How many tennis rackets do you take on court?

Very good question?
I take three powerangle centric rackets on court, Why, Ok here goes.
One racket is strung at 50 Ibs  (my powerangle rackets max tension is 53Ibs but because I am using poly string I take off 5%) This racket I use when the balls are new and "flying" (I need the control!)
My middle racket is strung at 48Ibs this racket I use when the balls have settled down and are easier to control, but I still want the same power I had earlier.
The third racket is strung at 47Ibs for when the balls have gone off or are damp / wet, I still have the depth of shot with the same swing as normal :-)

I will change the rackets to the conditions: Example If I am serving into the wind I will use the third racket (more power to punch through ) same effort from me!

Serving / playing down wind I use the first tight strung racket for control.

A bit like using winter tyres on snow / ice or summer tyres in the dry conditions!
With three rackets at different tensions you have the choice to adapt to the conditions.

Hope this helps!
daveg