I guess there may be some out there that may not know and are wonderin' what the radio trick is...so I guess we ought tell em.
...If you tune your radio to a AM band and place the dial so it is not picking up a station, you will hear static...your in the right spot. If there is electrical discharges in your area (this can be mile and miles and miles away) you will hear a POP, or click or ticks....this is the discharge bouncing off the ionosphere...I think, er somethin' like that...you can Google it.
have a nice day