[Elecraft] External wattmeter calibration

[Craig Rairdin]

I picked up a Waters 334 1KW dummy load and wattmeter on eBay last week for
about $100. It appears to work OK -- output from the K2 is about what I'd
expect.
 
I don't have any other test equipment to speak of short of a DMM. Is there a
way to calibrate this wattmeter without buying another wattmeter to compare
it against (i.e. without spending more money)?
 
Craig