hey ,,what is an Amplitude modulation ,frequency modulation and phase modulation ,,what is the difference between them ,,,how the information is transmitted over long distances respective to these methods

Question

anonymous · Answer

i know about the amplitude modulation : 
when u work with amplitude it's amplitude modulation . for ex DSB and SSB 
but what is called amplitude modulation is adding a dc with msg signal then multiple the product with a high frequency

anonymous · Answer

As far as I know the difference lays in the variation of the signal.. In AM, the frequency is kept constant while the amplitude can varied while in FM the frequency varries.. You should really check out wikipedia on this subject.. I am aware that it's not great reference material but it has some very clear pictures and several external links which are extremely helpfull..