new player seeking advice

[Wuss]

i have recently started playing SHV and would like some help on a couple of things.
sometimes when plotting waypoints i get what appear to be ghost contact images on the nav map.so i plot a course to try and intercept them,use the time compresion to speed things up but when i get there,there is nothing there,no sound contacts visuals nothing.
is that some sort of glitch in the game or am i using time compression wrong,going too fast or something.
which brings me nicely to my next question,what is the best way to use the time compression.are there any rules of thumb so to speak.
one last thing,is there a n00bs way of converting the co-ordinates you get in the radio messages to something i could understand.
sorry for the wall of text guys.