Phase Shift through a 75m Texas Bugcatcher Coil
 

If a Texas Bugcatcher Coil could be turned into a
traveling wave device instead of a standing wave
device, the inherent phase shift through the coil
would become obvious. I used the Helix option in
EZNEC to generate a reasonably close model of a
75m Texas Bugcatcher coil and loaded it with a
resistance equal to the coil's characteristic impedance
which essentially eliminated the reflected current,
leaving the forward current intact and visible. All
of the data points on the following web page came from
EZNEC. All of the files are available for downloading.
Please take a look at:

http://www.w5dxp.com/current2.htm
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

"Cecil Moore" wrote in message
...
If a Texas Bugcatcher Coil could be turned into a
traveling wave device instead of a standing wave
device, the inherent phase shift through the coil
would become obvious. I used the Helix option in
EZNEC to generate a reasonably close model of a
75m Texas Bugcatcher coil and loaded it with a
resistance equal to the coil's characteristic impedance
which essentially eliminated the reflected current,
leaving the forward current intact and visible. All
of the data points on the following web page came from
EZNEC. All of the files are available for downloading.
Please take a look at:

http://www.w5dxp.com/current2.htm
--
73, Cecil http://www.w5dxp.com

Soooo, W8JI and his worshippers were right! Current is just about constant
through the loading coil (for traveling wave) but they did not know the
case, in which this happens in the antenna circuit, while they were sticking
with DC circuit analysis.
I hope Roy approves your use of EZNEC for this demonstration and perhaps
will admit that they were wrong, and indeed the RF current through standing
wave antenna circuit, such a quarter wave resonant vertical monopole, the
loading coil has the current drop along the coil (standing wave circuit).

This exercise, and Walt's, and whole commotion of reflections and
interference has open my antenna eyes a bit wider and allow me to understand
better wasaaaap in antenna circuits, which should lead to mo' betta' antenna
designs.
The only problem I have swallowing Gaussian soup, to understand how on earth
and 100 years of antenna tinkering could not see the magic of this
(another) miraculous way of getting much more and better signals out of
antenna with given power.

Thanks guys, this is the best antenna NG, allowing good and questionable
posts and free discussion, unlike the TowerTalk antenna reflector where any
"heresy" against W8JI crapola "teachings" gets suspended.

Yuri, K3BU.us

Phase Shift through a 75m Texas Bugcatcher Coil
 

Yuri Blanarovich wrote:
Soooo, W8JI and his worshippers were right! Current is just about constant
through the loading coil (for traveling wave) ...

Especially since I modeled the coil with lossless wire. :-)

*Traveling wave current* amplitude is just about constant
at both ends of a loading coil but there's a phase shift
as can be seen at: http://www.w5dxp.com/current2.htm
In the middle of the coil, the current increases because
of the adjacent coil coupling. There is a little drop off
(unit percents)in amplitude end-to-end because of I^2*R
losses and radiation. But one can consider the coil to be
lossless and non-radiating and still get within a few percent
of reality.

The problem is that W8JI used *standing wave current* for
his measurements. What is flowing through the coil is the
forward current and reflected current, not the standing
wave current. The standing wave current is just standing
there as indicated by the cos(kz) term. The amplitude of the
standing wave current at any point in the coil or on the
antenna has more to do with the phase difference between
the forward and reflected currents than anything else. At
the tip of the antenna, the forward current and reflected
current are equal in magnitude, 180 degrees out of phase,
and thus sum to zero.

I hope Roy approves your use of EZNEC for this demonstration and perhaps
will admit that they were wrong, and indeed the RF current through standing
wave antenna circuit, such a quarter wave resonant vertical monopole, the
loading coil has the current drop along the coil (standing wave circuit).

The current "drop" is an illusion. The current decreases primarily
because of out-of-phase addition of the forward and reflected
current. If one makes the antenna longer and places the loading
coil somewhere else, one can measure a current "rise" through the
coil which is still an illusion created by the in-phase addition
of the forward and reflected currents.

I verified these findings on the bench a couple of months ago
using my 75m Texas Bugcatcher coil loaded with a 3K ohm resistor.
But I wanted to see if EZNEC agrees. It does.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

On May 6, 9:05 am, Cecil Moore wrote:

In the middle of the coil, the current increases because
of the adjacent coil coupling.

I'd like to see your Norton analysis of that one.

73, ac6xg

Phase Shift through a 75m Texas Bugcatcher Coil
 

Jim Kelley wrote:
I'd like to see your Norton analysis of that one.

RF is not DC. Edison questioned how one could measure
100 volts between any two of three terminals. :-)
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Jim Kelley wrote:
I'd like to see your Norton analysis of that one.

Take a look at: http://www.k6mhe.com/n7ws/Loaded%20antennas.htm

"Figure 2 and Figure 3 clearly show the peaking of the current
that Hansen and Cebik write about."
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

On 7 May, 06:54, Cecil Moore wrote:
Jim Kelley wrote:
I'd like to see your Norton analysis of that one.

Take a look at:http://www.k6mhe.com/n7ws/Loaded%20antennas.htm

"Figure 2 and Figure 3 clearly show the peaking of the current
that Hansen and Cebik write about."
--
73, Cecil http://www.w5dxp.com

Thanks for pointing that out Cecil. He did a really good job of
explaining things
Art

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil Moore wrote:
Jim Kelley wrote:

I'd like to see your Norton analysis of that one.


RF is not DC. Edison questioned how one could measure
100 volts between any two of three terminals. :-)

Are you implying yours is a 3-phase antenna? :-)

ac6xg

Phase Shift through a 75m Texas Bugcatcher Coil
 

Jim Kelley wrote:
Are you implying yours is a 3-phase antenna? :-)

No, just that phasing of RF signals is what is confusing
the DC gurus, just like AC phasing confused Edison.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil Moore wrote:

Jim Kelley wrote:

Are you implying yours is a 3-phase antenna? :-)


No, just that phasing of RF signals is what is confusing
the DC gurus, just like AC phasing confused Edison.

What is a DC guru, and why do you address comments to them?

As a suggestion, you might consider increasing the current for the
EZNEC simulation on your webpage. At 20 amps per division it's plus
or minus a pixel at 1024x768.

73, ac6xg