How TrueD™ diversity works:  Imagine dropping a pebble into a still pond.  If the pebble is far enough away from the shore, the ripples continue away from the point of impact undisturbed.  But what happens if we drop the same pebble near the shore?  On the side facing away from the shore, the wavelets will be as before, undisturbed.  If we look at the side facing the shore, what do we see? 

If the shore is rocky, we may see that the waves are reflected back from the rocks into the incoming waves.  If we look closely, we will see that the reflected waves combine with these incoming waves.  Depending on their position relative to each other, they may combine and add to make a larger wave, or if the top of one wave and the bottom of another meet, they will even out leaving no sign of a wave at all.

This is what happens to radio waves as well.  We have few reception problems when the Transmitter and Receiver are situated over flat land or water and the radio waves are undisturbed. 

But in an urban environment, the radio waves are reflected from buildings, cars, light posts and metal objects in general,  and may be absorbed by trees, shrubs and people. Inside a building, high frequency radio waves will be reflected by filing cabinets, metal studs in walls, lighting fixtures, metal desks, etc.

This is why when we try to use a cellular phone inside a building we may experience good reception only a foot or two from a problem area as the waves may combine and cancel in one area and add in another. 

Now if we get tricky, we can place three antennas, several radio wavelengths apart, and look at the signal coming from each one.  Statistical studies show that almost 100% of the time, one of the three signals will be good as long as they are within range.