View Single Post
  #13   Report Post  
Old November 18th 03, 09:30 PM
Cecil Moore
 
Posts: n/a
Default

Richard Harrison wrote:
Trying to use ordinary circuit analysis on standing-wave antennas is
problematic, but it`s been tried in this thread. Here is what R.W.P.
King wrote in "Transmission Lines, Antennas, and Wave Guides", King,
Mimno, and Wing, 1945, on page 86:
"Inductance and capacitance as used in near-zone circuits with uniform
current cannot be defined, and ordinary circuit analysis does not
apply." This has not stopped efforts in this thread to analyze LC
circuits as if we were dealing with low frequencies.


Very true. The basic problem, as I see it, is in assuming that the standing-
wave current only has one component. For standing-wave antennas, the
standing-wave current must necessarily have two components, If and Ir, as
explained by Balanis in _Antenna_Theory_, (page 489, 2nd edition).

In general, when forward waves and reflected waves exist in the circuit,
lumped circuit analysis fails and distributed network analysis is the only
method that yields the correct result. So even if one allows that the forward
current magnitude is constant through a coil and the reflected current
magnitude is constant through a coil, the net current magnitude will not
be constant because of the phase differences in the two superposed currents
at each end of the coil.

I've been told by the gurus that I can ignore the forward and reflected
waves and still obtain the correct steady-state solution. A mobile bugcatcher
coil on 75m seems to disprove that assertion. But I have been called a
"Grasshopper" and thus apparently have a lot yet to learn.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----