Jim Kelley wrote:

One point: Isn't the input impedance of a dipole normally specified at
a wavelength equal to twice the electrical length of the antenna? As
far as I know, dipoles have infinite DC resistance at zero Hertz. ;-)

No, you can calculate or specify the input impedance of a dipole at any
frequency. As frequency approaches zero, a dipole's input resistance
approaches zero and its reactance approaches minus inifnity. That is, it
looks like a capacitor, and the capacitive reactance gets larger as the
frequency gets lower. Which is just what you'd expect from a couple of
electrically very short wires having no DC connection.

Roy Lewallen, W7EL

Roy Lewallen wrote:

Jim Kelley wrote:


One point: Isn't the input impedance of a dipole normally specified
at a wavelength equal to twice the electrical length of the antenna?
As far as I know, dipoles have infinite DC resistance at zero Hertz. ;-)

As frequency approaches zero, a dipole's input resistance
approaches zero and its reactance approaches minus inifnity. That is, it
looks like a capacitor, and the capacitive reactance gets larger as the
frequency gets lower. Which is just what you'd expect from a couple of
electrically very short wires having no DC connection.

Roy Lewallen, W7EL

I'll give you a Mulligan on that one if you like, Roy. ;-)

73, ac6xg