[AMPS] Grid current: Rich's Rules of Engagement.

[measures]

>Rich, you are the master of the red herring.
>
>You argue that the G2DAF circuit cannot be linear because it draws grid
>current.  

I argue that the DAF produced roughly 1% distortion during on the air 
tests. 

>Class AB1 does not draw grid currrent.  Class AB2 and B is allowed
>to draw grid current.  

Grid driven AB2 produces way more feculence than AB1 grid-driven. 

>Most amateur linear amplifiers are running class B
>and do draw grid current.

Please name three.   
>
>Let us examine tube data for the 4-125A tube in a grounded cathode circuit:
>
>    Class AB2
>    Plate volts = 2000; Screen volts = 350
>    Screen current = 3 ma
>    Grid current = 7 ma
>
7ma of grid current is Class C.  For typical linear operation, Eimac 
shows 0mA of grid current and 6mA screen current.  

>Source is Single Sideband for the Radio Amateur, Published by ARRL in 1965,
>page 252.
>
>This information is only cited to show that tubes can run grid current and
>still be linear.  

You have not shown this.  You presumed it.  

> It is not proof that the G2DAF circuit works.  

I know that the DAF circuit exhibits about 10db gain.  In other words, it 
works. 

>The data
>also suggests that the 4-125A series of tubes would be ideal to test the
>G2DAF circuitry - especially since the original tube used by G2DAF was
>similar to the 4-125A.
>
>The 4CX250 series of tubes would not be a good candidate for the G2DAF
>circuitry.  Bill Orr's Radio Handbook, 18th Edition, 1970 at page 720 says
>that "a high perveance tetrode... cannot be used in conventional zero-bias,
>class-B grounded-grid circuitry, since the element geometry within the tube
>leads to abnormally high values of grid current and possible destructive
>values of grid dissipation".  That same reasoning applies to use of the
>4CX250 series in G2DAF circuitry.

€    Orr is talking about cathode-driven.  The DAF is not.  
>
>Finally, I have come up with "Rich's Rules of Engagement"
>
>    1.  Rich is always right!
>    2.  Facts that interfere with Rich's beliefs should be ignored or 
rejected!
>    3.  Conclusions that conflict with Rich's beliefs should be distorted!
>    4.  Logical thought will be rejected unless it is consistent with Rich's 
beliefs!
>    5.  Those who question Rich's beliefs are cultists and should be 
ridiculed!
>    6.  Rich is always right!
>
€  Rich's guidelines:
1.  When I don't know about something, keep mouth shut and listen to what 
the big boys say.  
2.  Never Ever accept anything at face value, even from Pres. Bill 
Clinton.  .   
3.  If I become aware of a technoblunder by yours truly,  admit to it 
within 1-minute and apologize.  
4. Never forget that everybody makes mistakes from time to time.  
5.  I am not an amplfier "expert"..  .  
6  Murphy was right about things being more complicated than they look - 
especially in the case of RF linear amplifiers. 
7.  Always be polite to anal retentive and/or anal expulsive amplifier 
builders / kibitzers.  
  
.  
cheers, Colin

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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