Um, that's just not true. SInce the radiation pattern is reduced at higher
altitudes, the chance for frequency congestion is every bit as probable. If
all signals are reduced proportionally, then the RELATIVE signal strengths
remain constant.

Jim



Since the radiation pattern is reduced at higher altitudes, there is less
chance
of frequency congestion and receiving a signal you don't want.
With limited frequencies available, you have to depend on other
limits to prevent unwanted reception of other signals.