>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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