Member-only story
Python Radio 14: QRSS Mode
How slow can you go?
Amateur radio operators have many shorthand codes called Q signals that are used to speed communication. This is particularly useful when sending CW, as spelling things out in Morse code takes time.
A conversation is a QSO. A location is a QTH. Interference is QRM. There are dozens more. One that is often used by beginners is QRS. It means please send more slowly. Not everyone can copy code at 20 words per minute or more.
Going even further, there is a communication mode known as QRSS, because it is super extra slow. People don’t listen to it (because that would be very boring, as messages can take minutes or hours to complete). Instead, they receive it visually in a waterfall display on a computer screen.
Something you may have missed in the last bit of code we saw was that the speed was set to 0.1 words per minute. At ten minutes per word, our 83-character message would take about 160 minutes to be received.
That slow speed means our message takes up very little bandwidth. We can use very narrow digital filters in our SDR receiver, and that brings the signal to noise ratio up considerably, since we filter out almost all of the non-signal radio energy.
When we have a high signal-to-noise ratio, our signal can be received farther away, and we can use…
