Step 1: Formula for Radio Horizon The distance to the radio horizon, d, can be found using the formula: d=√2Rh Here, R is the radius of the Earth and h is the height of the antenna. Step 2: Plug in the Values Let R=6.4×106 meters (which is 6400 km ) and h=39.2 meters. Step 3: Calculate Inside the Square Root Multiply them: 2×6.4×106×39.2 Step 4: Take the Square Root Find the square root of the product: d=√2×6.4×106×39.2 When calculated: d=22.4×103‌ meters ‌ This is the same as 22.4 kilometers. So, the radio horizon is 22.4 km away.