Line of sight propagation when land is 700m above sea level

[pokie_panda]

Homework Statement

A 200 MHz signal is to be transmitted over a point-to-point wireless link. Assume the earth’s surface is flat over the entire propagation distance, and is 700 metres above sea level. The transmitter is at ground level, and the receiver is situated on top of a multi-storey office building, 80 metres from the ground. If the earth’s radius at sea level is 6,371 km, what is the maximum distance possible between transmitter and receiver (assuming no reflections off any objects)?
A.88.9km
B.31.9km
C.99.7km
D.50.5km
E.94.5km

Homework Equations

For this i got two equations
d=√2×R×H
or
d= 3.57√h

The Attempt at a Solution

Because R and the sea land is 700m above sea level.
R= 7071 km
h= 0.08km
using the first equation
d=√(2×R×H)
I get 33.63 km

but because the other one is on ground H is zero
The d=0.
making d= 33.63 isn't a option.

So i tried formula 2
I get B.31.9km.
Also when i use the first equation i used the Earth radius at sea level 6,371 km
and also get also get B.
But i have a leaving that it should be greater.

Any help appreciated

 

[gneill]

Be careful when adding meters to kilometers --- check your radius calculation!