Richard Clark wrote:
On Sat, 10 Mar 2007 09:33:46 +0000, Ian White GM3SEK
wrote:

Quantum theory describes electromagnetic energy as being divided into a
series of packets called photons, so (total energy in a stream of
photons) = (number of photons/second) x (energy of individual photons).

Energy is not expressed with a time in the denominator. The standard
quantum theory expression for energy is eV - time is wholly absent as
it should be.


Sorry, that was an editing mistake: obviously it's power that includes
the time dimension, energy does not.


This also means that EM energy doesn't exist in pure sine-waves

EM theory does not exclude the classic description of pure sine waves.
This is not a neither/nor situation.

- the
waveform is actually built up in steps, very much like digitized audio.

This appears to be the beginnings of a description about to fall off
the edge. What waveform? This is a conceit of time.

The step size is the energy content of one quantum.

No, the step size as you describe is the potential difference of
quantization, an engineering term, not a quantum mechanics term. It
is quantisizing an amplitude to construct the wave in a time domain.
Quanta is the complete wave in a frequency domain.


Richard is right about that. Please ignore my remarks about quantization
within the waveform itself. The quantization only affects the total
quantity of energy; or the power level if you wish to consider the rate
of energy transfer.

However, that doesn't affect the main point: at normal radio
frequencies, RF energy is composed of unimaginably small packets, in
unimaginably large numbers. This means that quantization effects in
energy or power levels are utterly negligible, and we can always think
of RF energy or power as a continuous stream.

It's rather similar to being aware that electric current is actually
made up of individual electrons - it's interesting information, but
electronic engineering very rarely needs to acknowledge the existence of
individual electrons. Even less does antenna engineering need to
acknowledge the existence of individual RF photons.

As I said in the previous posting, the energy of EM photons is
proportional to the frequency, so quantization effects only begin to be
noticeable at frequencies of hundreds of gigahertz, and still only as a
small correction in measurements of the very lowest power levels we can
detect.

Richard cited the following as a claimed exception:

A photon is emitted in the cM band when an electron orbiting a
Hydrogen atom flips its magnetic pole. This event is vastly below the
short wavelengths you describe by a million-fold. A good number of
correspondents here are fully capable of detecting this event with
commercial gear already suitable for the Ham market. They could have
done it 50 years ago too.

That is an example of a quantum effect determining the *frequency* of an
RF emission... but the origin of the RF energy doesn't change its
character. If a signal generator is tuned to that frequency, it will
produce exactly the same kind of RF energy - a torrent of quanta so tiny
that their individual existence is irrelevant.



--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek