RadioBanter - View Single Post

March 23rd 06, 05:45 PM posted to rec.radio.amateur.antenna

John Popelish wrote:
wrote:

A two-terminal network that transforms impedance, now there's a
concept!

(My opinion follows, please correct me. Dang, I should put that in my
sig.)

In reality, there is no such thing as a two terminal network, unless one
of those terminals is grounded. For all other cases, there is an
unavoidable implied ground terminal that covers all the stray
capacitance of the device.

So the bug catcher coil is recognized as a 3 terminal device, with
ground being the third terminal. It can be modeled as a pi, T or
transmission line structure, as long as you want to understand what to
quantify it at only one frequency (or a narrow band), and the choice is
arbitrary. If you are concerned with modeling a large frequency range
(that goes well past the first self resonance), one of those models (or
a more complicated one) will be superior.

You fellows lack imagination. As long as you're trying to morph a coil
into a transmission line, why not just imagine it as a shorted stub?
There's more than one way to make an inductive reactance.
73,
Tom Donaly, KA6RUH