Phase Shift through a 75m Texas Bugcatcher Coil
 

Yuri Blanarovich wrote:
Which brings me back to my question: How important is the Q and low
resistance of the coil and stinger?

As the loading coil is moved from base-loading to
top-loading, the average net current through the coil
decreases (assuming no top hat loading). The importance
of coil Q is related to how much net average current
is flowing through the coil.

For instance, the net average current through a
hamstick coil is enough to burn your hand even
after the power has been shut off.

I've always had it in the back of my mind to
install a 16'x6' piece of hardware cloth at
12.5 ft above ground above my GMC pickup,
supported by fiberglass poles. I would mount
the loading coil about a foot below the top
hat. I'll bet that would win any 75m mobile
antenna shootout.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil Moore wrote:
...
For instance, the net average current through a
hamstick coil is enough to burn your hand even
after the power has been shut off.

I've always had it in the back of my mind to
install a 16'x6' piece of hardware cloth at
12.5 ft above ground above my GMC pickup,
supported by fiberglass poles. I would mount
the loading coil about a foot below the top
hat. I'll bet that would win any 75m mobile
antenna shootout.

Cecil:

Have you been designing and setting up antennas out at Area 51, again?

ROFLOL!!!

Regards,
JS

Phase Shift through a 75m Texas Bugcatcher Coil
 

I undesrtand delay in coils but I don't see anyone arguing delay.
more important is i don't see any differences but everyone is saying
this and that is better than something else. coke is better than
pepsi = who cares?

On May 11, 9:30 pm, (Richard Harrison)
wrote:
Herbert wrote:

"Do you know how to explain this so normal people can understand?"

I `m not a Guru, but I`ll try.

First, there was adispute about delay in an antenna loading coil. That
provoked attempts to measure the delay. Then the argument turned to the
measurement methods.

The antenna signal travels from the transmitter through the coil and
through the stinger until it reaches the tip where it is forced to
reverse course by the open circuit. All the signal which has not been
radiated or lost in waste enroute starts its journey back toward the
transmitter. This reflected energy from the antenna tip is of no help in
determining delay through the loading coil but the ripples it makes,
when it adds and subtracts from the waveform of the forward energy,
makes measurements difficult. Frequently a directional coupler is used
to measure the energy moving in one direction, while ignoring the energy
moving in the opposite direction, to get a meaningful measurement. Cecil
proposed a resistor matching the impedance at the tip of the antenna to
avoid a reflection. This also eliminates the troublesome ambiguity.

Testing is convincing, perhaps, but not really necessary as the delay
through a coil has been understood and quantified at least since Ampere
who died in 1836.

The ARRL Handbook, mine is from 1976, explains inductance on page 25:
"Since the induced emf opposes the emf of the source, it tends to
prevent the current from rising rapidly when the circuit is closed."

Delay is a well known function of inductors. In early times they were
often called "retard coils".

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

what is average net current? is there a peak net current?

On May 12, 7:17 am, Cecil Moore wrote:
Yuri Blanarovich wrote:
Which brings me back to my question: How important is the Q and low
resistance of the coil and stinger?

As the loading coil is moved from base-loading to
top-loading, the average net current through the coil
decreases (assuming no top hat loading). The importance
of coil Q is related to how much net average current
is flowing through the coil.

For instance, the net average current through a
hamstick coil is enough to burn your hand even
after the power has been shut off.

I've always had it in the back of my mind to
install a 16'x6' piece of hardware cloth at
12.5 ft above ground above my GMC pickup,
supported by fiberglass poles. I would mount
the loading coil about a foot below the top
hat. I'll bet that would win any 75m mobile
antenna shootout.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

wrote:
I undesrtand delay in coils but I don't see anyone arguing delay.

The following web page is representative of the side that
asserts there is virtually zero delay through a 75m loading
coil. But the backers of that argument have grown strangely
silent as of late.

http://www.w8ji.com/inductor_current_time_delay.htm
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

wrote:
what is average net current?

Average net current is the RMS value of the standing-wave
current. Here is a graph of such from Kraus: "Antennas"
for a 1/2WL dipole:

http://www.w5dxp.com/krausdip.jpg

Half of that graph would represent a 1/4WL monopole.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

Cecil, W5DXP wrote:
"Here is a graph of such from Kraus: "Antennas" for a 1/2WL dipole."

The Fig. 9-6 that Cecil posted is from an older edition of Kraus. In the
new 3rd edition, the same graph is Fig. 14-2 on page 464.

Best regards, Richard Harrison, KB5WZI

Phase Shift through a 75m Texas Bugcatcher Coil
 

i see nothing about average or peak net current there a t the link
i see no differences by value only of maytters of taste.
Is there someone else here who knows how to explain not fact things so
a normal person can understand what this is all about?

On May 12, 9:58 am, Cecil Moore wrote:
wrote:
what is average net current?

Average net current is the RMS value of the standing-wave
current. Here is a graph of such from Kraus: "Antennas"
for a 1/2WL dipole:

http://www.w5dxp.com/krausdip.jpg

Half of that graph would represent a 1/4WL monopole.
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

there is nothing there that shows any difference
virtually zero means anything

what does it matter anyway when no one can show simple difference?

On May 12, 9:52 am, Cecil Moore wrote:
wrote:
I undesrtand delay in coils but I don't see anyone arguing delay.

The following web page is representative of the side that
asserts there is virtually zero delay through a 75m loading
coil. But the backers of that argument have grown strangely
silent as of late.

http://www.w8ji.com/inductor_current_time_delay.htm
--
73, Cecil http://www.w5dxp.com

Phase Shift through a 75m Texas Bugcatcher Coil
 

wrote:
i see nothing about average or peak net current there a t the link
i see no differences by value only of maytters of taste.

Don't worry, Don, many of the gurus on this newsgroup
don't comprehend it either. Maybe when the light dawns
upon them, they will explain it better than I can.
--
73, Cecil http://www.w5dxp.com