Re: DO ALL AM RADIO WAVES REFLECT OFF THE ATMOSPHERE, OR DO SOME ESCAPE...

Some of the radio waves will always escape, but some are more likely to escape than others are. Visible light, for example, penetrates the atmosphere quite well. Ultraviolet, on the other hand, along with x-rays and gamma rays are absorbed by the atmosphere. Infrared is usually reflected back from the atmosphere, which is why we worry about the greenhouse effect. An interesting region is in radio waves, because some of them are reflected, some go right through, and some do a little of both. It all depends on the length of the waves, which is related to the frequency of the radiation (longer wavelength radiation has a lower frequency).

What makes this region interesting is that we also make a transition in how the electromagnetic radiation interacts with the atmosphere. Infrared is much like visible light, and what affects its transport through the atmosphere are familiar things like opacity (the amount of "stuff" in the atmosphere). Electrical properties don't affect it much. On the other hand, radio waves are very affected by electrical properties, which is why they reflect from the ionosphere.

As the frequency of the radio waves increases, the radio waves are more likely to reflect from the electrically charged particles. This means that the shorter wavelengths of FM radio are more likely to penetrate the atmosphere, as are the shorter TV wavelengths, while longer AM wavelengths are more likely to be reflected back to earth (remember that AM radio stations are about 600 - 1700 kHz while FM radio is in the megaHertz region). This is why we can hear AM radio stations for hundreds of miles, while FM and TV stations die out after only 30-50 miles or so.

What this means with respect to your question is this: you are correct that FM and TV are more likely to escape the atmosphere than AM, so our radio "signal" has been stronger since these were invented. But AM radio waves will escape, too - the reflection is not perfect, so some of our early AM broadcasts are "out there" somewhere. They are just not as strong as the FM and TV signals - in part because less escapes the atmosphere and in part because the early transmitters just weren't as powerful as later ones.