[Elecraft] Calibrating Bird Wattmeters (WAS: Wattmeters)

[Ron D'Eau Claire]

Got a couple of off-reflector questions and comments about the famous BIRD
meters that ought to be of general interest: 

One was asking how the slugs or "elements" are calibrated. The ones I've
seen have a pot under the cover that shows the frequency and power range.
I've known the calibration lab to say my wonky slug was due to a noisy pot.
They have also been known to move when the slug is bumped or vibrated. 

Bob, W7AVK, observed: "...the calibration on some of them is just a wire
probe that is moved around to get the correct reading.  A good drop will do
wonders to the calibration.  :-)" 

To which I can only rely, "Egad!"

Ron AC7AC