How do I determine / where can look up the input impedance for grid driven tetrodes? I'm not satisfied with the input circuit I have in there now and want to give it another try. THX, Bill N2BC -- FAQ on WWW: http://www.contesting.com/ampsfaq.html Submissions: amps@contesting.com Administrative requests: amps-REQUEST@contesting.com Problems: owner-amps@contesting.com Search: http://www.contesting.com/km9p/search.htm