RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while tying up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
All trademarks, copyrights, patents, and other rights of ownership to images
and text used on the RF Cafe website are hereby acknowledged.
Shive Wave Machine with tapered section transitioning between
large and small sections.
Sometime around 1985, I was enrolled in a second-semester physics class (AACC) while working
on earning my BSEE. Along with covering topics like electricity, magnetism, heat
conduction, optics, etc., my professor, a moonlighting oceanography instructor from
the nearby U.S. Naval Academy,
conducted a laboratory exercise wherein he wanted to demonstrate the action of sea
waves breaking against the shore and underwater shelf discontinuities. He used an
impressive contraption that was comprised of coplanar parallel metal rods that were
attached in their centers to a spring steel bar for torsional continuity. The tips
of the rods were painted white so that when the end bar was perturbed with a vertical
impulse, a sinewave shape could be seen propagating along the length of the device
- both an incident and, eventually, a reflected wave.
Depending on whether the last bar at the far end of the device, which I now know
is called a Shive Wave Machine, is free to move or held rigidly, the reflected wave
would be either in phase or out of phase with the incident wave. He then attached
to the far end a smaller Shive Wave Machine to demonstrate what happens when something
between an open and shorted connection terminates the larger machine. Finally, he
inserted a Shive Wave Machine section between the large and small machines that
had rods that tapered linearly from the large to the small size. That addition caused
the reflections in the initial section to nearly (but not totally) disappear.
Upon watching the action of the Shive Wave Machine, I immediately recognized
the parallel between its mechanical motions and those of electromagnetic signals
on a transmission line (and in free space for that matter). The professor confirmed
my assertion and noted that with his dedication to the mechanical aspects, he had
not thought to relate it to electrical waves during a demonstration, although he
certainly was aware it. I have written about this guy in the past, regarding him
as being one of the more inspirational instructors I have had in all my engineering
classes. He could work out any problem in my physics book (Halliday & Resnick),
whether it be on gravitational forces, electric fields, black body radiation, or
I have thought about the Shive Wave Machine often over the years, but never knew
its name until I ran across a video of it on YouTube. I honestly cannot recall the
website where I saw it posted or I would give credit to the author of the article
for reminding me of it. The video is embedded below.
Dr. John N.
Shive, of Bell Telephone Laboratories, was the inventor. He also invented the
Video of the Shive Wave Machine being demonstrated by its inventor,
Dr. John N. Shive, of Bell Telephone Laboratories.
Posted January 11, 2016
Please Support RF Cafe by purchasing
my ridiculously low−priced products, all of which I created.