1. In an AM transmitter, how does a circuit (as in what components are used and how do these components) merge a carrier wave with the input audio signal?
2. How does a circuit amplify a wave?
3. When a crystal oscillator is used to generate a sine wave, is the amplitude constant or does it vary?

 

Hello,

Did you have a look at the link I gave you in the other thread?
http://www.williamson-labs.com/
There you will find a link about the AM modulation:
http://www.williamson-labs.com/480_am.htm#top

There is also a lot of info in the links of this page of the EDUCYPEDIA:
http://educypedia.karadimov.info/electronics/radiotuning.htm

Bertus

 

I did get it thanks, I read it through and understood most of it, however I was more interested in the way a circuit does these things. (Like the components it uses and why they lead to modulation).

 

You need to study different circuits likethis one for example of an AM transmitter/receiver,

the oscillator( at the bottom) formed by the crystal and Q4 is "Modulated" or altered by the audio amp by transistors Q1,2,3, they alter the DC supply of the carrier through the inductor J2, this squeezes the carriers amplitude thus producing an AM signal.

The receiver (top diagram)is produced by the IC U1, amplified by Q1,2 and the audio is stripped off from the carrier by the diode D1, this is a common way to decode an AM signal its just an half wave rectifier,and the audio is fed to an amplifier U2 for listening.

more AM/FM/SSB Transmitter receivers here for reference.