Obtaining electromagnetic radiation from accelerating electrons
 

Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

Does that mean a column of salt water could not be
used as an antenna?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Obtaining electromagnetic radiation from accelerating electrons
 

On Mon, 06 Jul 2009 13:19:09 -0500, Cecil Moore wrote:

Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

Does that mean a column of salt water could not be used as an antenna?

It just means that moving the water back and forth won't cause
radiation. Waves on the surface of the ocean don't make radio signals.
(C'mon, Cecil. You knew the answer to your question, didn't you? ;-) )

The column of water will conduct a current, which will radiate, but I
think I'd rather use copper or aluminum :-)

--
Rich

Obtaining electromagnetic radiation from accelerating electrons
 

Rich Griffiths wrote:
(C'mon, Cecil. You knew the answer to your question, didn't you? ;-) )

Actually, I had never thought about it. I assumed that any
conductor would radiate.

I've been working on a particle beam that ionizes 33 feet
of air for use as an efficient mobile antenna on 40m. Have
I been wasting my time?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

Obtaining electromagnetic radiation from accelerating electrons
 

"Cecil Moore" wrote

I've been working on a particle beam that ionizes 33 feet
of air for use as an efficient mobile antenna on 40m. Have
I been wasting my time?

Unless you can stuff that antenna into a container the size
of two shoe-boxes, and achieve a 9 point something dBi
gain on 160M at the same time, yeah, you're wasting time.
Art's already beat you to it. And Art's antenna doesn't
care one never-mind about the phase information in the
standing wave current ;) good luck in the contest.

Mike W5CHR
Memphis

Obtaining electromagnetic radiation from accelerating electrons
 

On Mon, 06 Jul 2009 15:39:34 -0500, Cecil Moore wrote:

snip

I've been working on a particle beam that ionizes 33 feet of air for use
as an efficient mobile antenna on 40m. Have I been wasting my time?

Wasting your time? Heavens no! That would be WAY cool!

Even if it didn't work as an antenna, think how exciting it would be for
birds, people watching the highway from overpasses, ....

--
Rich

Obtaining electromagnetic radiation from accelerating electrons
 

"Cecil Moore" wrote in message
...
Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.

Does that mean a column of salt water could not be
used as an antenna?

If a VEE antenna were formed of two hoses, these "elements" could be
partially filled with brine and tuned by draining or adding brine. The
metal fittings on the lower ends of the VEE elements would be the feedpoint.

Reductio ad absurdum

LXXIII,
Sal

Obtaining electromagnetic radiation from accelerating electrons
 

Sal M. Onella wrote:
"Cecil Moore" wrote in message
...
Jim Lux wrote:
But the important thing is that there's an equal number of positive and
negative charges floating around there, so there's zero net charge. An
possible radiated field from a negatively charged electron will be
exactly matched by the opposite field from a positively charged
something else.
Does that mean a column of salt water could not be
used as an antenna?

If a VEE antenna were formed of two hoses, these "elements" could be
partially filled with brine and tuned by draining or adding brine. The
metal fittings on the lower ends of the VEE elements would be the feedpoint.


been done, been patented too, I think.

(conductive liquid as a changeable antenna element)

Obtaining electromagnetic radiation from accelerating electrons
 

"Jim Lux" wrote in message
...

snip

If a VEE antenna were formed of two hoses, these "elements" could be
partially filled with brine and tuned by draining or adding brine. The
metal fittings on the lower ends of the VEE elements would be the
feedpoint.


been done, been patented too, I think.

(conductive liquid as a changeable antenna element)

Aw, phooey! I never get to invent ANYTHING!

Obtaining electromagnetic radiation from accelerating electrons
 

Richard:

Actually [cfr: Feynman's Lectures on Physics] it is not the acceleration of
charge that produces photons (radiation), rather it is the rate of change of
the acceleration of charge that results in radiation.

As we all know, 'velocity' v is the rate of change of distance or space s,
expressed in terms of the differential calculus this would be written in
scaler form as (v = ds/dt) while 'acceleration' a is the rate of change of
velocity v, (e.g. a = dv/dt = d(ds/dt)/dt). In Engineering and Physics, the
next level of differential change or rate of change of acceleration is
usually termed 'jerk'. Jerk j then is j = da/dt. Jerk is not often
mentioned in elementary presentations of mechanics, but as far as I know
even with more in depth presentations there are apparently no 'standard'
terms for higher derivates of distance change than jerk. [distance,
velocity, acceleration, jerk, and then...]

Since, like their relative, the exponential functions, the sinusoidal
functions, sine, cosine, etc... "sort of" replicate each other every time
they are differentiated the higher order differentials of each such function
'look' simply like a scaled version of the other derivatives. Thus, for
sinusoidal waveforms, which are the usual functional form assumed for most
Engineering work, it is relatively easy for one to come up with a
mathematical expression which provides exact values for radiation levels in
terms of charge acceleration instead of charge jerk. Since of course if the
charge velocity is sinusoidal, so is the acceleration and so is the jerk.

Notwithstanding that there are well known formulas that relate radiation
levels to charge acceleration for sinusoidal waveforms, it is not charge
acceleration per se that causes radiation. Charge jerk causes radiation.

If one desires an exact formulation for radiation caused by charge motion
then perforce to be exact for general non-sinusoidal waveshapes such
formulae must be related to charge jerk not acceleration.

If you do not have access to Feynman' Lectures on Physics (I believe he
discusses this in Vol. 3) there was a recent more accessible discussion of
this topic by the editor of QEX in an article published in QEX several years
ago.

-- Pete k1po
-- Indialantic, FL


"Richard" wrote in message
...
Is it not true that if I were able to accelerate my cup of coffee at light
speeds at a frequency of 14Mhz my cup of coffee would radiate a 14Mhz
carrier?