# Why AM is preferred over FM in long distance communication?

In almost all long distance communication AM is preferred over FM. Do type of modulation has anything to do with this or it is just depending on transmitting frequency?

• I think you need to justify your assertion. – Andy aka Aug 28 '14 at 7:11
• I second that. May that be that the traditionally allocated slots for AM are in the f range where the EM waves follow the earth/bounce on the ionosphere? AM is usually less energy efficient than FM but the receiver is trivial to build... Nothing to do with distance though. – Vladimir Cravero Aug 28 '14 at 7:24
• Are you linking carrier frequency and modulation scheme and asserting its the modulation scheme that is more attractive over long distances? – JonRB Aug 28 '14 at 7:25
• – JYelton Aug 28 '14 at 15:57

link loss (dB) = = 32.45 + 20$log_{10}$(f) + 20$log_{10}$(d)