In Asia, specifically in Bangladesh, we often listen to FM radio. But the signal is not clear everywhere, that means it produces some noise.
From my childhood till today, I have observed that, if I keep the radio in a fixed position and I increase distance between me and it, the signal starts to be more and more noisy.
And sometimes, if I touch the antenna, the signal become more clearer. This is an observation from real life. But I don't know the exact reason behind it.
Would you please describe the exact reason behind it?
Note:
This question came in my mind few days before, but I was confused which site best suits for this question. However, I thought this site is the most suitable one to ask the question. If you think it is off-topic here, then don't hesitate to have a migration request to the appropriate site.
I am also sorry for my bad English.
Best Answer
No one is surprised by the general phenomenon that radio signals get weaker, the further you are from the transmitter. However, most people are surprised at how much the signals will vary within a short distance, locally.
This effect is called multipath fading, and is caused by multiple reflections of radio waves off walls, cars outside, people etc. At the receiver, the signals can combine to be bigger or smaller than the signal would have been with the multiple reflections. Of course, you don't notice a problem when the signals are bigger.
A particular issue with FM radio in the 100MHz band is that a typical human is about half a wavelength tall. This means that moving a human around in the region close to a receiver is particularly effective at changing the multipath reflections.