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Old April 2nd 09, 09:36 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_] Cecil Moore[_2_] is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default colinear representation in NEC

Jim Kelley wrote:
The term x is the phase of the cosine function, Cecil. The phase of the
standing wave function varies by 90 degrees along the length of a 1/4
wave resonant standing wave antenna.


I'm sorry, Jim, that is just not true. The standing-wave
function has a *constant phase* along the length of a 1/4WL
monopole for any fixed (t). Cos(x) is the *envelope amplitude*
function (not phase function) for any fixed (t).

What Gene Fuller said previously is true regarding the
cos(kz)*cos(wt) term in a standing wave:

Gene Fuller, W4SZ wrote:
In a standing wave antenna problem, such as the one you describe,
there is no remaining phase information. Any specific phase
characteristics of the traveling waves died out when the startup
transients died out.

Phase is gone. Kaput. Vanished. Cannot be recovered. Never to be
seen again.

The only "phase" remaining is the cos (kz) term, which is really
an amplitude description, not a phase.


One can ask EZNEC to display the phase of the total current.
When one does that, one will see that the phase is ~constant
for a 1/4WL thin wire monopole over mininec ground. The change
in amplitude is what allows us to calculate the actual delay
through the wire using an ARCCOS function.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com