# How do you calculate the range of a VHF transmitter that is on-board an aircraft?

I'm trying to calculate the range of a VHF transmitter on an aircraft output power 50W, frequency 130MHz, and reciever sensitivity of -100dBm.

The calculations I have made give me ridiculously high numbers in the regions of thousands of Kilometres. The formula I used for this is as follows: Is there perhaps a different formula that I am not aware of?

• – ymb1 Sep 14 '18 at 12:25
• What are the values you're using for the rest of the variables? Gt and Pr would be needed to compute the R value. Is your wavelength in meters, or in what unit of measure? – Javier Larroulet Sep 14 '18 at 15:41
• Antenna and recievers gain can be treated as negligible i.e. 1 in each case. The recieved power is -100dBm. I am getting crazy values when I utilise the above formula since -100dBm the lowest signap strenth that the reciever should pick up. But that translates into 0.1pW which then means ghe distances is far greater. How do I factor in line of sight and the curvature of the earth? – Cyom Sep 14 '18 at 15:43

VHF radio transmissions are primarily limited by line of sight. The formula for this is d = 1.23 * (√h1 + √h2) where h1 and h2 are the altitude s in feet, and d is the max range in miles.