Re: can so please double check my math for me

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Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 




Your 900 ft. length is correct.

The calculation goes something like this:

C = pi * dia = 3.14 * 3 inches = 9.2 inches per turn

Next, you need to mike your wire to determine it's precise dia.  By dividing
this number into 1.000 inch you will now have the number of turns per inch.
It's important to mike the wire because enamel magnet wires have different
diameters depending on the temp rating of the wire (important in AC
transformer design).  Any local machine shop can do this for you in about 5
seconds.  All you have to do it take them a sample of your wire.

Let's assume you are using a standard single coating enamel finish, for 16
AWG, average dia. is 18.9 turns per inch.

18.9 turns/inch * 58 inch long winding length = 1096.2 total turns.  Let's
round off to 1096 turns of wire.

Next, take the number of turns * the circumference of your coilform.

1096 turns * 9.2 inches/turn (your circumference) = 10,083.2 total inches

10,083.2 inches / 12 inches/ft  =  840.3 feet


That's all there is to it, but actually this design looks really bad.  Your
coil height/dia. ratio is way off.  Your height/dia ratio = 58/3 = 19.3:1

Most efficient coils use 4.5:1 or a max of 5:1.   With your 3 inch dia.,
then,

3 inch x 4.5 = 13.5 inch long winding length

Assume 1,400 turns for a good # turns value, then

13.5 inch winding length / 1,400 turns  =  .00964 dia. wire

 >From the ARRL Radio Amateur's Handbook (available in most large libraries or
thru interlibrary loan at you small town library, you can find the best size
wire to use.

Looking up this .00964 dia. wire (this is 9.64 mils), so wire guage = 30 AWG

Using 30 AWG wire with 90.5 turns per inch, you repeat the above
calculations to determine total wire length required.  Most wire this size
is sold by the pound and 1 lb. is usually enough wire to do 4 or 5 coils
this size.

Happy coiling,


Dr. Resonance

 >
 > i figure i am going to need a little over 900 feet of 16 awg wire to cover
 > a 58 inch coil for that is 3 inch in diameter that seems like a whole lot
 > to me and math has always been my weak point and i think i might of goofed
 > something some where's thank you all for you precise time jimbo
 >
 >
 >