Information about my experience with Magnetic Loop antenna's on my homepage
 

Today I have put my homepage online with information about the Magnetic Loop
Antenna.

http://www.qsl.net/pa7nr/

PA7NR

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Wed, 23 Feb 2011 16:00:57 +0100, "RadioWaves" radio@oidar wrote:

Today I have put my homepage online with information about the Magnetic Loop
Antenna.

http://www.qsl.net/pa7nr/

PA7NR

Hi OM,

I especially like your coverage of your antenna from I3VHF.

On your second page, unfortunately, you have some misconceptions about
loop antennas.

All antennas exhibit the same noise characteristics. If you erected
a conventional (electric) dipole in the same space, it would exhibit
the same characteristics.

It is quite curious how you describe a front/back ratio for a dipole
(the loop is a magnetic dipole, and as such "should" show a
conventional dipole pattern).

As for loop efficiency, you state:
"When a magnetic loop antenna is used for
3.5 MHz with a perimeter of 4 meter (13.3 foot) ,
it has an efficiency of approximately 3%."
Please show the math.

73's
Richard Clark, KB7QHC

Information about my experience with Magnetic Loop antenna's on my homepage
 

Hi Richard,

Thank you for your reply and your interest in my homepage. I will answer
your questions between the lines.

I will use the remarks that I get to improve the content of the article on
my site.

Hi OM,

I especially like your coverage of your antenna from I3VHF.

On your second page, unfortunately, you have some misconceptions about
loop antennas.

All antennas exhibit the same noise characteristics. If you erected
a conventional (electric) dipole in the same space, it would exhibit
the same characteristics.


I agree that they are electrically equivalents. However, my point is that
the magnetic loop has useful benefits over the dipole antenna for RX under
certain circumstances. I believe the magnetic loop construction will in many
cases deliver an acceptable signal at the receiver with less disturbances
such as atmospheric noise.

About external noise sources:

The loop is smaller (less surface) and therefore picks up less static noise.
The dipole covers a larger area in which there can be sources of noise.

The pickup loop that connects the coax to the loop antenna is isolated from
the antenna and it forms a shortcut for DC. The signal transfer is
inductive.

The magnetic loop tunes to the frequency and there is no external antenna
tuner needed.

About intenal receiver noise and mix-products:

The magnetic loop in itself is a band pass filter at the source of the
receiving signal. It eliminates strong signals outside the received
frequency. Therefore the receiver can receive the wanted signals with
maximum sensitivity. The band pass functionality of the loop protects the
radio from overloading. And as a result of that the radio will be quiet and
doesn't need to pick a weak signal from an overloaded band. The bandwidth of
the I3VHF is very small in the 40 m band. AM modulation is not possible as
the bandwidth of the loop is too small here for passing a standard AM
signal. The signal will be clipped and the transceiver react to that which
can be seen on the SWR meter. SWR starts to alternate on the rhythm of the
modulation. The bandwidth of the antenna gets larger in the higher bands. I
believe that in the 40 meter band the I3VHF only lets trough one frequency
in SSB. The receiver is almost mute tuning higher or lower.

As for receiving the readability is more important than signal strength. The
lower RX signal from the magnetic loop is often more readable than when
using a full size dipole at ideal height. I think that the advantages are
best in the Low bands, e.g. 80, 40, 30 meter.

For TX there are advantages of the magnetic loop over the full size dipole.
When one has shortage of space. The high small band pass filter that the
Magnetic Loop is, makes the radiated signal free of harmonics. Therefore
there is a smaller chance of rfi to be expected .

Maybe some of the points here are not based on solid scientific research.
But it is what I found doing experiments with the loops.

It is quite curious how you describe a front/back ratio for a dipole
(the loop is a magnetic dipole, and as such "should" show a
conventional dipole pattern).


The data is based on the specifications of the manufacturer of the I3VHF
loop antenna.

http://www.ciromazzoni.com/English/L...oop%20Baby.htm

In the manual, page 42, 43 there is a picture of the radiation pattern:

http://www.ciromazzoni.com/English/L...nna/Manual.pdf

It also surprised me as I expected a dipole pattern.

As for loop efficiency, you state:
"When a magnetic loop antenna is used for
3.5 MHz with a perimeter of 4 meter (13.3 foot) ,
it has an efficiency of approximately 3%."
Please show the math.

The 3 % efficiency is hypothetical based on the outcome of calculations
software that is available on the Internet.

For example the loop calculation software of G4FGQ.


73's
Richard Clark, KB7QHC

Best Regards,

Norbert , PA7NR

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Wed, 23 Feb 2011 21:53:00 +0100, "RadioWave" radio@oidar wrote:

Hi Richard,

Thank you for your reply and your interest in my homepage. I will answer
your questions between the lines.

I will do the same.

I will use the remarks that I get to improve the content of the article on
my site.

Hi OM,

I especially like your coverage of your antenna from I3VHF.

On your second page, unfortunately, you have some misconceptions about
loop antennas.

All antennas exhibit the same noise characteristics. If you erected
a conventional (electric) dipole in the same space, it would exhibit
the same characteristics.


I agree that they are electrically equivalents. However, my point is that
the magnetic loop has useful benefits over the dipole antenna for RX under
certain circumstances. I believe the magnetic loop construction will in many
cases deliver an acceptable signal at the receiver with less disturbances
such as atmospheric noise.

Hi Norbert,

Demonstrable proof shows otherwise.

About external noise sources:

The loop is smaller (less surface) and therefore picks up less static noise.

Static is indistinguishable from the RF you want to hear. In other
words static is RF, signals are RF. If your small loop picks up less
of one, it picks up less of both. However, this "picks up less" is
arguable.

The dipole covers a larger area in which there can be sources of noise.

Reread my statement: "If you erected a conventional (electric) dipole
IN THE SAME SPACE."

The pickup loop that connects the coax to the loop antenna is isolated from
the antenna and it forms a shortcut for DC. The signal transfer is
inductive.

This is a tautology, not a reason.

The magnetic loop tunes to the frequency and there is no external antenna
tuner needed.

Here, the Q of the tuned loop DOES contribute to less interference of
out-of-band signals. It does not reduce interference to in-band
signals. Noise is not specific to frequency, although single
frequency emitters can be called noise (unwanted).

About intenal receiver noise and mix-products:

The magnetic loop in itself is a band pass filter at the source of the
receiving signal. It eliminates strong signals outside the received
frequency. Therefore the receiver can receive the wanted signals with
maximum sensitivity. The band pass functionality of the loop protects the
radio from overloading. And as a result of that the radio will be quiet and
doesn't need to pick a weak signal from an overloaded band. The bandwidth of
the I3VHF is very small in the 40 m band. AM modulation is not possible as
the bandwidth of the loop is too small here for passing a standard AM
signal. The signal will be clipped and the transceiver react to that which
can be seen on the SWR meter. SWR starts to alternate on the rhythm of the
modulation. The bandwidth of the antenna gets larger in the higher bands. I
believe that in the 40 meter band the I3VHF only lets trough one frequency
in SSB. The receiver is almost mute tuning higher or lower.

Barring problems of lacking a choke on your control line introducing
SWR issues, I would tend to agree.

As for receiving the readability is more important than signal strength. The
lower RX signal from the magnetic loop is often more readable than when
using a full size dipole at ideal height. I think that the advantages are
best in the Low bands, e.g. 80, 40, 30 meter.

You have a lower signal because you have a lower antenna. Let's not
turn a deficit into a glowing recommendation - especially when you go
to transmit you lose that same gain from low height.

For TX there are advantages of the magnetic loop over the full size dipole.
When one has shortage of space. The high small band pass filter that the
Magnetic Loop is, makes the radiated signal free of harmonics. Therefore
there is a smaller chance of rfi to be expected .

A small (electric) dipole is identical in characteristics. It simply
doesn't come built with its own tuning mechanism.

Your arguments are not about antenna, but tuning.

Maybe some of the points here are not based on solid scientific research.
But it is what I found doing experiments with the loops.

It is quite curious how you describe a front/back ratio for a dipole
(the loop is a magnetic dipole, and as such "should" show a
conventional dipole pattern).


The data is based on the specifications of the manufacturer of the I3VHF
loop antenna.

http://www.ciromazzoni.com/English/L...oop%20Baby.htm

First thing I noticed was the loop on a tower.

In the manual, page 42, 43 there is a picture of the radiation pattern:

http://www.ciromazzoni.com/English/L...nna/Manual.pdf

It also surprised me as I expected a dipole pattern.

As for loop efficiency, you state:
"When a magnetic loop antenna is used for
3.5 MHz with a perimeter of 4 meter (13.3 foot) ,
it has an efficiency of approximately 3%."
Please show the math.

The 3 % efficiency is hypothetical based on the outcome of calculations
software that is available on the Internet.

I presume this is for the MIDI loop with a 2M diameter. The claim
offered is that it exhibits a Q of 1500 at 3.5MHz. The radiation
resistance for that size of loop is 0.49 Ohm. So, if 3% of the power
goes to 0.49 Ohm, then 97% of the power must go to heating up the
large tubular structure's Ohmic resistance (which would be very high,
and quite remarkable for that mass). Let's consider that you took an
Ohmmeter and measured half an Ohm in the structure, then you would be
losing only 50%, not 97%.

If you short your Ohmmeter leads together, I bet they have less than
half an Ohm resistance, why should this massive structure have more
loss than simple wire?

The argument would also have to answer the high Q (that much loss is
very low Q).

For example the loop calculation software of G4FGQ.

Give us the entry data and the formula.

73's
Richard Clark, KB7QHC

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 23, 7:17*pm, Richard Clark wrote:
Static is indistinguishable from the RF you want to hear.

EM wave static is indistinguishable from RF waves. Pstatic, for
instance, is not caused by EM waves and is therefore, distinguishable.
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's on my homepage
 

All antennas exhibit the same noise characteristics. If you erected
a conventional (electric) dipole in the same space, it would exhibit
the same characteristics.


I agree that they are electrically equivalents. However, my point is that
the magnetic loop has useful benefits over the dipole antenna for RX under
certain circumstances. I believe the magnetic loop construction will in
many
cases deliver an acceptable signal at the receiver with less disturbances
such as atmospheric noise.
Demonstrable proof shows otherwise.


Where can I read about the proof?


About external noise sources:

The loop is smaller (less surface) and therefore picks up less static
noise.

Static is indistinguishable from the RF you want to hear. In other
words static is RF, signals are RF. If your small loop picks up less
of one, it picks up less of both. However, this "picks up less" is
arguable.


Precipitation Static (p-static) can be different.


The dipole covers a larger area in which there can be sources of noise.

Reread my statement: "If you erected a conventional (electric) dipole
IN THE SAME SPACE."


In a practical situation, for instance a 20 meter long dipole over a
building picks up electro smog from the floors underneath, the loop covers a
small space and is physically further away from part of the sources.


In free space high in the sky they will pick up the same noise, I
agree.


The magnetic loop tunes to the frequency and there is no external antenna
tuner needed.

Here, the Q of the tuned loop DOES contribute to less interference of
out-of-band signals. It does not reduce interference to in-band
signals. Noise is not specific to frequency, although single
frequency emitters can be called noise (unwanted).




The bandwidth is so narrow in the 40 meter band (I3VHF) that only a few kHz
so there is a smaller chance of strong out
of band signals.

By the way, having to tune the loop every time when changing frequency is a
mayor disadvantage of tuned magnetic loops. The MFJ loop can be tuned rather
fast and the larger bandwidth makes it easier to hear within several kHz
from the tuned frequency.


As for receiving the readability is more important than signal strength.
The
lower RX signal from the magnetic loop is often more readable than when
using a full size dipole at ideal height. I think that the advantages are
best in the Low bands, e.g. 80, 40, 30 meter.

You have a lower signal because you have a lower antenna. Let's not
turn a deficit into a glowing recommendation - especially when you go
to transmit you lose that same gain from low height.


I don't think that it's just a matter of height. But maybe you are right. I
can't put up a full size verticale on my balcony to compare.

A magnetic loop will work indoor and outdoor. Low on the ground and high in
the sky. And without a counterpoise. Dipoles require space. Verticals
require counterpoise. When there is little space or other restrictions the
loop is a nice alternative.

For transmitting a magnetic loop can be also interesting when there is no
space for a full size antenna.

One could also for example use the full size antenna for TX and the magnetic
loop as an
alternative for RX.

It's not that I'm against dipoles because I reviewed some magnetic loops. I
appreciate the concept of the magnetic loop. I would use a dipole with open
feeding line and symetric tuner where possible.

For TX there are advantages of the magnetic loop over the full size
dipole.
When one has shortage of space. The high small band pass filter that the
Magnetic Loop is, makes the radiated signal free of harmonics. Therefore
there is a smaller chance of rfi to be expected .

A small (electric) dipole is identical in characteristics. It simply
doesn't come built with its own tuning mechanism.

Your arguments are not about antenna, but tuning.


To me the antenna start at the Antenna connector of the tranceiver.



As for loop efficiency, you state:
"When a magnetic loop antenna is used for
3.5 MHz with a perimeter of 4 meter (13.3 foot) ,
it has an efficiency of approximately 3%."
Please show the math.

The 3 % efficiency is hypothetical based on the outcome of calculations
software that is available on the Internet.

I presume this is for the MIDI loop with a 2M diameter. The claim
offered is that it exhibits a Q of 1500 at 3.5MHz. The radiation
resistance for that size of loop is 0.49 Ohm. So, if 3% of the power
goes to 0.49 Ohm, then 97% of the power must go to heating up the
large tubular structure's Ohmic resistance (which would be very high,
and quite remarkable for that mass). Let's consider that you took an
Ohmmeter and measured half an Ohm in the structure, then you would be
losing only 50%, not 97%.


If you short your Ohmmeter leads together, I bet they have less than
half an Ohm resistance, why should this massive structure have more
loss than simple wire?

The argument would also have to answer the high Q (that much loss is
very low Q).




Maybe you can ask the manufacturer and post his explanation here.



For example the loop calculation software of G4FGQ.

Give us the entry data and the formula.




You can download the loop calculation software and enter the dimensions of
the loop. I don't provide software.
I don't know the formula.



73's

Norbert, PA7NR

Information about my experience with Magnetic Loop antenna's on my homepage
 

All antennas exhibit the same noise characteristics. If you erected
a conventional (electric) dipole in the same space, it would exhibit
the same characteristics.


I agree that they are electrically equivalents. However, my point is that
the magnetic loop has useful benefits over the dipole antenna for RX under
certain circumstances. I believe the magnetic loop construction will in
many
cases deliver an acceptable signal at the receiver with less disturbances
such as atmospheric noise.
Demonstrable proof shows otherwise.


Where can I read about the proof?


About external noise sources:

The loop is smaller (less surface) and therefore picks up less static
noise.

Static is indistinguishable from the RF you want to hear. In other
words static is RF, signals are RF. If your small loop picks up less
of one, it picks up less of both. However, this "picks up less" is
arguable.


Precipitation Static (p-static) can be different.


The dipole covers a larger area in which there can be sources of noise.

Reread my statement: "If you erected a conventional (electric) dipole
IN THE SAME SPACE."


In a practical situation, for instance a 20 meter long dipole over a high
building picks up electro smog over the full length from the floors
underneath, the loop covers a
small space and is physically further away from most of the sources.


In free space high in the sky they will pick up the same noise, I
agree.


The magnetic loop tunes to the frequency and there is no external antenna
tuner needed.

Here, the Q of the tuned loop DOES contribute to less interference of
out-of-band signals. It does not reduce interference to in-band
signals. Noise is not specific to frequency, although single
frequency emitters can be called noise (unwanted).




The bandwidth is so narrow in the 40 meter band, only a few kHz.
So there is a smaller chance of strong out
of band signals.

By the way, having to tune the loop every time when changing frequency is a
mayor disadvantage of tuned magnetic loops. The MFJ loop can be tuned rather
quickly and the larger bandwidth (lower Q) makes it easier to hear stations
within several kHz
from the tuned frequency.


As for receiving the readability is more important than signal strength.
The
lower RX signal from the magnetic loop is often more readable than when
using a full size dipole at ideal height. I think that the advantages are
best in the Low bands, e.g. 80, 40, 30 meter.

You have a lower signal because you have a lower antenna. Let's not
turn a deficit into a glowing recommendation - especially when you go
to transmit you lose that same gain from low height.


I don't think that it's just a matter of height. But maybe you are right. I
can't put up a full size verticale on my balcony to compare.

A magnetic loop will work indoor and outdoor. Low on the ground and high in
the sky. And without a counterpoise. Dipoles require space. Verticals
require counterpoise. When there is little space or other restrictions the
loop is a nice alternative.

For transmitting a magnetic loop can be also interesting when there is no
space for a full size antenna.

One could also for example use the full size antenna for TX and the magnetic
loop as an
alternative for RX.

It's not that I'm against dipoles because I reviewed some magnetic loops. I
appreciate the concept of the magnetic loop. I would use a dipole with open
feeding line and symetric tuner if possible.

For TX there are advantages of the magnetic loop over the full size
dipole.
When one has shortage of space. The high small band pass filter that the
Magnetic Loop is, makes the radiated signal free of harmonics. Therefore
there is a smaller chance of rfi to be expected .

A small (electric) dipole is identical in characteristics. It simply
doesn't come built with its own tuning mechanism.

Your arguments are not about antenna, but tuning.


To me the antenna start at the Antenna connector of the tranceiver.



As for loop efficiency, you state:
"When a magnetic loop antenna is used for
3.5 MHz with a perimeter of 4 meter (13.3 foot) ,
it has an efficiency of approximately 3%."
Please show the math.

The 3 % efficiency is hypothetical based on the outcome of calculations
software that is available on the Internet.

I presume this is for the MIDI loop with a 2M diameter. The claim
offered is that it exhibits a Q of 1500 at 3.5MHz. The radiation
resistance for that size of loop is 0.49 Ohm. So, if 3% of the power
goes to 0.49 Ohm, then 97% of the power must go to heating up the
large tubular structure's Ohmic resistance (which would be very high,
and quite remarkable for that mass). Let's consider that you took an
Ohmmeter and measured half an Ohm in the structure, then you would be
losing only 50%, not 97%.


If you short your Ohmmeter leads together, I bet they have less than
half an Ohm resistance, why should this massive structure have more
loss than simple wire?

The argument would also have to answer the high Q (that much loss is
very low Q).




Maybe you can ask the manufacturer and post his explanation here.



For example the loop calculation software of G4FGQ.

Give us the entry data and the formula.




You can download the loop calculation software and enter the dimensions of
the loop. I don't have information about the formula.

Best 73's

Norbert, PA7NR

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Thu, 24 Feb 2011 20:17:33 +0100, "RadioWave" radio@oidar wrote:

Demonstrable proof shows otherwise.


Where can I read about the proof?

Hi Norbert,

Usually in the first chapter of any college text on antennas.

Precipitation Static (p-static) can be different.

An electrical discharge that is harmonic rich still qualifies as RF.
That pulse electric discharge is going to create a pulse magnetic
field. Guess what? A magnetic antenna (as a loop is often described)
will pick up that field as readily as an electric antenna.

The bandwidth is so narrow in the 40 meter band, only a few kHz.
So there is a smaller chance of strong out
of band signals.

By the way, having to tune the loop every time when changing frequency is a
mayor disadvantage of tuned magnetic loops. The MFJ loop can be tuned rather
quickly and the larger bandwidth (lower Q) makes it easier to hear stations
within several kHz
from the tuned frequency.

These are operational characteristics of a tuned loop. Look at your
own subject heading: Magnetic Loop - not the same thing.

In fact, the term Magnetic Loop is an invented term. RF is both
magnetic and electric simultaneously. All antennas respond to both.
Your tuned loop exhibits astronomically high electric potentials.
Would you care to guess how high the potentials are for receive as
compared to the field potential it experiences?

Let's put some fantastical numbers to this last question. A reception
field of 1V/M will exhibit ______ V on the capacitive elements of a
resonant tuned loop with a Q of 1500.

I don't think that it's just a matter of height. But maybe you are right. I
can't put up a full size verticale on my balcony to compare.

A magnetic loop will work indoor and outdoor. Low on the ground and high in
the sky. And without a counterpoise. Dipoles require space. Verticals
require counterpoise. When there is little space or other restrictions the
loop is a nice alternative.

A 2 meter wide dipole occupies less space than a 2 meter wide loop.
Once the dipole is matched, performance will be identical.

For transmitting a magnetic loop can be also interesting when there is no
space for a full size antenna.

You could as easily say the same for a full size loop. Do you notice
any irony?

One could also for example use the full size antenna for TX and the magnetic
loop as an
alternative for RX.

Why?

To me the antenna start at the Antenna connector of the tranceiver.

Then a lot has been unsaid for a tuner to any dipole.

As for loop efficiency, you state:
"When a magnetic loop antenna is used for
3.5 MHz with a perimeter of 4 meter (13.3 foot) ,
it has an efficiency of approximately 3%."
Please show the math.

The 3 % efficiency is hypothetical based on the outcome of calculations
software that is available on the Internet.

I presume this is for the MIDI loop with a 2M diameter. The claim
offered is that it exhibits a Q of 1500 at 3.5MHz. The radiation
resistance for that size of loop is 0.49 Ohm. So, if 3% of the power
goes to 0.49 Ohm, then 97% of the power must go to heating up the
large tubular structure's Ohmic resistance (which would be very high,
and quite remarkable for that mass). Let's consider that you took an
Ohmmeter and measured half an Ohm in the structure, then you would be
losing only 50%, not 97%.


If you short your Ohmmeter leads together, I bet they have less than
half an Ohm resistance, why should this massive structure have more
loss than simple wire?

The argument would also have to answer the high Q (that much loss is
very low Q).

Maybe you can ask the manufacturer and post his explanation here.

Actually, you need to do this yourself as these are all your choices.
This is your offered explanation and your offered testimony. In fact,
in this, a technical forum, there is every expectation that you could
reasonably perform these technical matters and respond with results.
Do you have an Ohmmeter? Are you proficient in its use?

If you cannot on your own, and without prompting, reconcile 3%
efficiency with a Q of 1500, then you shouldn't be offering technical
advice about Q or efficiency.

For example the loop calculation software of G4FGQ.

Give us the entry data and the formula.

You can download the loop calculation software and enter the dimensions of
the loop. I don't have information about the formula.

I have corresponded with G4FGQ the software designer for YEARS.
Consult the archives. I understand how it works. The question was
for you to write what YOU did, and not what someone else might do.

73's
Richard Clark, KB7QHC

Information about my experience with Magnetic Loop antenna's on my homepage
 

"Richard Clark" schreef in bericht
...
On Thu, 24 Feb 2011 20:17:33 +0100, "RadioWave" radio@oidar wrote:


Hi Richard,



Thank you for the explanations. I have not had the intention to start a
scientific discussion here on this subject. To me it is a hobby. With my
homepage I just want to share some of my experience with magnetic loop
antennas, just like many other radio amateurs do. And of course I am willing
to reply to reactions from readers. But I will not further discuss about
scientifically details.



Thank you.



Best Regards

73,

Norbert PA7NR

Information about my experience with Magnetic Loop antenna's on my homepage
 

"RadioWave" radio@oidar wrote
...

A magnetic loop will work indoor and outdoor. Low on the ground and high
in
the sky. And without a counterpoise. Dipoles require space. Verticals
require counterpoise. When there is little space or other restrictions the
loop is a nice alternative.

Your loop is not magnetic. Look at Fig. 2:
http://www.antiquewireless.org/otb/lodge1102.htm

Radio wavesare are radiated from the nodes. In dipole the nodes are created
by reflected wave (waves in the opposite direction). In the loop the waves
travel in oppsite direction and create the nodes also.

Verticals work like the Kundt's tube. Dipoles like the two Kundt's tubes.
A loop is like a dipole where the reflected wave is replacesd by the on from
the second wire.

Hertz has the dipole and the loop:
http://people.seas.harvard.edu/~jone...ertz/S_p11.gif

S*

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 9:11*am, "Szczepan Bialek" wrote:
*"RadioWave" radio@oidar . ..



A magnetic loop will work indoor and outdoor. Low on the ground and high
in
the sky. And without a counterpoise. Dipoles require space. Verticals
require counterpoise. When there is little space or other restrictions the
loop is a nice alternative.

Your loop is not magnetic. Look at Fig. 2:http://www.antiquewireless.org/otb/lodge1102.htm

Radio wavesare are radiated from the nodes. In dipole the nodes are created
by reflected wave (waves in the opposite direction). In the loop the waves
travel in oppsite direction and create the nodes also.

Verticals work like the Kundt's tube. Dipoles like the two Kundt's tubes.
A loop is like a dipole where the reflected wave is replacesd by the on from
the second wire.

Hertz has the dipole and the loop:http://people.seas.harvard.edu/~jone...res/lecture6/h...

S*



don't bother arguing with him, he is stuck in about 1880 with jumping
electrons and a charged aether.

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 6:04*am, K1TTT wrote:
he is stuck in about 1880 with ... a charged aether.

If there is no charged aether, where does the "quantized field in a
vacuum" come from? From Wikipedia: "In quantum field theory, the
Casimir effect and the Casimir-Polder force are physical forces
arising from a quantized field. The typical example is of two
uncharged metallic plates in a vacuum, ..."
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 12:41*pm, Cecil Moore wrote:
On Feb 25, 6:04*am, K1TTT wrote:

*he is stuck in about 1880 with ... a charged aether.

If there is no charged aether, where does the "quantized field in a
vacuum" come from? From Wikipedia: "In quantum field theory, the
Casimir effect and the Casimir-Polder force are physical forces
arising from a quantized field. The typical example is of two
uncharged metallic plates in a vacuum, ..."
--
73, Cecil, w5dxp.com

i am referring to a theory from around 1880 that had a sea of
electrons as the aether for propagating electromagnetic waves.

Information about my experience with Magnetic Loop antenna's on my homepage
 

"K1TTT" napisal w wiadomosci
...
On Feb 25, 12:41 pm, Cecil Moore wrote:
On Feb 25, 6:04 am, K1TTT wrote:

he is stuck in about 1880 with ... a charged aether.

If there is no charged aether, where does the "quantized field in a
vacuum" come from? From Wikipedia: "In quantum field theory, the
Casimir effect and the Casimir-Polder force are physical forces
arising from a quantized field. The typical example is of two
uncharged metallic plates in a vacuum, ..."
--
73, Cecil, w5dxp.com

i am referring to a theory from around 1880 that had a sea of
electrons as the aether for propagating electromagnetic waves.

It is from 1846: http://www.padrak.com/ine/FARADAY1.html
Faraday wrote:
"I suppose we may compare together the matter of the aether and ordinary
matter (as, for instance, the copper of the wire through which the
electricity is conducted), and consider them as alike in their essential
constitution; i.e. either as both composed of little nuclei, considered in
the abstract as matter, and of force or power associated with these nuclei."

Aether and a sea of electrons (as the rare plasma) is not the same.The other
scientists needs a mystery aether where a strain, stress and flows take
place. Faradays electrons vibrate.
S*

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 5:02*pm, "Szczepan Bialek" wrote:
"K1TTT" napisal w ...
On Feb 25, 12:41 pm, Cecil Moore wrote:

On Feb 25, 6:04 am, K1TTT wrote:

he is stuck in about 1880 with ... a charged aether.

If there is no charged aether, where does the "quantized field in a
vacuum" come from? From Wikipedia: "In quantum field theory, the
Casimir effect and the Casimir-Polder force are physical forces
arising from a quantized field. The typical example is of two
uncharged metallic plates in a vacuum, ..."
--
73, Cecil, w5dxp.com
i am referring to a theory from around 1880 that had a sea of

electrons as the aether for propagating electromagnetic waves.

It is from 1846:http://www.padrak.com/ine/FARADAY1.htmlFaraday wrote:

"I suppose we may compare together the matter of the aether and ordinary
matter (as, for instance, the copper of the wire through which the
electricity is conducted), and consider them as alike in their essential
constitution; i.e. either as both composed of little nuclei, considered in
the abstract as matter, and of force or power associated with these nuclei."

Aether and a sea of electrons (as the rare plasma) is not the same.The other
scientists needs a mystery aether where a strain, stress and flows take
place. Faradays electrons vibrate.
S*

sorry, 1846, even older than i thought... aether, sea of electrons,
rare plasma, none are necessary for electromagnetic waves.

Information about my experience with Magnetic Loop antenna's on my homepage
 

Uzytkownik "K1TTT" napisal w wiadomosci
...
On Feb 25, 5:02 pm, "Szczepan Bialek" wrote:
"K1TTT" napisal w
...
On Feb 25, 12:41 pm, Cecil Moore wrote:

On Feb 25, 6:04 am, K1TTT wrote:

he is stuck in about 1880 with ... a charged aether.

If there is no charged aether, where does the "quantized field in a
vacuum" come from? From Wikipedia: "In quantum field theory, the
Casimir effect and the Casimir-Polder force are physical forces
arising from a quantized field. The typical example is of two
uncharged metallic plates in a vacuum, ..."
--
73, Cecil, w5dxp.com
i am referring to a theory from around 1880 that had a sea of

electrons as the aether for propagating electromagnetic waves.

It is from 1846:http://www.padrak.com/ine/FARADAY1.htmlFaraday wrote:

"I suppose we may compare together the matter of the aether and ordinary
matter (as, for instance, the copper of the wire through which the
electricity is conducted), and consider them as alike in their essential
constitution; i.e. either as both composed of little nuclei, considered in
the abstract as matter, and of force or power associated with these
nuclei."

Aether and a sea of electrons (as the rare plasma) is not the same.The
other
scientists needs a mystery aether where a strain, stress and flows take
place. Faradays electrons vibrate.
S*

sorry, 1846, even older than i thought... aether, sea of electrons,
rare plasma, none are necessary for electromagnetic waves.

EM are a paper waves. Real radio waves need a medium.
S*

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 6:05*pm, "Szczepan Bialek" wrote:
Uzytkownik "K1TTT" napisal w ...
On Feb 25, 5:02 pm, "Szczepan Bialek" wrote:



"K1TTT" napisal w
...
On Feb 25, 12:41 pm, Cecil Moore wrote:

On Feb 25, 6:04 am, K1TTT wrote:

he is stuck in about 1880 with ... a charged aether.

If there is no charged aether, where does the "quantized field in a
vacuum" come from? From Wikipedia: "In quantum field theory, the
Casimir effect and the Casimir-Polder force are physical forces
arising from a quantized field. The typical example is of two
uncharged metallic plates in a vacuum, ..."
--
73, Cecil, w5dxp.com
i am referring to a theory from around 1880 that had a sea of

electrons as the aether for propagating electromagnetic waves.

It is from 1846:http://www.padrak.com/ine/FARADAY1.htmlFaradaywrote:

"I suppose we may compare together the matter of the aether and ordinary
matter (as, for instance, the copper of the wire through which the
electricity is conducted), and consider them as alike in their essential
constitution; i.e. either as both composed of little nuclei, considered in
the abstract as matter, and of force or power associated with these
nuclei."

Aether and a sea of electrons (as the rare plasma) is not the same.The
other
scientists needs a mystery aether where a strain, stress and flows take
place. Faradays electrons vibrate.
S*

sorry, 1846, even older than i thought... aether, sea of electrons,
rare plasma, none are necessary for electromagnetic waves.

EM are a paper waves. Real radio waves need a medium.
S*

my em waves are made out of energy not paper... while Einstein says
they are interchangeable my radio would have a hard time receiving
paper.

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 6:54*am, K1TTT wrote:
i am referring to a theory from around 1880 that had a sea of
electrons as the aether for propagating electromagnetic waves.

Change "sea of electrons" to "quantum soup" and the aether theory is
alive and well. Even photons need a structure through which to
propagate.
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 24, 2:18*pm, Richard Clark wrote:
*A magnetic antenna (as a loop is often described)
will pick up that (P-static) field as readily as an electric antenna.

Actually the "P-static field" originates directly from electrons while
the EM field originates from photons. What a closed loop does with
those excess electrons is quite different from what a single-wire
dipole does with them. All points on a well-designed loop system have
a path to ground in addition to the signal path. That's not true for a
single-wire dipole. From 1/2 of a dipole, the signal path is the only
path. That's why undischarged dipole systems can arc during conditions
of P-static while loops don't arc. Wouldn't you say that an absence of
arcing is less noisy than the presence of arcing?
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 3:11*am, "Szczepan Bialek" wrote:
Radio wavesare are radiated from the nodes. In dipole the nodes are created
by reflected wave (waves in the opposite direction). In the loop the waves
travel in oppsite direction and create the nodes also.

In a dipole, the reflections are naturally from the impedance
discontinuity at the open ends of the dipole. In a loop, the
reflections on the antenna are from the impedance discontinuity at the
feedpoint.
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 25, 11:07*am, K1TTT wrote:
sorry, 1846, even older than i thought... aether, sea of electrons,
rare plasma, none are necessary for electromagnetic waves.

On the contrary, a quantum soup is indeed required. If photons could
propagate without a structure, they could exit the universe but they,
like us, are trapped and confined to the universe.
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's onmy homepage
 

Hello Richard,

I agree with you that several statements on Norbert's site will not
hold when scientifically reviewed. However I think the way you
respond will likely not result in better statements.

As the name of the newsgroup indicates; this is a radio amateur group
and Norbert site starts with "Dutch amateur radio station". This may
require another approach then you should use in a professional
environment. If you prefer that, Edaboard.com (just an example) is a
more suitable place.

Now the result is a professional reaction of Norbert:

Thank you for the explanations. I have not had the intention to start a
scientific discussion here on this subject. To me it is a hobby. With my
homepage I just want to share some of my experience with magnetic loop
antennas, just like many other radio amateurs do. And of course I am willing
to reply to reactions from readers. But I will not further discuss about
scientifically details.

Thank you.

Best Regards

73,

Norbert PA7NR

Because of rain, I had to stop some activity so I took a pocket
calculator, some of my own course material and a used envelope within
reach.

A loop with diameter = 1.27m (4m perimeter), made from 20mm (diameter)
copper has an inductance of about 3.4 uH (reactance of about 77 Ohm at
3.6 MHz).

Radiation resistance (no coupling with other objects) will be about 1
mOhm.

AC copper resistance due to skin effect will be about 30 mOhm (based
on uniform current distribution over the circumference of the
tubing).

Q factor should be in the range of 2500
Radiation efficiency will be about 3%
Directivity is 1.5
Voltage between ends (100W input): 6.3 kVp.
Current through loop about 82 Ap

A half wave dipole will have about 1kVp at each end (depends on
conductor thickness).

Effective area of antenna will be about 23 sqm (in free space).

1Vrms incident plane wave field (2.65mW/sqm) will result in about 61mW
output power (about 150Vp across the tuning capacitor).

You probably know that measuring a lower Q factor may result in less
overall efficiency (coupling to dissipative objects) or higher overall
efficiency (coupling to metallic conductors that reradiate).

With kind regards,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me very likely

Information about my experience with Magnetic Loop antenna's on my homepage
 

Uzytkownik "Cecil Moore" napisal w wiadomosci
...
On Feb 25, 6:54 am, K1TTT wrote:
i am referring to a theory from around 1880 that had a sea of
electrons as the aether for propagating electromagnetic waves.

Change "sea of electrons" to "quantum soup" and the aether theory is
alive and well. Even photons need a structure through which to
propagate.

Waves need medium to propagate. Some scientists prefer mystery aether some
ordinary matter. Faraday and Ludwig Lorenz were sure that in space is enough
mater and no mystery aether. Now everybody know that in space is ISM (rare
plasma + dust). It is ordinary matter (electrons, ions and dust). But radio
waves will be always the aether waves. So we also can say that aether
consists of ordinary particles.
S*
--

Information about my experience with Magnetic Loop antenna's on my homepage
 

"Cecil Moore" napisal w wiadomosci
...
On Feb 25, 3:11 am, "Szczepan Bialek" wrote:
Radio wavesare are radiated from the nodes. In dipole the nodes are
created
by reflected wave (waves in the opposite direction). In the loop the waves
travel in oppsite direction and create the nodes also.

In a dipole, the reflections are naturally from the impedance
discontinuity at the open ends of the dipole. In a loop, the
reflections on the antenna are from the impedance discontinuity at the
feedpoint.

I do not understand. A loop can be made of wires without any discontinuity
at the feedpoint. Pulses send from supply must collide in the loop. The
nodes appear like in a dipole but without reflections. For what you need
reflections in a loop?
S*

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 26, 12:21*pm, "Szczepan Bialek" wrote:
So we also can say that aether
consists of ordinary particles.

It depends upon how one defines "ordinary". The structure of free
space has existed since the big bang but man has only recently
discovered the structure and is still somewhat ignorant of its
configuration and characteristics. There is some evidence that the
structure of space in which ordinary non-dark matter and non-dark
energy exists, is made up of dark matter and dark energy.

I do not understand.

A loop, like a dipole, is a standing wave antenna with a
characteristic impedance in the few hundred ohms, e.g. 600 ohms. The
reflections on a standing wave antenna have to originate from an
impedance discontinuity. The feedpoint impedance of a standing wave
antenna is Zfp = (Vfor + Vref)/(Ifor + Iref) where phasor math is
used. Let's assume that the feedpoint impedance is 100+j0 ohms and the
antenna is being fed with Z0=100 ohm feedline. There are no
reflections on the feedline which means a Z0-match to 100 ohms exists
at the antenna feedpoint. Assume the characteristic impedance of the
antenna wire over ground is 600 ohms. The 600 ohm to 100 ohm impedance
discontinuity at the feedpoint creates a reflection coefficient of
0.7. That's where the reflections on the standing wave loop antenna
are coming from. One reason the feedpoint of a resonant loop is higher
than for a 1/2WL dipole is that the reflection coefficient for the
loop is 0.7 while the reflection coefficient for a dipole is obviously
1.0 at the ends of the dipole.

The concept may be easier to understand using a rhombic example. A
terminated rhombic is terminated in the characteristic impedance of
the antenna wire above ground, e.g. 600 ohms, which eliminates
reflections on the antenna and turns it into a traveling wave antenna
where the feedpoint impedance of the antenna is equal to the
characteristic impedance of the antenna over a wide frequency range,
i.e. Zfp = Vfor/Ifor, independent of frequency.

Removing the termination turns the rhombic antenna into a standing
wave antenna and the feedpoint impedance becomes Zfp = (Vfor + Vref)/
(Ifor + Iref), i.e. the feedpoint impedance is frequency dependent
like other standing wave antennas.
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Sat, 26 Feb 2011 07:30:00 -0800 (PST), Wimpie
wrote:

Hi Wimpie,

This may
require another approach then you should use in a professional
environment. If you prefer that, Edaboard.com (just an example) is a
more suitable place.

Now the result is a professional reaction of Norbert:

Curious combination of conflicting sentiments, there. What is
suitable, and how should we recognize it?

Radiation resistance (no coupling with other objects) will be about 1
mOhm.

There are many source for computation, I chose one that closely agrees
with several at hand. Perhaps I made an entry error, so I will take
the opportunity to examine that possibility he
Rr = 80 · pi² · (dl/lambda)²
80 · 9.87 · (2/80)²
790 · (0.025)²
790 · 0.0006
0.49 Ohm

Of course, the possibility of mis-entry remains, and cross checking is
helpful given an in dependant validation. If I examine my text
further it uses as an example a smaller loop at a lower frequency
dl = 1m
F = 1MHz
(lambda = 300)
resulting in
Rr = 0.0084 Ohm
which is roughly 10 times your computed radiation resistance for a
larger loop at a smaller wavelength.

Now, having said that, and examining my text for further possibilities
of error, I find that, yes, I made an error. My computation was based
for an electric dipole, not a loop. Let us examine the Rr for a loop
from the equation from the same source:
Rr = 320 · pi^6 · (r/Lambda)^4
320 · 961 · (1/80)^4
307,645 · 2.44^-8
0.0075 Ohm
This, too, is very different from your calculation, but certainly that
error is eclipsed by my own first reckoning. However, what does this
say about efficiency based upon the original design (but computed for
another)?

However, I did first ask Norbert for the equation used and the
parameters entered. Testing those results did not appear to be
appealing in the face of contradicting testimonial. It should come as
no surprise that many testimonials are tested here. Testimonials
stand or fall in such tests, and those tests are retested (as has
given rise to this and your response).

Curiously we entered into this with how the loop has superior
qualities over the standard dipole, and then the same loop is cited as
being very inefficient. How such contradictions are held within the
space of a short thread is certainly a denial of engineering
professionalism, but denial is not the standard of merit that is
typically lauded in this forum. A hearty defense of wounded ego
raises suspicion even further.

One consequence of that demurral brings us to a rather remarkable
insight in comparing the radiation resistance of the electric dipole
to the loop within the same spread of the loop (and in certainly a
smaller volume of space). The electric dipole enjoys 60 times more
radiation resistance that certainly impacts efficiency to the same
degree. This, of course, presumes no further errors in computation or
application.

73's
Richard Clark, KB7QHC

Information about my experience with Magnetic Loop antenna'son my homepage
 

On 2/27/2011 11:03 PM, Richard Clark wrote:
On Sat, 26 Feb 2011 07:30:00 -0800 (PST),
wrote:

Hi Wimpie,

This may
require another approach then you should use in a professional
environment. If you prefer that, Edaboard.com (just an example) is a
more suitable place.

Now the result is a professional reaction of Norbert:

Curious combination of conflicting sentiments, there. What is
suitable, and how should we recognize it?

Radiation resistance (no coupling with other objects) will be about 1
mOhm.

There are many source for computation, I chose one that closely agrees
with several at hand. Perhaps I made an entry error, so I will take
the opportunity to examine that possibility he
Rr = 80 · pi² · (dl/lambda)²
80 · 9.87 · (2/80)²
790 · (0.025)²
790 · 0.0006
0.49 Ohm

Of course, the possibility of mis-entry remains, and cross checking is
helpful given an in dependant validation. If I examine my text
further it uses as an example a smaller loop at a lower frequency
dl = 1m
F = 1MHz
(lambda = 300)
resulting in
Rr = 0.0084 Ohm
which is roughly 10 times your computed radiation resistance for a
larger loop at a smaller wavelength.

Now, having said that, and examining my text for further possibilities
of error, I find that, yes, I made an error. My computation was based
for an electric dipole, not a loop. Let us examine the Rr for a loop
from the equation from the same source:
Rr = 320 · pi^6 · (r/Lambda)^4
320 · 961 · (1/80)^4
307,645 · 2.44^-8
0.0075 Ohm
This, too, is very different from your calculation, but certainly that
error is eclipsed by my own first reckoning. However, what does this
say about efficiency based upon the original design (but computed for
another)?

However, I did first ask Norbert for the equation used and the
parameters entered. Testing those results did not appear to be
appealing in the face of contradicting testimonial. It should come as
no surprise that many testimonials are tested here. Testimonials
stand or fall in such tests, and those tests are retested (as has
given rise to this and your response).

Curiously we entered into this with how the loop has superior
qualities over the standard dipole, and then the same loop is cited as
being very inefficient. How such contradictions are held within the
space of a short thread is certainly a denial of engineering
professionalism, but denial is not the standard of merit that is
typically lauded in this forum. A hearty defense of wounded ego
raises suspicion even further.

One consequence of that demurral brings us to a rather remarkable
insight in comparing the radiation resistance of the electric dipole
to the loop within the same spread of the loop (and in certainly a
smaller volume of space). The electric dipole enjoys 60 times more
radiation resistance that certainly impacts efficiency to the same
degree. This, of course, presumes no further errors in computation or
application.

73's
Richard Clark, KB7QHC


Wimpie is right, Richard.

Please go back to your laboratory and speak to someone who understands
your dumb-ass dialect. Also, please don't discourage those who are
trying to contribute their experiences here. Try to be positive for a
change.

John

Information about my experience with Magnetic Loop antenna's on my homepage
 

"Cecil Moore" napisal w wiadomosci
...
On Feb 26, 12:21 pm, "Szczepan Bialek" wrote:
So we also can say that aether
consists of ordinary particles.

It depends upon how one defines "ordinary". The structure of free
space has existed since the big bang but man has only recently
discovered the structure and is still somewhat ignorant of its
configuration and characteristics. There is some evidence that the
structure of space in which ordinary non-dark matter and non-dark
energy exists, is made up of dark matter and dark energy.

I prefer this: "It seems to be a natural consequence of our points of view
to assume that
the whole of space is filled with electrons and flying electric ions of all
kinds. We have assumed that each stellar system in evolutions throws off
electric corpuscles into space. It does not seem unreasonable therefore to
think that the greater part of the material masses in the universe is found,
not in the solar [sic] systems or nebulae, but in 'empty' space" (Birkeland
1913).
Thorndike (1930) noted that "it could scarcely have been believed that the
enormous gaps between the stars are completely void. Terrestrial aurorae are
not improbably excited by charged particles from the Sun emitted by the Sun.
If the millions of other stars are also ejecting ions, as is undoubtedly
true, no absolute vacuum can exist within the galaxy."



A loop antenna' is a radio antenna consisting of a loop of wire or other
conductor with its ends connected to a two-wire transmission line. They have
a radiation pattern similar to a dipole antenna"

I do not understand.

A loop, like a dipole, is a standing wave antenna with a
characteristic impedance in the few hundred ohms, e.g. 600 ohms. The
reflections on a standing wave antenna have to originate from an
impedance discontinuity. The feedpoint impedance of a standing wave
antenna is Zfp = (Vfor + Vref)/(Ifor + Iref) where phasor math is
used. Let's assume that the feedpoint impedance is 100+j0 ohms and the
antenna is being fed with Z0=100 ohm feedline. There are no
reflections on the feedline which means a Z0-match to 100 ohms exists
at the antenna feedpoint. Assume the characteristic impedance of the
antenna wire over ground is 600 ohms. The 600 ohm to 100 ohm impedance
discontinuity at the feedpoint creates a reflection coefficient of
0.7. That's where the reflections on the standing wave loop antenna
are coming from. One reason the feedpoint of a resonant loop is higher
than for a 1/2WL dipole is that the reflection coefficient for the
loop is 0.7 while the reflection coefficient for a dipole is obviously
1.0 at the ends of the dipole.

The concept may be easier to understand using a rhombic example. A
terminated rhombic is terminated in the characteristic impedance of
the antenna wire above ground, e.g. 600 ohms, which eliminates
reflections on the antenna and turns it into a traveling wave antenna
where the feedpoint impedance of the antenna is equal to the
characteristic impedance of the antenna over a wide frequency range,
i.e. Zfp = Vfor/Ifor, independent of frequency.

Removing the termination turns the rhombic antenna into a standing
wave antenna and the feedpoint impedance becomes Zfp = (Vfor + Vref)/
(Ifor + Iref), i.e. the feedpoint impedance is frequency dependent
like other standing wave antennas.

See: http://paws.kettering.edu/~drussell/Phys302/09.html

"Electromagnetic pulse in a coaxial cable reflects from a short circuit with
the opposite polarity (upside down)"

A loop is like a short circuit. What do a Electromagnetic pulse in a loop?
It simply travel trough the loop and looks like the "reflected with the
opposite polarity ". Why am I wrong and D. Russell is right?
S*
--

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On Feb 28, 3:52*am, "Szczepan Bialek" wrote:
A loop is like a short circuit. What do a Electromagnetic pulse in a loop?
It simply travel *trough the loop and looks like the "reflected with the
opposite polarity ". Why am I wrong and D. Russell is right?

What you are missing is that the loop is an antenna, not a
transmission line. On a transmission line, the currents are
differential, i.e. 180 degrees out of phase and a short-circuit is
possible. At the antenna feedpoint the left differential current takes
a 90 degree turn to the left. The right differential current takes a
90 degree turn to the right. *That puts the antenna currents in
phase*, i.e. in common-mode, so a short circuit on an antenna 40 feet
in the air is not possible. The fields that are 180 degrees out of
phase no longer cancel because of the physical distance between them.

From the feedpoint of the antenna, there is no such thing as waves
launched in opposite directions on the wire *at the same time*. What
you are missing is there is no short-circuit half way around a loop
because there is no impedance discontinuity at that point. Forward
waves continue traveling forward and reflected waves continue to
travel backwards at that point because there is no impedance
discontinuity at that point. It takes an impedance discontinuity to
cause a reflection. Assuming a circular horizontal loop (for the sake
of conceptual simplicity) the only impedance discontinuity is at the
feedpoint.
--
73, Cecil, w5dxp.com

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Sun, 27 Feb 2011 23:14:34 -0600, John - KD5YI
wrote:

Wimpie is right, Richard.

I presume Wimpie can speak for himself. As he offered musings that
were done on the back of a handy envelope, there is every chance he is
not right. I offered a similar chance that I was not right either,
but I offered complete (two in fact) equations that no one has
disputed, and none have faulted for computation. I admitted a
misapplication of one - which also passed without comment.

Considering Wimpie's work was not done for the antenna under
consideration (the size of his being much smaller where radiation
resistance varies by the FOURTH POWER of size) - what does "right"
mean?

73's
Richard Clark, KB7QHC

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On 28 feb, 20:53, Richard Clark wrote:
On Sun, 27 Feb 2011 23:14:34 -0600, John - KD5YI
wrote:

Wimpie is right, Richard.

I presume Wimpie can speak for himself. *As he offered musings that
were done on the back of a handy envelope, there is every chance he is
not right. *I offered a similar chance that I was not right either,
but I offered complete (two in fact) equations that no one has
disputed, and none have faulted for computation. *I admitted a
misapplication of one - which also passed without comment.

Considering Wimpie's work was not done for the antenna under
consideration (the size of his being much smaller where radiation
resistance varies by the FOURTH POWER of size) - what does "right"
mean?

73's
Richard Clark, KB7QHC

Hello Richard,

Your formulas can be disputed:

When using (from http://www.ece.msstate.edu/~donohoe/ece4990notes5.pdf):

Rr_loop = 320*(pi)^4*A^2/lambda^4

for f = 3.6 MHz, Dloop = 1.27m (so A = 1.27 m^2),

Rr_loop = 0.001 mOhm.

This result agrees the number in my previous calculation (for the same
situation).

From the same source, but for a dipole of 1.27m with large end-
plates,

Rr_dipole = 80*(pi)^2*le^2/lambda^2 = 0.18
Rr_dipole = 0.045 Ohm (without large end-plates).

This is roughly a factor 45 or 180 more (for the dipole).

Maybe somebody can confirm the above calculations.

The actual efficiency depends on the required (space consuming)
reactive component to cancel the capacitive (dipole) or inductive
(loop) behavior.

The advantage of the loop (especially for reception) is that you need
a variable capacitor instead of a variable loop, and matching / balun
function can be made easily. He also mentioned the vertical radiation
component (NVIS operation) together with the nulls in the horizontal
plane.

Regarding claims, Norbert didn't make claims about the high
efficiency. Please read his conclusion that starts with "despite the
low efficiency of 3%….". His stated 3% reasonably agrees with my 3%
(though you think that the calculation may be wrong). The claim with
regards to performance comparable to a half wave or vertical antenna
is for higher frequencies (where the loop's efficiency increases
significantly).

Of course I have serious doubts about the conclusions regarding
general noise cancelling properties, but the conclusions can be right
for that special RF-environment. Whether they apply for another
situation, can be food for the radio amateur experimenter (or
professional?).


With kind regards,

Wim
PA3DJS
www.tetech.nl

Information about my experience with Magnetic Loop antenna's onmy homepage
 

The link should be:
http://www.ece.msstate.edu/~donohoe/ece4990notes5.pdf

Wim
PA3DJS
www.tetech.nl

Information about my experience with Magnetic Loop antenna'son my homepage
 

On 2/28/2011 1:53 PM, Richard Clark wrote:
On Sun, 27 Feb 2011 23:14:34 -0600, John -
wrote:

Wimpie is right, Richard.

I presume Wimpie can speak for himself. As he offered musings that
were done on the back of a handy envelope, there is every chance he is
not right. I offered a similar chance that I was not right either,
but I offered complete (two in fact) equations that no one has
disputed, and none have faulted for computation. I admitted a
misapplication of one - which also passed without comment.

Considering Wimpie's work was not done for the antenna under
consideration (the size of his being much smaller where radiation
resistance varies by the FOURTH POWER of size) - what does "right"
mean?

73's
Richard Clark, KB7QHC


I didn't mean Wimpie was right about his technical response. I meant he
was right about a part of his message which you cut:

"I agree with you that several statements on Norbert's site will not
hold when scientifically reviewed. However I think the way you
respond will likely not result in better statements."

"As the name of the newsgroup indicates; this is a radio amateur group
and Norbert site starts with "Dutch amateur radio station". This may
require another approach then you should use in a professional
environment. If you prefer that, Edaboard.com (just an example) is a
more suitable place."

John

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On 28 feb, 20:53, Richard Clark wrote:
On Sun, 27 Feb 2011 23:14:34 -0600, John - KD5YI
wrote:

Wimpie is right, Richard.

I presume Wimpie can speak for himself. *As he offered musings that
were done on the back of a handy envelope, there is every chance he is
not right. *I offered a similar chance that I was not right either,
but I offered complete (two in fact) equations that no one has
disputed, and none have faulted for computation. *I admitted a
misapplication of one - which also passed without comment.

Considering Wimpie's work was not done for the antenna under
consideration (the size of his being much smaller where radiation
resistance varies by the FOURTH POWER of size) - what does "right"
mean?

73's
Richard Clark, KB7QHC

Hello Richard,

you used r = 1m (as you have r in your formulas), that is D = 2m,
6.28m circumference.

I used D = 1.27m (4m perimeter), that is r = 0.635 m.

Quote from Norbert's site:
"When a magnetic loop antenna is used for 3.5 MHz with a perimeter of
4 meter (13.3 foot) , it has an efficiency of approximately 3%."

Maybe this helps you to explain the difference between your and my
result,


Wim
PA3DJS
www.tetech.nl
Don't forget to remove abc in case of PM.

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Mon, 28 Feb 2011 15:36:27 -0600, John - KD5YI
wrote:

I didn't mean Wimpie was right about his technical response. I meant he
was right about a part of his message which you cut:

I selectively quote to make the response specific to the point being
responded to (like I am right now). It saves room, is not ambiguous,
and serves the technical community by confining discussion to
technical matters.

73's
Richard Clark, KB7QHC

This has been a good thread, I have little room for an antenna, a mag loop may be just the ticket for my small Tampa QTH ?

Information about my experience with Magnetic Loop antenna'son my homepage
 

On 2/28/2011 7:24 PM, Richard Clark wrote:
On Mon, 28 Feb 2011 15:36:27 -0600, John -
wrote:

I didn't mean Wimpie was right about his technical response. I meant he
was right about a part of his message which you cut:

I selectively quote to make the response specific to the point being
responded to (like I am right now). It saves room, is not ambiguous,
and serves the technical community by confining discussion to
technical matters.

73's
Richard Clark, KB7QHC

Then I'll just have to put the "point" back in

Quote Wim
I agree with you that several statements on Norbert's site will not
hold when scientifically reviewed. However I think the way you
respond will likely not result in better statements.

As the name of the newsgroup indicates; this is a radio amateur group
and Norbert site starts with "Dutch amateur radio station". This may
require another approach then you should use in a professional
environment. If you prefer that, Edaboard.com (just an example) is a
more suitable place.
/Quote

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Mon, 28 Feb 2011 14:13:29 -0800 (PST), Wimpie
wrote:

you used r = 1m (as you have r in your formulas), that is D = 2m,
6.28m circumference.

It is the specified diameter/radius of the 80M antenna at the link of
the antenna manufacturer. I stated that quite clearly. I choose to
go to the source rather than rely on possible transcription errors in
amateur postings.

I used D = 1.27m (4m perimeter), that is r = 0.635 m.

That antenna does not exist.

Quote from Norbert's site:
"When a magnetic loop antenna is used for 3.5 MHz with a perimeter of
4 meter (13.3 foot) , it has an efficiency of approximately 3%."

There is no Ciro Mazzoni antenna with that dimension.

I specifically asked if this statement was for the MIDI loop antenna
with a 2 meter diameter (and is designed for 80M operation). To this
point no one has affirmed or denied this my natural selection from the
manufacturer. The page quite clearly reveals three photos of the
distinctive design. The Mazzoni antennas also come in distinctive 1m,
2m, 4m integral sizes. There is no 1.27m diameter tuned loop
offering.

Maybe this helps you to explain the difference between your and my
result,

The original page (2) contains errors or misattribution (same thing),
that is why I am careful to trim away the textual noise and restate
what I perceive to be the model under investigation.

73's
Richard Clark, KB7QHC

Information about my experience with Magnetic Loop antenna's on my homepage
 

On Tue, 1 Mar 2011 02:25:00 +0000, ka7niq
wrote:

This has been a good thread, I have little room for an antenna, a mag
loop may be just the ticket for my small Tampa QTH ?

Hi OM,

Well, as you can imagine (barring the numerous errors and moral
judgments), it all depends upon the band you want to operate - with
the 40M and higher frequencies quite well served.

A lot of myth surrounds what are called "magnetic loops" and this
thread has corralled some of them - including from Norbert as his page
which forces the argument that fairly agrees that below 40M
performance dives. However, through sloppy bookkeeping, the Ciro
Mazzoni line is not one I would walk away from for stated
"inefficiencies."

The principle consideration is the ratio between radiation resistance
(power that is expressed into making contacts) and Ohmic loss (bulk
metal conductivity power that is expressed into making heat). Wimpie's
choice of 20mm diameter stock (how that arrived in the mix is a
mystery) compares poorly with the Ciro Mazzoni 50mm tubing for its
smallest design.

The 80M design from the vendor uses 75mm stock for good reason and
this should be a selection guide for your application. Their second
80M design uses 140mm stock! Pushing this further with conductance
now nailed down, you want a large loop because the radiation
resistance varies by the fourth power of dimension. That is to say,
if you double the loop radius, you obtain 16 times the radiation
resistance. Small changes in loop radius can quickly escalate or
emasculate efficiency. Radiation resistance is the beneficial
characteristic of how we manage to couple a signal out into space and
which is typically thought of as being 50 Ohms (although this is
rarely the actual value that more often varies between 35 and 70 Ohms
for simple wire antennas of conventional length).

As you can see from these resistance figures, the difference between a
radiation resistance in the thousandths of an Ohm, and typical values
in the tens of Ohms is a hallmark for caution. When paired with metal
resistance in the Ohms (something that ordinarily only comes with
using wire-wrap wire for long runs), you want to boost radiation
resistance as high as possible. When paired with metal resistance
that is in the thousandths of Ohms, there is every chance you are
looking at 50% efficiency for 1 meter diameter loops.

Bigger radius comes with its own problem, however. It limits the high
band of operation as these designs are optimized for being a small
portion of wavelength. Observe the various design options from Ciro
Mazzoni, and you will observe they are specified over only two octaves
for any particular design. That should give you a clue if you want to
homebrew your own, because you will encounter the same limitations of
coverage regardless of construction method.

So, this returns us to the first statement above: it all depends on
which band(s) you want to work. It further depends upon your pain
threshold for poor efficiency if you choose to push beyond the
coverage limits. Professionals describe this in terms of a
cost/benefit ratio. If we restrict discussion to non-professional
qualitative expressions of benefit: super, great, fantastic, maximum
and peg escalating dollar amounts to each with corresponding
breathless emphasis - then there are many deals for sale on those
terms for the gullible.

73's
Richard Clark, KB7QHC

Information about my experience with Magnetic Loop antenna's onmy homepage
 

On 1 mar, 03:25, ka7niq wrote:
'Wimpie[_2_ Wrote:



;734551']On 28 feb, 20:53, Richard Clark wrote:-
On Sun, 27 Feb 2011 23:14:34 -0600, John - KD5YI
wrote:
-
Wimpie is right, Richard.-

I presume Wimpie can speak for himself. *As he offered musings that
were done on the back of a handy envelope, there is every chance he is
not right. *I offered a similar chance that I was not right either,
but I offered complete (two in fact) equations that no one has
disputed, and none have faulted for computation. *I admitted a
misapplication of one - which also passed without comment.

Considering Wimpie's work was not done for the antenna under
consideration (the size of his being much smaller where radiation
resistance varies by the FOURTH POWER of size) - what does "right"
mean?

73's
Richard Clark, KB7QHC-

Hello Richard,

you used r = 1m (as you have r in your formulas), that is D = 2m,
6.28m circumference.

I used D = 1.27m (4m perimeter), that is r = 0.635 m.

Quote from Norbert's site:
"When a magnetic loop antenna is used for 3.5 MHz with a perimeter of
4 meter *(13.3 foot) , it has an efficiency of approximately 3%."

Maybe this helps you to explain the difference between your and my
result,

Wim
PA3DJS
www.tetech.nl
Don't forget to remove abc in case of PM.

This has been a good thread, I have little room for an antenna, a mag
loop may be just the ticket for my small Tampa QTH ?

--
ka7niq

Hello Chris,

Which antenna will fit your needs depends on many factors (tuning
range, indoor/outdoor, aesthetics, local regulations, your experience/
preference, available volume, house construction, buy or homebrew,
available materials, local or DX use, etc). So I can't judge whether a
loop is good solution in your situation.

In addition, "the" best antenna for the transmitting case will very
likely not be the best one for the reception case.

Best regards,


Wim
PA3DJS
www.tetech.nl