ORIGINAL MESSAGE: On Sun, 12 Aug 2012 01:51:55 -0400, WA4LAV wrote: >. That is shunted by the >tube's input capacitance, 15.7pF. REPLY: Where did that figure come from? According to the Eimac 4CX1500B data sheet, the input capacitance in grounded cathode mode is between 75 and 88 pF. 73, Bill W6WRT