Some airports run a frequency jammer that will jam a frequency range when real close to the airport to prevent interference with their radar and ALS/ILS system . Also, if it’s near military aircraft, there’s other gadgets that can interfere as well. But generally the closer you are to Doppler radar, the worst all your other freqs will be. There’s a spot along I70 near the Indianapolis Center Radar tower that for a mile in each direction, you get only 1 FM radio station
