JS8 is a weak signal mode similar to FT8. JS8 provides keyboard-to-keyboard chat, mailboxes, station query and more functionality.

The official JS8 website can be found at: https://js8call.com/

The JS8 installation is simple! JS8 is available for Linux, MacOS and Raspberry Pi.

You can download the JS8 binaries from: http://files.js8call.com/latest.html

OR - JS8 is an open source project, you can download the source from: Source code on BitBucket

1. Open the settings with F2 or the File, Settings… drop down menu.
2. On the General - Station tab
   1. Set your Callsign, e.g., M7ABC
   2. Set your Maidenhead Grid Locator, e.g., IO94
   3. You may wish to add @OARC to your Callsign Groups
   4. You may also wish to change the default Station Info and Station Status messages, these will be described later
3. On the General - Behaviour tab
   1. Check any behaviors you find suitable to your use
   2. If you find that Callsigns or Messages disappear from the main window too quickly, you can increase the delay it takes here, or reduce it if you think they appear for too long
   3. It is recommended not to change the End of Transmission Character Indicator as this is easily identifiable by default, this also applies to the Missing Frame Character Indicator
4. Under the General - Networking & Autoreply tab
   1. It is recommended to ensure Pause heartbeat transmissions while in a QSO is checked
   2. Configure the other options as desired
5. The Radio tab will allow you to setup CAT/PTT controls
6. The Audio tab will allow you to configure the soundcard(s) used by JS8
   1. The Notification Soundcard should be set to the audio device you would usually use for headphones or speakers for you to hear, not your rig
7. Under the Reporting tab you can configure spotting for PSKReport, APRS-IS and more
8. We will ignore the Frequencies tab as you shouldn't need to change anything here
9. The Saved Messages tab can be used to create standard messages which you can send to other amateurs on JS8
10. If you want to receive notifications, you can configure them under the Notifications tab
11. The UI tab is used for configuring the look of JS8, configure your fonts and colours here

JS8 has four (4) different speeds, each mode has a trade off between bandwidth and speed.

When should you switch modes?

It may be preferable to start QSOs using Slow or Normal modes, once a QSO has been established and signal reports sent, you may wish to change to a faster or slower mode based on your report and any other information provided by the other station such as if they are suffering from QSB.

By default JS8 only decodes transmissions of the same mode as you have selected. To change this behavior check the Enable Simultaneous Decoding of All Speeds (MULTI) option under the Mode drop down menu.

From the same menu, the Decoder Sensitivity option determines how many passes the decoder uses to detect JS8 signals. The higher the value, the more processing power required, lower power systems such as the Raspberry Pi 2 may require a lower number of passes. As a reference point, a Raspberry Pi 400 is capable of processing on (4x) Four Decode Passes mode with ease.

JS8 has a set of standard Query Messages which an operator may send to your station, enabling Autoreply will allow your station to reply to these message automatically.

Heartbeats are a “Networking” mode for JS8, a station sends a HB and any station configured to Autoreply with Heartbeats enabled will respond with a signal report. Heartbeats can be sent manually or automatically every N minutes. Heartbeats are opt-in so you may see that stations on PSKReporter (and similar) are reporting they can hear you, but they may not be setup to respond to a HB.

Stations that respond to HB requests may be suitable for other Autoreply messages such as those listed above.

JS8 provides “Mailbox” store and forward type messages using the “MSG” and “MSG TO:” commands. These messages are stored for later reading.

The MSG command identifies to the receiving station that the message is for them and they should store it for when the operator returns.

M7ABC: 2E0XYZ MSG Hello 2E0XYZ from M7ABC!

The MSG TO: command identifies to the receiving station that the message is to be stored ready for another station to request, these messages take the form:

M7ABC: 2E0XYZ MSG TO:M0XXX Hello M0XXX from M7ABC!

For store and forward messages, if the destination station is seen sending a heartbeat, the storing station will respond to the station identifying they have a message for them, indicating the message ID. The destination station can then request the message be sent to them. This is done with the QUERY messages identified in the previous section

Similar to the store and forward mailbox feature, stations can also act as relays, where a message is sent immediately to the destination as opposed to stored and sent on request. This would allow a QSO to take place using a middle man station, note that this method of communication would be very slow.

When responding to a station, select them in the station list on the right, here you can send them a directed message. There are some predefined messages such as the QUERY messages but also others such as REPLY which is used to respond to a CQ call and SNR which is used in response to a REPLY message. After this establishment you can use free text messaging by typing into the message box and hitting Enter/Return to send the message. You can continue to write your message while it is sending to avoid delays or doubling however, if the software reaches where you are typing it will consider this the end of the message and the new text added will be a new message which is sent, this may cause confusion so use this feature carefully.

The longer your message is, the longer it takes to send. Keep in mind your mode of operation when writing your messages, use acronyms and shorthand where possible.

JS8 QSOs can take a long time, try to keep messages as short as possible however sometimes a 5 (five) minute message is unavoidable if you're having a proper long form QSO.

If you have a good signal, try using one of the faster messaging modes, remembering to be mindful of adjacent stations as you increase your bandwidth.

If a station is operating in AUTO mode and the operator is away, this may be a good time to send them a long message using the MSG function.

Due to the slow nature of JS8, many operators will use a variety of acronyms in addition to QCodes to help pack more information into their messages with minimal impact to the time taken to send a message.