Today in Science History -
Sometime around 1980, while stationed at
Robins AFB, Georgia, I finally succumbed to the peer pressure of other more sophisticated
audiophiles in the barracks and bought a "real" stereo. Unlike my roommate who had
a full compliment of rack-mounted gear, my meager enlisted military pay only allowed
for a mid-grade instrument. The solution was a
Sansui TA−300 Integrated Tuner Amplifier. It put out a whopping 30 watts per
channel, but unlike my existing radio (a Readers Digest 800−XR), those 30 watts
were nearly distortion free when driving good speakers. Having only the pathetic
5 W speakers that came with the 800-XR, I designed a set of speakers rated
for 60 W, and built the enclosures myself in the base woodshop. Unfortunately,
in preparation for a household move about 20 years ago, I sold the Sansui and the
In case you forgot to put it on your calendar,
today, May 20th, is World Metrology Day. To commemorate the occasion, this is the
day that the official definition of the kilogram is being changed from a physical
cylinder of metal to the equivalent mass (recall Einstein's E=mc2) derived
from a photon energy-to-frequency ratio measured to its most precise value. Per
the new definition, the magnitude of a kilogram would be "set by fixing the numerical
value of the Planck constant to be equal to exactly 6.626 069… × 10–34
when it is expressed in the SI unit s–1 m2 kg (J s) ..."
This is a nice short article covering the
calculation of inductances for coils wound on cores and wire sizes. It appeared
in a 1932 issue of Short Wave Craft, but of course inductance has not changed
since then so it is still relevant. The author recognized that standard formulas,
although concise and accurate, are sometimes difficult to work with when calculations
for a large number of values is needed for a particular circuit design. To address
the situation, he presents a handy nomograph, chart, and a table of typical values.
He also introduces a rarely seen term "Nagaoka's correction factor*" for skin effect.
A smartphone app, a spreadsheet, or a desktop computer program would be used today
to calculate inductance ...
"The Indian Institute of Science claims the
first enhancement-mode (e-mode) operation of aluminum gallium nitride / gallium
nitride (AlGaN/GaN) high-electron-mobility transistors
(HEMTs) using p-type aluminum titanium oxide (AlTiO) gate insulation. The metal-oxide-semiconductor
(MOS) gate stack combined the high-k dielectric properties of TiO2 (k greater than
60) with the p-type properties supplied by Al2O3 doping (k ~9). The Al2O3 substitutes
the 2Als on Ti sites and the 3Os have a deficit of one vacancy that is doubly positively
charged. The charged O vacancy can release two holes, which can subsequently be
reabsorbed by uncharged O vacancies ..."
5G is providing plenty of challenges for filter
designers. The issue is probably no so much achieving narrow bandwidths with extremely
sharp rejection regions as implementation in available media. Peter Matthews, of
Knowles Precision Devices, as an article entitled, "Approaching the 5G mmWave Filter Challenge,"
on the Microwaves & RF website that discusses some of the issues. "In the
world of LTE, developers are very familiar with the available filtering technologies
that work, namely surface acoustic wave (SAW) and bulk acoustic wave (BAW) filters.
These filters cover a range of frequencies up to 6 GHz, come in small sizes and
offer good performance-to-cost trade-offs ..."
Since 2003, Bittele Electronics has consistently
provided low-volume, electronic contract manufacturing (ECM) and turnkey PCB assembly
services. It specializes in board level turnkey
for design engineers needing low volume or prototype multi-layer printed circuit
boards. Free Passive Components: Bittele
Electronics is taking one further step in its commitment of offering the best service
to clients of its PCB assembly business. Bittele is now offering common passive
components to its clients FREE of Charge
This week's crossword puzzle will keep you
busy for a while. Since 2000, I have been creating
custom engineering- and science-themed crossword puzzles for the brain-exercising
benefit and pleasure of RF Cafe visitors who are fellow cruciverbalists. The jury
is out on whether or not this type of mental challenge helps keep your gray matter
from atrophying in old age, but it certainly helps maintain your vocabulary and
cognitive skills at all ages. A database of thousands of words has been built up
over the years and contains only clues and terms associated with engineering, science,
physical, astronomy, mathematics, chemistry, etc. You will never find a word taxing
your knowledge of a numbnut soap opera star or the name of some obscure ...
The problem of and concern about our country's
youngsters seemingly not being overly interested in
pursuing technical career paths is a theme often heard in the tech news media
and workplaces. As our world grows increasingly automated and everything from light
bulbs to telephones and automobiles are so packed with "no user serviceable parts
inside," there seems to be little motivation for an otherwise potential budding
tinkerer to take stuff apart to discover what makes it work. In the "old days" like,
say, 1955, products were much more accessible to kids' curious nature and explains
why fostering the next crop of engineers, scientists, and technicians took care
of itself. You might think so, but alas, the dilemma evidently persists with each
succeeding generation ...
Jim Holbrook has a useful guide on the Microwaves &
RF website entitled, "What Are the 8 Most Important Oscillator Specs?"
It begins: "What’s the first thing you think of when selecting electronic components?
Chances are it’s the processor or something else central to the system. The timing
component may be the last thing on your mind, even though the clock provides the
heartbeat that all signals in the system depend on. Selecting these essential timing
components may appear to be a straightforward process, but one must consider a number
of factors that affect system performance. So, what are the most important specifications
and considerations? Here's a short rundown of the top oscillator parameters ..."
Here is a fairly simple
quiz on AC circuit analysis. If you are not already comfortable with adding
series and parallel circuits containing resistors, capacitors, and inductors, you
will appreciate the simple formula presented that will keep the sweat level down
;-) . An even simpler form that solves explicitly for the four variables are
VTotal = √ [(VL - VC)2
VR = √ [(VT)2 - (VL - VC)2]
VL = VC + √ [VT2 - VR2]
VC = VL - √ [VT2 - VR2]
OK, pick up your pencils... now ...
Altum RF, a supplier of high-performance millimeter-wave
to digital semiconductor solutions for next generation markets and applications,
announces the opening of its Eindhoven, Netherlands office located on the campus
of Eindhoven University of Technology. "Opening
an office on this university campus gives us the strategic advantages of access
to top engineering talent and to leading-edge electrical engineering research and
development," stated Greg Baker, Altum RF CEO. "We work closely with electrical
engineering research groups and collaborate with other start-ups to develop ground-breaking
technology, so this location is ideal for our company. There is also an excellent
source of high-tech talent in this region, which is important for our expansion ..."
Back in 2012, I posted a video of the PBS
"Frontline" show (Cell Tower Deaths) that highlighted the dangers cell tower climber
technicians face while working for very low wages. Other news stories since then
have reported on new regulations from OSHA and other agencies that have helped make
the safety issue better, but I haven't seen anything on whether the pay has gotten
any better. There are lots of videos and photos online of
all over the world, but this one showing tower climber Kevin Schmidt making the
ascension to the very top of the now inactive KDLT TV analog broadcast antenna near
Salem, SD, is unique in that the recording was made from a drone platform. It has
more than 12 million views. Capturing this kind of video requires a drone with a
wireless live feed so the pilot ...
This is pretty amazing: "A recent article
in The New York Times reported that many garage door openers and
keyless vehicle entry fobs in an Ohio town near
Cleveland mysteriously stopped working. While the article invoked The X-Files
and hinted initially that a NASA research center somehow could be involved, the
cause was not so much mystifying as arcane. 'Garage door repair people, local ham
radio enthusiasts, and other volunteer investigators descended on the neighborhood
with various meters,' the May 4 article by Heather Murphy recounted. 'Everyone agreed
that something powerful was interfering with the radio frequency that many fobs
rely on, but no one could identify the source ..."
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An alternate title for this article that
appeared in a 1969 issue of Radio-Electronics magazine could have been,
to Build a J-K Flip-Flop." Author Leonard Geisler takes the reader through a
step-by-step assembly of a functional J-K flip-flop using a collection of 1- 2-
and 3-input NAND gates. The 1-input NAND, in case you are wondering, is used as
an inverter. The piece reads like an in-depth first-semester electrical engineering
technician course textbook. In the process of building the J-K, an R-S (reset/set)
flip-flop is described. Nowhere does Geisler offer an explanation of from where
the "J" and the "K" input labels come. According to electrical engineer Sourav Bhattacharya
blog, it was Dr. Eldred Nelson of Hughes Aircraft who first coined the term J-K
Testing multi-antenna systems such as phased
array or beamforming antennas requires a test system capable of providing multiple
signals with constant phase relationships between them. The coherent test signals
must have a specific or definable phase difference (relative phase) and definable
amplitude. Some of the challenges for such a test system include compactness, phase
control capability and simplicity in handling. In particular, phase stability between
the channels is of importance. This
Generating Multiple Phase Coherent Signals–Aligned
in Phase and Time application note explains how to generate phase coherent signals.
It details what to consider and how to configure the test setup ...
This you need to see. The full story behind
this video is unknown, but supposedly customers were complaining about poor reception
associated with the Bear Creek Road microwave station somewhere in northern California.
Upon inspection, the technicians discovered a small hole in the radome. When the
cover was pulled away, according to the video somewhere between 35 to 50 gallons
of acorns spilled
out. You can see the bulge in the radome before emptying. The tech probably thought
the water drain hole was clogged and it was full of water. From a National Geographic
story: "Walter Koenig, a senior scientist with the Cornell Laboratory of Ornithology,
says he's pretty sure the the acorn woodpecker ..."
The term "ovonic" - a fairly unfamiliar word
these days - appeared in the May edition of Radio-Electronics, in an article
entitled, "All About Ovonics," just a few months after this news item ran in the
January issue (which I posted last month). Ovonics is a portmanteau of "Ovshinsky"
(from Stanford R. Ovshinsky, the inventor) and "electronics." Read the "All About
Ovonics" article for a deeper dive into the subject. The big deal, which turned
out to be not a big enough deal, was the use of
amorphous "glassy" compounds as semiconductors rather than the standard crystalline
silicon structures. Maybe someday an enterprising genius inventor type will give
a rebirth to the concept ...
"The Air Force said it successfully shot
missiles out of the sky with a ground-based laser system that it plans to make small
enough to fit on its aircraft. The Self-Protect High Energy Laser Demonstrator Advanced
Technology Demonstration Program, or
SHiELD , conducted the tests on April 23, an
Air Force Research Laboratory statement said Friday. 'The successful test is a big
step ahead for directed energy systems and protection against adversarial threats,'
said Maj. Gen. William Cooley, AFRL commander. 'The ability to shoot down missiles
with speed-of-light technology will enable air operation in denied environments.'
During the tests at White Sands Missile Range, N.M., the laser system engaged and
shot down multiple air-launched missiles in flight. It was not immediately clear
whether the laser ..."
One of the monthly columns in R/C Modeler
magazine, written by Chuck Cunningham, entitled "Cunningham on R/C," that reported
on the current state of radio control, which had only fairly recently evolved into
fully solid state, proportional control systems. Anyone involved in electronics
is painfully familiar with the weird kinds of issues that crop up in complex circuits
that operate in hostile environments. The March 1970 issue contained part of an
article authored by D. L. Klipstein, Director of Engineering, Measurement Control
Devices, entitled, "Murphy's Law: The Contributions of Edsel Murphy to
the Understanding of the Behaviour of Inanimate Objects.*" Only a few of the
items were printed in Cunningham's column, but I managed to locate ...