Information about my experience with Magnetic Loop antenna's on my homepage
RadioWaves
Antenna.
PA7NR
Richard Clark
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
RadioWave
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/Loop%20Antenna/Loop%20Baby.htm
In the manual, page 42, 43 there is a picture of the radiation pattern:
http://www.ciromazzoni.com/English/Loop%20Antenna/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
Richard Clark
>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/Loop%20Antenna/Loop%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/Loop%20Antenna/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.
Cecil Moore
> 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
RadioWave
>>> 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.
>
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
RadioWave
>>> 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.
>
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
Richard Clark
>> 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.
RadioWave
"Richard Clark" <kb7...@comcast.net> schreef in bericht
news:8addm61mp9pjvcffs...@4ax.com...
> 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
Szczepan Bialek
"RadioWave" <radio@oidar> wrote
news:4d66adfe$0$24947$bf49...@news.tele2.nl...
>>>>>
> 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/~jones/cscie129/nu_lectures/lecture6/hertz/S_p11.gif
S*
>
K1TTT
> "RadioWave" <radio@oidar> wrotenews:4d66adfe$0$24947$bf49...@news.tele2.nl...
>
> S*
>
>
don't bother arguing with him, he is stuck in about 1880 with jumping
electrons and a charged aether.
Cecil Moore
> 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
K1TTT
i am referring to a theory from around 1880 that had a sea of
electrons as the aether for propagating electromagnetic waves.
Szczepan Bialek
"K1TTT" <k1...@arrl.net> napisal w wiadomosci
news:2c5774de-dea2-47c6...@a11g2000pro.googlegroups.com...
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*
K1TTT
> "K1TTT" <k1...@arrl.net> napisal w wiadomoscinews:2c5774de-dea2-47c6...@a11g2000pro.googlegroups.com...
> On Feb 25, 12:41 pm, Cecil Moore <w5...@hotmail.com> wrote:
>
> > On Feb 25, 6:04 am, K1TTT <k1...@arrl.net> 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.
>
>
> "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.
Szczepan Bialek
Uzytkownik "K1TTT" <k1...@arrl.net> napisal w wiadomosci
news:a76e1b84-3764-4c5f...@l14g2000pre.googlegroups.com...
EM are a paper waves. Real radio waves need a medium.
S*
K1TTT
> Uzytkownik "K1TTT" <k1...@arrl.net> napisal w wiadomoscinews:a76e1b84-3764-4c5f...@l14g2000pre.googlegroups.com...
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.
Cecil Moore
> 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
Cecil Moore
> A magnetic antenna (as a loop is often described)
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
Cecil Moore
> 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
Cecil Moore
> 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
Wimpie
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
Szczepan Bialek
Uzytkownik "Cecil Moore" <w5...@hotmail.com> napisal w wiadomosci
news:5225cb62-a264-454d...@a21g2000prj.googlegroups.com...
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*
--
Szczepan Bialek
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*
Cecil Moore
> 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
Richard Clark
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 here:
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.
John - KD5YI
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
Szczepan Bialek
On Feb 26, 12:21 pm, "Szczepan Bialek" <sz.bia...@wp.pl> 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.
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*
--
Cecil Moore
> 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
Richard Clark
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?
Wimpie
> On Sun, 27 Feb 2011 23:14:34 -0600, John - KD5YI <soph...@invalid.org>
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?).
Wimpie
John - KD5YI
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
Wimpie
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.
Richard Clark
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.
John - KD5YI
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>
ka7niq
'Wimpie[_2_ Wrote:
> ;734551']On 28 feb, 20:53, Richard Clark kb7...@comcast.net 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
> but I offered complete (two in fact) equations that no one has
> 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
>
> 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
Richard Clark
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.
Richard Clark
<ka7niq....@radiobanter.com> 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.
Wimpie
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
J.B. Wood
> Today I have put my homepage online with information about the Magnetic Loop
> Antenna.
>
> http://www.qsl.net/pa7nr/
>
> PA7NR
>
>
Hmmm. A "magnetic" loop antenna. Must be some other types of loop
antennas as well. Maybe there are also "electric" loop antennas.
Guess they left something out of all those antenna textbooks I have ;-)
Sincerely, and 73s from N4GGO,
--
J. B. Wood e-mail: arl_1...@hotmail.com
Wimpie
Hello John,
When you cut the loop at two opposite positions, yes, you can make
your "electric" loop.
It will generate lots of E-field, you may need another coil for
matching, and it is probably less efficient then a short straight
dipole with massive capacitive disks to get larger I*delta(le)
product.
Best regards,
Wim
PA3DJS
www.tetech.nl
In case of PM, please remove abc first.
J.B. Wood
Hello, and the not-so-subtle point is that there aren't magnetic,
electric, or any other such "types" of loop antennas. There are just
loop antennas that can further be described as shielded/unshielded,
balanced/unbalanced, electrically small or large. Just like we don't
transmit (propagate) electric (E) or magnetic (H) fields by themselves.
The purpose of an antenna is to radiate and/or intercept an
electromagnetic field. By definition energy radiated by a transmitting
antenna is not temporarily stored in the antenna's local electric or
magnetic field. It's been released into free space subject to
interception by a receiving antenna(s) or any other parasitic
structures. The receiving antenna transfers part the intercepted energy
to the load (receiver and other dissipative losses) and scatters the
rest back into free space.
By contrast, a transformer, for example, is a "magnetic" device that is
intended to transfer energy by a localized means (induction) other than
the propagation/interception of electromagnetic radiation.
To further confuse the issue, a conductor in the near (reactive) field
of a transmitting antenna will have current induced in it by the
antenna's local electric and/or magnetic fields. However, that's not
the usual purpose for which we design antennas. An exception might be
the immoboliser (PATS) system used in late-model motor vehicles that
incorporates a ring antenna embedded in the steering column that is
closely coupled at RF frequencies to the transponder chip and loop
antenna embedded in the vehicle ignition key. So is it a
transmit-receive antenna configuration or a primary coil-secondary coil
transformer configuration? Given the proximity of the inserted key to
the steering column I would guess the latter. Sincerely,
--
J. B. Wood e-mail: arl_1...@hotmail.com
J.B. Wood
> On 3/2/2011 8:40 AM, Wimpie wrote:
>
> To further confuse the issue, a conductor in the near (reactive) field
> of a transmitting antenna will have current induced in it by the
> antenna's local electric and/or magnetic fields. However, that's not the
> usual purpose for which we design antennas.
Hello, all. I should also add that in stating the above I was only
considering nearby conductors (towers, metal on buildings, etc) and
wasn't including the local directors/reflectors that may be incorporated
into an antenna to provide the desired radiation pattern
characteristics. Sincerely,
Wimpie
If in your opinion there do not exist antennas that generate a
dominant magnetic or electric field (in the near field), then you are
contradicting yourself, as you can't transfer energy with a magnetic
field or electric field only. So your transformer also involves
electric fields. Maybe you should look into the Poynting theorem.
> To further confuse the issue, a conductor in the near (reactive) field
> of a transmitting antenna will have current induced in it by the
> antenna's local electric and/or magnetic fields. However, that's not
> the usual purpose for which we design antennas. An exception might be
> the immoboliser (PATS) system used in late-model motor vehicles that
> incorporates a ring antenna embedded in the steering column that is
> closely coupled at RF frequencies to the transponder chip and loop
> antenna embedded in the vehicle ignition key. So is it a
> transmit-receive antenna configuration or a primary coil-secondary coil
> transformer configuration? Given the proximity of the inserted key to
> the steering column I would guess the latter. Sincerely,
>
> --
> J. B. Wood e-mail: arl_123...@hotmail.com
When a noise source is about 5..10m away from an 3.6 MHz antenna, the
coupling of that noise source towards a "magnetic" loop antenna may be
different from the coupling towards an "electric" antenna, though
both antennas may produce the same far field radiation. This is not
from a textbook, but from experience (I am also working in power
electronics).
I fully agree with you on the far field statements, but when you live
in an apartment (where significant spurious emission from home
equipment are in the near field of your 3.6 MHz antenna), a so-called
magnetic loop antenna may behave different (w.r.t. a short "electric"
dipole). It can be worse or better. Many radio amateurs know this from
experiments, without knowing the EM theory behind it.
I have no problems when people talk about a "magnetic loop antenna".
It shows me that they are discussing an antenna with a circumference <
0.2 lambda. When people talk about a "loop antenna", it can be
anything.
Richard Clark
wrote:
>When a noise source is about 5..10m away from an 3.6 MHz antenna, the
>coupling of that noise source towards a "magnetic" loop antenna may be
>different from the coupling towards an "electric" antenna, though
>both antennas may produce the same far field radiation. This is not
>from a textbook, but from experience (I am also working in power
>electronics).
Text books would enlarge that volume to one half to several
wavelengths for the "near field." The text books would further
clarify this with math (yes, I know, professional and academic
discussion in light of this being an amateur forum is anathema) and
define the difference with the terms Fresnel diffraction (near-field)
and Fraunhofer diffraction (far-field). The operative physical length
of the antenna becomes meaningful, but this is getting ahead of what I
call the "benchmark" method below.
To give the magnetic loop aficionados the benefit of this, all local
noise within 100 feet would be susceptible to interfering and it
wouldn't be nullable (which is a characteristic only observed in the
far-field) except by polarization which is very haphazard in the
near-field. I have never seen a magnetic loop mount with the
necessary degrees of freedom to employ this method of "nulling." As
such, the vaunted characteristic is elusive and thus becomes legendary
rather than fulfilled.
However, the term "near-field" is rather vague. The more appropriate
discussion is found in "reactive near field" and "radiative near
field." The discussion of loop coupling to magnetic (while ignoring
electric) fields would suggest "reactive near field." In this regard,
the 80M volume of reactive interference is still roughly 100 feet in
all directions. The "radiative near field" would encompass a volume
out to 80 meters (roughly 250 feet). In either case, apartment living
finds no panacea in loop antennas.
There is another, non-textual (at least to the casual reader),
benchmark that such issues are measured by the physical spread of the
antenna itself (this usually attends discussion of capture area to
many's frustration). Here, I am returning to the allusion above of
Fresnel diffraction (near-field) and Fraunhofer diffraction
(far-field). The math (non-techs, turn your eyes away) is as simple
as:
2·D²/lambda
Let's work some examples from the sublime to the ridiculous on 80M.
The traditional half-wave dipole antenna that exhibits the traditional
usage for distinguishing between near and far:
2·40²/80 = 40 meters
a smaller quarter-wave dipole antenna
2·20²/80 = 10 meters
a tenth wave dipole antenna
2·8²/80 = 1.6 meters
a fortieth wave dipole antenna
2·2²/80 = 10 centimeters
Let's see where discussion follows in this regard.
ka7niq
Richard Clark;734631 Wrote:
> On Tue, 1 Mar 2011 02:25:00 +0000, ka7niq
> ka7niq....@radiobanter.com wrote:
> This has been a good thread, I have little room for an antenna, a mag
what are the ones to look at that are for sale, and why ? AEA once made
one when I left Tampa and lived out west in Seattle. I live in a small,
non deed restricted house in Tampa with a flat membrane roof. I could
get a loop on my roof I suppose, if the installation looked clean.
--
ka7niq
Wimpie
On 2 mar, 23:10, Richard Clark <kb7...@comcast.net> wrote:
> On Wed, 2 Mar 2011 12:56:23 -0800 (PST), Wimpie <wimabc...@tetech.nl>
where is your square?
Fraunhofer region starts at (22.5 degrees phase shift):
r = 2*D^2/lambda
D = largest antenna size (excluding structures that doesn't carry
current).
Formula is only valid for electrically large structures, so not an
electrically small loop or dipole.
For electrically small loops, reactive fields are dominant for:
r < 0.16*lambda
Smaller loop size does not result in smaller reactive field zone. The
correct formulas you can find everywhere. To make it easy for you:
http://www.conformity.com/past/0102reflections.html shows the
complete formulas for the electric and magnetic case, and a graph at
the end.
Richard Clark
<ka7niq....@radiobanter.com> wrote:
>
>OK, IF you just wanted to buy a magnetic loop antenna vs build one,
>what are the ones to look at that are for sale, and why ? AEA once made
>one when I left Tampa and lived out west in Seattle. I live in a small,
>non deed restricted house in Tampa with a flat membrane roof. I could
>get a loop on my roof I suppose, if the installation looked clean.
Hi OM,
The specifications of the major vendors that I have seen are usually
reliable.
You still need to answer what bands do you want to transmit on? If it
is 40M and up, you are pretty sure to find a lot of useful designs.
Richard Clark
wrote:
>Formula is only valid for electrically large structures, so not an
>electrically small loop or dipole.
"Large" or "small" are not quantities.
>For electrically small loops, reactive fields are dominant for:
and how small (quantifiable) is small (qualifiable)?
> r < 0.16*lambda
given that I have already demonstrated that, and more, what importance
do you attach to this that hasn't already been shown?
>Smaller loop size does not result in smaller reactive field zone.
What a curious defense for magnetic antennas's noise immunity.
However, the magnetic antenna is not immune from the reactive fields
of noise emitters that are very much larger than any loop discussed
here. It is the field of the emitter that is important. I thought I
would wait and see if anyone cottoned on to that aspect of the
discussion. If we proceed with the assumption (repeated here):
>Smaller loop size does not result in smaller reactive field zone.
then the magnetic antenna is doomed to noise in the same sense as an
electric antenna is. Offhand I would speculate that in an apartment
situation, a magnetic antenna on the balcony is saturated with
reactive noise fields.
John - KD5YI
> On Wed, 2 Mar 2011 15:29:55 -0800 (PST), Wimpie<wima...@tetech.nl>
> wrote:
>
>> Formula is only valid for electrically large structures, so not an
>> electrically small loop or dipole.
>
> "Large" or "small" are not quantities.
>
>> For electrically small loops, reactive fields are dominant for:
> and how small (quantifiable) is small (qualifiable)?
>> r< 0.16*lambda
> given that I have already demonstrated that, and more, what importance
> do you attach to this that hasn't already been shown?
>
>> Smaller loop size does not result in smaller reactive field zone.
>
> What a curious defense for magnetic antennas's noise immunity.
>
> However, the magnetic antenna is not immune from the reactive fields
> of noise emitters that are very much larger than any loop discussed
> here.
Very much larger is not a quantity. How much larger?
Wimpie
> What a curious defense for magnetic antennas's noise immunity.
Where did I mention that this relates to noise immunity? I only tried
to point you to a misconception regarding the use of the 2*D^2/lambda
formula.
[start quote]
> The traditional half-wave dipole antenna that exhibits the traditional
> usage for distinguishing between near and far:
> 2 40 /80 = 40 meters
> a smaller quarter-wave dipole antenna
> 2 20 /80 = 10 meters
> a tenth wave dipole antenna
> 2 8 /80 = 1.6 meters
> a fortieth wave dipole antenna
> 2 2 /80 = 10 centimeters
>
> Let's see where discussion follows in this regard.
[end quote]
You want to believe us that a usable antenna with size=2m and
lambda=80m satisfies far field conditions at 10 cm, I really hope I
understood you wrong.
> However, the magnetic antenna is not immune from the reactive fields
> of noise emitters that are very much larger than any loop discussed
> here. It is the field of the emitter that is important. I thought I
> would wait and see if anyone cottoned on to that aspect of the
> discussion. If we proceed with the assumption (repeated here):
>
The dominant reactive field from a small "magnetic" loop or "electric"
antenna at lambda=80m extends to somewhat more then 10cm, think of
about 5m. Though the far fields may be similar, the reactive fields
are completely different in orientation, strength and E/H ratio. See
for example the link posted earlier:
http://www.conformity.com/past/0102reflections.html
This will result in complete different coupling to conductors present
in the reactive field zone. When using reciprocity, this will also
affect the coupling from noise current in the conductors towards the
antenna. So I can't follow your statement below:
>wimpie: Smaller loop size does not result in smaller reactive field zone.
> then the magnetic antenna is doomed to noise in the same sense as an
> electric antenna is.
Of course I agree with you for the case the noise source extends over
large distance.
What antenna is better, you cannot say beforehand and is food for the
experimenter (as I mentioned earlier).
This topic becomes lengthy. Do you think that it will result in better
statements from other people on there websites (that was the subject
of my first contribution)? The second part was just to show that the
3% claim for a 4 m loop (circumference) at 80m isn't bad.
I have real doubts about it, so I decided to send PM to Norbert some
days ago to setup a more constructive discussion.
Richard Clark
wrote:
>Very much larger is not a quantity. How much larger?
Twice - at least.
Richard Clark
wrote:
>http://www.conformity.com/past/0102reflections.html
>This will result in complete different coupling to conductors present
>in the reactive field zone. When using reciprocity, this will also
>affect the coupling from noise current in the conductors towards the
>antenna.
Reciprocity does not appear in the text at your link and the concept
you are offering appears to be an invention that is unsupported. Let's
stick with unraveling one thing at a time.
So, working with your link's assertions give me a simple quantified
indicator of a reactive field.
Wimpie
> On Wed, 2 Mar 2011 18:34:12 -0800 (PST), Wimpie <wimabc...@tetech.nl>
Hello Richard,
As I assume you understand complex calculus, that link (
http://www.conformity.com/past/0102reflections.html ) was just to help
you to figure out field orientation and strength versus distance for
the magnetic and electrical case.
If you still believe in the 2*D^2/lambda far field formula for
electrically small antennas, I doubt whether it is useful to continue.
J.B. Wood
> If in your opinion there do not exist antennas that generate a
> dominant magnetic or electric field (in the near field), then you are
> contradicting yourself, as you can't transfer energy with a magnetic
> field or electric field only. So your transformer also involves
> electric fields. Maybe you should look into the Poynting theorem.
Hello, and that is correct. The Maxwell equations apply in all these
cases. When solving such problems, especially when dealing with
antennas, the total E-M field contains both reactive
(electric/capacitive & magnetic/inductive) and radiative components,
although certain components predominate depending on distance from the
excited structure.
When dealing with A.C. circuit problems where dimensions are a fraction
of a wavelength, one can usually ignore the the radiative/propagation
components. Why solve a problem with a sledgehammer when a small claw
hammer is adequate? Wouldn't you rather use Ohm's law in such case
rather than dealing with E and H fields? For example, the behavior of
A.C. power power distribution lines operating a 60 Hz can certainly be
modeled using transmission line equations but unless they're very long
(implying a propagation delay), a lumped-element/circuit approach is
much more easily dealt with (lumped lines. And yes, I'm intimately
familiar with the Poynting theorem and its derivation. (The designers of
the CFA obviously weren't).
> When a noise source is about 5..10m away from an 3.6 MHz antenna, the
> coupling of that noise source towards a "magnetic" loop antenna may be
> different from the coupling towards an "electric" antenna, though
> both antennas may produce the same far field radiation. This is not
> from a textbook, but from experience (I am also working in power
> electronics).
There's no such thing as "magnetic" and "electric" antennas. The
marketing departments of antenna vendors or others can call these
whatever they want but they can't change the laws of physics. Now, if
one dimensions a loop antenna or dipole antenna small enough (compared
to a wavelength, one obtains a magnetic or electric dipole,
respectively. Such dipoles (note the absence of the word "antenna") are
a theoretical concept but can be applied in practice to those structures
having electrically small radiators/interceptors.
> I fully agree with you on the far field statements, but when you live
> in an apartment (where significant spurious emission from home
> equipment are in the near field of your 3.6 MHz antenna), a so-called
> magnetic loop antenna may behave different (w.r.t. a short "electric"
> dipole). It can be worse or better. Many radio amateurs know this from
> experiments, without knowing the EM theory behind it.
Hey, I'm a fellow Ham and well aware of the contributions over the years
by hams to antenna design. Many times, however, established
electromagnetic theory is distorted to match the perceived observation.
In the case of noise immunity I would discuss the size of the victim
antenna, the antenna type (e.g. loop or dipole), antenna dimensions,
orientation and proximity wrt the offending noise source, and whether
the victim antenna is shielded and balanced. Unless one is referring to
an electrically small antenna treated as a magnetic or electric dipole,
typing an antenna as "magnetic" or "electric" is meaningless.
--
J. B. Wood e-mail: arl_1...@hotmail.com
J.B. Wood
> If in your opinion there do not exist antennas that generate a
> dominant magnetic or electric field (in the near field), then you are
> contradicting yourself, as you can't transfer energy with a magnetic
> field or electric field only. So your transformer also involves
> electric fields. Maybe you should look into the Poynting theorem.
Hello, and that is correct. The Maxwell equations apply in all these
cases. When solving such problems, especially when dealing with
antennas, the total E-M field contains both reactive
(electric/capacitive & magnetic/inductive) and radiative components,
although certain components predominate depending on distance from the
excited structure.
When dealing with A.C. circuit problems where dimensions are a fraction
of a wavelength, one can usually ignore the the radiative/propagation
components. Why solve a problem with a sledgehammer when a small claw
hammer is adequate? Wouldn't you rather use Ohm's law in such cases
rather than dealing directly with E and H fields? As an example, the
behavior of A.C. power power distribution lines operating a 60 Hz can
certainly be modeled using transmission line equations but unless
they're very long (implying a propagation delay), a
lumped-element/circuit approach is much more easily dealt with. And
yes, I'm intimately familiar with the Poynting theorem and its
derivation. (The designers of the crossed-field antenna (CFA) obviously
weren't).
> When a noise source is about 5..10m away from an 3.6 MHz antenna, the
> coupling of that noise source towards a "magnetic" loop antenna may be
> different from the coupling towards an "electric" antenna, though
> both antennas may produce the same far field radiation. This is not
> from a textbook, but from experience (I am also working in power
> electronics).
There's no such thing as "magnetic" and "electric" antennas. The
marketing departments of antenna vendors or others can call these
whatever they want but they can't change the laws of physics. Now, if
one dimensions a loop antenna or dipole antenna small enough (compared
to a wavelength, one approaches a magnetic or electric dipole,
respectively. Such dipoles (note the absence of the word "antenna") are
a theoretical concept but can be applied in practice to those structures
having electrically small radiators/interceptors. In these situations
solving those pesky E-M near and far field integral equations is greatly
facilitated.
> I fully agree with you on the far field statements, but when you live
> in an apartment (where significant spurious emission from home
> equipment are in the near field of your 3.6 MHz antenna), a so-called
> magnetic loop antenna may behave different (w.r.t. a short "electric"
> dipole). It can be worse or better. Many radio amateurs know this from
> experiments, without knowing the EM theory behind it.
Hey, I'm a fellow Ham and well aware of the contributions over the years
by hams to antenna design. Many times, however, established
electromagnetic theory is distorted to match the perceived observation.
In the case of noise immunity I would discuss the size of the victim
antenna, the antenna type (e.g. loop or dipole), antenna dimensions,
orientation and proximity wrt the offending noise source, and whether
the victim antenna is shielded and balanced. Unless one is referring to
an electrically small antenna treated as a magnetic or electric dipole,
typing an antenna as "magnetic" or "electric" is meaningless.
Sincerely, and 73s from N4GGO,
--
Wimpie
On 3 mar, 13:30, "J.B. Wood" <john.w...@nrl.navy.mil> wrote:
> On 03/02/2011 03:56 PM, Wimpie wrote:
>
> > If in your opinion there do not exist antennas that generate a
> > dominant magnetic or electric field (in the near field), then you are
> > contradicting yourself, as you can't transfer energy with a magnetic
> > field or electric field only. So your transformer also involves
> > electric fields. Maybe you should look into the Poynting theorem.
>
> Hello, and that is correct. The Maxwell equations apply in all these
> cases. When solving such problems, especially when dealing with
> antennas, the total E-M field contains both reactive
> (electric/capacitive & magnetic/inductive) and radiative components,
> although certain components predominate depending on distance from the
> excited structure.
>
> When dealing with A.C. circuit problems where dimensions are a fraction
> of a wavelength, one can usually ignore the the radiative/propagation
> components. Why solve a problem with a sledgehammer when a small claw
> hammer is adequate? Wouldn't you rather use Ohm's law in such case
> rather than dealing with E and H fields? For example, the behavior of
> A.C. power power distribution lines operating a 60 Hz can certainly be
> modeled using transmission line equations but unless they're very long
> (implying a propagation delay), a lumped-element/circuit approach is
> much more easily dealt with (lumped lines. And yes, I'm intimately
> familiar with the Poynting theorem and its derivation. (The designers of
> the CFA obviously weren't).
Whoops, we have to be careful to not getting involved in a new
discussion, but I agree on your statement regarding that "special"
antenna and the statements regarding whether or not to use distributed
versus lumped circuit approach.
>
> > When a noise source is about 5..10m away from an 3.6 MHz antenna, the
> > coupling of that noise source towards a "magnetic" loop antenna may be
> > different from the coupling towards an "electric" antenna, though
> > both antennas may produce the same far field radiation. This is not
> > from a textbook, but from experience (I am also working in power
> > electronics).
>
> There's no such thing as "magnetic" and "electric" antennas.
That is why I added the word "dominant", as you can't transfer energy
with H or E only and we were discussing small antennas as shown on
Norberts website.
One may imagine the electrically small magnetic loop antenna as the
primary of a transformer where there is no secondary coil in the
reactive field. The RF leakage (far field radiation) by accident hit
the antenna of another amateur.
The
> marketing departments of antenna vendors or others can call these
> whatever they want but they can't change the laws of physics. Now, if
> one dimensions a loop antenna or dipole antenna small enough (compared
> to a wavelength, one obtains a magnetic or electric dipole,
> respectively. Such dipoles (note the absence of the word "antenna") are
> a theoretical concept but can be applied in practice to those structures
> having electrically small radiators/interceptors.
>
> > I fully agree with you on the far field statements, but when you live
> > in an apartment (where significant spurious emission from home
> > equipment are in the near field of your 3.6 MHz antenna), a so-called
> > magnetic loop antenna may behave different (w.r.t. a short "electric"
> > dipole). It can be worse or better. Many radio amateurs know this from
> > experiments, without knowing the EM theory behind it.
>
> Hey, I'm a fellow Ham and well aware of the contributions over the years
> by hams to antenna design. Many times, however, established
> electromagnetic theory is distorted to match the perceived observation.
I agree on the above. Let I mention the two letters "EH" in addition
to your three-letter combination to avoid a new discussion...
> In the case of noise immunity I would discuss the size of the victim
> antenna, the antenna type (e.g. loop or dipole), antenna dimensions,
> orientation and proximity wrt the offending noise source, and whether
> the victim antenna is shielded and balanced. Unless one is referring to
> an electrically small antenna treated as a magnetic or electric dipole,
> typing an antenna as "magnetic" or "electric" is meaningless.
John - KD5YI
So from twice to infinity. Still not a quantity. You seem to have the
same problem for which you berate others.
Richard Clark
wrote:
>> So, working with your link's assertions give me a simple quantified
>> indicator of a reactive field.
>>
>
>As I assume you understand complex calculus, that link (
>http://www.conformity.com/past/0102reflections.html ) was just to help
>you to figure out field orientation and strength versus distance for
>the magnetic and electrical case.
OK, so you cannot present a simple quantified indicator of a reactive
field from your own source.
It is quite apparent without going into math (I thought that appeals
to professionalism and academics like complex calculus were verboten
here) and I see it quite plainly ILLUSTRATED in Figure 3.
However, if you cannot vouchsafe for this source and agree to what it
represents, you are right, there is no basis for discussion.
>If you still believe in the 2*D^2/lambda far field formula for
>electrically small antennas, I doubt whether it is useful to continue.
I wish you wouldn't interpret beliefs and simple stick to what I've
written.
Richard Clark
wrote:
>So from twice to infinity. Still not a quantity. You seem to have the
>same problem for which you berate others.
2 (twice) is not a number? The antenna most frequently discussed is a
40th wave or 2 meters across. These are two more numbers (40th and
2). Twice that yields to more numbers (20th and 4).
Infinity is not a number.
John - KD5YI
You didn't say twice. You said "twice - at least". So what number is
that, Dick? I was taught that the phrase represented a range, not a
number. All you did was put a lower bound on a number you don't know.
Richard Clark
wrote:
>All you did was put a lower bound on a number you don't know.
>> However, the magnetic antenna is not immune from the reactive fields
>> of noise emitters that are very much larger than any loop discussed
>> here.
Choose a "loop discussed here," and you have a number (1, 1.6, 2, and
4). Double (at least) that number, for that loop, and you have a new
number for the noise emitter (2, 3.2, 4, and 8). If you want to more
than double the original number (1, 1.6, 2, and 4), there are probably
practical examples of noise emitters for those numbers too.
The lower bound works as a practical matter but is not exclusive of
other practical, larger emitters. One common example would be the
standard 80M dipole which would give you a number of 40, but that is
not the upper bound.
So, having said double (2, 3.2, 4, and 8) at least (which allows up to
40 which is more than twice any previous number) and there being
larger numbers that satisfy the observation, the larger numbers become
an issue of practicality, not number. There are Rhombics (certainly
impractical for many) that have dimensions of 320 meters:
http://www.pa6z.nl/PROJECTS/ANTENNAS/RHOMBIC/body_rhombic.html
I suppose now the point to argue is "Is 40 (or 320) very much larger
than 1?"
For the benefit of Wimpie and beliefs: "I would believe so, although I
am open to convincing argument that 40 (or 320) is NOT very much
larger than 1."