Question

Why do we hear some radio stations better at night than during the day?

Answer 1

As it turns out, the ionosphere reflects certain frequencies of radio waves. So the waves bounce between the ground and the ionosphere and make their way around the planet. The composition of the ionosphere at night is different than during the day because of the presence or absence of the sun.

Answer 2

Because radio signal are clear and  less troubled at night .. During daytime...Other frequencies also get intermingled with radio signal frequency