JS8 modulation JS8Call is a “directed calling” protocol to allow freeform messages to be sent and received. The messages are sent in blocks similar to the FT8 15 second send receive cycle however rather than a (semi) automated send receive in even and odd time slots you can send as much text as you like, the remote operator can then respond likewise.

In addition to the freeform messages there are a number of other interesting features within JS8Call which I’ll come on to in a future post.

How fast can JS8Call transmit?

JS8 uses similar transmission cycles to FT8 but has variable encoding, so some characters take longer to transmit than others, and there are currently (as of v2.1) 4 different speeds (this is from the documentation, see the latest documentation on http://js8call.com):

• Slow – 30 second frames – 25Hz bandwidth – around 8WPM decoded down to -28dB
• Normal – 15 second frames – 50Hz bandwidth – around 16WPM decoded down to -24dB
• Fast – 10 second frames – 80Hz bandwidth – around 24WPM decoded down to -20dB
• Turbo – 6 second frames – 160Hz bandwidth – around 40WPM decoded down to -18dB

The software will show you the average WPM of any message, I believe that the above WPM are taken from the classic PARIS calculation used in CW.

I recently volunteered to give a talk on the JS8 mode and JS8Call software for Warrington Amateur Radio Club. I don’t have a huge amount of experience with this mode so it was very much a talk that I needed to read up and have a go to prepare, I thought I’d pop an overview here for any who may be interested. Much of this was taken from the JS8Call website and the JS8Call guide.

What is JS8 and what is JS8Call?

So the first question that I had was the exact difference between JS8 and JS8Call, my understanding was that JS8 was the mode and that was correct. JS8 is a custom form of the FT8 modulation (Jordan Sherer designed 8-FSK modulation), I’m not 100% clear on the differences but I think one of the main ones is that JS8 uses variable encoding, so the characters don’t all encode to the same size, also there aren’t the character restrictions of FT8.

JS8Call is the software (which is largely based on WSJT-X), so JS8Call allows for the the directed calling (JS8 + Directed Calling), message relaying, message storage…

Installing and setting up JS8Call

JS8Call is fairly easy to install, download and follow the instructions… As JS8Call is based so heavily on WSJT-X it is fairly easy to set up if you’ve already got WSJT-X installed, the options are much the same and so setting up your rig and logging software shouldn’t differ much. If you don’t have WSJT-X installed then there are a lot of setup and trouble shooting guides around. The issues won’t always be the same but many won’t differ.

See below the similarities in the settings.