[Antennas] Inductors

[Chris BONDE]

I apologize for the mistake as pointed out.  I went through everything a number of 
times.  The mistake is that the 1in should be the radius, not the diameter.

Now, the description of the second 'coil'.  I described it similar as I thought that it 
could be made easily.  The following description may be better but almost 
impossible to make.

Use the same form, say a 2in diameter, 12 in long piece of PVC tube (maybe 1/8 in 
wall thickness).  Put the wire into the centre of the form from one end down to the 
other end, then move the wire outside of the form then up to the top of the form.  
This would make one loop or coil on the form.  Then continue around the 
circumference at spacing 1/8 in.

Or at one end of the cylinder put in plastic nails about 1/8 in apart, the same at the 
other end.  Then put the wire around nail 1 at the top down to nail 1 at the bottom, 
then back to nail 2 at the top, down to nail 2 at the bottom etc.

If we cut the cylinder open with one cut from one end to the other then open it to 
form a flat piece or plane, then the form may be considered a rectangle coil form.  
However, the inductance on this shape would be much different on the cylinder 
form.

On the other hand if we take a form 12 in by 2*pie*1 wide 1/8 thick, wrap wire aound 
it spacing 1/8 in to form a rectangle coil, then join the 12in sides to form a cylinder 
12 in long radius 1 in.  How would I calculate the inductance?


Info needed for inductors or loading coils.

If a have a cylindrical form (say 1in dia by 12 in+ long) and wrap wire around the 
circumference of the form with so many turns per inch ( 8 per in). Then I would have 

L = 2 * pie * r * l * t/in  = 2 * 3.14159* 1 *12 *8 = 50.25 ft

Inductance = a**2 * n**2 /  (9a + 10 b) = 1* (12*8)**2/ (9 + 10*12) = 71.44 uh.

Now, if instead of wrapping the wire around the circumference, I loop the wire from 
one end to the other then back to the first end, then down to the second end, etc 
working around the circumference spacing the wire at 8 stands per in, I will use the 
same amount of wire.  What would the inductance be?

Breaking the form open and making a flat coil would give a preposterous 
inductance.  How would the inductance be calculated?  Maybe easily measured.

Anyone know?

Chris opr VE7HCB