The crossband transponder on the ISS has been activated. It is possible to establish connections via the ISS as via a classic satellite FM transponder with an uplink at 437.800 MHz ± 10 kHz Doppler and a downlink at 145.800 MHz. Unlike other transponders, it is not necessary to use CTCSS.
Also keep in mind that during personal time off, astronauts can listen and possibly actively participate in communication.