>
>Rich:
>
>That is not my definition of the 3/2 power law. It is Eimac's.
>
? Reference, please. thanks
>Eimac also says:
>
>"the screen voltage is not critical for most applications and the value used
>has been chosen as a convenient value consistent with low driving power and
>reasonable screen dissipation. If lower values of screen voltages are used,
>more driving voltage will be required on the grid to obtain the same plate
>current. ... The value of screen voltage can be chosen to suit available
>power supplies or amplifier conditions."
>
>In the case of the G2DAF amplifier, the designer simply chose to vary the
>voltage on both the control grid and screen grid.
>
? choosing the screen potential does mean choosing it thousands of times
per second during operation. For linear operation, the screen potential
needs to be chosen once and fixed. For a tetrode to successfully exhibit
screen amplification, there must be a difference in potential between the
screen and the grid.
>Tubes are used quite frequently with variable voltages applied to two of the
>grids - even in designs by Collins and Hallicrafters. The tubes are
>heptodes and the circuits are commonly called mixers.
? The DAF configuration is undoubtedly a Mixer.
> They are linear and
>do not distort. Of course there are bad mixed designs which do cause
>distortion.
>
> You throw out the 1% distortion figure for the G2DAF design - but that is
>just a figure pulled out of your hat.
>
? The roughly 1% figure (which is 100% legal) was observed many times on
the air, using a double-filter receiver with a 6/60 db shape factor of
1.45. Relative signal levels were measured using a calibrated Hewlett
Packard step-attenuator set. No hat was used. Where did you get this
idea, Colin?
- Rich..., 805.386.3734, www.vcnet.com/measures.
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