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 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...
 My introduction to a
tesseract was during an episode of Carl Sagan's "Cosmos" series
in the 1980s, where he was demonstrating how beings in of dimension N would perceive
items of dimension N+1. The tesseract, Sagan explained, is a 3-dimensional projection
of 4-dimension hypercube. Watch the embedded video for more information. The Tesseract
website, which has nothing to do with a hypercube as far as I can tell, deals in
some very cool antique scientific instruments. I learned of it from an article in
Astronomy magazine where an editor recommended it when researching the potential
value of a collectible telescope. Run by Drs. David and Yola Coffeen, Tesseract
has a huge inventory of items...
 It is always nice to read an article that
encompasses more than one of my hobbies, whether it be amateur radio and amateur
astronomy like this one, amateur radio and model rocketry, or amateur radio and
radio controlled airplanes. I don't recall ever seeing an article that combined
astronomy and model airplanes. In this 1943 QST magazine piece, author
Hollis French expounds on the necessity for Hams to understand the effects that
atmospheric
phenomena, caused primarily by our sun's periodic and intermittent activity,
have on radio signal propagation. Properties of the ionospheric layers had by 1943
been pretty well surmised based on cause and effect relationships through indirect
observation since at the time no sounding rockets had been launched into the upper
atmosphere to obtain in situ measurements of ionization, magnetic fields, and free
electron activity...
 Maybe I suffer from cranial rectumitis at
the moment, but I'm having a hard time with a statement made about coaxial feedline
impedance, to wit, "102-ohm line (52-ohm lines in series)." I must be missing something
because I don't understand how placing two 52-ohm transmission cables in series
results in twice the impedance. Aside from that, author John Avery presents an interesting
article on multi-impedance dipole antennas. Empirical data is presented on
how the feedpoint impedance of a dipole varies with distance above the ground. His
results are very close to theoretical values which assumes non-sagging elements,
perfectly linear alignment, a perfectly conductive ground, etc. He then extended
his investigation into 2-wire (4x impedance)...
 How well received do you think this social
concept would be in today's easily offended world: "To bring together socially the
Wives and Mothers of Dallas Radio Amateurs; to promote mutual
sympathy, counsel, and interest in our husband's and our son's hobby; and with a
realization that theirs is an outstanding, fascinating, far-reaching and educational
hobby, it is our desire to further their interests in whatever way may present itself."
It would be roundly criticized as a backward, misogynistic, 1930-era mindset intended
to subject women to yet another form of domestic slavery beyond housekeeping and
child rearing - no doubt thought up by a man. Anyone thinking so...
 This article reports on the very earliest
form of
voice mail - recording a message on a reel-to-reel tape deck,
placing it in an envelope, and snail mailing it to its recipient. Sure, it was slow,
but unless you were under surveillance for some suspected crime, there was just
about zero chance that some government agency was going to hear your private message.
I had forgotten about it until reading this, but I remember that back in the 1960s,
my father bought an el cheapo tape deck for our family and one for his parents,
who lived in Buffalo, New York. My parents and four sisters and I had a pretty good
time hamming it up on the tape, and looked forward to receiving a reply tape a month
or two later. "Grandpa B," as we kids called him, was a real funny guy...
 Welcome to the
RF Attenuator Quiz,
a technical resource specifically designed for engineers and radio hobbyists who
demand precision in their signal chain analysis. Whether you are troubleshooting
high-frequency systems, optimizing cascaded RF stages for improved impedance matching,
or developing custom measurement tools like RF Cascade Workbook, a thorough understanding
of passive attenuation is essential for maintaining signal integrity. This assessment
challenges your knowledge across ten critical areas, including power handling limits,
thermal derating, noise figure degradation, and the strategic use of attenuators
to enhance system IP3...
 If anything qualifies for meeting the criteria
of the old adage that says "Necessity is the mother of invention," it is
coaxial transmission cable. Wireless communications during World
War II was the necessity that drove the rapid development and continuous improvement
of coax. Other than materials technology for wire, dielectric, protective jacket,
etc., the basics of coax cable have not changed. It was during the war that polyethylene
was developed and adopted as a dielectric material much superior to previously used
copolene. Understanding of how electromagnetic fields propagate within and, under
non-ideal conditions - on the outside of the cable has increased significantly...
 If you are just starting out in the realm
of electronics or maybe just need a little freshening up of your
basic
math skills, this rather extensive article from a 1942 issue of QST
magazine is just what you need. Author Dawkins Espy does a really nice job of laying
out the basics of algebraic operations, Ohm's law, trigonometry, and logarithms.
Examples are provided for each category. In this day of calculators doing all the
hard work of calculating logs, antilogs, and trig functions, it does even seasoned
veterans at electronics calculations a bit of good to do a quick read-through to
knock off cobwebs in the gray matter. How long has it been since you have seen tables
of sine, cosine, and tangent values and/or tables of logarithms? Not long enough,
you say?
 Astronomers consider all elements heavier
than helium to be metals. That definition obviously does not jive with the standard
chemical definition of a metal as an element that readily conducts electricity,
but a concept called "metallicity"
argues that from a star (and therefore the universe) formation perspective, extremely
high temperatures and pressures in first generation stars (like our sun) preclude
the identification of distinct elements other than hydrogen and helium. Heavier
elements, such as lithium (#3 on the periodic chart and a major component in LiIon
batteries, is classified as a metal in chemistry) are overwhelmingly created after
a massive enough hydrogen star collapses and begins fusing H and He into heavier
elements. The relative abundance of hydrogen in the universe is deemed to be about
92%, and helium is 7.1%, so together they comprise about 99% of all elements...
|
 • AI
Glasses Shipments Grow 322% in 2025
• ChatGPT
Solves Elusive Geometry Proof
• Elecraft
Donates Radio Station to W1AW
• FCC Accelerates
Access to High-Speed Networks
• Low Power
360 Gbps Laser Wi-Fi
 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.
 The
evolution of communications has been well documented both after
the fact and necessarily before the fact based on the vision and determination of
individuals and corporations. From grunts, hand and facial signals, and crude sketchings
on cave walls to spoken and written languages. From couriers on foot and horseback,
smoke signals, and light signals to wired telegraph and telephone. From wireless
telegraph and telephone to television and the Internet, advancement has been continual
both in large steps between the aforementioned fundamental communications venues
to incremental advancements in technologies - analog to digital, vacuum tubes to
semiconductors, simplex to multiplex, ever increasing access to regions of the electromagnetic
spectrum from DC to light. This 1945 advertisement by RCA expounding the benefits
of its recently implemented transcontinental microwave relay system was life changing
at the time, but two decades later those tower networks would be supplemented and
nearly replaced by satellite relay...
 Magnetic tape was the recording medium de
rigueur for more than half a century, after the era of wax and wire and before the
era of magnetic and optical disks. In fact, magnetic tape is still the storage medium
of choice when analog signals must be stored without first being digitized. Magnetic
data storage media each has its own characteristic lifetime because of factors like
the initial quality of the magnetic domains, the dimensional stability of the substrate,
and susceptibility to outside influences. Just as vinyl records and other vintage
technologies have been experiencing a comeback with both young and old alike, Kodak
recently announced it is ramping up in Rochester, NY, for higher production volumes
of its 35 mm film due to increasing demand. I wonder if home film processing
equipment is resurging, too...
 RF Cafe visitor Dave H. wrote to offer the
following additional information about the
history of mobile radio communications. It is fairly extensive, so it is posted
at the bottom of the page. "I liked the article about Don Wallace and his car to
home radio. I knew that in Detroit, the police had attempted to have car to car
transmissions. They were not overly successful however. They did implement a station
to car, 1 way transmission. I discovered the facts about the Detroit police radios
while researching a paper that I wrote entitled: 'SAW Filters : The Unsung Heroes
of the Cell Phone Revolution.' Did you know that that the phone developed by Martin
Cooper while at Motorola, circa 1973, had a filter board that measured 10 inches
by about 1 inch? That would be a tad hard to find..."
 Here are a few tech headlines from the January
1957 issue of Popular Electronics magazine. Sky-High Radar by Sikorsky
is a new high-powered
airborne search radar. The electronic Trial & Error Machine "differentiates
between right and wrong decisions and profits from its own mistakes," making it
the perfect gadget for today's environment where any freakish act gets rewarded
and eventually normalized. Lab Aloft Chases Cosmic Rays uses a UASF KC-97 Stratofreighter
for researching those mysterious and ubiquitous high energy entities which perpetually
bombard our Earthly existence. This Brain That Squirts reports on Bendix's prototype
carburetor that uses an electronically controlled "electrojector" to inject fuel
directly into the cylinder. Now, all of our internal combustion vehicles contain
an electrojector...
 Try as I did, I could not find any instance
of the Ness Clocks all-digital liquid crystal display (LCD) desktop clock which
appeared in this 1973 Popular Electronics article. There must not have
been many produced. LCDs had only been commercially available for a year or so when
this went on sale. Of the relatively few digital display clocks and watches available
in the 1970s, the vast majority used light-emitting diodes (LEDs), and most sold
for north of $100 (~$600 in today's money). Portable devices with digital displays
really began to flourish with the advent of both
CMOS circuitry and LCD displays; i.e., low current devices that extended battery
life. Wrist watches, which could only accommodate very small batteries with limited
energy storage capacity, were amongst the greatest beneficiary...
 Little did Ham radio operators know in April
of 1941 when they were enthusiastically buying equipment for their shacks that a
year later the Federal Communications Commission (FCC) would ban them from broadcasting
from their transmitters. This advertisement for a high-end Hallicrafters receiver
appeared in the April issue of Radio News magazine. Part of the feature
definition includes "calibrated bandspread
inertia controlled," and "micrometer scale tuning inertia controlled." I'm not
sure what the "inertia controlled" part is, unless it refers to how massive metal
disks were sometimes installed inside the chassis on the tuning shaft in order to
give a more solid feel to the control knob, as well as to enable the dial to be
spun and released to rapidly move through a large distance between adjustment points...
 This
Electronic Oscillator Theme crossword puzzle for September 19th, 2021, contains
only words and clues related to engineering, mathematics, chemistry, physics, and
other technical words. 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 (e.g., Hedy Lamarr or the
Bikini Atoll). The technically inclined cruciverbalists amongst us will appreciate
the effort. Enjoy!
 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...
 Old sci-fi movies were famous for displaying
Lissajous patterns on oscilloscopes in hopes of portraying a futuristic look.
The first time I hooked up signals to the x and y axes of a scope and played around
with the frequencies and amplitudes, I was mesmerized by the patterns and the fact
that it was me creating them. Of course that was 30-something years ago when I was
first getting into electronics and electricity, but even today it's a cool thing
to do. In a typical, male-dominated, Chauvinistic manner, this article from the
March 1957 edition of Popular Electronics magazine delves into the subject
of Lissajous patterns. The author dares to compares men's attraction to curvaceous
o-scope figures to a similar attraction to curvaceous women. Can you imagine the
hateful feedback the editor of a current magazine would receive if something like
this slipped...
 The newest release of RF Cafe's spreadsheet
(Excel) based engineering and science calculator is now available -
Espresso Engineering Workbook™. Among other additions, it now has a Butterworth
Bandpass Calculator, and a Highpass Filter Calculator that does not just gain, but
also phase and group delay! Since 2002,
the original Calculator Workbook has been available as a free download.
Continuing the tradition, RF Cafe Espresso Engineering Workbook™ is
also provided at no cost,
compliments of my generous sponsors. The original calculators are included, but
with a vastly expanded and improved user interface. Error-trapped user input cells
help prevent entry of invalid values. An extensive use of Visual Basic for Applications
(VBA) functions now do most of the heavy lifting with calculations, and facilitates
a wide user-selectable choice of units for voltage, frequency, speed, temperature,
power, wavelength, weight, etc. In fact, a full page of units conversion calculators
is included. A particularly handy feature is the ability to specify the the number
of significant digits to display. Drop-down menus are provided for convenience...
 National Radio Institute (NRI) was founded
in 1914 at the dawn of the radio age. It provided self-study courses as well as
classroom instruction on the art of electronics and radio communications. A bi-monthly
magazine entitled National Radio News was published by them from 1929-1953.
This article explaining how oscillators work appeared in the December 1940 edition.
Although circuits of the day used vacuum tubes, the principle of voltage and phase
relationships required to initiate and sustain oscillations are the same as for
transistor circuits. A step-by-step description is provided from the time the power
is applied until
stable oscillations are established. More is known nowadays regarding actions
at the atomic level regarding how oscillations begin, but the fundamental principles
are the same...
 This is the
RF Cafe electronics theme crossword puzzle is for December 31st. Hard to
believe it is the final crossword for 2023! This being the 31st day of the month,
many of the words begin and/or end with the letter "E." Since there are only 26
letters in the alphabet, I use the modulo function to derive the letter to use;
i.e., 31 mod 26 = 5. Clues for words containing "E" are marked with an asterisk
(*). Related clues are marked with an asterisk (*). 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 (e.g., Reginald Denny, Hedy
Lamarr, or the Tunguska event in Siberia). The technically inclined cruciverbalists
amongst us will appreciate the effort. Enjoy!
 With more than 1000
custom-built stencils, this has got to be the most comprehensive set of
Visio Stencils
available for RF, analog, and digital system and schematic drawings! Every stencil
symbol has been built to fit proportionally on the included A-, B-, and C-size drawing
page templates (or use your own page if preferred). Components are provided for
system block diagrams, conceptual drawings, schematics, test equipment, racks, and
more. Page templates are provided with a preset scale (changeable) for a good presentation
that can incorporate all provided symbols...
With more than 1000
custom-built stencils, this has got to be the most comprehensive set of
Visio Stencils
available for RF, analog, and digital system and schematic drawings! Every stencil
symbol has been built to fit proportionally on the included A-, B-, and C-size drawing
page templates (or use your own page if preferred). Components are provided for
system block diagrams, conceptual drawings, schematics, test equipment, racks, and
more. Page templates are provided with a preset scale (changeable) for a good presentation
that can incorporate all provided symbols...
 That's hot dog, not hotdog. In this third
installment in the adventures of John T. Frye's much-anticipated monthly exploits
of teenage electronics investigators
Carl Anderson and Jerry Bishop. In this December 1954 issue of Popular Electronics
magazine, pet mutt Bosco has developed a case of hot paw pads. Using a makeshift
Geiger counter and a homemade radio homing device, the two boys set out to discover
the source of Bosco's warmth. A buried, as-yet undiscovered lode of uranium is high
on their suspect list, and visions of untold wealth dance through their heads. Read
on to find out what they found out... |
