The MiG-19 series used the RSIU-4V radio transceiver.
Its frequency range is between 100 to 150 MHz in the 2 to 3 meter band.
Its range is:
Up to 1000 meters (3,280 feet) altitude: 120Kms (65 nmiles).
At 5000 meters (16,400 feet) altitude: 230 Km (124 nmiles).
At 10,000 meters (32,800 feet) altitude: 350Kms (189 nmiles).
As you can see it lacks any capability for manual frequency selection.
Although you can store 6 preset frequencies (via Mission Editor) for use while in flight.
IMO, this makes sense because the MiG-19's (any version) cockpit is an extremely busy environment. You have to operate multiple switches all the time when you need to enable/disable anything.
If you are using easy comms, the radio will self tune to the selected frequency. If you are not using easy comms, the only frequencies available are those in the preset channel. Plan your mission accordingly.
One interesting thing is that the audio output can be switched between radio communications or the ADF's NDB station identity morse code.