It's interesting that you should mention "GG" Don. I was just talking not long ago with Geoff, W5OMR, about the possibility of GG modulators. I think the main draw back of this would be an increase in effective plate resistance making damping not as good. This could be over come with inverse feed back to a predriver stage. You might need 100 watts of drive to get 1000 watts out but a very high portion of the drive would be included in the output and the linearity should be good. But wait, there is more! You would need a larger chassis to accommodate the extra filament XFMR and large driver XFMR. Hmmm, Could be a job for emitter follower PNP Xsistors as series drivers. One for each center taps of each filament XFMR. And a high current medium voltage negative supply to return the collectors to. WHAT A CONCEPT.
John, WA5BXO -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Donald Chester Sent: Sunday, December 12, 2004 1:37 PM To: [email protected] Subject: RE: [AMRadio] (no subject) Of course, amateurs have for years used pentodes and tetrodes, including 807's and 1625's, as triodes in grounded grid linear service. I have never seen the resistor used. They simply ground all the grids and feed rf to the cathodes. With 1625's and 807's, a modification is required, to bring the beam forming plates out to a separate pin so that it can be grounded along with the grids. This is possible on some brands of tubes. In others, the bf plates are internally connected to the cathode, rerdering them impossible to modify. Without the modification, they are unsatisfactory as g-g amplifiers because the bf plates produce undesirable coupling between the input and output. -k4kyv
