What is the maximum height above ground to which an antenna structure may be erected without requiring notification to the FAA and registration with the FCC, provided it is not at or near a public use airport?

# 200 feet

When you are 20,000 feet from the nearest runway edge your tower may rise to 20,000 x 0.01 = 200 feet. Similarly, for the shorter runway case, if you are 10,000 feet from the runway the tower may rise 10,000 x 0.02 = 200 feet.

With a heliport, the slope defining the maximum antenna height is 25:1, or the antenna may be 1/25 of the distance to the nearest edge of the heliport. At exactly the 5000 feet distance within which this must be considered, the antenna may again rise up to 200 feet high.

Read more: http://www.hamradioschool.com/g1b01-maximum-antenna-structure-height/