[AMPS] Pi-Net math Help

[Rich Measures]

>
>For the benefit of readers trying to learn something, read inserted 
>snippets below :
>
>
>> >
>> >Rich Measures wrote:
>> >>>>€  There is more than one way to figure Q.
>> >>>
>> >>>Evidently - like to tell us your definition?
>> >>>
>> >>€  I don't have one.  Eimac defines Q as the ratio between RL and the
>> >>reactance of C1.  None of the Eimac formulae can be used without choosing
>> >>a value of Q - as defined by their definition
>> >>.
>
>EIMAC defines nothing with those formulas.  The formulas are public 
>domain.  They're parrotted in EIMAC's book,  just like they are in all the 
>other handbooks.  EIMAC has not done anything original with Pi network 
>design.  EIMAC is not the author of these formulae.
>
>>
>> €  There are nevertheless two ways to define Q.
>> >
>
>WRONG.  There is one definition of Q.  

€  Isn't there a loaded Q and an unloaded Q?

>There is more than one formula for 
>calculating Q and it varies with the circuit under consideration.  The 
>formula for Q printed in the "sacred" EIMAC book, for Pi networks, is 
>incorrect.  It is also incorrect in any other book that uses the same set 
>of formulae. (Note that it is the correct formula for the Q of the C1 
>capacitor, but not for the network as a whole)
>
>> >>>The definition I'm using is Q = XL/Rs, where Rs is the transformed
>> >>>effect of all resistive components, when made to appear in a series loop
>> >>>with L.
>> >>>
>> >>€  A definition which does not work with Eimac's formulae.
>> >>
>
>Already stated,  "EIMAC's" formulae is incorrect.  Newcommers should 
>ignore all future references to the so-called EIMAC formulae.  Refer 
>instead to the ARRL handbook, 1995 and later editions only.  Earlier ARRL 
>editions have the same flaw as EIMAC.  The same is true of all the ORR 
>Radio Handbooks.

€  Agreed.  .  And how much improvement do the new, improved formulas 
afford the user?  Ian calculated 5.57 uH.  I calculated 5.06uH using the 
old, less than perfect formulas.  .  
>
>> >I still can't believe I'm reading this!
>> >
>> €  You can read it on pages 35, 36, and 37 in *Care and Feeding of Power
>> Grid tubes.  Q is used in all three formulas.  Q is not calculated.  Q is
>> selected by the designer.
>> >
>
>Q is selected by the designer in the corrected formulae too...no 
>difference.  However, Q is used to calculate the values of C1 AND C2 in 
>the corrected formuale...not just C1 as in Rich's EIMAC book.
>
€  Agreed.  

>Anyone with a copy of EIMAC's Care and Feeding...,  should remove pages 
>35, 36 and 37,  and deposit them on Bandini Mountain (forget where I heard 
>that one).
>
€  I can't unless I get Alzheimers.  
>>
-  -  However, the real issue here is not the less than perfect accuracy 
in the old Eimac formulae.  
>
-  cheers, Phil


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm