[Amps] Ferrite Rod

[Larry Carman]

    Maybe a combination of air wound choke on secondary and a floating
filament transformer would suffice. Use enough choke between tube & filament
transformer secondary to server for maybe 14 MHz to 30 and let the floating
transformer arrangement serve best below the 14Mhz. This helps to eliminate
some cost by eliminating the ferrite rods and the worry about saturating
them. 
Larry

Tom wrote:

A choke works easiest at higher frequencies, while an 
isolated transformer and no secondary choke works best at 
lower frequencies. A floating transformer can really be bad 
at the 30MHz  end.