Amps
[Top] [All Lists]

[AMPS] Finding the Q of a Coil

To: <amps@contesting.com>
Subject: [AMPS] Finding the Q of a Coil
From: 2@vc.net (2)
Date: Mon, 8 Oct 2001 06:38:43 -0700
>
>> >Accurate calculation of RF resistance definitely is the tough part. 
>> >There is more than one set of formulas from different sources for
>> >calculating this and the results don't agree. If I were forced to
>> >choose, I'd probably stick with the formulae in Terman's books.  
>> >Steve T. correctly outlined the general procedure.  I too will have a
>> >look at the Murphy file that Ian suggested.
>> >
>> I should have mentioned, it's all based on info from Terman.
>
>This is one of the cases I have found where you had just better 
>measure the component.
>
//   I have seen too many VHF antennas where the calculated gain was 
different than the measured gain.  It is no wonder that *QST* does not 
allow antenna manufacturers to make gain claims.  In CB rags, one finds 
gain claims of 11+db for 3-element yagis.

>It seems is difficult if not virtually impossible to get close to actual 
>component Q using formulas. Many things are at issue besides 
>wire resistance. Every Q formula working off coil dimensions or 
>program I have tried has never been close.
>
>The work by Czerwinski in August 26 1960 Electronics comes 
>closest, while some of Terman's stuff is miles from being correct.

//  Terman's inductance formula predicts that the L of 1-inch/25mm width 
copper strap is about 10nH per inch.  However, in the Rauchian world, an 
inch of such strap has zero inductance -- especially when it is used to 
ground a grid.  
>
cheers

-  R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.  
end


--
FAQ on WWW:               http://www.contesting.com/FAQ/amps
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com


<Prev in Thread] Current Thread [Next in Thread>