A short 160M antenna
 

Brian Reay wrote in :

A cross product of two vectors is a third vector orthogonal to the first
two. In the case of the EM wave, the E and H vectors are orthogonal so
the cross product is in the third dimension, the direction of propagation.


Ok, thanks. This reminds me of the Flemings 'hand rules', which I have never
been taught directly so have failed ot remember and have to look up on the
rare occasion I need to. Any relation? Or are those limited to motors and
generators?

A short 160M antenna
 

"Brian Reay" wrote in message
...

The question then is, "is the wire loop necessary to produce RF
radiation?"

Or something similar, yes.

Essentially, the rotating field can cause a current to flow in a
conductor, that current will produce another magnetic field. The current
is charge movement, therefore you have an electric field. That
and the 'new' magnetic field can produce an EM wave. No different to any
other coil 'excited' with an AC current- perhaps the method of exciting
the coil is a little unconventional ;-)

Sometimes I am astounded by the things that you come out with; things that
perhaps explains your daily output of bluster and the smokescreen that
you attempt to creat with your continual personal abuse?

A short 160M antenna
 

El 08-11-14 8:03, escribió:
In rec.radio.amateur.antenna wrote:
"Brian wrote in message
...

His whole grasp of antenna theory is flawed.
He was trying to (indirectly) argue the other day via his his
interpretation of Maxwell's Equations you could generate an EM wave
by waving a magnet about. When corrected, he introduced another
variation.

Well, Brian, M3OSN, Old Chum, as was pointed out to you, all of your
posts these days are personal attacks aimed at one or another.

Why do you behave like that?

Certainly, as I corrected myself, if you wave a magnet about fast enough,
say, 1000,000,000 times per second, you will certainly generate an EM wave
and no-one has corrected me on that point because that point is true.

No, that point is utterly, completely, and absolutely false and goes
once again to show you have no clue as to the difference between an
electric field, a magnetic field, and an electromagnetic field.



Without doing the math, can we be sure that there is no radiation from
a rotating magnetic dipole?

When using reciprocity, a permament magnet will rotate in an EM
radiation field (produced by an antenna-transmitter combination, far
field distance). Of course you need to spin-up the magnet as you don't
have a rotating field. Once it is synchronized, you can extract power
from it (resulting in a slip angle).

So the other way around, using reciprocity, the rotating magnet will
generate power in a load connected to the antenna that was used to
generate the EM field.



--
Wim
PA3DJS
Please remove abc first in case of PM

A short 160M antenna
 

Ian Jackson wrote:

snip

If a permanent magnet was oscillated inside a loop of wire, it would
produce an oscillating current in the loop. An oscillating current would
produce RF radiation (especially if it was tuned with a capacitor to the
frequency of the magnet's oscillation).

In which case you have a generator producing AC voltage.

The question then is, "is the wire loop necessary to produce RF
radiation?"

The wire loop is necessary to produce an AC voltage.

An AC voltage applied to an antenna produces RF radiation.

Before tubes were invented, high frequency AC generators were used to
generate high frequency AC voltage which was applied to antennas.


--
Jim Pennino

A short 160M antenna
 

Wimpie wrote:
El 08-11-14 8:03, escribió:
In rec.radio.amateur.antenna wrote:
"Brian wrote in message
...

His whole grasp of antenna theory is flawed.
He was trying to (indirectly) argue the other day via his his
interpretation of Maxwell's Equations you could generate an EM wave
by waving a magnet about. When corrected, he introduced another
variation.

Well, Brian, M3OSN, Old Chum, as was pointed out to you, all of your
posts these days are personal attacks aimed at one or another.

Why do you behave like that?

Certainly, as I corrected myself, if you wave a magnet about fast enough,
say, 1000,000,000 times per second, you will certainly generate an EM wave
and no-one has corrected me on that point because that point is true.

No, that point is utterly, completely, and absolutely false and goes
once again to show you have no clue as to the difference between an
electric field, a magnetic field, and an electromagnetic field.



Without doing the math, can we be sure that there is no radiation from
a rotating magnetic dipole?

You could ask someone who understands the math.




--
Jim Pennino

A short 160M antenna
 

El 09-11-14 23:01, escribió:
wrote:
El 08-11-14 8:03, escribió:
In rec.radio.amateur.antenna wrote:
"Brian wrote in message
...

His whole grasp of antenna theory is flawed.
He was trying to (indirectly) argue the other day via his his
interpretation of Maxwell's Equations you could generate an EM wave
by waving a magnet about. When corrected, he introduced another
variation.

Well, Brian, M3OSN, Old Chum, as was pointed out to you, all of your
posts these days are personal attacks aimed at one or another.

Why do you behave like that?

Certainly, as I corrected myself, if you wave a magnet about fast enough,
say, 1000,000,000 times per second, you will certainly generate an EM wave
and no-one has corrected me on that point because that point is true.

No, that point is utterly, completely, and absolutely false and goes
once again to show you have no clue as to the difference between an
electric field, a magnetic field, and an electromagnetic field.



Without doing the math, can we be sure that there is no radiation from
a rotating magnetic dipole?

You could ask someone who understands the math.

It is not that I don't understand the math, but I don't want to spend
time if we can get an answer by using reciprocity (the part of my text
you skipped).

Back to reciprocity:

When using reciprocity, a permament magnet will rotate in an EM
radiation field (produced by an antenna-transmitter combination, far
field distance). Of course you need to spin-up the magnet as you don't
have a rotating field. Once it is synchronized, you can extract power
from it (resulting in a slip angle).

So the other way around, using reciprocity, the rotating magnet will
generate power in a load connected to the antenna that was used to
generate the EM field.

If we can't prove that reciprocity (or other assumption) doesn't hold
for this case, then the rotating permanent magnet produces EM radiation.


--
Wim
PA3DJS
Please remove abc first in case of PM

A short 160M antenna
 

Wimpie wrote:
El 09-11-14 23:01, escribió:
wrote:
El 08-11-14 8:03, escribió:
In rec.radio.amateur.antenna wrote:
"Brian wrote in message
...

His whole grasp of antenna theory is flawed.
He was trying to (indirectly) argue the other day via his his
interpretation of Maxwell's Equations you could generate an EM wave
by waving a magnet about. When corrected, he introduced another
variation.

Well, Brian, M3OSN, Old Chum, as was pointed out to you, all of your
posts these days are personal attacks aimed at one or another.

Why do you behave like that?

Certainly, as I corrected myself, if you wave a magnet about fast enough,
say, 1000,000,000 times per second, you will certainly generate an EM wave
and no-one has corrected me on that point because that point is true.

No, that point is utterly, completely, and absolutely false and goes
once again to show you have no clue as to the difference between an
electric field, a magnetic field, and an electromagnetic field.



Without doing the math, can we be sure that there is no radiation from
a rotating magnetic dipole?

You could ask someone who understands the math.

It is not that I don't understand the math, but I don't want to spend
time if we can get an answer by using reciprocity (the part of my text
you skipped).

Back to reciprocity:

When using reciprocity, a permament magnet will rotate in an EM
radiation field (produced by an antenna-transmitter combination, far
field distance). Of course you need to spin-up the magnet as you don't
have a rotating field. Once it is synchronized, you can extract power
from it (resulting in a slip angle).

So the other way around, using reciprocity, the rotating magnet will
generate power in a load connected to the antenna that was used to
generate the EM field.

None of which has a permanet magnet spinning in empty space, which is
why I snipped it.

If we can't prove that reciprocity (or other assumption) doesn't hold
for this case, then the rotating permanent magnet produces EM radiation.

And rigously proving any of that is much more complex then F=ma.



--
Jim Pennino

A short 160M antenna
 

On 11/9/2014 4:09 PM, Wimpie wrote:
El 08-11-14 8:03, escribió:
In rec.radio.amateur.antenna wrote:
"Brian wrote in message
...

His whole grasp of antenna theory is flawed.
He was trying to (indirectly) argue the other day via his his
interpretation of Maxwell's Equations you could generate an EM wave
by waving a magnet about. When corrected, he introduced another
variation.

Well, Brian, M3OSN, Old Chum, as was pointed out to you, all of your
posts these days are personal attacks aimed at one or another.

Why do you behave like that?

Certainly, as I corrected myself, if you wave a magnet about fast
enough,
say, 1000,000,000 times per second, you will certainly generate an EM
wave
and no-one has corrected me on that point because that point is true.

No, that point is utterly, completely, and absolutely false and goes
once again to show you have no clue as to the difference between an
electric field, a magnetic field, and an electromagnetic field.



Without doing the math, can we be sure that there is no radiation from a
rotating magnetic dipole?

When using reciprocity, a permament magnet will rotate in an EM
radiation field (produced by an antenna-transmitter combination, far
field distance). Of course you need to spin-up the magnet as you don't
have a rotating field. Once it is synchronized, you can extract power
from it (resulting in a slip angle).

So the other way around, using reciprocity, the rotating magnet will
generate power in a load connected to the antenna that was used to
generate the EM field.

I don't follow this at all. I'm not familiar with the principle of
reciprocity and so can't say if you are applying it correctly.

But consider this. If the rotating magnet were sending out EM waves, it
would require energy to do that. But a rotating magnet will rotate
indefinitely bar other sources of friction. So clearly it is not
emanating EM waves. An example is a magnet suspended over a
superconductor. It can be set spinning and will not stop for a long time.

--

Rick

A short 160M antenna
 

rickman wrote:

snip

I don't follow this at all. I'm not familiar with the principle of
reciprocity and so can't say if you are applying it correctly.

The reciprocity situation has nothing to do with a permanet magnet
rotating in isolation.

Reciprocity for that would be battery rotating in isolation.

But consider this. If the rotating magnet were sending out EM waves, it
would require energy to do that. But a rotating magnet will rotate
indefinitely bar other sources of friction. So clearly it is not
emanating EM waves. An example is a magnet suspended over a
superconductor. It can be set spinning and will not stop for a long time.

All true and can be trivially verified in an evacuated container.



--
Jim Pennino

A short 160M antenna
 

El 10-11-14 3:51, rickman escribió:
On 11/9/2014 4:09 PM, Wimpie wrote:
El 08-11-14 8:03, escribió:
In rec.radio.amateur.antenna wrote:
"Brian wrote in message
...

His whole grasp of antenna theory is flawed.
He was trying to (indirectly) argue the other day via his his
interpretation of Maxwell's Equations you could generate an EM wave
by waving a magnet about. When corrected, he introduced another
variation.

Well, Brian, M3OSN, Old Chum, as was pointed out to you, all of your
posts these days are personal attacks aimed at one or another.

Why do you behave like that?

Certainly, as I corrected myself, if you wave a magnet about fast
enough,
say, 1000,000,000 times per second, you will certainly generate an EM
wave
and no-one has corrected me on that point because that point is true.

No, that point is utterly, completely, and absolutely false and goes
once again to show you have no clue as to the difference between an
electric field, a magnetic field, and an electromagnetic field.



Without doing the math, can we be sure that there is no radiation
from a
rotating magnetic dipole?

When using reciprocity, a permament magnet will rotate in an EM
radiation field (produced by an antenna-transmitter combination, far
field distance). Of course you need to spin-up the magnet as you don't
have a rotating field. Once it is synchronized, you can extract power
from it (resulting in a slip angle).

So the other way around, using reciprocity, the rotating magnet will
generate power in a load connected to the antenna that was used to
generate the EM field.

I don't follow this at all. I'm not familiar with the principle of
reciprocity and so can't say if you are applying it correctly.

Just do a search on reciprocity in electronic systems, it isn't
difficult.


But consider this. If the rotating magnet were sending out EM waves,
it would require energy to do that. But a rotating magnet will rotate
indefinitely bar other sources of friction. So clearly it is not
emanating EM waves. An example is a magnet suspended over a
superconductor. It can be set spinning and will not stop for a long time.

The reason that you don't need to take magnetic dipole radiation into
account in real mechanical systems is because of the radiated power is
very low (low RPM in practical mechanical systems). Friction
(bearings/air, eddy current, etc) is orders of magnitude more then the
"friction" caused by the EM radiation.

On an astronomical scale things are different.

--
Wim
PA3DJS
Please remove abc first in case of PM