Limit a radio to a single station
The radio tuning dial will be some form of a variable component (potentionmeter, variable capacitor). The radio I built had a tuning capacitor attached to the tuning knob.

If you don't want to hot glue the dial in place like Olin suggests, you could turn the dial to 88.3, then remove the variable capacitor and measure its capacitance (probably using an LCR meter). Then replace it with a set capacitor of the read value. The process would be the same if your radio uses a different tuning component, just replace with a set value of that component.