[BC] Another Technical Question

[Radiofldude@aol.com]

I've been chatting with a friend who's a weekend presenter at one of the  
major English speaking Commercial stations in the Canary Islands.   
(Incidentally, the station is networked and covers all 7 islands)
 
Anyways, He and I were talking about radio and i told him about the  
difference between AM and FM in relation to the power output in relation to  coverage 
on AM/FM, the type of antennas and etc.
 
We also discussed how lower end AM channels require less power, but more  
tower. he was quite intrigued by all this.....
 
Are there a few good sites I can point him out to that explain it in a  
manner someone whos not an engineering type can understand  it?

Thanks!