[Amps] Plate Impedance, ARRL

[Jim Kearman]

From: "Will Matney" <craxd1 at verizon.net>
> Class AB, K = 1.5

My understanding is that this value of K applies to triodes, where Ep can swing nearly to zero. For tetrodes, Ep cannot swing below the screen voltage. IIRC, this has the effect of increasing K. 

It's useful to consider the consequences of slight errors in component-value selection. Assuming your variable controls (plate tuning and loading) have enough range to get a close match, the negative consequence would be a Q different from what you calculated. But if you give yourself enough range in tuning and loading Cs, you should be able to tune for _best linearity_ (more important than best efficiency) and still get enough Q to reduce harmonics below FCC requirements. 

If you calculate a range of plate loads by varying K from 1.5 - 1.8, and then calculate tank circuit values based on a Q range of 12-15, you should come up with tuning and loading cap values that will do the job. 

73,

Jim, KR1S
http://kr1s.kearman.com/