>
>> sooner or later I'll get it right. I've been watching the discuusions
>> on
>> "neutralizing GG amps". It's interesting but I've never seen anything
>> in writing on the subject! Can anyone tell me where to get some info
>> on it?? I'm always willing to learn something, if that's possible at
>> this late date, HI, HI!! thanks. carl / kz5ca
>
>Hi Carl,
>
>Examples of GG tubes that often need neutralized include the
>3CX1200A7 and D7, pairs of 572B's, and (4) 811A's. The reason
>they need neutralized is the long grid leads and poor
>cathode/anode shielding inside the tube allows a considerable
>amount of feedback capacitance from anode to cathode.
>
>Regenerative feedback shows up as a lack of having maximum
>output at minimum plate current on higher HF bands, or as a
>stability problem near the operating frequency under "light" or no
>loading of the PA.
>
>The earliest commercial amps to neutralize the tubes include the
>Heath Warrior (4 811A's) and the Gonset 4 811A amplifier. In
>those amps, they added a third winding to the filament choke and
>used a conventional neutralizing-style capacitor between the
>ground end of that filament transformer end of that winding and the
>tuning cap end of the tank. The end of the winding nearest the
>filaments was grounded.
>
Gonset and Heath never built another "neutralized" g-g amplifier.
>The AL-1200, AL-811H, and AL-572 Ameritrons all use a separate
>broadband transformer to invert phase and the first two have a
>neutralizing probe while the 572 has a coaxial slide capacitor for
>neutralizing.
>
>This is actually
(key word)
>a form of bridge-type neutralization, and you can
>find it described in many books.
call for reference.
>It has many applications, including
>grid driven systems.
>
Not in any AB1 amp. I am aware of. The Bruene neutralization circuit is
the slam-dunk.
>This does not cure the "problems" wrongly attributed to
>"parasitics", ...
here we go again.
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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