Why is it that signals of same frequency interfere and others not ?

Question

even in communication methods like FDM , we see that we use signals of different freq.s which dont interfere ! but why is it so ?

cant two signals of different frequency NEVER interfer even to a small extent ???

Answer 1

Think of it this way, your in a small room with 100 people, each of those has paired off to talk to one other person. You now have a group with 50 conversations taking place in the same room at the same time and all of them are trying to be heard above the rest.  That is the same as ONE FREQUENCY being used by several "transmitters".

Now break these into 50 rooms divided by partitions. Now you only have 1 conversation per room. (same as say 50 channels). The people in each room can converse with each other fairly easily unless someone in ONE of these rooms is still VERY loud, they still "spill over" into the other rooms that are near them. (That is still interference but not as bad.)

Now outside those rooms is a man with a jackhammer! He can interfere with ALL the rooms just by the "noise" that he creates!

So can't two signals of different frequency NEVER interfere with each other,,, sure as long as they aren't running a jackhammer!  If they are very powerful or just next door they can interfere!

Overly simple but RF interference is very similar. The further apart in the Frequency spectrum the signals are the less likely they are to cause issues. If you are talking the wifi spectrum, all those channels are very close to each other and only three of them do not "overlap" so they do interfere very badly with each other!