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 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...
|
 • 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
• Elecraft
Donates Radio Station to W1AW
 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.
 This "drive-by" schematic and parts list
for the
Admiral Model 7C64 vacuum tube console radio and phonograph appeared in the
February 1948 issue of Radio News magazine. I refer to it as "drive-by"
because there was no description or maintenance verbiage provided. You might not
expect from the relatively simple circuit that the entire Model 7C64 was mounted
in a multi-sectioned wooden cabinet that included a phonograph. The thumbnail at
the left is from the RadioMuseum.org website - a great source for research on vintage
vacuum tube radios. Admiral Radio is a brand of electronic products that was founded
in Chicago in 1924. The company started out as a manufacturer of phonographs and
radios. In 1971, Admiral Radio was acquired by Panasonic.
 Having spent a lot of my career working for
defense electronics companies in classified programs, I am somewhat torn between
sympathizing with Hugo Gernsback from his perspective as editor of Radio-Craft
and what I know is a valid reason for guarding certain
technological information for the sake of military advantage.
It is often the case that people who have had no exposure to the 'black' side of
industry cannot appreciate the need for it. Their argument postulates that suppressing
knowledge does more harm than good because an opportunity for more people to gain
from breakthroughs will result in more rapid advancement in technology While that
is true, the downside is that the enemy rarely feels obliged to reciprocate in the
same manner, and will exploit your generosity...
 While reading through this article on copper-oxide
rectifiers, I am once again reminded of how much we take for granted the conveniences
of electrical test equipment on today''s shop benches. The advent of FET-input multimeters
was a huge step forward because the meter input impedance is so high that it has
practically no impact on the circuit being measured. Prior to that, most simple
meters drew their power from the circuit under test, thereby altering the true value
of current or voltage being measured. Of course there were vacuum tube voltmeters
(VTVM) with high input impedances, but few hobbyists or laymen could afford them.
This piece reports on how the advent of a
non-tube-based rectifier permitted alternating current (AC) measurements to
be made by DC-driven d'Arsonval meter movements so as to not excessively load the
circuit being measured. Rectox meters had the rectification components...
 "The year 1950 will be recorded historically
as the year the microwave relay made its impact felt." That was the closing sentence
by Philco Sales Engineer Leo Sands in his 1950 Radio & Television News
magazine article entitled, "The
Microwave Era Begins." Mr. Sands was not suggesting that it was the start
of the widespread use of microwaves in general, but specifically the use of microwaves
for long distance, broadband transmission of telecommunications signals. 1950 is
about the time microwave relay stations began appearing on hilltops and rooftops
of tall buildings all across the land, with the goal of replacing coaxial lines
which needed to be strung or buried from end to end. Great cost is associated with
a hardline approach for acquisition of land rights, installation, and maintenance.
Yes, those kinds of expenses are required for microwave relay stations, too, but
in the long run they tend to be much lower, and the service much more reliable and
"upgradable." Lots of people opposed the installation of the unsightly, behemoth
towers, and many people expressed concern over exposure to microwave energy. If
only they knew then how miniscule their worries were compared to today's situation
with cell towers within eyeshot of just about ever locations on earth...
 A few months ago, one of America's big-city
mayors made the proclamation, "We're not going to make America great again. It was
never that great." There has been a big push in the last decade to not only erase
the
significant accomplishments and sacrifices of America's and Western Europe's
past, but to vilify those people and institutions that make up that past.
Purging the records and rewriting history is a tried and true method of assuring
few have easy access to archival material documenting the accomplishments of the
nation's past. Along with desiring to provide useful and interesting material to
people seeking technical and historical information, my motivation...
 Electronics magazines of the last century
regularly published theme-based crosswords, like this "Electronic
Terminology Crossword Puzzle" one from a 1960 edition of Electronics World.
Working crossword puzzles has been shown to be a simple activity that can help
prevent or at least stave off some forms of mental atrophy. It is a medical fact
that as you grow old and/or cease presenting yourself on a regular basis with
mental and physical challenges, your brain actually begins to lose gray matter
and synapse interconnections are lost. Working crossword puzzles is a healthy
mental exercise that helps increase your vocabulary and improve cognitive
skills. That is one reason I create my own weekly crossword puzzle for RF Cafe
visitors...
 "Say again." That phrase is heard often in
telephony conversations both wired and wireless. It was coined near the end of World
War II by Air Corpsman 2nd Lt. Byron A. Susan, as reported in the January
1945 edition of Radio Craft magazine. Lt. Susan was responsible for setting
standards for "radio
phraseology" to eliminate ambiguity between aviators and ground forces. "Say
again" replaced "Repeat" because the latter is an artillery term used to order another
round of assault from a gun salvo. The history of the confirmation "Roger"
is murky, but many agree it comes from the older military phonetic pronunciation
of the letter "R" being "Roger," and in radio the letter "R" meaning "received."
Another common bit of radio phraseology is "Wilco," which is a contraction of the
words "will comply."
 "A
record 'Moocher' is one of the lowest forms of human life. He has no particular
habitat but can be found wherever there is a record owner." So says Norman Van Tubergen
in this 1958 Popular Electronics magazine article. Anyone who grew up in
the record player era, or for that matter the 8-track tape or cassette tape era
has known (or has been) such a moocher. This is the person who was always asking
to borrow your music media either for listening to on his personal equipment or
for copying onto his own tape (cassette or reel-to-reel). He rarely ever bought
any of his own music, but was more than happy to generously re-lend his copies to
fellow Moochers, and of course he never had anything you might want. The modern-day
equivalent is the person who is always bugging you to let him/her copy your music
file that you either paid for as a download or purchased in CD/DVD format...
 Most aviation enthusiasts upon hearing the
name
Pan American "Clipper" thinks of the large four-engined amphibious airliner.
There were other models of the Clipper, however, including the Douglas DC-4, the
Lockheed Constellation, and the Boeing 377. The latter appear to be the early concept
model depicted in this 1945 Raytheon vacuum tubes promotion in Radio-Craft magazine.
Raytheon was a major supplier of electronic components, equipment, and systems for
the military and government throughout World War II. Manufacturers came to
trust and rely on the big-name companies for high quality and dependable components.
By the time this advertisement appeared, Germany had recently signed an unconditional
surrender, and Japan was only a few months away from total defeat. Sadly, many of
the familiar names from the era have either been acquired by foreign firms (and
usually renamed) or have gone out of business due to poor management decisions (usually
from failing to keep up with changing times)...
RF Cascade Workbook is the next phase in the evolution of RF Cafe's long-running
series, RF Cascade Workbook. Chances are you have never used a spreadsheet
quite like this (click
here for screen capture). It is a full-featured RF system cascade parameter
and frequency planner that includes filters and mixers for a mere $45. Built in
MS Excel, using RF Cascade Workbook is a cinch and the format
is entirely customizable. It is significantly easier and faster than using a multi-thousand
dollar simulator when a high level system analysis is all that is needed...
 That John T. Frye was a great short
story writer is evidenced by his decades-long production of the "Carl & Jerry"
series in Popular Electronics, and "Mac's Radio Service Shop" series in Radio &
Television News and Electronics-World magazines. Mr. Frye also wrote many other
short tech-oriented stories. It is easy to look over the fact that he also had artistic
skills as well as evidenced by the pencil drawings that accompanied each installment.
In this episode, our two teenaged electronics hobbyists build a resistor anemometer
to measure wind speed from within their basement workshop. In the usually storyline
style, one boy gives a lesson in circuit design while the other (also you, the reader)
is the attentive student...
 Hobbyists in the technical realm have in
many ways contributed mightily to the advancement of professional scientific knowledge
and practice. This is partly because many hobbyists are also career technologists,
but the majority are tinkerers, experimenters and otherwise participants who come
from all walks of life geographically, economically, professionally, and socially.
Just as with university and corporate laboratories, some of the discoveries are
the result of structured, preconceived plans of action and designs of experiments
with certain goals in mind; many, however, are due to serendipitous events that
are recognized by their participants as being significant. Such is the case of "TV
DX" as related in this story. TV DX is the use of unique opportunities in the
atmosphere's ionization state to facilitate signal transmission and reception at
distance much greater than normally experienced. Data collected by amateurs were,
during the era of over-the-air VHF and VHF television broadcasting, included in
studies and theories created by professional scientists and engineers...
 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...
 Although the details about types of electronics
schools, locations, specific career goals, funding sources, etc., are a bit different
today than they were in 1952 when this "Selecting
the Right Radio School" article appeared in Radio-Electronics magazine,
the advice offered for consideration is still applicable. You are investing a significant
amount of resources - financially and commitment-wise - so the prudent approach
is to do as much up-front research as possible to help assure you will not regret
your decision. Of course there is always the chance that at some point you'll opt
for a different career - it happens to a lot of people. One big difference these
days is there is probably a lot more in the way of financial assistance available
than back in the 1950s. One of the best ways then and now is to enlist in the military
and take advantage of the schoolroom training and on the job training (OJT), while
collecting a paycheck and having some of the best medical coverage available...
 Here is the first of a two-part article
on
frequency modulation (FM). FM was a very welcome option for entertainment radio
listeners who had grown weary of static mixed in with their music and syndicated
adventure, drama, and comic programs like The Green Hornet, Lights Out, and The
Life of Riley, respectively. Amplitude modulation (AM) is susceptible to all sorts
of interference from car ignition systems, arcing in electric motors, light switches
being turned on and off, lightning, and a host of other sources. A commercial radio
with good noise and adjacent channel rejection was relatively expensive. Permanent
magnet speakers did not become a standard feature for first few decades of radio
(see my 1941 vintage Crosley radio speaker for an example), so the speaker coils
themselves ended up carrying a lot of the same static biases that the sound signals
contained. Combine far-away transmitters because of wide spacing between broadcasting
facilities with poor receiver sensitivity and the opportunities for interference
was large. FM solved most of the problem both because it inherently was immune to
amplitude modulation from noise... |
