On Jul 5, 5:24*am, "Richard" wrote:
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?


No.
You don't have to go the speed of light . Bigger the acceleration,
bigger the amplitude of the radiated signal.

And, it's the vibrating your cup of coffee back and forth at 14MHz
that would do it.

Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.


Consider a balloon which you've charged up by rubbing it on your hair
(or that fuzzy sweater...) If you move it back and forth, and have an
electric field meter some small distance away, you'll see the field
changing. Move the meter farther away, and the field is still
changing, but the amplitude is smaller.

Now look at the time delay between your moving the balloon and when
you see the field change. That delay is the time it takes for the
changed field to "propagate" to the meter.. aka the speed of light.

Jim Lux wrote:
Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.

How many free electrons in coffee? How about salt water?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

I don't care if it works or not, YOU are the one that's gonna have
to clean up that @#$ coffee mess!
- 'Doc

Cecil Moore wrote:
Jim Lux wrote:
Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.

How many free electrons in coffee? How about salt water?

pH = -log hydrogen ion concentration

the pH is about 7, so hydrogen ion concentration is 1E-7. It's
neutral, so there's an equal number of negative ions. How many of them
are free electrons is another question.


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.

On Mon, 06 Jul 2009 08:22:19 -0700, Jim Lux wrote:

Cecil Moore wrote:
Jim Lux wrote:
Another problem.. there's no net charge on your coffee.. so no
radiated field when you move it back and forth.

How many free electrons in coffee? How about salt water?

pH = -log hydrogen ion concentration

the pH is about 7, so hydrogen ion concentration is 1E-7. It's
neutral, so there's an equal number of negative ions. How many of them
are free electrons is another question.


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.

The pH of water in contact with the atmosphere tends to be about 6.5, due
to CO2 dissolving in the water and forming carbonic acid. Other commonly-
occurring ions that "match" the H+ are sulfate and nitrate. Of course in
salt water, most of the ions are sodium (Na+) and chloride (Cl-). Not
many free electrons. The motion of any ions could create electromagnetic
radiation, but as you note, the net charge is zero, so no radiation,
regardless how the cup is accelerated or what speed it travels at ;-)

--
Rich

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

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

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

"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

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