“The idea with JS8Call is to take the robustness of FT8 mode and layer on a messaging and network protocol for weak signal communication on HF with a keyboard-to-keyboard interface. JS8Call is heavily inspired by WSJT-X, Fldigi, and FSQCall and would not exist without the hard work and dedication of the many developers in the amateur radio community.”

Frequently asked questions

You’ve got questions, we’ve go the answers. If you cant find the answer to your question please have a read through the documentation. You can always contact us if you still need help.

What is JS8Call?

JS8Call is an experiment to test the feasibility of a digital mode with the robustness of FT8, combined with a messaging and network protocol layer for weak signal communication on HF, using keyboard-to-keyboard style interface. JS8Call is heavily inspired by WSJT-X, Fldigi, and FSQCall and would not exist without the hard work and dedication of the many developers in the amateur radio community.
FT8Call stands on the shoulder of giants…the takeoff angle is better up there.

JS8Call stands on the shoulder of giants…the takeoff angle is better up there.

How can I find out how to use JS8Call?

The best place to start is to read the documentation, it provides you with all the information you will need about JS8Call and its features, the documentation can be found by clicking on this link we encourage all users to please read this.

You can look at our User Guides and Videos that you will find on the Guides Page

And you can also join the groups.io email list.

Do I have to Pay for JS8Call?

JS8Call is Free Software.

It is and will always be free. Free as in beer and free as in speech.

Meaning, you will never have to pay for it, and, you can do with it what you want. It is a derivative of WSJT-X, is open source, and licensed under the GPLv3.

What frequency can I use for JS8Call?
The short answer is that you can use any frequency that allows data/narrow band modes. You can program new frequencies into the settings that will appear in the Frequency Drop Down, you can type the desired frequency into the frequency drop down, or you can manually tune your radio to a new frequency.

From version . 0.5.2 the default “centre of activity” frequencies set up in FT8Call are listed below, but please note as we previously said, these are not set in stone and can easily be changed in your settings, or you can simply manually retune your radio to another frequency if the frequency is in already in use.


1.842Mhz 3.578Mhz 7.078Mhz
10.130Mhz 14.078Mhz 18.104Mhz
21.078Mhz 24.922Mhz 28.078Mhz
What operating system can I run JS8Call on?

JS8Call is compatible with most modern operating systems Windows, MacOS, Linux – desktop and Raspberry Pi versions are available. The windows version has been tested on windows versions 7 to 10, some users have even got it running on Windows XP.

Check out the downloads section for your specific Operating System

Do I need to synchronise my computer's time to use JS8Call?
Yes, your computers clock needs to be within 2 seconds of everyone else. You can sync the clock using a variety of software if you are connected to the internet using the Network Time Protocol (NTP). If you have no access to the internet you can sync your time using an attached GPS or manually if your GPS does not connect to your computer. You copuld also manually sync your time but watching the signals on the waterfall display and setting the time when they begin to transmit,  not the most accurate way of syncing but it might be enough to get you up and running!

if you have internet access you can check how accurate your clock is by going to time.is

Do I need a connection to the internet to use JS8Call?

No you don’t, JS8Call only requires your computer to be connected to your radio.

You will of course need to make sure your computer’s clock is as accurate as possible, and your copy of JS8Call will not be able to report spots to PSKReporter or APRS-IS.

What are the random three (or six) characters at the end of relay and acked message commands?

These are a checksum for the message added to ensure all of the message frames were delivered correctly before retransmitting / alerting. If received in its entirety by the receiving station, these checksums will not be displayed to them.

What are the Center and Offset settings for?

Center is your rig center. If you don’t know, or don’t use the QSY feature, then leaving it 1500Hz is fine.

Offset is where you are transmitting. That’s up to you and the signals you’re responding to.

You said that all printable uppercase ASCII characters can be used. Do some take more time to send than others?

Yes. The characters that are sent in the messages are variable encoded, ranging from 3 to 19 bits in length based on their probability of being used in a sentence. The most common characters take the least amount of space, allowing us to send more than 13 characters per transmission cycle on average.

    • Example: Space and E are only 2.5 bits in length. You could send about 22 (!!) of them in a single transmission. Whereas a character like { is more like 14 bits in length, you could only send 4 of those. (But really, how frequently do you use that character?)
    • Here are some examples of phrases that could be sent in one 15 second transmit cycle:
      • EEEEEEEEEEEEEEEEEEEEEE (22 characters)
      • I HAVE EATEN A SHOE (20 words per minute)
      • WHICH WAY TO OHIO (16 words per minute)
      • NEVER HAVE I EVER (16 words per minute)
      • TU UR 599 4A GA (20 words per minute)
      • Etc
How fast does JS8Call transmit?

JS8Call uses the same 15-second transmission cycle as FT8. What is different is that due to the variable encoding of the characters, JS8Call can transmit up to 22 characters per transmission frame. For average sentences, JS8Call can pack words very tightly, at around 15 WPM.

    • Example:
      • This phrase is 35 words. It would take 11 transmission cycles to send (2 minutes 45 seconds). That is just under 13 WPM.
      • This phrase is 19 words. It would take 5 transmission cycles to send (1 minute 15 seconds). That is just over 15WPM.
      • This phrase is 5 words and takes 1 transmission cycle to send (15 seconds). That is 20 WPM
    • Morse code has a neat way of calculating WPM, timing how long it takes to transmit the word PARIS. In JS8Call, PARIS is encoded into 17 bits (3.4 bits/character). Each transmission cycle can pack up to 69 character bits. That equates to about 16 WPM. (69/17=4.05 words / (15 seconds * 4))
    • The app shows this in the status bar

Isn’t 10-20 WPM too slow to have a conversation?

If propagation is good enough for a faster mode, you should be using it instead! But, with poor conditions like we have experienced at solar minimum, JS8Call might just be the best balance.

It may seem really slow (and it is, relatively speaking). However, FT8 modulation is able to decode (theoretically) down to -24dB below the noise floor. Not many modes can say this, especially those which transmit at faster speeds. What does this mean? JS8Call may work when other modes cannot.

We believe that communicating slowly is better than not communicating at all.

What is the JS8Call Relay Challenge?

This is a friendly competition to maximize the number of continents one can pass a message back and forth to using the retransmit command.

We’ll be giving away an award (and prize) to the first team of operators to successfully relay a message from one continent across two other continents (NA, SA, EU, AF, AS, OC, AN) and relay an ACK back to the original station using JS8Call. All you need to do is submit your logs from each station and optionally photographic/video documentation of your effort.

For example, this is what the outgoing and incoming messages could be:


Does BEACON mode violate FCC 97.221 Automatically Controlled Digital Station rules in the United States?

For operators in the United States, here’s a reference to the rules: http://www.arrl.org/part-97-text

With this, keep in mind:

      • 1) The control operator is responsible for the station operation. The software makes a best effort to require a human to be present during operation (beacon off by default, a watchdog timer feature built-in, etc). It is up to the operator to make sure they are in compliance with the rules of their jurisdiction.
      • 2) Responses to directed queries by non-automatic stations fall under §97.221.C.1 exemption.
    • So, my recommendation to operators is to turn off BEACON when not at the station control point, but, they can feel comfortable leaving AUTO on while they are away since their station would only be responding to queries initiated by a non-automatic station.
Why isn't my station responding to ALLCALL?

Previous versions of JS8Call (FT8Call) had a directed message of “ALLCALL?” that had stations return SNR reports automatically. This has been replaced, starting in version 0.7 of JS8Call, with BEACON and BEACON ACKs. Stations will no longer respond to the “ALLCALL?” query.

I love what you’re doing. Do you have a PayPal or Patreon where I can I send you a donation as a “Thank you?”

I appreciate the gesture! I continue to work on this project as a donation of my time to the Amateur Radio ecosystem. I’m not looking for payment of any kind. If you feel so obliged, however, I’d appreciate if instead you sent along any donation you’d like to make to a local charity of your choosing. Something like the American Red Cross, Salvation Army, or even a local Amateur Radio club. They’d put that money to far better use!

How to Download the JS8Call software

Simple, just click the button to go to the downloads page!