Tv. sweep tubes were never intended to be used as linear rf amplifiers, so there is no info on the "driving impedance" that I know of . Can anyone out there tell me how to determine that impedance??? thanks... carl / kz5ca -- FAQ on WWW: http://www.contesting.com/FAQ/amps Submissions: amps@contesting.com Administrative requests: amps-REQUEST@contesting.com Problems: owner-amps@contesting.com