loop antennas
 

"J.B. Wood" napisal w wiadomosci
...
On 06/14/2012 12:48 PM, Szczepan Bialek wrote:
"J.B. napisal w wiadomosci
...
On 06/13/2012 06:11 PM, garyr wrote:
This site http://www.frontiernet.net/~jadale/Loop.htm states that: "A
properly designed Loop primarily responds to the magnetic component of
the
radio wave. Note that noise resides primarily in the electrical
component..."

Hello, and a loop (dipole) antenna doesn't "respond" to just the
magnetic
(electric) component of a propagating electromagnetic wave. A
(receiving)
loop or dipole antenna intercepts the incoming electromagnetic (EM)
wave.
Last time I checked an EM wave had both electric and magnetic
components.
Just because an orientation of an axis of the antenna resulting in
maximum
signal strength is parallel to the electric or magnetic component of an
EM
wave doesn't mean that it's responding to just that component.

I wish hams and others would quit trying to redefine electromagnetic
theory. Hams have designed and constructed novel and practical antennas
over the years but their explanations about how they work are often just
plain wrong. Sincerely, and 73s from N4GGO,

The explanations are wrong because the radio waves are simply the
electric
waves or the electron waves.

Hello, and they are most certainly not "electric" waves.

For the all Fathers of the radio they are the electric waves.

What part of "electromagnetic" don't you understand?

I understand the Maxwell's and the Heaviside's. What are you asking about?

(It's just this kind of stuff that prompted my previous post) I take it
you're not an EE or have ever taken any undergrad/grad courses in EM
theory.

Father's of the radio also.
Maxwell's model was discarded by Royal Society and the Heaviside's was done
after the fundamental experimments.
Radio waves and light are the oscillatory flow of electrons (L. Lorenz
1869).

In any event someone else can continue this starting-to-drift off topic
thread. Sincerely,

You wrote: "Hams have designed and constructed novel and practical antennas
over the years but their explanations about how they work are often just
plain wrong."

Could you give as the correct explanation?
S*

--
J. B. Wood e-mail:

loop antennas
 

"Szczepan Bialek" wrote in message
...


Hello, and they are most certainly not "electric" waves.

For the all Fathers of the radio they are the electric waves.
You wrote: "Hams have designed and constructed novel and practical
antennas over the years but their explanations about how they work are
often just plain wrong."

Could you give as the correct explanation?
S*

Hello Szczepan.

We've tried to assist you but you seem to prefer to stay with 19th century
knowledge rather than learn modern knowledge. If you ask for help and don't
accept the answers you get then there's not a lot we can do ... other than
disregard your postings and go and operate our radio stations.

You need to get a modern textbook on radio theory. One suitable for amateur
radio should be okay. Have a look at www.rsgb.org.and www.arrl.org

Kindest regards, Ian.

loop antennas
 

I agree with your second link (by VK1OD).

The time varying magnetic field generates an electric field and that is
received by the loop. When you screen it completely, it doesn't work,
you need the gap.

By placing the gap opposite to the feed point, you get a balanced loop
without the need of ferrite or other constructions. If you can get balance
via other means, you don't need the screen. Balancing the loop reduces
noise due to common mode issues. This isn't different from using a balun
between a coaxial cable and a symmetrical dipole.

Your option three may behave competently different, as the coaxial cable,
power supply cable, switch mode power supply, etc may contribute to
reception of signal and noise due to common mode to differential mode
conversion.

From my experience (reception) with electrically small well-balanced
indoor loops and indoor dipoles, I found some advantage of the loop over
the electric dipole at low frequencies (say below 3 MHz). I contribute
this mainly because of the nulling capability. Whether is applies to your
location depends on the field distribution of the noise at your location.

At higher frequencies there is difference in S/N ratio, but not in favor
of one antenna. Sharp nulling wasn't possible. So to know what option is
best for you, you need to try it. Maybe install both options and select
the antenna that gives best results as this will depend on frequency and
the angle of arrival of the radiation you want to receive.

Other thing that may really help is to find your local source(s) of noise,
use lots of ferrites and try to find a sweet spot for best S/N ratio.

--
Wim
PA3DJS
www.tetech.nl
Please remove abc first in case of PM

So you are saying that cases 1 & 2 above are essentially equvalent if the
loops are balanced. In terms of noise rejection, there is no analogy to be
drawn between a shielded loop and a shielded cable.

loop antennas
 

"Ian" napisa³ w wiadomo¶ci
...
"Szczepan Bialek" wrote in message
...


Hello, and they are most certainly not "electric" waves.

For the all Fathers of the radio they are the electric waves.
You wrote: "Hams have designed and constructed novel and practical
antennas over the years but their explanations about how they work are
often just plain wrong."

Could you give as the correct explanation?
S*

Hello Szczepan.

We've tried to assist you but you seem to prefer to stay with 19th century
knowledge

In 1846 Faraday wrote: "It seems to me, that the resultant of two or more
lines of force is in an apt condition for that action which may be
considered as equivalent to a lateral vibration; whereas a uniform medium,
like the aether, does not appear apt, or more apt than air or water."
http://www.padrak.com/ine/FARADAY1.html

rather than learn modern knowledge.

In 1929 Tesla wrote: " On repeating the Hertz experiments with much improved
and very powerful apparatus, I satisfied myself that what he had observed
was nothing else but effects of longitudinal waves in a gaseous medium, that
is to say, waves, propagated by alternate compression and expansion. He had
observed waves in the ether much of the nature of sound waves in the air."
http://www.tfcbooks.com/tesla/1929-09-22.htm

If you ask for help and don't accept the answers you get then there's not a
lot we can do ... other than disregard your postings and go and operate our
radio stations.

If you have a trouble in explanation about how receiving antennas work use
the Faraday's and Tesla's explanation.

You need to get a modern textbook on radio theory. One suitable for
amateur radio should be okay. Have a look at www.rsgb.org.and www.arrl.org

Is it right?
"Hams have designed and constructed novel and practical
antennas over the years but their explanations about how they work are
often just plain wrong."
S*

loop antennas
 

"Szczepan Bialek" wrote in message
.. .
We've tried to assist you but you seem to prefer to stay with 19th
century
knowledge
In 1846 Faraday wrote:
rather than learn modern knowledge.

Is it right?
"Hams have designed and constructed novel and practical
antennas over the years but their explanations about how they work are
often just plain wrong."
S*

It depends on the individual amateur, doesn't it. That's why we experiment,
write articles, read textbooks and discuss and debate theory and practise.

loop antennas
 

On Friday, June 15, 2012 2:44:39 AM UTC-5, Szczepan Bialek wrote:
Radio waves and light are the oscillatory flow of electrons (L. Lorenz
1869).

Lorenz (and all other physicists and mathematicians) were obviously ignorant of photons in those days. Here is what a more knowledgeable physicist has said more than a century later:

Quoted from: "The Strange Theory of Light and Matter", (c)1985, by Richard P. Feynman

"So now, I present to you the three basic actions, from which all the phenomena of light and electrons arise:

-Action #1: A photon goes from place to place.
-Action #2: An electron goes from place to place.
-Action #3: An electron emits or absorbs a photon."

When Feynman says "light", he is including RF. Photons travel at the speed of light in the medium which is impossible for electrons which possess rest mass. There are no electrons in a pure vacuum, yet light and radio waves pass through it at the speed of light with no problem.

Following your "logic", why go back to 1869? Why not question the periodic table of elements because a few millennia ago, men of science asserted that there are four elements: earth, air, fire, and water. So why not adopt the four element argument as well?
--
73, Cecil, w5dxp.com

loop antennas
 

On 6/15/2012 1:39 PM, W5DXP wrote:
On Friday, June 15, 2012 2:44:39 AM UTC-5, Szczepan Bialek wrote:
Radio waves and light are the oscillatory flow of electrons (L. Lorenz
1869).

Lorenz (and all other physicists and mathematicians) were obviously ignorant of photons in those days. Here is what a more knowledgeable physicist has said more than a century later:

Quoted from: "The Strange Theory of Light and Matter", (c)1985, by Richard P. Feynman

"So now, I present to you the three basic actions, from which all the phenomena of light and electrons arise:

-Action #1: A photon goes from place to place.
-Action #2: An electron goes from place to place.
-Action #3: An electron emits or absorbs a photon."

When Feynman says "light", he is including RF. Photons travel at the speed of light in the medium which is impossible for electrons which possess rest mass. There are no electrons in a pure vacuum, yet light and radio waves pass through it at the speed of light with no problem.

Following your "logic", why go back to 1869? Why not question the periodic table of elements because a few millennia ago, men of science asserted that there are four elements: earth, air, fire, and water. So why not adopt the four element argument as well?
--
73, Cecil, w5dxp.com

Cecil,

I think our Polish friend here is just a troll trying to get attention.

It is a complete waste of time reading his posts, just put him on your
kill list.

In the end for almost all amateur radio operators it does not matter one
wit how an antenna works. It most certainly matters if it works and how
well.

I have used a 75 meter loop antenna here where I live for the past 5
years. It works very well. I live right in town on a lot surrounded by
other homes. I started with a dipole but was advised that a loop would
hear less noise. It turned out to be quite true. I am now a convert to
the loop antenna. Have no idea of the physics of how it works, but it
sure does work well on bands between 75 and 20 meters. It actually seems
to work best on 40 meters.

I don't care about electrons or the names of past pioneers in radio. I
mean no offence to them, I just have moved on since being a child
studying radio.

Michael

loop antennas
 

El 15-06-12 16:09, garyr escribió:
I agree with your second link (by VK1OD).

The time varying magnetic field generates an electric field and that is
received by the loop. When you screen it completely, it doesn't work,
you need the gap.

By placing the gap opposite to the feed point, you get a balanced loop
without the need of ferrite or other constructions. If you can get balance
via other means, you don't need the screen. Balancing the loop reduces
noise due to common mode issues. This isn't different from using a balun
between a coaxial cable and a symmetrical dipole.

Your option three may behave competently different, as the coaxial cable,
power supply cable, switch mode power supply, etc may contribute to
reception of signal and noise due to common mode to differential mode
conversion.

From my experience (reception) with electrically small well-balanced
indoor loops and indoor dipoles, I found some advantage of the loop over
the electric dipole at low frequencies (say below 3 MHz). I contribute
this mainly because of the nulling capability. Whether is applies to your
location depends on the field distribution of the noise at your location.

At higher frequencies there is difference in S/N ratio, but not in favor
of one antenna. Sharp nulling wasn't possible. So to know what option is
best for you, you need to try it. Maybe install both options and select
the antenna that gives best results as this will depend on frequency and
the angle of arrival of the radiation you want to receive.

Other thing that may really help is to find your local source(s) of noise,
use lots of ferrites and try to find a sweet spot for best S/N ratio.

--
Wim
PA3DJS
www.tetech.nl
Please remove abc first in case of PM

So you are saying that cases 1& 2 above are essentially equvalent if the
loops are balanced. In terms of noise rejection, there is no analogy to be
drawn between a shielded loop and a shielded cable.





Hello Gary,

You are right, it is what I am saying.

There is no analogy between the shielding function of the braid in a
coaxial transmission line and the shield in your loop.

For the "shielded" loop, the received voltage is across the gap in the
shield. The shield is the actual single turn loop. The inner
conductor is just there to transport the received signal to the
opposite side of the gap where you can go down (with coaxial cable) to
your receiver, maintaining balance.

Theoretically a coaxial transmission line system is completely closed.
Water from the outside can't reach the inner conductor, source or
load. When cutting a gap in the screen, the coaxial transmission line
system will leak.

Shielded loop with more turns
If you run more turns within the shield of the loop, you pass the gap
many times. When you pass it 3 times, you will get three times the
voltage, hence the impedance and loop inductance increase.

--
Wim
PA3DJS
www.tetech.nl
Please remove abc first in case of PM

loop antennas
 

On 6/15/2012 2:23 PM, Boomer wrote:


I have used a 75 meter loop antenna here where I live for the past 5
years. It works very well. I live right in town on a lot surrounded by
other homes. I started with a dipole but was advised that a loop would
hear less noise. It turned out to be quite true. I am now a convert to
the loop antenna. Have no idea of the physics of how it works, but it
sure does work well on bands between 75 and 20 meters. It actually seems
to work best on 40 meters.

It is not true. Only in the cases of corona buildup, etc, on the
elements would that be the case.
If you hear less noise with the loop, vs the dipole, it's due to
the change in pattern. Not due to any qualities of the loop itself.
Noise is RF the same as any other signal, and follows all the same
rules. It's no different than an actual signal.
If what you/they say is true, and the loop received less noise, it would
also receive less "desired" signals. Or in other words, everything
would be down vs the dipole.
The most likely explanation is the change in pattern less favored
the direction the noise is coming from. Either that, or the noise is
local to your shack, and for some reason the loop's feed line is better
decoupled than the one feeding the dipole.
If I had to bet, I'd say it's the change in pattern.
There are no magical anti noise properties with loops.

loop antennas
 

On Friday, June 15, 2012 4:06:25 PM UTC-5, NM5K wrote:
Only in the cases of corona buildup, etc, on the
elements would that be the case.

He may be talking about precipitation static which was considerably reduced for me in the AZ desert when I converted my dipole to a folded dipole. My problem was dust storms even on a sunny day.

http://www.its.bldrdoc.gov/fs-1037/dir-028/_4096.htm

P-static is unrelated to the reception of EM RF far-field signals. It is a static charge transferred from charged particles in the air directly to an antenna. It was so bad in AZ that arcing occurred at my coax connector. I have actually seen the p-static envelope on my IC-756PRO's display.

The problem with a dipole is that one element of the dipole normally does not have a DC path to ground. When the p-static discharge takes place, it may be through the series capacitor in the receiver. With a loop antenna, including a folded dipole, the p-static usually has a path directly to ground from any point in the antenna system. It's not the only path but it certainly reduces the p-static noise although not completely eliminating it.

Of course, it is possible to reduce the p-static problems on a dipole with a parallel resistor/choke, a 4:1 voltage balun, or heavily insulated wires. Hams who live in low p-static areas of the country will invariably say that there is no such thing because they have never seen it. But hams who have lived in the AZ desert know better.
--
73, Cecil, w5dxp.com