[Amps] figuring tube output impedance

[Partain, Chuck]

I see a lot of  formulae(is that plural???) on determining the output impedance of a tube.
some say just plain plate volts divided by plate current, some have a 1.8 x formula  and so on. I Want to determine
this gu-84b impedance so I can start work on the tank setup. I run 3.9kv and I'm GUESSING 2 amp.
 I stuck a 2k in there and played some with the values so far and things look ok, no suprises. this is
 my motive for the question. lets hear some opinions! thanks as always.





Chuck Partain
http://home.comcast.net/~KA1MWP