[Amps] Plate impedance

[Will Matney]

All,

I started reading through the RCA Radiotron Handbook this evening looking for where the factor of 1.8 is listed for calculating the plate impedance of a class AB amplifier, and I can not find it. The edition I have was the older one back in the 40's with the black cover. The red one was from the 50's and had more in it if I recall, but I don't have it. I was wanting to find where it gives this factor, and the ones for Class A, AB1, AB2, B, and C. Bill Orrs handbook gives the factor of 1.8 on his Pi tank values table, but doesn't mention anywhere in the text where it came from. I also looked in a RCA receiving tube book and could not find it there either, or I am overlooking it somewhere. I could have sworn it was in the Radiotron Handbook. The Handbook does say that the plate impedance is twice the peak voltage swing times the peak anode current. What I'm wanting to know is where are these factors located in print, as I'd like to read the whole texts concerning this? Any help would be deeply appreciated. Thanks to all in advance.

Best,

Will