Hey Farley,
A true radio link is done through something called repeaters. If the Earth were still flat like in the days before Radio, we wouldn’t have this problem, but since we invented Radio Waves and the Round Earth thing, we encountered a few problems:
A ( ) B
See the problem was we couldn’t get the signal from A to B without drilling a hole in the Earth. Since we are superior to everything except dolphins and whales, we figured out that if we put a repeater between A & B, we could send the signal to B from A.
We’ve even got this thing to work in space. Now we can send a signal to a satellite above Earth and send it out to Mars and beyond. We are Magnificent!
OH, the dolphin and whale thing. They’ve figured out their own version of CDMA (currently used in many cell phones and devloped about 20 years ago). Dolphins and whales are able to send their sonar sounds, together, along the same channel for miles underwater, even many times, not in a straight line. When the sound gets to the other side of an area, dolphins and whales are able to pick out the sound they are looking for, process it and send a message back!
I’ve always found that part exciting!
James in San Diego