You need to be using dogbone Silver mica capacitors or you might get away with? 600 V ceramic capacitors.? You can't use standard ceramics at 50 or 100V rating on this duty.? ?Diz at Kits and parts / Toroid king sells Silver mica capacitors from the US.? Other than that they can be hard to find.? There are also specialised tongue in metal tube SM capacitors for transmitting power but they are also very expensive and not for self constructor use unless you have large amounts of spare cash.?
