[Elecraft] where to search information

[mc]

sometimes it is hard to find specific information, I am trying to understand the relationship between power out put and antenna length and its line losses .

example: suppose I have a random length of wire hook-up of 20 meters (ok, would that be 60 feet) and I have two watts output. if I shorten the wire to 10 meters what will my watts output be, frequency would stay the same for this example.