How does an antenna work?

[Donsjii]

Does it draw the frequencies it's made for, or just stand in their way and gather them as they hit it?

What is the difference between a round antenna rather than one with straight lines?

 

[Floid]

Stands in the way and gathers.

The gain in particular directions.

 

[berkeman]

Does it draw the frequencies it's made for, or just stand in their way and gather them as they hit it?

What is the difference between a round antenna rather than one with straight lines?

Antennas generally resonate with EM frequencies that they are designed to receive. In a way, you can think of them as "bells" designed to resonate at some frequency. The resonating action gives you gain that helps to make the receive and transmit functions efficient.

Here is some introductory reading:

http://en.wikipedia.org/wiki/Antenna_(radio [Broken])

Let us know if you have specific questions in that material.