ORIGINAL MESSAGE: On Sun, 26 Apr 2009 07:14:14 -0500, Bruce Osterberg <n9bx at mchsi.com> wrote: > My question is for this calculation do you use the Voltage that >appears on the tube plate key Up, ( my case 3900 VDC) or Key Down 3500 >VDC. REPLY: Use the key down value, since that is what is actually generating the RF. 73, Bill W6WRT