|
 The
bridged-T filter is a quick-and-dirty construct used to notch out a specific
frequency that is interfering with a desirable frequency or band of frequencies.
It is a resonant LC (inductor-capacitor) circuit consisting of a single inductor
"bridging" a pair of series capacitors having a resistor to ground between them,
or, if preferred, a capacitor bridging one or two inductors. A convenient
nomogram (aka nomograph) is provided by the author in this 1964
Radio-Electronics magazine article for quickly selecting values, which was
a very popular design aid in the pre-calculator era. A slide rule could be used
to calculate a range of values when only a single variable was in play, but
juggling more than one variable (component value) was greatly aided by a
multivariable nomograph. Truth is nomographs can still...
 Television, in 1955, was still a relatively
new phenomenon to many - maybe even most - people. According to multiple sources,
the portion of American households with a TV set went from under 20% in 1950 to
nearly 90% ten years later in 1960. That was a meteoric rise, particularly considering
the expense of even a minimal TV. The technology was not even available commercially
when most people were born, so the rush to join in on the craze was akin to the
mass adoption of cellphones in the 1990s. "Carl &
Jerry" creator John Frye used his pair of electronics-savvy teenagers to help
make the "magic" behind recreating a moving picture on a CRT miles away from where
it was created. Water flowing through a garden hose has often been employed as an
analogy for current flowing through a wire to explain electricity to laymen and
beginning students of the craft. Here, it is not water flowing through the hose
but water leaving the hose and flowing through the air that serves to represent
an electron stream travelling from the electron gun to the phosphor-coated glass
front of a CRT. Frame rates, scan lines, deflection coils, and other relevant terms
are i
 "The
RF front-end (RFFE) industry, valued at $21 billion, is expanding beyond its
traditional focus on mobile and infrastructure to drive innovation in the automotive
sector. Each segment within the industry presents unique dynamics and growth opportunities.
After a difficult 2022, the smartphone market is showing signs of recovery, with
expected year-over-year growth of 4%, projected to reach 1.2 billion units by 2024.
The mobile RFFE market is predicted to hit US$18 billion by the end of 2024, though
it may face stagnation due to market saturation and pricing pressures. This
market is expected to expand, with the 2027 launch of RedCap..."
 I'm having a hard time writing this with
my eyes rolled back in my head. The last time I experienced this level of overwhelmedness
was probably the third or fourth week of my feedback and control class at UVM. Even
though
electricity and magnetism shares many complimentary and parallel concepts, for
some reason thinking in terms of magnetics when describing amplifiers, mixers, modulators,
etc., has always caused brain freeze. Maybe it has to do with an ingrained bias
due to my earliest dealings with circuits being from a technician background before
earning an engineering degree. The equations of electric fields and magnetic fields
are very similar so that helps lower...
 Temwell is a manufacturer of
5G wireless communications filters for aerospace, satellite communication, AIoT,
5G networking, IoV, drone, mining transmission, IoT, medical, military, laboratory,
transportation, energy, broadcasting (CATV), and etc. An RF helical bandpass specialist
since 1994, we have posted >5,000 completed spec sheets online for all kinds
of RF filters including helical, cavity, LC, and SMD. Standard highpass, lowpass,
bandpass, and bandstop, as well as duplexer/diplexer, multiplexer. Also RF combiners,
splitters, power dividers, attenuators, circulators, couplers, PA, LNA, and obsolete
coil & inductor solutions.
 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..."
|
 Television, in 1955, was still a relatively
new phenomenon to many - maybe even most - people. According to multiple sources,
the portion of American households with a TV set went from under 20% in 1950 to
nearly 90% ten years later in 1960. That was a meteoric rise, particularly considering
the expense of even a minimal TV. The technology was not even available commercially
when most people were born, so the rush to join in on the craze was akin to the
mass adoption of cellphones in the 1990s. "Carl & Jerry" creator John Frye used
his pair of electronics-savvy teenagers to help make the "magic" behind recreating
a moving picture on a
cathode ray tube (CRT) miles away from where it was created. Water
flowing through a garden hose has often been employed as an analogy for current ...
 This
technically
themed crossword puzzle for November 14th contains only clues and words are
directly to RF, microwave, and mm-wave engineering, optics, mathematics, chemistry,
physics, and other science 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 or the Tunguska event in Siberia). The technically inclined cruciverbalists
amongst us will appreciate the effort. Enjoy!
 Since 2000, I have been creating custom
science and technology-themed crossword puzzles for the
brain-exercising benefit and pleasure of RF Cafe visitors who are fellow
cruciverbalists. The jury is out on whether or not this type of mental challenge
helps keep your gray matter from atrophying in old age, but it certainly helps
maintain your vocabulary and cognitive skills at all ages. A database of
thousands of words has been built up over the years and contains only clues and
terms associated with engineering, science, physical, astronomy, mathematics,
chemistry, etc. You will never find a word taxing your knowledge of a numbnut
soap opera star or the name of some obscure village in the Andes mountains. You
might, however, encounter the name of a movie star like Hedy Lamarr...
 This
Engineering-Theme Crossword Puzzle for March 21st has many words and clues related
to... you guessed it... engineering - including RF, microwave, 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., Hedy Lamarr or the Bikini Atoll). The technically inclined cruciverbalists
amongst us will appreciate the effort. Enjoy!
 Many months have passed since I last posted
one of the Radio Service Data Sheets for vintage radio sets. This one for the
Sentinel Model 217-P portable appeared in the August 1940 issue of
Radio-Craft magazine. Hobbyists and professional electronics service
shops relied on these back in the day because obtaining the information from manufacturers
could be difficult or even impossible. Some companies would not provide service
information for alignment and troubleshooting to businesses that were not officially
endorsed to do so. That left some of the smaller shops and most do-it-yourselfers
without a means to work on sets. Once places like SAMS Photofacts came along with
information packets that could be purchased ...
 That would be President Ford in the background
atop the platform, behind where the
OSCAR ground station was set up. He was there as part of the dedication of the
new National Air & Space Museum in Washington, D.C., in 1976. The event was
part of the nationwide series of bicentennial celebrations marking America's founding
with the signing of the The unanimous Declaration of the thirteen united States
of America. Apollo 11 astronaut Michael Collins directed the event. The Space
Race was in its heyday and most people were still in awe of anything related to
spacecraft - both manned and unmanned. Just about anyone other than a Ham radio
operator believed communicating with a satellite was the exclusive domain of governments,
so the presence of AMSAT...
 When you were a kid, did your mother warn
you about sitting too close to the television because doing so would cause you to
be near-sighted or otherwise "ruin" your eyes? Mine did, and I'm now very near-sighted,
but it is doubtful that sitting too close to the TV is the reason. In fact, according
to Linus Van Pelt's comments to his sister, Lucy, in this 1962 Peanuts comic strip,
ophthalmologists tried to counter the misconception about too-close boob tube viewing.
There is another strip where Linus challenges Lucy's assertion that reading in dim
lighting can hurt your eyes. The real concern as it turns out, according to professional
alarmists, was the massive doses of
x-radiation pouring out of the front of the early color TV
sets. To hear the distractors tell it, you could almost see the skeleton of
anyone sitting in close proximity to a color TV screen. The high voltage
(25-35 kV) on the cathode ray tube (CRT) produced x-rays...
 Here is another instance that shows how much
expectations have changed over the years. Except maybe for an experimenter or someone
set on reproducing original equipment as closely as possible, nobody would even
consider trying to build capacitors from scratch. Compared to when this "Roll
Your Own Capacitors" story appeared in a 1956 issue of Popular Electronics
magazine, components nowadays are so inexpensive that it's just not worth the trouble.
If you are one of the extreme do-it-yourself type people, then this story is for
you. Come to think of it, another use for this article is to provide material for
a physics class laboratory exercise where the student calculates a predicted value
for capacitance based on surface area, dielectric constant, and plate separation
distance...
 The
Underwriter's Laboratory (UL) is an entity that seems to have
been around forever. A lot of people - maybe most people - assume that it is a government
entity. In fact, it is a non-profit organization sponsored by the National Board
of Fire Underwriters (later changed to American Insurance Association, then to APCIA).
Its roots are traceable back to the Chicago World's Fair in 1893. Concern over the
potential fire hazard of Edison's light bulbs was the impetus for the effort. Another
aspect of the UL that a lot of people don't know is that the UL label of approval
is no guarantee that the device works properly, only that is passes standards of
safety as it relates to fire hazards. This article in the August 1955 edition of
Popular Electronics magazine gives a brief history.
 There is no denying that in 19th and 20th
Century America and most other industrialized countries, non-white males dominated
the academic, commercial, and industrial design and service workforce. Societal
norms were much different in those times, and the truth is most women did not desire
to enter into the "professional" market. Many performed low skill labor and assembly
functions, serving an essential yet less demanding role in providing goods and services
for the world. This 1949 "Lady
Television Engineer" story appearing in Radio-Electronics magazine
celebrated Tex Barbarite as a ground-breaking and glass-ceiling-breaking woman
in the commercial television broadcast industry. As was common in the era, Ms. Barbarite's
public platform was used to give encouraging insight into her path to success -
not to complain and dwell on resistance met in her effort. BTW, would it be politically
incorrect to point out, as evidenced by the complaints of others, that it was mostly
White males who envisioned and created the most of the modern world...
 It was a lot of work, but I finally finished
a version of the "RF &
Electronics Schematic & Block Diagram Symbols"" that works well with Microsoft
Office™ programs Word™, Excel™, and Power Point™. This is an equivalent of the extensive
set of amplifier, mixer, filter, switch, connector, waveguide, digital, analog,
antenna, and other commonly used symbols for system block diagrams and schematics
created for Visio™. Each of the 1,000+ symbols was exported individually from Visio
in the EMF file format, then imported into Word on a Drawing Canvas. The EMF format
allows an image to be scaled up or down without becoming pixelated, so all the shapes
can be resized in a document and still look good. The imported symbols can also
be UnGrouped into their original constituent parts for editing...
 A large portion of the U.S. has experienced
prolonged periods this winter with temperatures substantially below long-term averages.
That means heating systems have been running much more often than usual, and if
you have a forced hot air system, that means the indoor humidity level has been
much lower than normal. In northern areas like where I live, humidity can easily
drop to near zero. Because of that, triboelectric charging to high voltage potential
occurs merely by walking a few steps across a carpet, resulting in a sometimes painful
discharge arc when a metal object is touched. The only way to mitigate low humidity
conditions is to add water back into the air. The preferred option, IMHO, is to
install a whole-house humidifier that resides on the furnace ductwork, has its own
regulated water supply, and is controlled by a humidistat. After a couple weeks
of refilling three free-standing humidifiers two to three times a day and listening
to the fans, I decided it would be worth the expense and effort to install a whole-house
humidifier. The
Honeywell HE240A whole-house humidifier with a couple additional parts...
 One aspect of advertising on the RF Cafe
website I have not covered is using
Google AdSense.
The reason is that I never took the time to explore how - or even whether it is
possible - to target a specific website for displaying your banner ads. A couple
display opportunities have always been provided for Google Ads to display, but the
vast majority of advertising on RF Cafe is done via private advertisers. That is,
companies deal with me directly and I handle inserting their banner ads into the
html page code that randomly selects and displays them. My advertising scheme is
what the industry refers to as a "Tenancy Campaign," whereby a flat price per month
is paid regardless of number of impressions or clicks. It is the simplest format
and has seemed to work well for many companies. With nearly 4 million pageviews
per year for RFCafe.com, the average impression rate per banner ad is about 225,000k per
year (in eight locations on each page, with >17k pages)...
 Power, energy, force, and work are all
physical entities whose definitions are often incorrectly interchanged. As with
most cases in physics, knowing the unit associated with each entity is a way to
remember what it represents. For instance, force is fundamentally understood as
a mass being acted upon by an acceleration - whether it be gravity or motion. Its
SI units are kg·m/s2 (newton, with dimensions of mass x length / time2).
Energy is a force in motion (or its potential by virtue of relative position) with
units of force x mass (joule, with dimensions of mass x length2 / time2),
and an electrical unit of watt·seconds (power x time). Work is force through a distance,
with dimensions of mass x length2 / time2, which is the same ...
 It seems most of the articles we see on the
subject of
attenuator pads are based on signal reduction in terms of decibels for units
of power. Although it is a simple matter to convert power decibels to voltage decibels,
it would be more convenient if you are working with voltage to have formulas and
tables of values based on voltage ratios. This article does just that. As a reminder,
the decibel representation of a ratio is always 10 * log10 (x). If
you have a voltage ratio of V1/V2 = 0.5, then 10 * log10 (0.5) = -3.01 dB.
If you have a power ratio of P1/P2 = 0.5, then 10 * log10 (0.5) = -3.01 dB.
Does that mean that -3.01 dB of voltage attenuation is the same as 3.01 dB
of power attenuation? Confusingly, no. Let's say for the sake of simplicity that
you have 1 V across a 1 Ω resistor...
 In keeping with a very common practice of
using water flowing through a garden hose as a teaching aid analogy for newcomers,
the title of this chapter of the NAVPER 10622 Basic Navy Training Courses, "Generators - Electrical Pumps," is likening electrical generators
to water pumps. It is an apt analogy, but whereas a water pump can cause water pressure
and flow of a physical substance already on-hand, electrical "pumps," aka generators,
literally creates its "flow" from thin air (even a vacuum with no air). An electrical
generator exploits the phenomenon discovered by (or at least credited to) Michael
Faraday whereby a conductor moving through a magnetic field - or a magnetic field
moving past a conductor ...
 Aircraft electronics has always been on the
bleeding edge of technology because of the ever-increasing need to fly in the widest
range of atmospheric conditions possible. Accordingly, skills needed by avionics
servicemen are amongst the highest required in any electronics field. There are
still many pieces of vintage equipment in service that need to be maintained, but
even 20- to 30-year-old airborne radars and navigational units require top-notch
techs to troubleshoot and align. One topic in particular that plagues electronics
operation even in modern airframes is that of static electricity build-up and lightning
strikes. We all face those kinds of static discharge hazards in non-aviation environments,
but for the most part a failure on the ground or water is not as imminently life-threatening
as a failure in the air...
 Interestingly, when I searched for the
Hallicrafters TG-10-F Radio Keyer, the first thing that came up was an eBay
offering for a Gray Manufacturing Army Signal Corps "Keyer TG-10-F" Morse Code Practice
Machine. Evidently more than one manufacturer was contracted to make the model.
It looks like a tape record / playback machine, but it feeds a reel of paper strips
with dots and dashes followed by straight lines forming letters and words. An optical
reader encodes the audio signal for code practice students - up to 300 at a time
using the built-in amplifier. Morse code was a primary mode of communication during
World War II because the transmit and receive equipment was simple and reliable,
and could perform acceptable in the presence of noise and weak signals. It also
had the advantage of some level of privacy since most people could not understand
code, especially when sent at high data rates (WPM). There does not seem to be a
feed speed adjustment on the control panel... (see
update on Technical Manual)
 This week's
engineering crossword puzzle features a special end-of-the decade message, comprised
of three words and clues, for RF Cafe visitors. As with my hundreds of previous
engineering and science-themed crossword puzzles, this one contains only clues and
terms associated with engineering, science, physical, astronomy, mathematics, chemistry,
etc., which I have built up over nearly two decades. Many new words and company
names have been added that had not even been created when I started in the year
2002. You will never find a word taxing your knowledge of a numbnut soap opera star
or the name of some obscure village in the Andes mountains. You might, however,
encounter ...
 I found a copy of the 1941 Radio Engineering
Handbook, by McGraw-Hill Book Company at a Goodwill store. The cover was beat-up,
but the inside pages are all good. The "Mathematical and Electrical Tables" section
has an interesting method for calculating up to the sixth harmonic of any periodic
waveform by dividing the period into twelve equal parts (in time) and noting the
amplitudes at each point - aka "The
Twelve Ordinate Scheme." Those values are plugged into a host of equations that
yield essentially the Fourier coefficients for a 12-element polynomial describing
the curve. The text also provides equations for calculating harmonic content. Calculating
the polynomial coefficients is a simple process of doing iterations of sums and
differences of amplitudes, a la the Fourier analysis. Care must be taken to get
the numbers right or the resulting equation will not reproduce the original waveform.
In 1941, the user needed to look up in a table or find on a slide rule the sines
and cosines of nωt angles associated with each term, then multiply that by the calculated
coefficient. Finally, after all twelve points were figured... |
