Which of the following can reduce interference to a 2-meter band transceiver from a nearby commercial FM station?
Why A nearby commercial FM broadcast station (88 to 108 MHz) puts a very strong signal into the receiver front end, which is close enough in frequency to overload it. A band-reject (notch) filter placed in the antenna line attenuates that FM broadcast band while passing the 144 to 148 MHz signals you want. Removing the offending energy before it reaches the first receiver stage stops the front-end overload.
Watch out An RF preamplifier is the opposite cure: it amplifies the strong broadcast signal along with everything else and usually makes overload worse. Double shielding and bypass capacitors address energy leaking into cables, not a strong signal arriving through the antenna.
Strong out-of-band signal? Notch it out. Filter first, never a preamp, which only amplifies the problem.