>I've been following this nice discussion, and want to ask something
>about Ian's post, ¿what's bad with running exciter at a lower level and
>to have the amplifier "seriously under-driven"? (it seems to be not only
>a lower power output matter).
>My modest guess is something related with operating points due to
>distortion considerations, is it?.
** Yes. The easiest way to control power is with the microphone gain
control. When the microphone gain is reduced to the point that the
amplifier's anode current is constant during modulation, the amplifier
seriously underdriven. Welcome to Class A - the most linear mode
possible. If more power is needed to communicate, all that's needed is
to up the microphone gain.
>
cheers, Guillermo
>Ian White, G3SEK wrote:
>
>> R. Measures wrote:
>>
>>> ** The grid does not and can not draw current when a competent
>>> operator sets the grid potential just above the level where it can
>>> draw grid-current with the max PEP drive that's available.
>>
>>
>> That is only true if the grid input circuit is guaranteed to be able
>> to soak up all possible levels of drive without allowing grid
>> current... but that also has disadvantages: either the exciter runs
>> flat-out and generates unnecessary IMD of its own, or else the exciter
>> runs at a lower level and the amplifier is seriously under-driven.
>>
>> I truly cannot see why anyone should design (or defend) a
>> high-impedance bias supply whose voltage regulation will collapse at
>> the first trace of either normal or negative grid current. What's the
>> point, when a better-regulated supply is just as easy?
>>
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