I'm designing a grounded grid amp for 20M using two 813's. Tube spec shows output capacitance of 14pf per tube. So in my tank calculations I used 28pf plus 5 stray cap plus 5 minimum on my 23pf tuning variable. Total of about 38. With Q of 12 and load resistance of 3050 ohms (2200V, 400 ma), tank values are 44pf, 3.1uh, 262pf. However in "Radio Transmitters" (Gray, 1961), says output capacitance in grounded grid is about 1/2. I would suppose this is because, as per W8JI, input and output circuits of GG are in series. Since input capacitance on 813's (2) is about 32pf and output is 28pf, that would be about 1/2. There have been tons of 813 GG amps built, but other than that one book I haven't seen anything about the output capacitance. Comments?