Signal Strength
Like any other signals, radio signals (including those signals being transmitted from an RPAS), will encounter interference.
A radio operator will use a simple number system to indicate the strength of an incoming signal.
VHF Radio Signal Obstacles: Transmitter Power, Intervening Topographical Features, and what can be considered to be the most important factor affecting VHF range, antenna height
1: unreadable
2: readable now and then
3: readable with difficulty
4: readable
5: perfectly readable
