Do you have tubes in your practice amp? My Ampeg BA115T picks up a classical station... however it's definitely the amp (tube electronics) picking up some stray fequencies in my case... I'm not sure there's much you can do in this case...
I've never heard of a bass itself picking up radio frequencies...I've never heard of anything other than tubed amps doing this.
Browntree
And David spake to the chief of the Levites to appoint their brethren to be the singers with instruments of music, psalteries and harps and cymbals, sounding, by lifting up the voice with joy. I Chronicles 15:16