a question from aviation tire..
For a given set of ionospheric conditions, as the frequency of an HF signal is increased:
A) the size of the dead space increases due solely to the decreasing minimum skip distance.
B) the size of the dead space decreases because the surface wave coverage decreases, and the minimum skip distance decreases.
c) the size of the dead space increases due solely to the increasing minimum skip distance.
D) the size of the dead space increases because the surface wave coverage decreases, and the minimum skip distance increases.
the answer given is c is not D?