Jim Brown wrote:
> On Sun, 27 Jul 2008 20:10:42 +0100, Dr. David Kirkby wrote:
>
>> I wish to know if the reactance of a dipole that is physically 0.5000
>> wavelengths in length depends on the diameter of the wire or not.
>
> So study a book on antennas! It is very well known (not far from the
> beginning of the discussion in almost any text) that the physical length of a
> resonant conductor depends on its cross section. There are many excellent
> texts on antennas, including the one by Kraus. The ARRL Antenna Book is also
> quite good. Both are widely available new and used. And yes, it is quite far
> off topic for this list.
>
> This sure sounds like a troll, but for a hot minute, let's pretend that it
> isn't. :)
>
> The confusion here is between a wavelength in air (or free space) and a
> wavelength in the conductor that makes up the antenna. When we decide how
> long the antenna should be, we're concerned with the wavelength in that
> conductor, not the wavelength in free space. When we design for the spacing
> between elements of a parasitic array (like a Yagi), we are concerned with
> the wavelength in free space.
>
> 73,
>
> Jim K9YC
>
>
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schelkunoffhalf.jpg
I've stuck another graph up, which shows the indepdance better around
0.5 lambda. The point of intersection of the lines if j 41.2 Ohms.
http://www.g8wrb.org/schelkunoffhalf.jpg
Also see the other one I posted
http://www.g8wrb.org/schelkunoff-full.jpg
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