Here we are with another set of three "What's
Your EQ?" circuit challenges, these from the February 1962 issue of Radio-Electronics
magazine. As usual, those challenges provided by Jack Darr are the purview of television
servicemen of the era. The photo shown of the problematic CRT display looks like
a chest x-ray or maybe hieroglyphics in the dark corner of a cave, but evidently
the artifacts are readily identifiable to an initiated few. The Forbidden Current
Path circuit answer is not what I thought it would be. I maintain that whether my
answer or the designer's answer is correct depends on the physical...
"A new
world record
in wireless transmission, promising faster and more reliable wireless communications,
has been set by researchers from UCL. The team successfully sent data over the air
at a speed of 938 Gb/s over a record frequency range of 5–150 GHz. This speed
is up to 9,380 times faster than the best average 5G download speed in the UK, which
is currently 100 Mb/s or over. The total bandwidth of 145 GHz is more
than five times higher than the previous wireless transmission world record. Typically,
wireless networks transmit information using radio waves over a narrow range of
frequencies..."
Sputnik refers to the first series of satellites
launched by the Soviet Union. The word "Sputnik" means "satellite" in Russian. The
launch of Sputnik 1 on October 4, 1957, marked a monumental moment in human history,
heralding the dawn of the Space Age and sparking a fierce technological competition
known as the Space Race between the United States and the Soviet Union. This satellite,
the world's first artificial one, orbited Earth at an altitude of roughly 215 to
939 kilometers and broadcast a radio signal that astonished the world, particularly
in the United States, where it spurred rapid advancements in aerospace and scientific
research. The successful launch of Sputnik was an achievement that was years in
the making, involving a combination of visionary planning, political motives, and
intensive engineering by some of the Soviet Union's top scientists.
Blog: Air Quality Measurements with Particle Counters
Transcat | Axiom Test Equipment, an electronic test equipment rental and sales company has published a new blog post entitled "Provide Essential Air
Quality Measurements with These Particle Counters" that covers how particle
counters can provide essential measurement capabilities that can help avoid
contamination and support high manufacturing yields. These measurement tools can
detect and measure microscopic particles suspended in air that can contaminate
the most carefully planned manufacturing lines. Air particle counters can be
designed for various...
In 1958, most people were not accustomed
to seeing the now-familiar maps plotting
sinusoidal
courses of satellites across the face of the earth. It had only been in October
of the previous year that any object other than the moon was in orbit around our
home planet - that was U.S.S.R.'s Sputnik. Just as people of all ages and all backgrounds
enthusiastically joined in the newfangled phenomenon of aeroplanes after the Wright
Brothers flew their fragile craft at Kitty Hawk, electronics communications and
scientists worldwide hopped aboard the satellite train. This article from a 1958
issue of Radio & TV News magazine provided insight into the construction
and flight characteristics...
LadyBug Technologies was founded in 2004
by two microwave engineers with a passion for quality microwave test instrumentation.
Our employees offer many years experience in the design and manufacture of the worlds
best vector network analyzers, spectrum analyzers, power meters and associated components.
The management team has additional experience in optical power testing, military
radar and a variety of programming environments including LabVIEW, VEE and other
languages often used in programmatic systems. Extensive experience in a broad spectrum
of demanding measurement applications. You can be assured that our Power Sensors
are designed, built, tested and calibrated without compromise.
What were some of the
top issues of the radio and television industry half a century ago? In a lot
of respects, the same things that concern it today. A ready supply of service technicians
was a concern that was taken seriously by the Electronics Industry Association (EIA).
While there are not many local repair shops for electronics products nowadays, there
is still a huge demand to techs who are willing and able to do the hard work of
keeping the world's communication infrastructure operational - climbing towers,
repairing cell equipment. Now, as then, good pay, job security, benefits, and respect
for the job being done were at the top of...
In a parallel to the traditional test setup
of signal generation and signal acquisition, RIGOL Technologies announced today
the latest additions to its portfolio of
performance measurement equipment with the introduction of the DG5000 Pro Series
Generators and DHO/MHO5000 Series Oscilloscopes. The DHO/MHO5000 Series bring next-level
performance to RIGOL's respected line of high-resolution oscilloscopes, while the
DG5000 Pro generators do the same for the company's capable Pro Series arbitrary
waveform generators...
When selecting articles for posting here
on RF Cafe, I like to include ones that are directed toward newcomers to the field
of electronics as well as for seasoned veterans. This piece from a 1958 issue of
Radio & TV News magazine entitled "Basic Electronic Counting," is a
prime example in that it introduces the concept of binary numbers. We've all been
there at some point in our careers. A big difference between now and when this article
appeared is that in 1958, almost nobody was familiar to binary numbers, and fuggetabout
[sic] octal and hexadecimal. Only those relatively few people designing and working
with multimillion dollar, vacuum tube-based digital computers installed in universities,
megacorporations, and government research facilities had ever dealt with digital
numbers. The earliest example of powers of two I remember was back in junior high
school. It had to do with a
"Every invention begins with a problem -
and the creative act of seeing a problem where others might just see unchangeable
reality. For one 5-year-old, the problem was simple: She liked to have her tummy
rubbed as she fell asleep. But her mom, exhausted from working two jobs, often fell
asleep herself while putting her daughter to bed. 'So [the girl] invented a teddy
bear that would rub her belly for her,' explains Stephanie Couch, executive director
of the Lemelson MIT Program. Its mission is to nurture the
next generation of inventors
and entrepreneurs. Anyone can learn to be an inventor, Couch says, given the right
resources and encouragement. 'Invention doesn't come from some innate genius, it's
not something that only really..."
Mechanical filters of the type described
in this 1969 Electronics World magazine article are yet another example
of the genius of some people. They are actually a form of electromechanical device
in that the applied electrical signals are first converted into mechanical signals,
followed by resonant mechanical elements that discriminate according to frequency,
and finally a conversion back to an electrical signal is made. It is fundamentally
the same principal as a crystal, SAW, or BAW filter, albeit each with distinctly
different methods and topologies. Mr. Donovan Southworth, of Collins Radio, presents
the basics of mechanical filters in this brief write-up...
LadyBug Technologies was founded in 2004
by two microwave engineers with a passion for quality microwave test instrumentation.
Our employees offer many years experience in the design and manufacture of the worlds
best vector network analyzers, spectrum analyzers, power meters and associated components.
The management team has additional experience in optical power testing, military
radar and a variety of programming environments including LabVIEW, VEE and other
languages often used in programmatic systems. Extensive experience in a broad spectrum
of demanding measurement applications. You can be assured that our Power Sensors
are designed, built, tested and calibrated without compromise.
Attempts at making an
electronically printed facsimile (fax) of an original document at a location
distant from the source have been around for quite a while. As mentioned by
Radio-Electronics magazine editor Hugo Gernsback in this article, Samuel Morse
had a crude working device for printing messages on paper even before his eponymously
named code of dots and dashes became famous in 1837. A couple decades earlier, a
fellow named John Redman Coxe, of Philadelphia, Pennsylvania, devised a method of
electronically printing images and text on paper using a conductive solution and
a direct current pile (aka battery). Dr. Coxe, a physician, is not a well-known
figure in the electronics world, but in his day...
"Researchers have discovered how the 'edge
of chaos' can help electronic chips overcome signal losses, making chips simpler
and more efficient. By using a metallic wire on a semi-stable material, this method
allows for long metal lines to act like superconductors and amplify signals, potentially
transforming chip design by eliminating the need for transistor amplifiers and reducing
power usage. A stubbed toe immediately sends pain signals to the brain through several
meters of axons, which are composed of highly resistive fleshy material. These axons
operate using a principle known as the 'edge of chaos,' or semi-stability, enabling
the swift and precise transmission of information..."
The January 1969 issue of Electronics
World magazine published an extensive list of
Japanese company trade names and their addresses. Many of them went out of business
or were bought by other corporations long ago, as occurs in all countries. "Aiwa"
is listed twice, but that might have been a legitimate duplication due to separate
locations (BTW, I owned an Aiwa stereo at one time). My first "real" cassette tape
deck was made by TEAC (founded in 1953 as the Tokyo Electro Acoustic Company) and
my first "real" stereo receiver was made by Sansui. I remember the line in "Back
to the Future 3" where Doc Brown, having time-travelled from 1955, makes a
disparaging remark about a circuit in the DeLorean failing because of it being labeled
"Made in Japan." Marty counters...
• ARRL Defends
902-928 MHz Amateur Radio Band
• FCC's
Auto Safety Spectrum Rules
• $5M in U.S.
Chips Act Money to Metrology Projects
• U.S. State Department Approves
Surveillance Radar System Sale to Romania
•
5G Americas ITU IMT-2030 Vision for 6G White Paper
John Redman Coxe was a prominent American
physician, scientist, and innovator born on September 20, 1773, in Philadelphia.
Coxe's intellect and curiosity drove him toward an illustrious career in both medicine
and early scientific exploration, which included experimentation in electrochemistry.
He graduated with a degree in medicine in 1794, setting the course for his lifelong
journey into medicine and early scientific innovation. Coxe broadened his approach
to medicine and science, inspiring him to explore the convergence of scientific
methods and practical applications. John Redman Coxe is most remembered not only
for his contributions to medicine but also for his interest in experimental physics,
particularly in the field of electrochemistry...
TotalTemp Technologies has more than 40
years of combined experience providing thermal platforms.
Thermal Platforms are
available to provide temperatures between -100°C and +200°C for cryogenic cooling,
recirculating & circulating coolers, temperature chambers and temperature controllers,
thermal range safety controllers, space simulation chambers, hybrid benchtop chambers,
custom systems and platforms. Manual and automated configurations for laboratory
and production environments. Please contact TotalTemp Technologies today to learn
how they can help your project.
When I saw this 1966 Radio-Electronics
magazine article entitled, "Vibration
and Shock - Nature's Wrecking Crew," for some reason the first thing I thought
of was "The Wrecking Crew," that anonymously played the music for a huge number
of popular singers - mostly those without prominent bands of their own during the
1960s and 1970s rock-and-roll era. ...but I digress. My introduction to the potential
deleterious effects of vibration on electronics was in the 1970s, with airborne
receivers and servos in my radio controlled model airplanes. Even though they were
transistorized, vibration from glow fuel engines could wreak havoc with potentiometers
in servos and solder joints everywhere, including battery packs. I remember seeing
the control surfaces jitter...
You don't see jobs advertisements like this
anymore. Here is an ad that appeared in the the July 1944 edition of QST
(the American Radio Relay League's, ARRL's, monthly magazine), placed by Raytheon
Manufacturing Company (now just Raytheon Company), looking for
vacuum tube design, test, and processing engineers. Licensed amateur radio operators
were in high demand during the war years because of their knowledge and enthusiasm
for electronics and wireless communications. I hope you didn't come to this page
hoping to really find a tube designer job available. Of course, there are still
vacuum tubes being designed for TWTs and magnetrons, but those are few and far between...
The "carborundum"
signal detector, an innovative device developed by engineer General H. H. C. Dunwoody
in the early 20th century, represents a significant advancement in radio technology,
particularly in the context of crystal detectors used for receiving radio signals.
This device utilized the unique properties of silicon carbide, also known as carborundum,
which was synthesized in the late 19th century by Edward Goodrich Acheson. The connection
between Dunwoody and the material lies in the application of carborundum as a semiconductor
in radio signal detection. The operational theory of the carborundum signal detector
is rooted in its ability to rectify alternating current (AC) signals. When radio
waves, which are essentially electromagnetic waves...
"Researchers have created a cutting-edge
structure by placing a very thin layer of a special insulating material between
two magnetic layers. This new combination acts as a quantum anomalous Hall insulator,
significantly broadening its potential use in developing ultra-efficient electronics
and innovative solar technology. A Monash University-led research team has found
that a structure featuring an ultra-thin topological insulator, sandwiched between
two 2D ferromagnetic insulators, transforms into a large-bandgap quantum anomalous
Hall insulator. This heterostructure opens the door to ultra-low energy electronics
and even topological photovoltaics..."
This is another of a series of articles
on
printed circuit boards (PCBs) that appeared in the October 1969 issue of Electronics
World magazine, reporting on the latest and greatest advances in printed circuit
board technology. Already in production were rigid multi-layer laminates, flexible
plastic laminates, and special-purpose laminates for hazardous duty applications.
Author Norman Skow does not mention how many layers were routinely accomplished
at the time. Plated-through holes were a relatively recent thing for high volume
manufacturing. Of course population of PCB components was still a completely manual
procedure since pick-and-place machines were still a couple decades away...
This "Beyond
the Transistor" article by Hugo Gernsback, which was printed in a 1963 issue
of Radio-Electronics magazine, had as its subject not the transistor in general,
but specifically its potential use as a low noise, high sensitivity radio frequency
signal detector. Mr. Gernsback does a useful historical review of signal detectors,
beginning with Heinrich Hertz's radio detector in 1888, then progressing through
Edouard Branly's 1892 coherer, Gustave-Auguste Ferrie's and Reginald Fessenden's
electrolytic detector of 1903, then Greenleaf Pickard's crystal detector in 1906.
Lee de Forest's early work on vacuum tubes was directed toward a signal detector,
and ultimately resulted in his Audion amplifier. In 1948, Bell Laboratories' Shockley,
Brattain and Bardeen...
"Researchers have developed a groundbreaking
method to create more compact and energy-efficient computing devices using
magnonic circuits. By utilizing alternating currents to generate and steer spin
waves in synthetic ferrimagnetic vortex pairs, this new approach promises significant
advancements over traditional CMOS technology, potentially leading to the next generation
of computing systems. The central processing units (CPUs) in our laptops, desktops,
and phones rely on billions of transistors built with CMOS technology. As the demand
to shrink these devices..."
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If you are just entering the field of electronics,
the concepts presented in this half-century-old article for basic
field effect transistors are still relevant. Significant improvements have been
made since then, but the fundamentals stand. One of the most useful items in this
article is Table 1, which compares and contrasts vacuum tubes, bipolar junction
transistors, and field effect transistors. Topics covered include general properties
of FETs, source followers (a la emitter followers in BJTs), common source amplifiers
(a la common emitter amplifiers in BJTs), the Miller oscillator, combinations of
FETs and BJTs, and a gated amplitude modulator ...
Electric induction heating has been used in
manufacturing processes since shortly after Benjamin Franklin invented electricity.
Of course I jest about Franklin; he didn't invent electricity but discovered that
lightning was a form of electrical discharge. One of the most energy-consuming forms
of induction heating is that used by Alcoa for smelting aluminum. Beyond that are
many thousands of processes ranging from forming, tempering, and joining metal parts
to cooking food and curing adhesives. Both Tocco and Ajax-Northrup, now Ajax Tocco,
brands of equipment are featured in this 1955 article which appeared in Popular
Electronics magazine. Some processes work by directly inducing a high current
in the primary target object - usually metallic - being treated ...
Optical illusions have always been a big
attention-getter. Many companies have employed their intrigue to promote their products
and/or services. This
optical illusion was used by Littelfuse (not Littlefuse), a company founded
in 1927 and still in business today, to draw attention to a full-page advertisement
in a 1953 issue of Radio-Electronics magazine. More interesting than the illusions,
though is the information presented is about how their proprietary glass-encased
fuse design will always burn out in the center of the link, where it is visibly
obvious. It might seem trivial, but having tested fuses that appeared to be good
but tested bad, that is a great feature. Modern plastic-encased fuses with spade
terminals like those found in automobiles have a similar feature that makes visual
inspection very easy and unmistakable. In another Littelfuse ad, they educate the
reader about how a fuse's amperage rating is not the amperage level at which it
will blow...
This story reads like an infomercial for
IBM, which it probably is. Of course infomercials had not been invented by 1957,
so IBM was ahead of its time. The answer to the article's title, "How
Far Can You Go in Electronics Without a Degree?" was the same 55 years ago
as it is today: As far as your intellect and ambition will take you. Back then,
as with today, few people could rise to the level of design engineer without a
college degree. However, there are many aspects of electronics that requires no
formal education at all if you possess the requisite skills. I never have bought
into the feel-good lie about anyone being able to be whatever he or she wants to
be. Some people simply cannot achieve the mastery necessary to do a particular
job...
Call forwarding, call waiting, call holding,
speed dialing, conference calling, all of these features are taken for granted with
mobile phone and VOIP phone service and are included in the base service package.
It will cost you extra if you subscribe to a local legacy POTS (Plain
Old Telephone Service) provider. What is standard now was considered ground-breaking
technology in the early1960s when this article appeared in Popular Electronics
magazine. When phone calls were processed via human operators manipulating patch
cords and then electromechanical relays, it was enough to simply place a successful
call and not be interrupted or disconnected. Once transistorized circuits entered
the scene, much more was possible, and phone system engineers were quick to exploit
the technology. Sophisticated decision making requires both logical circuits and
a form of memory. Logic could be provided using hard-wired diode steering...
Mr. Lothar Stern, of Motorola Semi, published
a 3-part series on transistor theory in Popular Electronics magazine in
1973. This is part 3. Part 1 introduced the basics of the bipolar transistor,
and Part 2 addressed transistor circuit configurations - common emitter, common
gate, common collector, Darlington, differential - as well as presenting gain equations
and delving a bit into the physical construction of the semiconductor elements.
Finally, the author talks about the newest processes in use at the time and what
was available for low power and high power RF applications. In 1973, high power
semiconductors were just pushing past the 100 MHz barrier. GaAs and GaN were
still in university and corporate laboratories being prepared for the amazing devices...
When Charles Feldman published this article on
thin-film transistors (TFTs) in a 1964 issue of Electronics magazine, he had
no idea that the devices would eventually play a major role in liquid crystal
displays (LCDs) in everything from wristwatches to large screen television and
computer displays. Materials and fabrication techniques have evolved
considerably since 1964, but the fundamentals remain the same. Other than LCDs
and some solid-state sensors, I am not familiar with any other applications that
are heavy users of TFT technology. This 2016 paper titled, "Review on thin- film
transistor technology, its applications, and possible new applications to
biological cells," gives a little historical perspective and a comparison of
CMOS versus TFT...
With today being the 77th anniversary of
America's entry into World War II with the Japanese bombing of Pearl Harbor,
I thought this advertisement from a 1942 issue of the ARRL's QST magazine
would be of interest. Most of us have heard about the neighborhood collections for
tires, glass, newspaper, cans, and cloth in order to help support the war effort.
Probably not many have also heard about the
Signal Corps' call for milliammeters! That's right, the huge,
rapid build-up of electrical and electronic equipment for radios, vehicles, and
factory equipment. Many meters were needed for monitoring status and making
process adjustments. America had an ample supply of meters in the hands of
Amateur radio operators; all that was required was to separate the Hams from
their meters. Fortunately, an appeal to patriotism was sufficient motivation
back then...
Upon seeing this advertisement by Bell Laboratories
for their "Twistor"
form of magnetic memory data storage in a 1958 issue of Radio News magazine,
my thought was that it was just another flash in the pan, so to speak, in the history
of breakthrough, paradigm-changing inventions. It was a variation of the non-volatile
magnetic core memory that used sections of ferromagnetic wire twisted around copper
wire in such a way that electrical currents directed to particular intersections
in an x-y grid would cause a magnetic orientation to be set (store a bit) and a
set or read and sense wires permitted detection of the stored magnetic field to
be determined (read a bit). The Twistor was hailed as a much more manufacturable
form of the magnetic core memory, which required production workers with small hands
and finger to manually thread...
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...
I tried to find some information on "direct-impedance
amplification," but alas none could be located. At first, I suspected that it being
in the April edition of Radio-Craft might have meant it was a ruse on readers,
especially since author L. Mitchell Barcus focused on the nearly sub-audible portion
of the sound spectrum down to around 16 Hz. Careful reading of the article reveals,
however, that his pièce de résistance was designing the circuit with a minimum of biasing
resistors, capacitors, and inductors that might otherwise attenuate low frequencies.
Success was in the form of direct coupling of stages sans Rs, Ls, and Cs. I'm guessing
the...
Westinghouse is yet another of the original
stalwart titans of companies that helped build America to her state of greatness,
but is now mostly a footnote in the historical notes of the many companies which
over the past few decades have bought out portions of the business. Founded in the
late 1800s by George Westinghouse as a locomotive air brake manufacturer, the company
added other markets including, notably, electric power generation and distribution.
Emerging as the winner in the famous "War of the Currents" fought between Westinghouse
and Thomas Edison secured George's place in history. Westinghouse also got into
the commercial, military, and domestic electronics and appliance markets. I worked
at the Westinghouse Oceanic Division in Annapolis, MD, from 1982 through 1986 and
though it was a great company to work for. This advertisement for "Westinghouse
Directional Equipment;" i.e., antennas, appeared in a 1945 issue of Radio News
magazine.
Hidden away on page 134 of a 1959 issue of
Electronics World, at the end of a Mac's Service Shop-like electronics
shop docudrama (Another Day in the Shop) is this handy tip on how to fabricate
a make-shift
thermal wire stripper from a soldering gun or a soldering iron. The beauty of
thermal strippers over mechanical strippers is that they do not nick the underlying metal
wire. Heated elements melt the insulation and then a blunt edge is used to slide the
insulation off the end of the wire. Another advantage is that you can strip a wide range
of wire gauges and insulation types without needing to adjust the jaws or change to a
different hole location - although a proper temperature setting is required to avoid
a gloppy, stringy mess...
Most people have heard of the incredibly accurate
Norden bombsight that was credited for revolutionizing accuracy of heavy bombers like
B-17s, B-25s, and B-29s. It was an electromechanical device that took bombardier inputs
of altitude, airspeed, heading, and wind speed and direction, then calculated the impact
point of the bomb. An accuracy of 75 feet was claimed under ideal conditions - provided
by a mechanical computing device. By 1956 when this article was published, the Norden
had been replaced by radar-integrated bombing systems. Additionally,
ground-based radar measurement systems were...
September 27th's custom
Engineering themed crossword puzzle contains only only words from my custom-created
lexicon related to engineering, science, mathematics, chemistry, physics, astronomy,
etc. (1,000s of them). You will never find among the words names of politicians,
mountain ranges, exotic foods or plants, movie stars, or anything of the sort. You
might, however, find someone or something in the otherwise excluded list directly
related to this puzzle's technology theme, such as Hedy Lamarr or the Bikini Atoll,
respectively. The technically inclined cruciverbalists amongst us will appreciate
the effort...
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...
At first look this antenna from Bell Telephone
Laboratories appears to be a
phased array, but in fact it is a "lens" that uses reflecting metal fins to
direct incoming and outgoing radio waves into a narrow beam. This is a new approach
to the standard method of using a curved (usually parabolic) reflective dish with
a feedhorn. No detail is given about how, if at all, the phases of the received
signals are phase-adjusted at the point they converge on the back-side waveguide
feed. It is sort of akin to the Osgood optical lens used in lighthouses. Shortly
after the end of World War II, Bell Telephone Labs began a major effort to
interconnect the entire country with microwave relay stations to enhance efficiency
and reliability of long distance telephone calls...
The decade of the 1960's was an exciting and fast-moving
time for electronics, being that it was the beginning of a major paradigm change from
vacuum tubes to transistors, from discrete circuit components to integrated circuits,
and from point-to-point wiring to printed circuit boards. Computers were on the verge
of moving out of university labs and corporate research and development centers to small
businesses and retail headquarters. Electronic calculators were replacing mechanical
calculators. Digital systems were replacing analog systems.
Electronics training schools were in their collective heyday. Training
prospects lined up in droves and competed to gain acceptance into the
institutes. Home-study courses provided theory and hands-on building and
troubleshooting...
Waveform shaping is essential in today's
crowded communications spectrum. Spectral masks are precisely defined in order to
prevent "spreading" beyond the allocated frequency ranges at defined power levels.
Whenever anything other than a continuous sinewave is being broadcast, there is
spectral content generated in addition to the fundamental frequency. A Fourier transform
of the waveform reveals which frequencies at what power levels comprise the waveform.
The CW signal used by Morse code operators is a pure sinewave (or nearly so), but
there is a spectral problem with it every time the signal turns on or off because
of the square-ish edges involved during switching. RC networks are used in the transmitter
circuits to tame the edges so that they do not turn on and off so quickly and in
doing so reduce the extraneous frequency content. Author George Grammer argues that
even though the signal could theoretically be made "clickless" (aka "chirpless"),
there is an auditory benefit to the clicks or chirps that aids operators listening
to high speed code transmissions...
National defense needs have pushed back
the frontiers of science and technology since time immemorial. Mechanics, chemistry,
medicine, mathematics, psychology, astronomy, electricity, and as of the late nineteenth
century, electronics. Astronomy was useful as a navigational tool and required a
very sophisticated knowledge of geometry and algebra to make it accessible to seafaring
men, cartographers, and land surveyors. Since the early 1900s,
radio astronomy has played a huge role in the advancement of super-sensitive
receiver designs. Most people think of information arriving to them in two or maybe
three forms: sound, visible light, and some (but not many)
even consider radio waves. As over-the-air AM and FM radio broadcasts die out, even
fewer people are aware of radio waves; they certainly don't think of their WiFi
or cellphone signals... |