Many years ago we started broadcasting radio signals for terrestrial use which inadvertently also radiated out into space. Possibly a civilization with appropriate equipment many light years away could have already detected these signals. But recently things have changed. By some estimates there are now 4.5 billion “new” small radio transmitters in use: mobile phones. Each phone transmits about 1 watt so the total power would be about 4.5 billions watts (4.5 gW) I am not sure of the physics here, that’s why I am asking! The basic question is simple: Are mobile phones making it easier for extraterrestrial civilizations to detect us. Obviously not all of this 4.5 gW radio signal would be effectively transmitted, something like the Drake equation might apply. Not all of the phones are on, say 0.60 are on at any one time Even if the phones were uniformly distributed over the Earths surface not all would be visible, say only 0.40 would be in line of sight to a distant point. In addition to the phones there are also the transmitter towers, these are not as numerous but possibly do make a positive contribution, use 1.20 So 0.60 x 0.40 x 1.20 x 4.5 gW = 1.296 gW Much less then 4.5 gW but 1.3 gW is still a significant radio signal. Is this argument reasonable? Does any of the radio signal from mobile phones even make it out of our atmosphere? How does this compare with the Earth’s existing total artificial radio emission?