Ask A Scientist© Engineering Archive

Index Key:   ENG056
Author:      davidjones
Subject:     Frequency modulation explanation.
I am having difficulty understanding how a FM signal is modulated on to a
carrier wave.  My text book just not seem to explain it to my satisfaction. 
AM modulation is fairly easy to understand, so maybe we you can relate the
two somehow, showing me the similarities and the differences.

Response #:  1 of 1
Author:      jade hawk
AM modulates the AMPLITUDE of a fixed frequency carrier; FM modulates the
FREQUENCY of a fixed amplitude carrier.  Actually, it does not have to be
fixed amplitude:  one of the main reasons for developing FM technology was
to become immune to amplitude changes; like lightening produces static on AM
but not on FM.  



Response #:  2 of 2
Author:      wildman jackson
Also, there is a satellite now in operation that uses cryogenic cooling.  I
am not sure what the coolant is, but the satellite parts are cooled down to
about 6-12 Kelvin.  Pretty cold, eh?  I believe it is a NASA satellite aimed
at observing different kinds of radiation reaching the Earth from other
galaxies/stars, etc.  It was in one of the issues of Aviation Week and Space
Technology magazine.