"Peter O. Brackett" wrote in message
ink.net...
OK RRAA Group Let's get Real:

DC to daylight! Which end of the spectrum is most interesting?

There often seems to be disagreement, dare I say "rancourous", among the
denizens of RRAA on certain details of the dynamics of em waves and
certain
wave phenomena, dare I say "reflections".

Most hams are practical folk, interested in phenomena that occur (only)
within our legally assigned frequency bands. A select few are interested
in
what happens outside our legally assigned frequency bands, and at least
one
of our RRAA bretheren often takes us on excursions all the way up to
"daylight" to make his points futher down the spectrum! i.e. He takes us
up into the nether regions of optical frequencies to make his points.
(God
Bless "Hecht"!)

Throughout all of the ensuing discussion that we "lurkers" overview, I
have
always been curious about what happens if we were to take or frequency
excursions to the other extreme.

I believe that we are legally allowed to radiate in the DC band!

Most of us RRAA'ers seem to accept the physical reality inherent in the
assertions of James Clerk Maxwell's (Actually Oliver Heavisides!) elegant
and widely celebrated simple set of four partial differential equations
and
their auxilliary relations. Where is dear old Reg when we need him?

Most of us RRAS'ers alos seem to "know" that, at least at Radio
Frequencies
(RF), there exist both guided and free space electromagnetic "waves", and
that during the "life" of such waves, the situation of the simultaneous
existence of both "incident" and "reflected" waves often occurs. We all
agree, because of "optical" excursions we have been taken on by our
"ptical
frontiersman", that situation occurs whether or not those waves are
"guided"
(by transmission lines, a.k.a waveguides) or "free".

Aside: We all seem to know that it is strictly the "acceleration" of
electric charges that causes the radiation of radio waves, or if you
prefer,
the emission of photons. I believe that the extant wave versus particle
"paradox" is irrelant to my following comments, assertions and questions.
Also I believe that the dividing line between transient and steady state
phenomena may be considered to be insignificant and so considered to be
irrelevant as well.

Frequency, or spectrum, through the Supreme Force of the Universe's gift
to
us of "The Sinudoids" is intimately related to circular motion.
Acceleration we know is the rate of change of velocity. In the steady
state
at DC electric charges are moving at a constant velocity. Thus when
moving
in a straight line at constant velocity there should be no "waves"
launched
or radiated, no?

However, as mechanics or Engineers, we all understand the reality of
centrifugal force and centripial acceleration. Some of us may actually
recall Coriolis acceleration. [grin] I was in New Zealand last year and
indeed the water does go down the sink with the opposite circulation. The
water would not do that without the existence of the Coriolis Force. But
I
digress!

The reality of electric charges is clearly accepted by all denizens of
RRAA,
although some might argue about "holes" [grin].

Clearly then... even constant velocity steady state charges (DC) that
circulate at a constant linear and angular velocity around the guided
helical path of a solenoidally shaped conductor, otherwise known as a
coil
or inductor, say for instance the ubiquitous loading coil of a Bug Catcher
whip, are subject to CENTRIPIAL ACCELERATION and must perforce emit
photons,
no? Does a coil carrying DC radiate? If so how efficiently?

My point here is the assertion of the real existence of DC waves either
guided or free!

Q0: Is there electromagnetic radiation (are photons emitted) from a
solenoidal (helix) carrying DC because of the centripital acceleration of
the charges?

No. The electrons are constrained within the winding of the solonoid. A
magnetic field is
formed by the movement of the electrons but this has nothing to do with
centripedal
acceleration of charges.

Q1: Do electromagnetic "waves" exist at DC, whether guided or free?

No. However there is not sharp cut off point. Any change in voltage or
current over a
period of time will generate an electromagnetic disturbance. The initial
inrush of electricity
when a circuit is first energised creates a detectable electromagnetic
pulse. When a circuit
is de-energised or switched of, a similar pulse is generated as voltage and
current decay.

Q2: Can incident DC "waves", whether guided or free ever be "reflected"?

DC is DC and once a constant current/voltage is established only a magnetic
field around
the conductors will exist.

Q3: Can a VSWR be measured (at zero frequency) on a transmission
line/waveguide that supports DC?

No. There can be no standing waves at DC for the reason stated above.

Q4: Is the VSWR at DC related, in any way at all to the VSWR at higher
frequencies?

As there can be no VSWR, this question is pointless.

Pete, just plain crazy, none of this is reality!

Let's get practical then... most RRAA'ers seem to agree that a Bird Model
43
clearly measures indident and reflected waves. The generic name for a
Bird
is "reflectometer". Bird's, being "real practical devices" do have
practical frequency range limitations and their accuracy and precision of
the measurement of actual reality falls off below and above their (rated)
the frequencies that define their rated bandwidth of operation. i.e.
Bird's
are not "accurate" from DC to daylight! But if one had a "Perfect Bird"
and
we could measure transmission line guided waves all the way down to DC.

Q4: If the Bird can't do it, is it even possible to construct a
reflectometer instrument that can measure reflected waves all the way down
to DC (zero frequency)? I have one here at home that I made myself.
Where
can I buy one?

Any repetitive change in voltage and frequency over any period could be
construed
as an alternating current (AC) and theoretically is capable of being coupled
to a
suitable antenna and radiated as an electromagnetic wave. Given the
components to
construct a measuring device with a long enough time constant it is possible
to
measure reflections along a conductor or feedline. DC is a theoretical
construct,
rather like the concept of absolute zero. You can get very close, but you
will never
ever have a truely DC voltage/current just as you can never attain absolute
zero, or
for that matter, accelerate an object with mass to the speed of light.

Q5: If waves do not exist at DC, then at what magic frequency, lets call
this frequency f(mgc), do waves cease to exist?

As stated above, DC doesn't really exist, other than as a theoretical
concept. The
voltage and current will always vary slightly in any practical circuit.

Q6: Below what magic frequency, lets call it f(mgc), do radiation and or
reflection phenomena stop?

Radiation and reflection phenomena do no stop. All electrical circuits
radiate some
energy as heat and electromagnetic pulses. These emissions may be below
measurable
limits but they exist none the less.

Q7: What is the difference between a "conjugate match" and a "Zo-match"
at
DC?

I have no idea.

Food for thought, eh?

I miss dear old Reg!

Thoughts comments...

--
Pete k1po
Indialantic By-the-Sea, FL

All of the phenomena associated with electromagnetic waves and electron flow
can be
simulated in water tanks with supended particles in solution. When waves are
generated
at suitable frequencies, they travel along the tanks and matched stubs in
exactly the same
wave as electromagnetic theory predicts. Standing waves can be generated at
resonance
and these also behave as predicted. Examination of the particles in solution
using a laser
show that while waves propogate, individual particles move very slowly or
oscillate
around a fixed position. Again very similar to observed performance in
antennae and
feed lines. There is a tendency to look rather too deeply into some
electromagnetic
phenomena which although apparently strange, have parallels in other
branches of science.

Big antennas work better than small antennas at every frequency and provided
a decent
impedence match is achieved between the transceiver output and is impedence
of free
space (about 377 ohms) then maximum signals are broadcast and received.

The efficiency with which the impedence match can be achieved is really at
the crux of
all antenna theory.

My two pennies worth.

Mike G0ULI