Testing the flat Earth idea with broadcast FM radio
From
Kevin Alfred Strom@21:1/5 to
All on Sun Jul 6 12:07:58 2025
Testing the flat Earth idea with broadcast FM radio signals (roughly 100
MHz):
If the transmitting antenna is on a mountain near Los Angeles, for
example, at 300 meters high, and the receiving antenna is on a Pacific
island on a hill at say, 300 feet, with only ocean in between, there
would be no mountains or other obstacles to alter our calculations.
Let us say that the FM broadcast transmitter is running 50,000 Watts
(+77 dBm) into a unity-gain antenna, the receive antenna is also unity
gain, and the goal is a 20 dB signal-to-noise ratio, good enough for
decent high-fidelity reception. This would typically take a signal
strength of -73 dBm at the receiver antenna terminals. Therefore, the
allowable path loss is 150 dB.
The question then is, how far away could the island be from Los Angeles?
On a flat Earth, you would only be limited by path loss; the horizon
could never block anything at surface level or above. So path loss
strictly follows the inverse square law rule (loss increases 6 dB every
time you double the distance). Running the numbers, the island could be
4,700 miles away and still give you perfect reception.
On a spherical Earth, the radio horizon must be taken into account. For
the antenna heights given, the radio horizon is at 60 miles. The signal
would still be more than adequately strong at 60 miles, but would
attenuate very precipitately beyond that distance. So, on the real
Earth, the island could be no more than 60 miles away.
There actually is a Pacific island in just the right place to use Los
Angeles FM stations to test whether or not the Earth is flat. It's
called Oahu. It's 2,560 miles from LA.
If Los Angeles FM stations are booming in all the time there, the Earth
is flat.
If they are not, then the Earth is not flat.
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