[AMRadio] (no subject)

[Donald Chester]

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