[TowerTalk] inductance of tubing vs bar or strip

Thu Aug 20 06:46:20 PDT 2009

```Richard (Rick) Karlquist wrote:
> Steve, W3AHL wrote:
>
>> No, you can't just multiply the inductance of one foot of wire by ten to
>> find the inductance of 10'.  Use the calculator.
>
> Can you give us more details on what you mean here or a citation
> from a text book?  AFAIK, inductance is proportional to length,
> assuming the whole length is the same distance from ground, as long
> as the length is small compared to a wavelength.  (~10% error
> at 1/10 wavelength).

And the length is big, relative to the cross section of the conductor.

There are some "end effects" (a piece of the wire at the end sees the
field only from conductors on one side of it, and a piece in the middle
sees the field from both sides) but, without actually looking it up or
calculating it, I think they are "small"  (that is, the difference in L
per meter for an infinitely long wire and a 10 meter long wire is <1%
and for a 1 meter long wire <10%)

```