[AMPS] The 3/2 Power Law

[measures]

>
>Reference on Eimac's definition of the 3/2 power law.
>
>Page 97, Care and Feeding of Power Grid Tubes, copyright 1967 by Varian,
>third Printing 1978.
>
€  You stated 

"The 3/2 power law simply states that if you change all of the 
interelectrode voltages applied to a power grid tube by a factor of 2, 
that the current
will change by a factor of 2.8".  

-  -    RE:  "change all of the interelectrode voltages"?   Eimac's 
comments are only in regards to fixed screen potential and interpolation 
between constant-current curves.  . Fabricating "Eimac" quotes will 
assuredly not earn high marks.  

>Re: Pulling out of hat.

indeed  
>
>Rich has cited the measurement method used and the results on the received
>end of one transmitted signal.  However, he has never documented the
>equipment used at the transmitting station.  

€ The equipment used at the transmitting station was never a 
consideration.  Measurement of transmitted distortion was the whole 
ballgame.  
-  Ham radio distortion measurement:  Once upon a time, on 75m SSB, when 
Challenger fell into the Atlantic, I happened across NBC's science 
advisor, K6DUE, Roy Neal, and another chap.  Roy was driving a solid 
state amp - that was designed for 50w drive - with a 100w exciter, and 
generating bad news splatter.  .  I broke in and asked Roy if he was 
interested in a distortion measurement.  He said yes and I gave it.  .   
Then the other guy comes to Roy's defense and tells him that his signal 
absolutely vanishes when he tunes away 500Hz.    . 

>From earlier statements, I am
>advised that it was Norm, W6EDD at the transmitting end.  One published
>circuit from Norm is a G2DAF variation.  

€  I would like to see this circuit.  Who "advised" you.  

>That circuit has a substantial flaw
>and would have to splatter.  

€  Any grid-driven amplifier that runs substantial grid-current generates 
substantial distortion.  

>Publication of this circuit would indicate that
>Norm did not understand the G2DAF circuitry and did not understand linear
>amplifiers in general.  That circuit would have to distort.  

but of course.  

> Perhaps Norm
>tried the genuine G2DAF circuitry, but his carelessness in publishing

€  where is Norm's circuit published.  thanks.

>
> a defective circuit - which was claimed to be clean - would cast doubt about
>any of his work.  

€  Hardly.  Most people know that Norm eventually came up with an 
amplifier that produced acceptable distortion -- pretty much as clean as 
the rest of the amps on the Combat Zone.  Arriving there required no 
grid-current and c. 350v of fixed screen potential

>  So, reception of his signal using his unspecified and
>undocumented equipment under his unknown operating conditions is what I call
>"pulling the numbers out of a hat".  Arriving at  inflexible conclusions
>based upon this sort of test and documentation is unscientific.

€  From experience, I know that the only distortion test that is valid is 
unannounced, on the air and minimally scientific.  .  It is well know 
that well planned Scientific (two-tone) distortion tests tend to produce 
pretty good results.  
>
cheers, Colin

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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