Re: [TCML] BIGPIG secondary dies...but may be resurected

[bartb <bartb@xxxxxxxxxxxxxxxx>]

Hi Scot,

bunnykiller wrote:
> What would be the effect of winding a coil with say 18 ga for 3/4 
> length of tube and then finishing it off with 22 or 24 ga on the last 
> 1/4 length?? Since the current is less towards the top of the coil, 
> the thinner wire "should" be able to handle it.  And how would I 
> calculate L for the secondary if this is to be wound in this manner? ( 
> calc each as individual L's and then add inductance for a total??)

From the DC standpoint of inductance, you should be able to calc the 
two L's and add them, but regarding L at the coils frequency, there will 
likely be a shift. You can at least ballpark it with the two L's. I 
think your better off just winding it and then measuring Ldc and Fres. 
Then you can simply adjust the primary to suit.

If you actually wanted to model one coil against the other, then best to 
use Javatc for that. When doing this type of analysis, a little "play" 
is needed. Model the fine wire upper coil in it's position with the 
lower wire coil modeled as a cylinder (top load object with "grounded" 
selected). Then vice-versa with the lower larger wire coil (top coil 
modeled as a cylinder with "topload" selected). From this, you can then 
add the Les values for a ballpark of the L at resonance. However, the 
full coil resonance you will be required to use paper and pencil. There 
are a lot of ways to ballpark, but none of the "calculators" are set up 
for this particular situation, so the actual resonance is unknown. This 
is why I believe it's easiest and best to simply measure in this situation.

Sorry to hear about the burned secondary. Yes, just remove the damaged 
turns and splice as necessary. No big deal. I've done that a few times 
on my 13" diameter coil due various mishaps.

Take care,
Bart
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