1) Cannot enter 30 MHz.
The pilot cannot enter 30.000(0) into the UFC.
Anything over 30.000 works, like 30.0001 and 30.001.
30.000 can be entered as preset using the mission editor, and this will work.
2) Decimal representation under 100 MHz
The radio appears to mandate 6 digits frequencies at all times, which means frequencies lower than 100 MHz have four decimal places instead of three.
3) Any kHz value can be entered
I'm not entirely sure if this is a bug, since I don't know the details of the radio, but in DCS, you can enter any value in the kHz field.
So e.g. 123.456, 99.9999, and 30.0001 are valid frequency entries in the UFC.
Harrier_Radio_Freq_entry_bug.trk