[TowerTalk] Calculating CableLoss With Wattmeter HELP

[sarky]

Hello all

I have the Bird 43 Wattmeter, and i am trying to calculate Cable loss.
I am using a PSG Power Source Generator sold by YDI.com and 
i dont seem to be able to figure out how to calculate the LOSS .

what i get now if i turn the slug towards the termincator i get a reading
and if i turn it 180deg towards the powersource i get 0.

PSG ==== Wattmetert (1W 2.4 - 2.5Ghz Slug) -50Ohms Terminator.

As you can see i am new to this any help will be apreciated.

Sarky