[TowerTalk] OT: Inductor Calculator

Jim Thomson jim.thom at telus.net
Thu Feb 28 14:05:48 EST 2019


Date: Wed, 27 Feb 2019 11:12:37 -0800 (PST)
From: terry burge <ki7m at comcast.net>
To: Jim Thomson <jim.thom at telus.net>, towertalk at contesting.com
Subject: Re: [TowerTalk] OT: Inductor Calculator

<It just seems for TV stuff. Could not seem to get anything to work for a large coil for 160 mtrs made of copper tubing?
<Terry
<KI7M

## It gets  a lot worse.  K6STIs  latest version called ..coil 3.44  isnt even close to reality !   Doesnt work, dont use it. 

##  I looked at steve,  VE6WZs  screen shots of the original    k6sti coil  program from the 90s... and that
was for the  oem cush craft  40 m coils.   They consist of  68 turns of  12 gauge magnet  wire, wound butt tight, on a
.75 inch solid fiberglass form.    OLD coil  program depicts   15.076  uh  for a single  coil.    Steve has a pix on his site with the  MFJ
across  the coil, and mfj depicts   15.114  uh...close enough. 

## stuffing the  identical  68 turns of  12 gauge magnet wire, wound tight, on  the same  .75 inch solid fiberglass  form, the  new   ..coil  3.44  
software  depicts    just    8.549 uh   which is  clearly incorrect.   And yes, I entered it correctly, same lead lengths, and same length. 

##  I then tested the  new  coil  3.44  program on known stuff  I have in the shop....  its out to lunch, not even close to reality.
Thats  using  either of my 2    x  B+K  digital LCR meters, and also my  MFJ-259B.   I tested several coils, both tubing  types,
and also  wire types like a  half dozen air dux coils.  

##  also baffling, is the  Q on the old  coil software , on the oem  40m  cush craft coil  is shown as  just   81.    
On  the  new  coil 3.44  software, Q  is depicted as a lot higher, like   252. 

##  Ok, fine, BUT..when comparing  large  tubing coils, like the  .375 inch  OD  silver plated  copper  tubing  variety, .... on the old software,
they show up as sky  high  Q, like  1920.     On the new software,   Q is  down to   1230.   This is on 7 mhz. 

##  Not only is the uh  way outa whack on the new  coil  3.44  software, the  Q  is way higher for small wire wound coils....... and way lower  for 
tubing coils..go figure.

## Forget Q  for a minute, thats  semantics.  Copper tubing is a helluva lot higher  Q  vs  aluminum  tubing, for the same  OD  tubing...period. 
Same deal  with  copper wire  vs  aluminum wire...for the same gauge.   Dont believe me, try winding an aluminum tubing coil, identical to whats
in a  hb linear amp, then  compare the difference.  The aluminum  coil will run a helluva lot hotter.  

##  If you want to get real close  with calculated uh values,  use any of the other popular   coil calculators that can be found on line... most will
come out extremely close to what I measure on a LCR meter. 

Jim   VE7RF
   


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