These radioÍs are normally supplied by the manufacturer operating on 28 MHz only.
When sold by dealers they have usually had this mod done, but occasionally there is a need for this infomation
There is also a jumper near the center front of the main board which enables the pull switch band functions.
On a super star 3900 that there are 4 resisters near the front to the right side of the radio that kept the radio from going 25.615 to 28.305 remove the resisters and the frequencies are expanded.
information provided by the defpom