View Single Post
  #29   Report Post  
Old March 18th 09, 10:23 PM posted to rec.radio.amateur.antenna
Jim Kelley Jim Kelley is offline
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 666
Default colinear representation in NEC

Cecil Moore wrote:
Owen Duffy wrote:
Thinking some more about it, my current thinking is that my analysis
was flawed. I was using the standing wave currents, when I should be
using the travelling wave components.


That's exactly the flaw committed by w8ji and w7el when
they tried to measure the delay through a 75m loading
coil using standing wave current which doesn't appreciably
change phase through a loading coil or through the entire
90 degree length of a monopole. Using standing wave
current, w8ji measured a 3 nS delay through a 10 inch
long coil, a VF of 0.27.

http://www.w8ji.com/inductor_current_time_delay.htm

W7EL reported: "I found that the difference in current
between input and output of the inductor was 3.1% in
magnitude and with *no measurable phase shift*, despite
the short antenna... The result from the second test was
a current difference of 5.4%, again with *no measurable
phase shift*."

Of course, phase shift is not measurable when one is
using standing wave current with its almost unchanging
phase. EZNEC supports that assertion. Bench measurements
support that assertion.

When traveling waves are used to measure the delay through
a 75m loading coil, the correct delay through w8ji's 10
inch coil turns out to be about 26 nS (~37 degrees) at 4 MHz
with a more believable VF of 0.033.

http://www.w5dxp.com/current2.htm


I agree that electromagnetic traveling waves are the kinds of waves that
propagate on and cause radiation to emanate from an antenna. But your
claims about 'standing waves not changing phase along the antenna'
provoke the following questions:

1.) what relation (if any) do you believe the wavelength of the standing
wave has to the wavelength of the radio frequency waves traveling on an
antenna? And,

2.) what relation (if any) does the phase of a sinusoidal wave have to
its amplitude?

73, ac6xg