Original poster: Steve Conner <steve@xxxxxxxxxxxx>
transmissions that go All The Way Round.
Such occurs with SW, on varying freqs, depending on time of day/year, etc,
sometimes called 'long path'.
I've heard it when listening to high powered amateur stations on the
HF bands. They sometimes have an echo caused by their transmission
reaching you both ways round the globe.
I've never run more than 100w, but I guess if you have a real high
powered station, when you let go the push-to-talk you will hear the
echo of your own transmission going all the way round the world and
right back to you.
It's probably the closest you'll ever get to "Resonating the earth"
like Tesla wanted to.
You could almost imagine hooking up a DSP that would analyse the
incoming echo and fire off another burst from your transmitter that
would be exactly in phase and reinforce it. But the path loss is so
high. You fire off 1500 watts (if you're a US ham) and you're lucky
if you get one picowatt back, which is totally negligible compared to
1500 watts, so there's no way you could get anything to build up.
On a closely related note, I've never ever heard two echoes with a
spacing that would indicate the signal made it round the globe twice.
Maybe some more experienced ham operators have?