It is said that a transmitted UWB pulse should not have any DC because
of the transmitting antenna:



"Without getting into the details of the physical generation of UWB
waveforms, it is sufficient to note in this regard that the
transmitting antenna has the general effect of differentiating the time
waveform presented to it. As a consequence the transmitted pulse does
not have a DC (direct current) value-the integral of the waveform
over its duration must equal zero."

(page 4,
http://www.antd.nist.gov/wctg/manet/...rt_April03.pdf)

Would someone please explain that for me?

Thanks!

-- Harry

Harry wrote:
Would someone please explain that for me?

DC steady-state does not cause electrons to emit photons.
For RF photons to be emitted from a copper wire dipole, the
free electrons must be accelerated and decelerated. The DC
component cannot accomplish that feat.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Harry wrote:

Would someone please explain that for me?


DC steady-state does not cause electrons to emit photons.

Except in flashlights, apparently.

For RF photons to be emitted from a copper wire dipole, the
free electrons must be accelerated and decelerated. The DC
component cannot accomplish that feat.

Quantum mechanics is completely unnecessary here, Cecil. I think
Faraday still provides the best explanation.

ac6xg

Jim Kelley wrote:
Cecil Moore wrote:

Harry wrote:

Would someone please explain that for me?


DC steady-state does not cause electrons to emit photons.

Except in flashlights, apparently.

For RF photons to be emitted from a copper wire dipole, the
free electrons must be accelerated and decelerated. The DC
component cannot accomplish that feat.

Quantum mechanics is completely unnecessary here, Cecil. I think
Faraday still provides the best explanation.

ac6xg

With a ns pulse into a zero resistance conductor in free space all
energy should be radiated, so no DC component if you look at the input
power. However if you introduce the same pulse to a circuit that has
magnetic properties, i.e. a ferrite inductor as an example, there is
energy used to align the molecules in the material, not radiated, which
results in a DC component. In a flashlight, most of the energy is
heat, which will result in a big DC component with no radiation rf
wise.
That's really advanced stuff for a Ham Radio Newsgroup.
Gary N4AST

Iok so i am confused on a few things

the photo part

so regardless of weither or not there is or isn't ac or dc , when i
xmit (ham or other freq's) are photons being generated??


where would they be?? nearfield? around the antenna?

how would i measure the presence/qty of such??


the other thing i got fuzzy on

static polar field as Mr. clark mentions so why does the battery
produce it /how?? are you referring to the fact that is has 'mass' and
therefore.... or did i miss the obvious



thanks


fuzzylogic
fuzzynavels
fuzzypeaches

ml wrote:

Iok so i am confused on a few things

the photo part

so regardless of weither or not there is or isn't ac or dc , when i
xmit (ham or other freq's) are photons being generated??


where would they be?? nearfield? around the antenna?

how would i measure the presence/qty of such??


the other thing i got fuzzy on

static polar field as Mr. clark mentions so why does the battery
produce it /how?? are you referring to the fact that is has 'mass' and
therefore.... or did i miss the obvious



thanks


fuzzylogic
fuzzynavels
fuzzypeaches

Don't listen to these guys. They're changing the subject by changing the
scale of the argument in order
to digladiate with one another. The truth is, that if an antenna really
differentiates a signal so that what it radiates is based on the rate of
change of the original signal, then the DC part of the original signal
won't contribute to the radiation because the rate of change of a
constant(the DC part)is zero. It isn't any more complicated than that.
73,
Tom Donaly, KA6RUH

Jim Kelley wrote:
Quantum mechanics is completely unnecessary here, Cecil. I think
Faraday still provides the best explanation.

In this particular case, quantum mechanics offers the
easiest-to-understand explanation. As Feynman put it:
"So now, I present to you the three basic actions, from
which all the phenomena of light (including RF) 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."

QED^2 :-)
--
73, Cecil http://www.qsl.net/w5dxp

Jim Kelley, AC6XG wrote:
"I think Farqaday stilll provides the best explanation."

Yes. Faraday showed d-c had nothing to do with wireless. It was the a-c
motivating wireless electrical coupling.

An Englishman, Faraday, constructed a transformer in 1831. He used two
isolateed coils of wire wound on the same spool. He connected a
galvanometer across one coil. He noticed a brief deflection of the
galvanometer each time he connected or disconnected a battery to the
second coil.

Joseph Henry, a professor at Albany Academy in New York was
independently making the same observations at the same time as Faraday.
When Henry got news of Faraday`s discoveries, he made no effort to claim
credit for his own work but often referred to Faraday`s discovery.

It was the change in the magnetic field which induced electricity
without a direct connection, not the value of the steady magnetic field
itself.

Same with antennas. A battery connected to an antenna sends no signal. A
varying field is required to produce a signal in an antenna.

Best regards, Richard Harrison, KB5WZI

On Wed, 28 Sep 2005 11:16:05 -0500, (Richard
Harrison) wrote:

Same with antennas. A battery connected to an antenna sends no signal. A
varying field is required to produce a signal in an antenna.

Hi Richard,

As much as the practical consequence is supported by this statement,
it is not literally true.

The battery (which requires no attachment, but neither does it suffer
one) does send a signal. It happens to be a static polar field. Any
charge within the vicinity (and arguably that is out to the edge of
the cosmos) will perceive its presence, OR its absence. Hence it
contains at least binary information. If we know the polarity of the
charge, then it contains at least quadratic information.

Within the dynamics and scope of life, there are many static charge
signals that hinge upon these 2 bits of information. Now, given I
used the terms dynamic and static in the same breath....

73's
Richard Clark, KB7QHC

Joseph Henry, a professor at Albany Academy in New York was
independently making the same observations at the same time as Faraday.
When Henry got news of Faraday`s discoveries, he made no effort to claim
credit for his own work but often referred to Faraday`s discovery.

It was the change in the magnetic field which induced electricity
without a direct connection, not the value of the steady magnetic field
itself.

Slight correction: it is the change in the magnetic flux that gives
induced EMF. You can get an induced current from a constant
magnetic field if the circuit loop moves in or out of the field,
changing the flux throught the loop.

Tor
N4OGW