|
 This is Part II of a 3-part series of articles
on
magnetostriction devices. At audio and low IF frequencies, the
use of ferrite elements to construct relatively high-Q resonant circuits for filtering
was a big deal in the middle of the last century. Although not presented in this
article, design formulas and tables were published to implement the familiar Butterworth,
constant-k, Chebyshev, Gaussian, and other types. Tuning, particularly for higher
order filters, could be a chore since it involved a cut--and-try method on the ferrite
rods. However, that is what was available in the day, and it evidently worked well
enough to be worth the trouble for desired...
 Electronics World magazine often published
electronics-themed crossword puzzles. Unlike RF Cafe engineering crosswords
I created for two decades that use only technical words and clues, this one does
include some unrelated words. A couple clues I was surprised to see pertain to
radar; e.g., 32A: Small visible mark on a radar or scope screen, and
44A: Identification Friend or Foe. Some words require a familiarity with
technology of the era, but you shouldn't have much trouble. You'll need to print
this out on paper to work it..
 Advances in
transformer technology are driven by the need for miniaturization and efficiency,
particularly in airborne and high-frequency military equipment. By optimizing core
materials and fabrication, engineers can significantly reduce the weight and physical
dimensions of transformers. A major technical milestone highlighted in this 1964
Electronics World magazine article, was the development of grain-oriented silicon
steel, which, through precise crystal alignment, offers superior magnetic properties
and reduced energy losses compared to traditional soft iron. Modern design further
mitigates power loss from hysteresis and eddy currents by employing thin, insulated
laminations...
 It didn't take much in the early days of
radio to capture the curiosity of consumers with buzz phrases like a "Mystic Hand"
to keep the radio tuned properly - really just AFC control, and a "Phantom Conductor"
circuit that boosted the volume of high level audio (a nonlinear amplifier). Here
are 4 more Radio Service Data Sheets from Radio-Craft magazine.
Crosley Model 1316 Radio Service Data Sheet,
Westinghouse Model WR 207 & WR 208 5-Tube Dual-Band Superheterodyne
Radio Service Data Sheet,
RCA Victor "High-Fidelity Electrola," Model R-99 Radio Service
Data Sheet...
 Back in the days when I built a lot of prototype
electronic gear, project enclosures were generically referred as a "Bud
Box." Lab stock rooms always had a good variety of sizes and configurations
of the soft aluminum and sometimes plastic boxes that were easily drilled, punched,
filed, and painted to make professional looking equipment. Not all the project boxes
were made by Bud Industries, but just as everyone knows you're talking about
a cola when you say "Coke," it was understood that a "Bud Box" was a chassis for
a home-brewed circuit. They are still seen in construction articles of electronics
hobby magazines today. I have even seen test equipment and utility items for sale
that are obviously in a Bud Box type of chassis. This full-page advertisement for
Bud Radio appeared in a 1930 issue of Radio Craft magazine - a mere two years after
opening their doors...
 This week's crossword puzzle sports a radar
and radio theme. All RF Cafe crossword puzzles are custom made by me, Kirt Blattenberger,
and have only words and clues related to RF, microwave, and mm-wave engineering,
optics, mathematics, chemistry, physics, and other technical subjects. As always,
this crossword contains no names of politicians, mountain ranges, exotic foods or
plants, movie stars, or anything of the sort unless it/he/she is related to this
puzzle's technology theme...
 The
traveling-wave tube (TWT), invented by Dr. Rudolph Kompfner during World War
II, revolutionized microwave amplification by providing exceptional bandwidth without
the limitations of traditional resonant cavities. By utilizing an electron gun,
a precision-wound helix, and a magnetic focusing circuit, the TWT transfers energy
from an electron beam to a propagating signal wave. This design enables high-gain,
low-noise performance essential for radar, missile guidance, and high-capacity telecommunications
systems like the TH radio-relay. Although early production faced challenges regarding
reliability and manufacturing complexity, ongoing engineering refinements achieved
the stability necessary for critical applications, including the Telstar communications
satellite...
 Authors Cohen and Hessinger warn about the
need to consider the capacitive loading effects of shielded and closely-space test
leads when measuring other than direct current or very low audio or line frequencies.
Lead capacitance is especially likely to affect measured values
when the frequency is high and/or the source and load impedances are high. As was
common in the day, capacitance units of μμfd (micro-micro
farads = 10-6 x 10-6 = 10-12 F) are cited,
which is equivalent to units of pF (10-12 F)...
 An old electrician's saying goes "Ground is ground the world around," implying that every point
on Earth's surface is at the same potential - specifically 0 volts. We know, of
course, that it is not so. Maybe on average such a claim could be made, but just
as "sea level" is not the same at all points on the ocean's surface (hence we speak
of "mean sea level"), neither is the voltage potential the same everywhere. Further,
just as the salinity of all points on the ocean surface do not have the same salinity
(and thereby conductivity), the conductivity of various places on dry land vary
- often significantly. Electric power systems are very concerned with soil electrical
conductivity in the vicinity of power generation installations...
 Byron Goodman published a very thorough
diode
modulator article in a 1953 issue of QST magazine. It was one of the
first of such articles that used the very recently available semiconductor diodes
rather than the previously used vacuum tubes. Single-balanced bridge and ring modulator
circuits are presented, along with the theory behind their operation. It would be
a few years more before double balanced mixers with their abilities to reject even
intermodulation products, and triple balanced mixers with very high overall spurious
product rejection, would become commonplace...
 Back in the 1960s, Electronics Illustrated
magazine ran a series of monthly Q&A columns titled "Electronic
Brain," where readers wrote in to query the staff on particular quandaries.
Even if you have been in the electronics game for decades, there were plenty of
questions that probably invoked the "I'm sure I could have answered that at some
point, but it's been so long that I couldn't say for sure," thought. The magnetomotive
force topic in this set of three items did it for me. I knew there was a magnetic
flux equivalent of electric current flow, but I probably would not have been able
to write the equation using the precise...
 We are accustomed these days with stores
having "no questions asked" return policies for just about anything. I once watched
a guy successfully return a 4" PVC plumbing fitting that had clearly been smeared
with glue in the coupling areas. Another time a guy returned a painting drop cloth
that was full of paint, declaring that it wasn't what he wanted. The return counter
bins of Walmart and other stores are always chock full of stuff. Such was not always
the case, though. This episode of
Mac's Radio Service Shop, mentions, among other thing, how busy
he and sidekick Barney had been right after Christmas doing troubleshooting and
repair on various electronic equipment that had been received as gifts. Imagine
receiving...
 San Francisco Circuits, a leading printed
circuit board fabrication and assembly supplier serving commercial and defense markets,
today announced that it has achieved Final
Cybersecurity Maturity Model Certification (CMMC) Level 2 Certification
status following a successful independent assessment by an accredited Certified
Third-Party Assessment Organization (C3PAO). San Francisco Circuits Achieves CMMC
Level 2 Certification The certification confirms that San Francisco Circuits'
enterprise information systems meet the cybersecurity requirements outlined in NIST
SP 800-171 Revision 2, as codified in 32 CFR Part 170, for the protection
of Controlled Unclassified Information (CUI)...
 Could this be the world's first publically
documented rack-mounted AC power strip? The
National Company
of Cambridge, Massachusetts, which began life as the National Toy Company, ran a
long series of advertisements in QST and other electronics magazines that
were heavy on text and light on pictures - definitely not the norm in advertising.
This one, number 62, from a 1939 issue describes, along with a reference frequency
oscillator, how their engineering team fabricated what we now call an AC power strip
for use in an equipment rack. According to the sketch provided, there does not appear
to be an On/Off switch and almost certainly not any form of surge protection as
is common (maybe even required by UL) for modern power strips. Someone at National
should have patented the idea; their heirs would be rich today...
 Presenting yourself or your company as being
modeled after a person of great accomplishment has been a common promotional tactic
for as long as there has been print media. The John Hancock chose in this issue
of The Saturday Evening Post to suggest, albeit by an indirect approach,
to elicit the admiration Americans had for
Thomas Edison's lust for innovation and desire to make people's
lives better in hopes that readers would associate Edison with the insurance company.
While the juxtaposition is strained, I do like one line in particular, "He lured
electricity into a bottle and taught it to glow with good cheer." This short tribute
to on of the world's greatest engineers is worth your a few moments of your valuable
time...
Authors Cohen and Hessinger warn about the
need to consider the capacitive loading effects of shielded and closely-space test
leads when measuring other than direct current or very low audio or line frequencies.
Lead capacitance is especially likely to affect measured values
when the frequency is high and/or the source and load impedances are high. As was
common in the day, capacitance units of μμfd (micro-micro farads = 10-6
x 10-6 = 10-12 F) are cited, which is equivalent to units
of pF (10-12 F)...
 Welcome to the
RF Filter Quiz, an
essential tool for radio enthusiasts and engineers dedicated to mastering frequency
selectivity in complex signal chains. Whether you are troubleshooting signal interference,
optimizing stopband rejection for a sensitive receiver, or designing your own ladder
networks, a thorough understanding of passive and active filter synthesis is vital
for achieving peak performance. This assessment tests your knowledge across ten
fundamental concepts, including the practical trade-offs between Butterworth, Chebyshev,
and Elliptic topologies, the impact of finite component Q-factors, and the critical
relationship between group delay and passband ripple. By evaluating your grasp of
these core principles...
 Author Howard Wright takes the opportunity
here to distill the
concept of modulation down to its basic operation while dispensing
with the garbled mix of "graphs, formulas, charts, vectors, diagrams, and Greek
letters which often enter into various discussions of modulation". Wright describes
how to the uninitiated radio dial spinner, the culmination of events occurring behind
the scenes in an AM reception is akin to knowing "that, to be reproduced, the picture
[in a magazine] was broken down into its primary colors, if all we had to go by
was the original print and the magazine?" That is a very apt comparison...
 Here is a fairly major treatise on
folded and loaded antennas that appeared in a 1953 issue of
QST magazine, with "Suggestions for Mobile and Restricted-Space Radiators."
It is not for the faint of heart or anyone with mathphobia. Integral calculus is
part of the presentation, although an understanding of calculus is not required
to get the gist of the article. Equations for calculating the antenna configuration
radiation resistances are given for the 3λ/4-wave folded dipole, the λ/8-wave
folded monopole, the bottom-, center- and top-loaded λ/8-wave monopole, the bottom-loaded
λ/16-wave monopole, and the λ/4-wave monopole folded twice, to name...
 Kite- and balloon-lifted antennas are very
popular in the amateur radio realm. They are primarily used for short-term activity
such as during a contest or during an emergency; however, some operators use them
on a more extended basis. A really good series of articles on the use of balloons
and kites for suspending antennas can be found
here. Equations
for calculating necessary balloon and kite sizes and predicting wind effects are
included along with lists of "Dos" and "Don'ts." This is not a new phenomenon. A
1940 edition of QST magazine described how to employ weather and sounding
balloons to provide needed antenna configurations...
 New:
Frequency Planner. RF Cafe's spreadsheet-based engineering
and science calculator,
Espresso
Engineering Workbook™, is a collection of electrical engineering and physics
calculators for commonly needed design and problem solving work. The filter calculators
do not just amplitude, but also phase and group delay (hard to get outside of a
big $$$ simulator). It is an excellent tool for engineers, technicians, hobbyists,
and students. Equally excellent is that Espresso Engineering Workbook™ is provided
at no cost, compliments of my generous sponsors. 50 worksheets to date...
 Take a quick break before - or while - hunkering
down for a long day's grueling work. Most of the
electronics-themed comics that appeared in QST magazine
were associated directly with particular columns. For example, the cartoons featuring
"Jeeves," the overtaxed manservant of a never-seen house master, was part of the
"How's DX" feature. Drawn by artist Phil Glidersleeve (aka "Gil"), W1CJD, poor Jeeves
was often found doing his boss's will in the most precarious situation with intemperate
weather making his assignments tough to complete. Situations involving Podunk Hollow
Radio Club were frequent subjects of Gil's drawing pen as well...
 Somebody get Al Gore on the phone - preferably
using Skype. It appears that maybe he did not invent the Internet after all. Sci-fi
writer William F. Jenkins, who went by the pen name "Murray Leinster," wrote
a short story entitled A
Logic Named Joe, that appeared in March 1946 issue of Astounding Science Fiction.
In the story, an amazingly prescient description of the modern Internet is laid
out. The works is copyrighted so I will not replicate the entire thing here, but
these are a few excerpts that sound a lot like Mr. Leinster was in cahoots with
DARPA during the development*. Before I forget, thanks to RF Cafe visitor Terry
W. for sending the link. My comments look like...
 "Do you think that F.C.C. would be engaged
in the present terrific expense and effort of getting our fingerprints and citizenship
histories if there were intention of shutting us down shortly?" That statement was
printed by the QST magazine editor in the issue that preceded the December
7, 1941, attack on Pearl Harbor by thirteen months. A few things about it are troubling.
First, the FCC was
collecting fingerprints of licensed amateur radio operators. Second,
the FCC was assimilating information about licensed amateur radio operators' citizenship
histories. Third, a combination of short-sightedness and apparent naiveté concerning
the FCC's willingness to shut down amateur radio operations once...
|
 • Apple-Intel Foundry Could
Reshape U.S. Chip Manufacturing
• China Loses Monopoly over
Rarest of Rare Earths
• Samsung
Memory Chip Worker Union Strike Averted
• AI
Glasses Shipments Grow 322% in 2025
• ChatGPT
Solves Elusive Geometry Proof
 The
RF Cafe Homepage Archive
is a comprehensive collection of every item appearing daily on this website since
2008 - and many from earlier years. Many thousands of pages of unique content have
been added since then.
 When the electronics product world consisted
of vacuum tube based circuits, the physical sizes of standard fixed-value passive
resistors, inductors, and capacitors were not of much concern in terms of
how much volume they consumed. R's, L's, and C's, had wire leads protruding from
their molded bodies, or in the case of larger power supply filtering capacitors
had solderable tabs. Point-to-point wiring consisted of components and hookup
wire suspended in the air between solder terminal strips and tube base tabs.
Even with miniature (peanut) tubes, all but the largest passives had no
significant impact on overall unit size. Once semiconductors came onto the
scene, everything changed. Suddenly, even the standard 1/4 W carbon resistor and
tantalum capacitor became a significant factor when attempting to reduce size...
 This photo of
Ray Dolby holding one of his prototype noise reduction circuits is probably
the most widely published of him and therefore the most iconic of the Dolby noise
reduction system. Audiophiles of the era (and today for that matter) immediately
recognize the man who took the hisses and pops out of their beloved music. I always
like to keep in mind when reading article like this one in a 1971 issue of Radio-Electronics
magazine is that when it was originally published, Dolby had not yet become a household
word and news of his accomplishment was just getting out. Many articles, books,
and research papers have been written on how the Dolby system works. At least five
of them from the groundbreaking era have been posted here on RF Cafe, so you can
get some insight into the excitement. The technical term "companding"
(compressing and expanding) was being seen in print for the first time...
 Here is another electronics
challenge for you to try - the "Resistor
Function Quiz." It covers basic functions of resistors in various circuits. The
quiz appeared in the January 1962 edition of Popular Electronics
magazine, compliments of
Robert P. Balin. I got 100%, just for the record - PhD not required, by the
way. Having worked with tubes in the days of yore helps with figure B since it does
not really have a direct transistor equivalent, but by process of elimination you
can get it...
 Since 2000, I have been creating custom
technology-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 village in the Andes mountains...
 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...
 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
as follows: VTotal = √ [(VL - VC)2
+ VR2]
VR = √ [(VT)2 - (VL - VC)2]
VL = VC + √ [VT2 - VR2]
VC = VL - √ [VT2 - VR2]
OK, pick up your pencils... now...
 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
tower climbers
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...
 An alternate title for this article that
appeared in a 1969 issue of Radio-Electronics magazine could have been,
"How
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 flip-flop...
 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...
 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 a copy of the
full article...
 This is a story with a lesson learned by
the author and thousands of others ever since electric power appliances and tools
first became available. Fortunately, his Ham buddy was not permanently harmed, but
even today with all the effort put into educating the public, people continue to
use ungrounded (2-wire type, or with the ground prong removed) extension cords in
conjunction with 3-wire power cords on tools and end up
electrocuting
themselves (or somebody else). I've told the story before about a friend of mine
from high school who shortly after graduation was making a piece of furniture in
a garage that had a damp dirt floor, and was electrocuted to death by the
metal-framed circular saw that had no ground connected. Nowadays we often have
power provided by a GFCI receptacle...
 "Rediscovery
of FM Broadcasting" could be a contemporary headline. The decline of
broadcast radio has been a major concern of station owners for well over a
decade since Internet and satellite radio has dominated the venue through which
listeners access radio stations. Local broadcasters have long aired syndicated
programs that include national advertising, but the money to pay for those
segments came from revenue supplied largely by local companies. FM broadcasting
began commercially around 1945 in the familiar 88-108 MHz band yielded by the
military following World War II, and grew in number of stations very rapidly in
the first few years. Then, it began a decline for a few more years until finally
leveling off after about a decade. Even though FM had a clear advantage
(literally) over AM because of electrical noise immunity...
 My daughter, Sally, in addition to owning
and operating a very successful horse riding school named Equine Kingdom Riding
Academy, has a rather large eBay store she uses as a venue for selling items purchased
at the local Goodwill "Bins" store. She often buys vintage toys with electronics
features - sometimes working and sometimes not. A properly functioning vintage toy,
be it a stuffed animal or a game of some sort, can make a huge difference in the
resale price. When that is the case, she sends them home with me to attempt a repair.
Many times the problem is corroded contacts from leaky batteries. A dental pick
and some isopropyl alcohol usually solves the problem. When that doesn't work, it's
time to open 'er up for a deeper look. Over the years I have found problems
ranging...
 All college curricula seem to have a number
of particular "weeding out" courses that cull the herd - so to speak - from the
eventual graduating class. The unfortunate victims are then faced with either dropping
out of college (not always such a dooming fate) or choosing a different major. For
mechanical engineers (MEs) it was often statics; for electrical engineers (EEs)
it was
AC circuits - the topic of this article. DC is relatively simple because
voltage and current is always in phase, thus no "hard" vector math is involved,
but throw in reactance with its attendant non-zero phase angles and suddenly the
student is faced with trigonometry - the kiss of death to mathphobes. My experience
in engineering school showed that for MEs who lived through statics, dynamics provided
the next level of weeding out (it nearly got me). For EEs it was Fourier and Laplace
transforms. Level three for MEs was thermodynamics (thermogodda**ics was a
popular alternate title)... |
