Reg Edwards wrote:

If you really understand what you're talking about,
you should be able to express it mathematically as an equation or
equations.

By far, the most sensible statement yet made in these interminable 'coil'
threads.

Well, I have already posted the equations. During steady-state, there will
be some magnitude of forward current (If) through the coil and some magnitude
of reflected current (Ib) flowing backwards through the coil caused by
reflections from the tip of the standing-wave antenna. The net current at
any position up and down the antenna is Ir+Ib. That's a pretty simple
equation. Since there is a phase shift in Ir and Ib through the large
bugcatcher coil, the sum of Ir and Ib will not be the same at each end.

In an electrical 1/4WL antenna, like a typical 75m mobile antenna with
no top hat, the If+Ib sum at the bottom will always be a larger magnitude
than the If+Ib sum at the top. Modeling the coil as an eight-sided helix
in EZNEC resulted in:

http://www.qsl.net/w5dxp/octcoil.gif

The net current at the bottom of the coil is obviously of a greater
magnitude than the net current at the top of the coil. That's because
If and Ib at the bottom of the coil are nearly in phase. Ir and Ib
are about 58 degrees different in phase at the top of the coil. That
tells me that the coil causes about a 29 degree phase shift when either
Ir or Ib flows through it. It's not that simple but let's stick with
simple for right now.
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000 Newsgroups
---= East/West-Coast Server Farms - Total Privacy via Encryption =---