[AMRadio] Re - response to input to screen grid amplifier

Bill Fondren bill.fondren at sbcglobal.net
Tue May 23 17:04:19 EDT 2006

Thanks for the quick response to my questions concerning this amp.   John, I was ready for some salty remarks (hihi)  and I did clean my glasses and take a second or third look at the thing.  I thought I had missed something since going to USAF Radio School in the early 50's. Guess that tells u why I mess with vacumn tube rigs.  Anyway thought I better get some expert opinions before starting to cut and chop to get it to a more conventional type.  The construction of the amp is above average for a homebrew rig.  A couple of other things     There is a RFC choke  coming off the G1 connections going to the 10K resistor then to the grid meter (0-30ma shunted with a 50 ohm 10 watt resistor)  It does read about half scale peaking normal as u tune the grid circuit. Also a .01 bypass cap at the meter.  The input coil is grounded in the middle through a RFC choke making a double coil, tuned by a split stator cap. One of the tuned circuits goes directly to the screen grids and the
 other feeds the neutralizing voltage back to the input from the plate. No bias circuits of any kind. The few times I used it I got good reports using a Elmac AF-67 exciter.   Will probably change it to a more conventional type.   Thanks again     Bill  K5PML


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