Peter,
See below,
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On 4/12/06 at 6:53 PM Peter Chadwick wrote:
>Will said:
>>Everything I've read says AB is around 60% efficient, not less.<
>I think you'll find that's the theoretical tube efficiency, and the real
>world has to take into account tank circuit transfer efficiency, too.
>>From memory, the old Mullard data sheets provided measured values with
>tank circuit efficiencies stated as around 90%. I've always worked on a
>rule of thumb of 50% efficiency, and haven't been let down that much,
>especially when you consider the measurement uncertainties involved.
Your correct. It can also vary too. It's according to how hard one drives the
amp, the load impedance changing, and even line voltage variations. There's
several others, but to save space, that's a few. However, I don't see a X3
plate current as that would be impossible with 50%. There's no way to have that
much current and claim an efficiency of 50-60%.
>And if your tank circuit when you've tuned and loaded for optimum ends up
>with a working Q of 15 instead of 12, I doubt if any of us has equipment
>with enough resolution to tell the difference, let alone make an absolute
>measurement.
>I guess we can get too hung up calculating (or worse, simulating) for the
>last fraction of a dB that can't be achieved in practice. Makes you wonder
>how they ever got radio to work in the first place!
I have to admit that after calculating the component values for every tank
circuit I've designed, it never did come out exact. Oh they worked, but the
values of tune C and load C came out different every time by some amount.
There's too many variables there to get it right like stray C and L. Designing
transformers is no different. They say in them it is still a cut-and-try
process. The formulas only get you there where you need to be.
>73
>Peter G3RZP
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Best,
Will
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