-=> On 12-21-97  22:59, Jeff Edmonson said to All,<=-
-=>"About Grid Coils...,"<=-
 
Hi, Jeff;
 
While cruising the echos, I chanced to hear my name...   :-}
 
 JE> Does anyone have a table for diameter and wire size for coils (IVY?)
 
The quick and simple answer is "Check the `bible' (handbook)."  I dont
know about the newer versions, but in the 1979 edition, there are
nomograms and formulas with the information you need on pages 2-11 to
2-14 and on 2-20.
 
It is impossible to say, "Wind so-many turns and you have your coil,"
because there are too many variables, including the diameter and length
of the coil, the core material, (if not air core), the number of layers
and the capacity range of the tuning cap.  If you are not restoring it
to origional, (like a musieum piece), you might also consider winding it
on a ferrite torroid, but that brings in a few new variables.
 
 JE> Need to build a grid coil for 80m for a friend who's had the original
 JE> one for  40 years himself, and it was used when HE got it...
 JE> I'm thinking around 20 to 22 turns over 1 3/4", around 2" in diameter.
 JE> I'll  also be wrapping a 3 turn link around the center.
 
There is an alternative to all the calculations: TRY IT!  I would expect
such a coil, tuned with a 10-365 Pf cap to resonate around 2 MHz so it
might work for you.
 
So wind it as you suggested, but add another 8-10 turns, put it in the
radio, (so it has the capacity it will have when finished), and check it
with a dipper.  It will probably be low in frequency.  Then take off a
couple of turns and try again.  Keep pruning until it has the correct
range.  Put the link coil at the cold (low RF potential) end of the coil,
and when you prune, take the turns off of the hot (high RF potential)
end of the coil.  This should bring it in to the correct value without
all the math.  
 
Good luck... Let me know how it turns out.
 
73 ES Merry Christmas DE KB9QPM.
   Ivy
 
 
 
... :<) What does that wire do?  =8>           ³
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