How does the wave get overridden? Minor edits of Grammar
This happens in the same manner as two people singing the same tone, such as the note C. As one or maybe two individuals are listening for this tone, they acknowledge it an try to listen. The time when waves are overridden is simply when one person speaks louder than another and then the listener/tuner cannot hear one person because the other is speaking too loudly. The same goes with waves of electronic schematics. When one wave is more amplified than another at the same frequency, the more powerful wave will drown the other out. This is to make the idea of waves getting overridden simpler to understand and this actually validly answers it because it deals with waves.
How can one emitter be stronger than another if there, for example are equal distance from the receiver and from each other?
answering how to amplify signal in a circuit
This is possible for many reasons. One, the antenna can have different amplification properties.Two there could as such thing as an Omp-Amplifier IC or Chip (same thing but different names) that can be used to amplify the signal. You can amplify a signal with an antenna or an IC that has amplification qualities. Less resistance in a circuit is also helpful in amplifying the current which could also amplify the signal. Any of these are good in this process of amplification
Is it harder to amplify signals on higher frequencies, e.g. WI-FI Internet?
No! All you need is a 2.4GHz antenna, such as a ceramic or actual WI-FI specific antenna. It is not any harder than using any other antenna, just make sure the hookup is compatible to the one you are using. Very simply, all you need is a WI-FI antenna, end of story. The only thing you would choose is the data rates, but that is irrelevant.
http://www.tp-link.us/article/?faqid=3 This is where the link of a better explanation is
What is the basic principle of devices that creates noise and blocks certain frequencies?
This explains how they send and receive frequencies, specifically speaking they oscillate at certain frequencies and then put the message overtones on top of this, so what the receiving is trained to vibrate at the same way as the receiver is only that frequency. It is constantly moving at that frequency, and that one only. So when a signal comes in with a message, it demodulates that frequency to find the overtone and then either play it or turn it into a digital message.