22 Apr
2011
22 Apr
'11
10:43 p.m.
Can someone here please explain to me, in ** simple English **, the
difference (in usage, not in how they work) between a "control grid
tube" and a "barrier grid tube" ... ?
I tried Googling but that led to me being more confused, not less. :)
22 Apr
22 Apr
11:54 p.m.
Evan, here is my stab at this -
control grid tube implies a simple triode - no other grids.
I will guess that a 'barrier grid' is the screen grid in a tetrode. its function
is to reduce the capacitance between the control grid and the plate, for higher frequency
operation.
A Pentode adds the suppressor grid, to reduce secondary emission from the plate (electrons
bouncing back).
Randy
Date: Sat, 23 Apr 2011 01:43:05 -0400
From: evan at snarc.net
To:
Subject: OT: vacuum tube question
Can someone here please explain to me, in ** simple English **, the
difference (in usage, not in how they work) between a "control grid
tube" and a "barrier grid tube" ... ?
I tried Googling but that led to me being more confused, not less. :)
23 Apr
23 Apr
12:09 a.m.
On 2011 Apr 22, at 10:43 PM, Evan Koblentz wrote:
Can someone here please explain to me, in ** simple
English **, the
difference (in usage, not in how they work) between a "control grid
tube" and a "barrier grid tube" ... ?
In an attempt to be concise:
- The control grid is just that: the grid which exerts primary control
over electron flow in (any) tube. As such, it is the grid to which the
input signal is generally applied. It is not usual to refer to a tube
as a "control-grid tube".
- On the other hand, "barrier-grid tubes" were a specialised form of
cathode ray tube (CRT) with a storage function.
Just for some confusion:
- CRTs also generally have a control grid, but it might be said to be a
bit of a misnomer as the input signal is often/usually applied to the
cathode.
- Depending on one's classification of storage CRT, not all storage
CRTs are barrier-grid tubes.
- The control grid is usually but not always the first grid after the
cathode.
I tried Googling but that led to me being more
confused, not less. :)
8:58 a.m.
On 23 Apr 2011 at 0:09, Brent Hilpert wrote:
- The control grid is usually but not always the first
grid after the
cathode.
Interestingly, some early models of the Audion put the grid on the
opposite side of the filament from the plate. If you look at
DeForest's patents, it's pretty clear that he had no idea of how his
Audion really operated.
There's a web site, showing how to emulate an audion using a 6AX5
full-wave rectifier (no "grid" per se):
http://www.angelfire.com/electronic/funwithtubes/Build_an_Audion.html
--Chuck
11:30 a.m.
On 2011 Apr 23, at 8:58 AM, Chuck Guzis wrote:
On 23 Apr 2011 at 0:09, Brent Hilpert wrote:
Yes, and he started with a flame detector - not a detector of flames,
but trying to detect radio-waves by passing them through a flame, as he
was hacking around trying to make a radio-wave detector that wouldn't
infringe on other's patents. It was some years later that people
realised the audion could amplify.
Armstrong was the more impressive in actually putting the tube to work.
- The control grid is usually but not always the
first grid after the
cathode.
Interestingly, some early models of the Audion put the grid on the
opposite side of the filament from the plate. If you look at
DeForest's patents, it's pretty clear that he had no idea of how his
Audion really operated. There's a web site, showing how to emulate an
audion using a 6AX5
full-wave rectifier (no "grid" per se):
http://www.angelfire.com/electronic/funwithtubes/Build_an_Audion.html
Fun writeup, I'll have to look at some 6AX5s to see if they're all
constructed that way.
1:18 p.m.
On 23 Apr 2011 at 11:30, Brent Hilpert wrote:
Armstrong was the more impressive in actually putting
the tube to
work.
DeForest is painted rather blatantly as nothing less than a slimeball
by the T.H. Lee chapter cited by the previous web site:
http://www-smirc.stanford.edu/papers/chapter1.pdf
In legal proceedings attempting to claim credit for the superhet,
DeForest made a perfect idiot of himself. He didn't have a clue.
--Chuck
1:52 p.m.
On 4/23/11 4:18 PM, Chuck Guzis wrote:
We call people like that "executive management" nowadays.
-Dave
--
Dave McGuire
Port Charlotte, FL
Armstrong was
the more impressive in actually putting the tube to
work.
DeForest is painted rather blatantly as nothing less than a slimeball
by the T.H. Lee chapter cited by the previous web site:
http://www-smirc.stanford.edu/papers/chapter1.pdf
In legal proceedings attempting to claim credit for the superhet,
DeForest made a perfect idiot of himself. He didn't have a clue. 
3:33 p.m.
On 4/23/11 1:52 PM, "Dave McGuire" <mcguire at neurotica.com> wrote:
On 4/23/11 4:18 PM, Chuck Guzis wrote:
We call people like that "executive management" nowadays.
-Dave
"Suit"
Armstrong
was the more impressive in actually putting the tube to
work.
DeForest is painted rather blatantly as nothing less than a slimeball
by the T.H. Lee chapter cited by the previous web site:
http://www-smirc.stanford.edu/papers/chapter1.pdf
In legal proceedings attempting to claim credit for the superhet,
DeForest made a perfect idiot of himself. He didn't have a clue.
6:44 p.m.
On 4/23/11 6:33 PM, Geoffrey Reed wrote:
We call people like that "executive management" nowadays.
"Suit"
Yes. :-( Naive is the society that allows those types of people to
survive.
-Dave
--
Dave McGuire
Port Charlotte, FL
Armstrong was
the more impressive in actually putting the tube to
work.
DeForest is painted rather blatantly as nothing less than a slimeball
by the T.H. Lee chapter cited by the previous web site:
http://www-smirc.stanford.edu/papers/chapter1.pdf
In legal proceedings attempting to claim credit for the superhet,
DeForest made a perfect idiot of himself. He didn't have a clue. 
24 Apr
24 Apr
7:11 a.m.
[...]
- CRTs also generally have a control grid, but it
might be said to be a
bit of a misnomer as the input signal is often/usually applied to the
cathode.
Agreed, particualrly with the 'often/usually' part. It's not 'always'
:-). I am sure I worked on something recently where the CRT brigthness
modulation was applied to the first grid ('control grid'). Possibly an
HP2623 terminal.
[...]
- The control grid is usually but not always the first
grid after the
cathode.
Indeed. I've seen valves (tubes) which were designed to operate at 24V
anode (plate) voltage and which had an acceletor grid (connected to a +ve
voltage source) betwene the cathode and control grid.
-tony
7:07 a.m.
Can someone here please explain to me, in ** simple English **, the
difference (in usage, not in how they work) between a "control grid
tube" and a "barrier grid tube" ... ?
I am not sure if the terms have different meanings in the States, but
over here, they're not really related at all...
A 'control grid' is an electrode that varies the strength of the electron
stream. Such as the grid in a triode, the first grid in a tetrode or
pentode, the first grid in a CRT, etc.
A 'barrier grid' is specific to a particular type of storage CRT, and
IIRC, it's an electrode ot equalise the potential across the storage
target.
-tony
4992
days inactive
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