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JS8-CALL
JS8Call
overview and international band-plan
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JS8Call
is a digital amateur radio communication mode that builds upon the
popular FT8 protocol, developed by Jordan Sherer (KN4CRD). It's
designed for keyboard-to-keyboard communication and weak-signal
operation, allowing real-time conversations rather than just
exchanging minimal information like in FT8. Here are some key
features and characteristics of JS8Call:
1.
Weak Signal Capabilities
JS8Call
inherits FT8's ability to operate under weak signal conditions,
often being able to decode signals that are well below the noise
floor. This makes it ideal for low-power operations (QRP) and for
communicating over long distances, even with poor propagation.
2.
Human-to-Human Interaction
Unlike
FT8, which is primarily used for automated signal exchanges, JS8Call
allows for more conversational, free-text communication. This makes
it useful for chatting and message relaying.
In
keyboard-to-keyboard mode, operators can chat in near real-time,
with messages being decoded and displayed as they're typed.
3.
Time Synchronization
Similar
to FT8, JS8Call relies on precise time synchronization, which is
typically achieved using a computer's internet time service or
GPS-based timekeeping. Messages are transmitted in synchronized
15-second intervals.
Required clock accuracy: Stations generally need to be synchronized within about ±1 second for reliable decoding.
Practical tolerance: The decoder can sometimes handle offsets up to about ±2 seconds, but beyond that, successful decoding becomes unlikely.
4.
Message Relay and Networking
JS8Call
has features for message relaying and store-and-forward operation,
allowing users to send messages to stations that may not be directly
reachable. This creates an ad-hoc network of stations capable of
forwarding messages.
5.
Auto-Reply and Directed Commands
JS8Call
includes auto-reply and directed commands, which can be used to
query other stations, request signal reports, or even relay
messages. This makes it useful for semi-automated operations,
especially during emergencies or in remote locations.
6.
Bandwidth and Transmission Speed
JS8Call
uses an 8-tone frequency-shift keying (FSK) modulation, occupying a
bandwidth of about 50 Hz. The transmission speed is slower than FT8,
but this trade-off allows for the flexibility of free-text
communication and additional features like relaying.
7.
Use Cases
Emergency
Communications: Its ability to operate under weak signal conditions
and relay messages makes JS8Call suitable for emergency
communications.
Ragchewing:
JS8Call allows for longer conversations, making it ideal for
operators who want to engage in casual conversation.
Low-Power/QRP
Operation: Because of its weak signal capabilities, JS8Call is
popular among QRP enthusiasts who want to make contacts using very
low power.
8.
Getting Started
Software:
The JS8Call software is available for Windows, macOS, and Linux. It
interfaces with your radio via a sound card, similar to other
digital modes.
Radio
Interface: Most operators use an audio interface like the Signalink
USB or other similar devices to connect their radio to their
computer.
Time
Synchronization: Ensure that your computer’s clock is synchronized
to within a second or two for optimal operation.
JS8Call
provides a blend of the robust weak-signal performance of FT8 and
the interactivity of conversational modes, making it a versatile
tool for amateur radio operators looking for both practical
communication and casual chatting.
JS8Call
Frequencies by Band (Dial Frequency in USB Mode)
|
Band |
Frequency |
Notes |
|
160
meters: |
1.843
MHz |
|
|
80 meters: |
3.578
MHz |
|
|
40 meters: |
7.078
MHz |
Can
be active |
|
30 meters: |
10.130
MHz |
|
|
20 meters: |
14.078
MHz |
Most
activity |
|
17 meters: |
18.104
MHz |
|
|
15 meters: |
21.078
MHz |
|
|
12 meters: |
24.922
MHz |
|
|
10 meters: |
28.078 MHz |
Can
be active |
|
6 meters: |
50.318
MHz |
|
|
2 meters: |
144.178
MHz |
|
|
Mode |
Bandwidth |
Speed |
Notes |
|
Slow |
25Hz |
30s
~8WPM |
This
mode is the most efficient for low power or reaching stations
who struggle to hear you, however it is the slowest mode |
|
Normal |
50Hz |
15s
~16WPM |
This
is the default mode for JS8, it provides good speed and range
with good speed. Most stations will be using this mode |
|
Fast |
80Hz |
10s
~24WPM |
When
you are being heard well by the other station, this mode
allows you to send messages quicker, you may be harder to
decode to some stations |
|
Turbo |
160Hz |
6s
~40PWM |
This
is the fastest mode JS8 offers, providing high speed messaging
between stations. The high bandwidth will make it much harder
for some stations to hear you |
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
Additional information: http://js8call.com/
Tracking
activity: https://hamspots.net/js8/
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Page initiated 5
October, 2024
Page
last revised 27 August, 2025
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