|Mode||Bandwidth||Speed||Frame Length||Mininum SNR|
|Slow||25 Hz||8 WPM||30 seconds||-28 dB|
|Normal||50 Hz||16 WPM||15 seconds||-24 dB|
|Fast||80 Hz||24 WPM||10 seconds||-20 dB|
|Turbo||160 Hz||40 WPM||6 seconds||-18 dB|
Table of Contents
JS8 using IC-7300
To get started, have a look at these pages:
- Rig: Icom IC-7300
- Serial Port: Depends on each computer
- Baud Rate: 9600
- Data Bits: Default
- Stop Bits: Default
- Handshake: Default
- PTT Method: RTS
- Port: Same as on the
- Mode: None
- Split Operation: Fake It
- Tx Delay: 0.2 s
- Soundcard Input and Output: (USB Audio CODEC)
At normal speed, JS8Call transmits in blocks of 15 seconds.1) For two stations to be able to communicate, the start of these blocks has to be synchronized to within about 2 seconds of the horizontal lines on each station's scope. That's why it's really important for everyone to keep their computer clock as accurate as possible (to within 2 seconds of each other). You can easily test the accuracy of your clock by going to https://time.is
Here's an example of a block that is within the horizontal lines, so it's well synchronized (with my station anyways):
There are three ways to adjust your clock:
- You can use an internet service to adjust your computer's clock such as Network Time. Here are the Network Time settings I changed so that it keeps my clock within 200 ms:
- If you're “offline”, you can use the WWV time signals2) on 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, or 20 MHz.
- You can use the Time Drift tool in JS8CALL, which adjusts the program's clock offset without changing the operating system's clock. To see the tool, make sure that this has a check mark:
Show Waterfall Controls→
Timingtab. Use the up and down arrows to adjust your time drift (more on this below):
Here's how to use the Time Drift Tool:
- If everyone's computers were perfectly synchronized, all these
Time Deltaentries would be 0 ms. Realistically, there's always be a bit of variance, but you should try to ensure that your clock is synchronized with most other operators.
- For example, suppose that most operators are around +500 ms, then you'd want to adjust your
Time Driftto -500 ms to cancel out the
Time Delta(and vice versa). Note the sign (+/-) of the
Time Driftis opposite that of the
Time DeltaFor example, here I had to put a
Time Driftof -100 on mine to match the other operators:
- The last thing to keep in mind is that this time drift might need to be adjusted periodically depending on how well your computer keeps time.
The Issue: Sometimes the QSOs in JS8Call don't get decoded properly: The waterfall shows the data blocks being received, but the text doesn't show, or parts of it do, but with gaps showing as “…” instead.
The Reason: At first, I thought that the YAAC (the APRS program I was running at the same time) was causing the issue because when I close it, JS8Call would start behaving again. But it turns out that it was simply a lack of CPU power. I'm running JS8Call on a cheap mini computer and was reaching 100% CPU when running JS8Call, YAAC, and Firefox at the same time.
Turns out that running any two of these programs is fine, but not all three.
To check on your CPU usage, press CTRL+ALT+DEL on your keyboard, then select
If the waterfall on the JS8Call screen shows a narrow light blue region with darker areas on either side, it could be that your radio filter is too narrow. Roughly, the filter should be set to 3kHz. I usually have mine set between 500Hz and 2700Hz.
- Sometimes, the band is really busy with stations sending Heart Beats. The region between 500Hz and 1000Hz seems to be used mostly for that sort of automated stuff. If you want to stop all those HB from filling up your screen, you can quickly tighten your filter between 1000Hz and 2700Hz.
- The notch filter is also useful sometimes to quiet down a really loud station or a random RTTY signal.