RBSK is available on the 49-meter shortwave band, at 6120 kHz.
Even today, some car radios — particularly those in Mercedes vehicles — still support this frequency range, and many car stereos actually make excellent shortwave receivers.
You might even have a vintage “grandpa radio” from your childhood that’s still in perfect working condition.
A more modern option is to tune in using a WebSDR receiver, such as KiwiSDR — freely available to everyone around the world.
With KiwiSDR, just follow this basic setup:
Open the site, set the modulation to AM, and tune the frequency to 6120 kHz.
If you want to dig deeper into the settings, there’s an online manual built into the KiwiSDR interface.
Good starting points are:
http://tredxk.no-ip.org:8075/?f=6120.00samz10