[AMRadio] Grounded grid amp

[David Folger]

Here is an Internet post on the subject:

http://jlandrigan.com/files/6dq5_and_other_tube_specs.pdf

In it the writer says that the problem having the beam electrodes attached to the cathode is that shielding created by grounding the control and screen grids is bi passed. So you would still need to neutralize the 6DQ5. So it might work, but one of the advantages of GG operation is lost.

BTW, this post contains some AB1 operating conditions for 6DQ5 that aren't in most of the tube data books.

I'm considering a small linear using some (probably 4) 6DQ5's grid driven with a swamping resistor and no tuned input circuit. Driving it through a 50 ohm non-inductive resistor should work, but we shall see.

I'm also considering using a couple 4D32's in AB1, grid driven. No one seems to ever use 4D32's as linears, but there are AB1 audio operating specs in the Raytheon data sheets. I don't see why that wouldn't work at RF.

Plus I have a bunch of 4D32s sitting in a box doing nothing -- and they are a very tough tube.

Dave

--- On Wed, 1/26/11, Robert Nickels <ranickel at comcast.net> wrote:

From: Robert Nickels <ranickel at comcast.net>
Subject: Re: [AMRadio] Grounded grid amp
To: "David Folger" <dbfolger at yahoo.com>
Cc: "Discussion of AM Radio in the Amateur Service" <amradio at mailman.qth.net>
Date: Wednesday, January 26, 2011, 5:47 PM

On 1/26/2011 11:30 AM, David Folger wrote:
> Thanks for correcting that.
> 
> I wanted to call my post back right after I sent it and say that the 6DQ5 would best be used in AB1 grid driven.
> 
> Some sweep tubes like the 6KD6 can be used in GG because the grids all come out to pins.
> 
> 

Hey Dave, don't go beatin' yourself up, I well know how often my brain gets out of phase with my fingers  ;-)

But moreover, I'm wondering if what I said about the 6DQ5 not working in grounded grid is reallly correct - here's why:   While it's true the G3 and cathode are connected internally, that's also the case for the 6L6 - yet McLaughlin says he tested the 6L6 and it works, and the internal connection is clearly shown on the schematic.

So if the 6L6 works in GG, why wouldn't the 6DQ5?

73, Bob W9RAN