So julianmartin is lying, but Lady Blount (flat Bedford Level pictures *) was telling the truth?
I'm not saying he's lying. He's just wrong. Here's what he said:
"Let me re-iterate. Directional Electromagnetic radition that circumnavigates the earth, is NOT possible on a dual flat plane of reflection; let alone omnidirectional. It would be emitted to into space."
This is obviously wrong, because it is freely admitted that Ham Radio and AM signals are not traveling in a straight line, but bounce between the ionosphere and the ground like rubber balls to reach far off destinations.
If this is happening at all directions and angles, obviously some of it will be reflected back when it hits the side of an angled hillside.
Let me re-explain that sentence, in doing so I'm giving you the benefit of the doubt Tom that you slightly misunderstood what I said.
It is possible to emit a signal in a very concentrated beam that is entirely directional using the correct antenna (example, Yagi Beam. My beam antenna is a Hex Beam, one of these:
http://www.hexbeam.com/ (just so you don't think I'm dicking you around)), and can only be received by people in the immediate path of transmission; and that stays true for many thousands of miles. Now on top of that, after an appropriate amount of time (which varies), one's signal can be received by oneself by an antenna that is oppositely arranged to the original transmission antenna. Now let me break it down further. The signal is entirely focused in the horizontal plane, we have already covered that. In the vertical plane...guess what, it's the same thing!! A nice pretty picture below shows EXACTLY what happens:
So the reflects can continue all around the globe. It is HIGHLY important in this theory that the waves are directional. What changes their direction are the various reflections. And bear in mind, only their vertical plane direction is changing, not their horizontal.
Now I mentioned it working with omnidirectional antennas too. In some circumstances the same thing can happen where part of the emitted signal reaches the ionosphere (pretty much all of it will, but at that height it is greatly dispersed), gets a good bit of propagation, bounces down to earth like the rest of the signal but perhaps a lot further, and by chance travels through atmosphere much more suitable for signal strength preservation, then the process is identical to what I have listed above.
Another sidepoint here - in roundearth, pretty much all long range communications (post 2000 miles I would say) that rely on HF signals, bounce off the ionosphere to get to their destination. From a round earth perspective, this is how radio signals get over the problem of the round earth and it otherwise being in the way for shorter wavelength signals.
I will have to modify the statement that on a flat earth, the signals would go into space. Ionospheric reflection depends wholly on angle of incidence. With a flat earth, this is probably going to be 90 degrees or thereabouts at the base of the atmosphere. The LIKELIHOOD is that it will be able to escape the ionosphere. Using appropriately adjusted transmissions, it's possible to ensure an HF signal to leave the atmosphere without being hindered too much. I know you will argue with this, but it's common knowledge that NASA use HF to talk to the ISS and their shuttles while in space.
Now it is possible on a flat earth, that the signal might not escape the atmosphere. In which case, this will happen:
Now it's difficult to say exactly what would happen at the base of the atmosphere in flat earth. Which is why I say it's likely it will escape to space. There would need to be some pretty interesting reflections to stop it doing so, possibly off your ice wall. But either way, however it happens, on a flat earth, the signal would ALWAYS be received in front of you rather than behind. And apologies for the poor pictures but you get the idea.
Hope that explains it better for you Tom.
I win again.
Edit:
Also in that flat earth picture, the angles of incidence due to the shape of your atmosphere would probably mean the majority of the signal would be lost to space before it could get to you.