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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...
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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.
 I recently was made aware that all four
"h- from T-Parameters"
conversion equations had errors. Also, Z22-from-T had a sign error. They have all
been corrected (marked with †). Thanks to Louis J. for bringing this to my
attention, and for graciously providing the new equations! He generated a Mathcad
worksheet for converting back and forth between all parameter sets. Says Louis,
"[There] is a bug in Frickey's document and you are unlikely to be able to do anything
about it. The h-Parameters from T-Parameters equation set fail to close the loop.
All four equations have an error that is in the same direction and of roughly the
same magnitude as measured in percentage. I suspect a problem with the denominator
value. I verified this assumption by adding in an offset (complex) into the denominator
and found all values fell into place. Without this offset, these simply refused
to 'close the loop' or match the results from other tools. I am far from a mathematician,
so I tend to rely on Mathcad to do my algebra, trig and calculus. I started with
the working T from h parameter equation set. It handled this matrix equation system
fairly easily..."
 As a life-long aircraft enthusiast, my attention
is always drawn to photos, drawings, and titles in articles dealing with any aspect
- but particularly a historical aspect - of aviation. This 1937 edition of Radio-Craft
magazine reported on the fledgling field of aircraft radio maintenance, and in particular
the opportunities presented to radio repairmen.
Aircraft electronics (aka avionics) have of course changed significantly over
the last 80 years. Accordingly, maintenance has become such a highly specialized
skill that other than swapping out entire pieces of equipment, relatively few facilities
exist that are qualified for the task. According to the article, at the time there
were a mere 5k privately owned airplanes. As of 2019, the AOPA estimated a total
of around 220k private aircraft (down from 224k in 2011), with 720k currently licensed
pilots (all categories) per the FAA...
 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...
 Is there such as thing as too many articles
on
transmission lines? I think not, at least for most visitors to RF Cafe. Since
the fundamentals of transmission lines have not changed in the last century, it
really doesn't matter when an article was written. This one covers the basics of
impedance and wavelength, and then delves briefly into the subjects of antenna feeder
transmission lines and using transmission lines as impedance transformers. As with
most topics these days, there are many software programs available that will calculate
parameters for you, but successful setup and operation requires a solid understanding
of what is happening with your electronic gear, antennas, and the transmission lines
that provide the interfaces...
 This vintage
Heathkit IM-2400, 512 MHz Handheld Frequency Counter kit is one the latest
unbuilt Heathkit kits which appeared on eBay. I have been saving the images in order
to preserve the history. The constantly growing list is at the lower right. The
first instance I could find for IM-2400 being offered for sale was in the Winter
1981 Heathkit catalog, at a cost of $139.95 ($429.59 in 2021 money per the BLS)
as a kit or $179.95($552.37 in 2021) assembled and tested. A comparable handheld
frequency counter today is the TTi PFM3000 3 GHz Hand-Held Counter, at a cost
just south of $200...
 When reading technical articles, I very often
see the authors incorrectly refer to a certain point on a curve as being the
inflection point.
It is not merely a point at which a curve changes direction. That was the case in
an article I read today that dealt with open-loop polar modulation in EDGE amplifiers.
There exists an unambiguous definition of an inflection point, and all engineers
were taught it in school. Pardon me if this seems trivial or picayune, but the purpose
of the magazine articles is to teach, so if this factoid can eliminate the misconception
in future articles, then it will have accomplished its objective. Here is a brief
review of what an inflection point is, and, equally important, what an inflection
point is not. An inflection point is the point at which the second derivative of
a continuous curve equals zero. Accordingly, it is the point where a curve changes
from concave up to concave down. A curved region is concave up if all the data points
in that region lie above a line tangent to it (in the positive-going y-axis direction).
A curved region is concave down if all the data points in that region lie below
a line tangent to it (in the negative-going y-axis direction). The Excel plot that
accompanies this article illustrates all of these concepts...
 A regular feature in the ARRL's magazine
QST during the early days of radio was "New Receiving Tubes." It usually
had your standard editorial listing of products, but the May 1941 installment included
a comic commissioned my the
Magnolia Radio Lab people that is done in the manner of Ripley's Believe It
or Not. I'm guessing that there really is no Magnolia Radio Lab because nothing
came up on a fairly extensive Internet search for the company. Most good humor has
an element of truth in it that makes the subject matter believable - almost. These
three comics meet that criterion. "Gil - W1CJD" (aka Philip "Gil" Gildersleeve)
was the artist...
 Unlike the Roll Your Own Foil Capacitors
article in the same issue of Popular Electronics magazine, this one advising
how to reactivate leaky capacitors might be of use to a lot more people. The process
is called "reforming," and consists of applying a DC voltage to the faulty capacitor,
beginning at a very low voltage, and then slowly raising the voltage until the rated
working voltage (WVDC) is reached. Doing so, if the capacitor is not beyond rehabilitation,
will reconstitute the oxide layer that serves as the dielectric. This particular
item was presented as the answer to a question posed by a reader. A Google search
on "reform
capacitor" will turn up more detail about the procedure. Most people recommend
against reforming unless you have no other option, as this writer from India might
have faced at the time...
 When I first read the title for this article,
"A Look at the PC Market," I was thinking personal computers, not
printed circuits. It being from a 1972 issue of Popular Electronics, my assumption
was that the photos of circuit boards were from early kit format computers, but
then it finally dawned on me that there were no personal computers in 1972 - not
even in kit form. Actually, that is not entirely true since there were advertisements
for hokey contraptions called "computers" that combined some switches, logic gates,
and LEDs for implementing simple multiple choice true/false testing boxes or rudimentary
(with emphasis on "rud[e]") calculators. Getting to the real story, though, the
1970s was the decade where printed circuit boards (PCBs) were replacing point-to-point
wiring wherever possible. If you opened a radio or television...
 OK, class, put your books away and take out
a pencil. Spread your chairs out because we're going to have a short test today.
A collective sigh permeates the room. Remember those days? I still have nightmares
over those moments, and they were decades ago for me. At least this "Electronic
Noise Quiz" from the August 1962 edition of Popular Electronics
won't affect your GPA. Sometimes PE's quiz illustrations are kind of hard to
interpret, but this one does a pretty good job (except item 'E', but I'm not
telling what it is since nobody helped me). You will need a fairly diverse
background in consumer type electronics to do well, and having a few gray hairs
will probably help as well. Good luck. BTW, my score was a somewhat embarrassing
80%...
 Although not specifically stated, some of
the technology reported in this August 1945 issue of Radio-Craft magazine
was not so long before classified technology developed during World War II.
The
Radiotype system of wireless teletype developed by General Electric
was an early attempt to provide a mobile means of sending and receiving hard copy
messages. It was a rather complex scheme that used a typewriter to drive a tape
punching apparatus, which was fed into a radio transmitter to send coded tones (as
opposed to CW pulses) for a receiver to then decipher and drive an Electromatic
typewriter. The demonstration used a police car to carry remote equipment. In related
news, RCA's wireless 488 word-per-minute (wpm) telegraph multiplexer using time
division multiplexing (TDM) Also featured was the FCC's decision to move the commercial
broadcast FM band from 54-88 MHz up to 88-106 MHz (now up to 108 MHz...
 This
vector circuit matching quiz will hurt the brain a little more
than most of the ones that were printed in Popular Electronics. In order to
score well, it helps to visualize the circuits relative to where they would
appear on a Smith Chart. Capacitive impedances lie in the bottom half and have
negative phases (-s, -jω). Inductance lie in the upper half and have positive
phases (s, jω). The familiar 'ELI the ICE man' mnemonic helps, too. Be sure to
pay attention to the color of the vector arrow heads. Example: In a purely
inductive circuit like #4, voltage leads current by 90°. Since phase rotation is
CCW, you need to look for lettered phase diagram where the white arrowhead
(voltage) is 90° ahead of the black arrow head...
 Thanks to RF Cafe visitor / contributor
Michael M. for letting me know about an update to
CNES RF Propagation
Calculations DLL download hyperlink. In the four months since posting the information,
CNES moved the file. This very handy RF propagation software tool is provided free
of charge by the French organization Centre National d'Études Spatiales (CNES, National
Centre for Space Studies). The PROPAGATION dynamic link library (DLL) contains functions
to compute propagation losses according to ITU-R P. recommendations. Versions
are available for both 32- and 64-bit Windows and Linux operating systems, as well
as for the C and Visual Basic programming languages. Very conveniently, the DLL
functions can be referenced from within an Excel spreadsheet as well...
 Genius
takes on many forms, not the least of which is the ability to concoct and compose
an [almost] believable a story describing in the utmost detail the technical workings
of a complex mechanical gadget. Items such as a mizule wrench, meta-phasic shielding,
blinker fluid, a left-handed screwdriver, and - one of my favorites - the muffler
bearing, have been heard in comic routines... er... routinely. No matter how many
times you hear them you always laugh again. Some are actually a portmanteau and
just sound funny while others are completely made up. This
Digital Decabulator article that appeared in a 1966 issue of
R/C Modeler magazine is amazing; it pegs the B.S. detector from beginning
to end...
 This week's
wireless engineering-themed crossword puzzle, as is the case every
week, contains only words pertaining to science, engineering, amateur radio, physics,
mechanics, mathematics, etc. Making a special appearance is the name of the most
recent company to support RF Cafe through advertising. You will see their banner
graphical ad appearing in the right page border sometime this week ... |
