Interesting discussion. It appears that Fry is searching for a reason
to both questions as opposed to an solution. If so then that can hardly
be understood by simply debating alternative solutions.

I propose a non-technical explanation. There are two fundamental factors:

1 Instances are always contingent.
2 The velocity of radiation is not infinite.

Give this understanding then a solutions rest with the modeling and
analysis of the inter-dependancy of the DC levels which exist in a
realistic time domain.

What more need be said?

regards,

bill.


Richard Fry wrote:
Why would varying the pulse width without changing the characteristics of
the pulse transitions (rise/fall) affect the harmonic content of the pulse?
No bandwidth and no harmonics at all are produced by the constant DC level
of the pulse before and after each transition.

Wouldn't the harmonic structure and bandwidth needed to produce/reproduce a
pulse be related only to the rise and fall times of that pulse, and the
transition shapes (sin^2, etc), and be independent of the width (time)
between the transitions?

RF

Visit http://rfry.org for FM broadcast RF system papers.

Richard Fry wrote:
"Please explain the reason why the bandwidth characteristics needed to
generate a single transistion from one DC level to another is different
than when repeating that same transition any number of times before or
after."

No answer from Reg Edwards has appeared on my screen and it`s 6 hours
later in England than in the central U.S.A., so Reg may be sleeping.

The transitions are likely quite similar from one repetition to the next
but more is involved. It`s true that the shorter the length of the
pulse, the higher the efficiency of the harmonic generator. It is also
true that there is an optimum pulse length for maximum output at the
harmonic frequency. Pulse duration as well as on-off transition times
are involved. Output of a harmonic generator is a multiple of the pulse
frequency.

Terman has harmonic generator information starting on page 473 of his
1955 edition. This is slanted toward Hollow-State devices which were
still dominant at the time.

Best regards, Richard Harrison, KB5WZI

On Mon, 22 Mar 2004 21:51:26 -0600 (CST),
(Richard Harrison) wrote:

Richard Fry wrote:
"Please explain the reason why the bandwidth characteristics needed to
generate a single transistion from one DC level to another is different
than when repeating that same transition any number of times before or
after."


Hi Richard (KB5WZI),

I liked your Hollow state reference, and it exposes how inordinately
complex such a topic becomes (what has it got to do with antennas
anyway? The ennui of bored continentals...). For decades, equipment
has subsisted quite well with the 1/10/100 KC XTAL marker generator
that pushed harmonics out through to the 10M band. Even simpler is a
Zener operating at its knee region of conduction with the entire
bandwidth awash in its wall-to-wall RF trash. Even the NE-2 does as
well. Tarting it up with poor illustrations of Fourier math (which
are actually FFTs) serves no better application.

Gee fellows, if we must ponder this math try analyzing a Chirp
function, or a ramp, or sawtooth, or sweep, or a damped sine. I think
the square wave and variants has been suitably covered. Try a 359
degree sine wave and discover the trash it leaves behind.

73's
Richard Clark, KB7QHC