|
 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..."
|
 For twenty years now, I have been creating
weekly crossword puzzles for the education and enjoyment of the technically minded
visitor like you. This
Radio
Theme Crossword Puzzle for June 6th has many words and clues related to RF,
microwave, and mm-wave engineering, optics, mathematics, chemistry, physics, and
other technical subjects. As always, this crossword contains no names of politicians,
mountain ranges, exotic foods or plants, movie stars, or anything of the sort unless
it/he/she is related to this puzzle's technology theme (e.g., Reginald Denny or
the Tunguska event in Siberia). The technically inclined cruciverbalists amongst
us will appreciate the effort. Enjoy!
 This online
calculator converts between return loss (RL), voltage standing wave ration (VSWR),
and reflection coefficient (Γ). It also calculates the amplitude and phase error
created by imperfect impedances. Two VSWR values are taken as input. Finally, VSWR
improvement due to attenuation is calculated. Numerical inputs are not error trapped.
Absolute values of inputs are used for calculation.
 Balsa is one of the lightest woods available,
and in many respects has the highest strength-to-weight ratio of any wood - even
oak. The chart at the right gives a comparison of a few familiar wood types. Hobby
grade balsa is harvested in the jungles of Ecuador, kiln dried, cut into large blocks,
and shipped to the U.S. for final cutting and sanding. Most balsa from hobby shops
is in the 8-10 lbs/ft3 realm. The rock-hard stock that nobody wants is sent to the
airplane kit manufacturers ;-) The vast majority of the balsa wood I use for building
model airplanes comes from Sig, Midwest, and Balsa USA. Other suppliers have materialized
in the past few years. Since the rise of mammoth wind turbines for electricity generation,
balsa's use as a core material for blades has caused a severe shortage in the modeling
realm. Balsa prices have skyrocketed in the past decade..
 Trigger Alert: Don't look at this advertisement
from a 1954 issue of Radio & Television News magazine if you are easily
offended by what used to be an effective marketing technique, but is now considered
too exploitative for use. The "Cancel Culture" mindset of today's easily offended
(often agenda-driven) citizenry would likely work to have Walter Ashe driven out
of business for such an ad. If you
dare to peek at the advertisement - and I'm not recommending that
you should if it might jeopardize your place in society, be sure to note the fire
hydrant...
 The ubiquitous presence and usage since the 1970s
of microwave ovens has made most people aware of the ability of
radio frequency (RF) energy to heat substances containing water. Both animate and
inanimate objects are included. In 1960, when this article was written, the effort had
really just begun to inform the general public about the potential hazards of RF energy
depending on its combination of wavelength (frequency) and power. The good news about
RF radiation versus beta radiation due to radioactive decay is that the former is not
potentially cancer-causing. The latter is termed "ionizing radiation" because it has
the ability to knock electrons off their attending atoms, and can cause cancer. Extremely
short electromagnetic (EM) wavelengths above the ultraviolet can also ionize atoms, but
that is well above the EM spectrum region considered to be RF...
 The
International Geophysical Year (IGY) began on July 1 of 1957 and ran through
December 31 of 1958. It was the dawn of space / high altitude flight and there was
a great need to learn as much as possible about the physics of the upper atmosphere
and the void of space. The USSR successfully flew their first three Sputnik satellites
and the U.S. was scrambling to get Echo into orbit (finally on August 12, 1960,
after the end of IGY). The Cold War was at its peak (Bay of Pigs incident was just
a few years away), and the science world was looking for a way to provide a unifying
tie between the planet's countries. "During this time, more than 5,000 scientists
and engineers of more than 60 nations ...
 When I saw this photo of a man holding a
fluorescent light bulb in the beam of a radar antenna, it reminded me of how
we used to do the same thing on our AN/MPN-14 radar system in the USAF. The unit
in the photo is a General Electric's FPS-6 height-finding radar, which operates
in the S-band 2,700-2,900 MHz region. The AN/MPN-14 is a mobile ground control
approach (GCA) with both an S-band airport surveillance radar (ASR) and an X-band
precision approach radar (PAR). Our S-band radar had a 600 kW peak power whereas
the FPS-6 put out a couple megawatts, but 600 kW was enough to light the bulb.
Of course these days you would never see a company-sponsored photo of a man standing
in front of a high power radar antenna with a fluorescent light bulb in his hand ...
 When is the last time you heard someone refer
to electronics as "solid state?" It was a necessary differentiator during the era
of transition from vacuum tubes to semiconductors. Mere utterance caused fear in
some, and futuristic hope in others. "Solid State" was a big buzz phrase in marketing
to household consumers and industry planners. Why, I ask, was "solid state" chosen
as the term to counter vacuum tube electronics? Did we ever refer to tubes as "gaseous
state" or "plasma state" devices? Maybe the "solid" part of "solid state" evoked
a sympathetic emotion with the coincident hippie / beatnik era population's usage...
 The July 1966 issue of Popular Electronics
began a series of
anecdotal instances of stupid and/or funny remarks made by people
about electronics. Some are supposedly by those who are in the trade and should
know better. I have to take issue with and question the veracity of one instance
in this first sequel, which claims a technician coming out of military service are
apt to make statements such as fuses being bad because they are "shorted." It must
have been submitted by an anti-military hippie of the era, because there's no way
anything other than a vanishingly small minority of techs who have spent two to
four years or more years servicing real electronic equipment would say ...
 Sunspot cycles repeat approximately every
11 years, so there had only been six solar maximums from the beginning of long distance
radio communications (Marconi in 1901) up until this article was published in 1957.
That year ('57) had the sun experiencing an extremely high number of sunspots (see
chart below), as had the previous few years, which caused communications to be profoundly
affected during the period. Under ideal conditions, high energy electrons typically
ejected from the sun (coronal mass ejection, CME) cause the Earth's ionosphere to
become an excellent reflector of RF energy at certain wavelengths, resulting in
phenomenal long distance contacts. Under the worst conditions, extreme levels of
"noise" are injected into radio signals, thereby severely degrading or even eliminating
communications. This story reports on a comprehensive study on the effect of such
activity on long distance communications...
 This
RF Engineering Theme crossword puzzle for January 31st contains
only words and clues related to engineering, mathematics, chemistry, physics, and
other technical words. As always, this crossword contains no names of politicians,
mountain ranges, exotic foods or plants, movie stars, or anything of the sort unless
it/he/she is related to this puzzle's technology theme (e.g., Hedy Lamarr or the
Bikini Atoll). The technically inclined cruciverbalists amongst us will appreciate
the effort. You will need to print out a hard copy. Enjoy!
 The extreme level of complexity and
consolidation of circuit functions in today's functional integrated circuit (IC)
blocks makes it so that people with almost no instruction or experience in
circuit and system design can assemble and make work some pretty impressive
creations. The days of vacuum tubes and early discrete semiconductors required a
designer to know how to properly bias and interface various sections of circuits
and systems. Nowadays, with the ready availability of impedance-matched
amplifiers, filters, mixers, couplers, detectors, and other pre-packaged
components, even RF and microwave frequency systems are within the reach of
relative amateurs. Likewise, people interested in digital and microprocessor
circuits...
 Very few people these days would have any
clue as to the causes of the CRT-type
TV picture problems shown here - I certainly don't, even after
looking at the answers (except for #4, which is pretty obvious given the choices
offered). What I can claim is to have likely seen each one of those types of issues
with all the cheap TV sets I've owned (especially #9). My current 26" LCD television
(I only own one TV), which is ten years old this year, is still working fine and
never displays any of those funny patterns. In the days of the Macs TV Service Shop
stories, survival in the business...
 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...
 Most people have heard of the incredibly
accurate
Norden bombsight (see video of the Norden bombsight) that was credited for revolutionizing
accuracy of heavy bombers like B-17s, B-24s, 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 (eleven years after WWII and three years
after Korea), the Norden had been replaced by radar-integrated bombing systems.
Additionally, ground-based radar measurement systems were in use to train aircrews
without the need to drop physical bombs. Instead, virtual bombs were launched and
computers in a Radar Bomb Scoring (RBS) unit...
 If you have seen many of the articles I post
from vintage electronics magazines, you know I often compare prices from the magazine's
era to today's prices. The online Inflation Calculator from the Bureau of Labor
Statistics (BLS) is as good as any, so it is used. This RCA advertisement in a 1946
issue of Radio-Craft magazine boasts of how drastically the
cost of
vacuum tubes has come down since 1923. It claims a $9 tube in 1923 costs a mere
80¢ in 1946; that is about 1/11th of the original price. Prior to around 1965, inflation
was very low, so the inflation-adjusted price for the $9.00 tube would be $9.80
in 1946 - a full 23 years later (a 9% increase, per the BLS). Therefore, the 80¢
price is an even better deal. Let us compare that to what a $9 item 23 years ago
(1998) from today (2021) would cost now. Per the BLS Inflation Calculator, it would
take $15.06 in 2021...
 Have you heard of an
Alford Loop antenna? I hadn't until reading this article. It is a four-sided
structure consisting of identical folded ½-wave dipoles on each side, with a common
feed. Opposing sides have their elements 180° out of phase with respect to each
other. The intention is to provide nearly omnidirectional FM radio reception across
the entire 88-108 MHz band. A little research on the Alford Loop reveals that
Mr. Andrew Alford developed this configuration to enable simultaneous, co-located
transmissions of FM radio stations. In that case the four antennas are individually
fed by transmitters on different frequencies. Alford is credited with inventing
antenna systems for the VFH Omnidirectional Range (VOR) and Instrument Landing System
(ILS) navigational aids...
 While this article is directed at amateur
radio operators who want to explore working in the microwave bands, it is good fodder
for anyone who wants a fundamental introduction to
waveguides, resonant cavities, distributed elements, and atmospheric propagation.
If that describes you, and particularly if you have formulaphobia, then start reading.
Even though the article appeared in a 1952 issue of Radio & Television News,
the list of frequency band allocations are not much different than today so the
information is useful. Unknown to many is that in the early part of the last century
Amateurs pioneered the use of microwave bands when the Federal Communications Commission
(FCC) allocated the spectrum to them since many "experts" considered it unusable ...
 Beginning in the middle of the 1930s, engineering
labs in the U.S. and Europe were experimenting with radar systems. Early radars
did not have the slick plan position indicator (PPI) displays that modern systems
use for plotting target movement for indication of azimuth (direction) and range
(distance). Instead, oscilloscopes showed radar returns as amplitude blips along
a time base that represented range. Azimuth was determined by where the operator
pointed the antenna (rotating versions came later). Since radar cross section stealth
technology had not been invented yet, the amplitude of the signal was useful a measure
of the size of the target. Prior to the invention of radar (RAdio Detection And
Ranging), other means were needed to detect...
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... |
