On Mon,1/12/2015 8:36 AM, greg greene wrote:
the difference between
theory and practice - is the difference between theory and practice' what
he meant by that was that theory is the guide - practice is result, when
the two don't match - review both. Theory is never 100% - that is why it
is theory
The word "theory" here is misapplied. Somehow, we in the radio world,
long before most of us became hams, divided the FCC exam into a written
exam, which was CALLED "theory" and the CW exam. What that exam covered
(and still does) is a combination radio Rules, operation, and
fundamental physical principles. NOT unproven "theory."
Human understanding of how things work has been well known for a LONG
time. Nearly 100 years ago, Bell Labs published the concept of the use
of feedback to reduce distortion in amplifiers with a corresponding
reduction in gain. The fundamentals of transmission lines and antennas
are also that old. Before that work was proven by disciplined
experiment, it could reasonably be called "theory," even though it was
clearly proven by the math.
- the more we observe the results of practice - the closer we get
to redefining the theory, and then the closer we get to refining the
practice.
Jim Garland addressed this quite well in his post. REAL components are
not ideal -- inductors have series resistance and parallel capacitance.
When we look at a circuit diagram that shows an inductor and ignore that
fact, WE have failed to apply fundamental principles. This is not a
failure of "theory" nor those principles. Likewise, when we look at a
resistor and fail to see it's self inductance (and even parallel
capacitance), and look at a capacitor failing to see it's series and
parallel resistances and series inductance, it is WE who have failed,
NOT "theory" -- those fundamental principles. And, of course, active
components -- tubes, transistors, and diodes also have strays.
I was trained as an EE, and spent much of my life in the field of
"engineering." Real engineers are trained to understand the whole
picture, the strays, the costs of eliminating or reducing them, and when
to stop with "good enough." We don't need, nor can we afford "ideal" --
we must work with the real estate that our home sits on, with the sky
hooks that are on it, and cash in our bank account to build antennas
that "work."
Inside our radios and amplifiers, we must look for and understand what
Henry Ott calls "the invisible schematic hiding behind the 'ground'
symbol," as well as the complete schematic that includes those stray Rs,
Ls, and Cs. Failure to do that is OUR failure, not "theory," those
fundamental principles.
Understanding HOW antennas work allows us to achieve a better result
faster. Sure, we could build a dipole, operate it at various heights in
increments of 5 ft, and use a drone with instruments attached take a lot
of measured data to see it's directional pattern, both vertical and
horizontal. Bring a very fat wallet to this process. OR, build a model
of that antenna in NEC and have it compute the 3D pattern at various
heights in increments of 5 ft. I've done that in a day or so. I now
KNOW, in dB, the value of 10 ft of additional height on 80, 40, and 20M.
That work, BTW, is on my website.
http://k9yc.com/VertOrHorizontal-Slides.pdf
73, Jim K9YC
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