[AMPS] The 3/2 Power Law

[measures]

>
>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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