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 Satellite direct-to-device (D2D) networks
represent the next frontier in mobile connectivity, promising to eliminate dead
zones by linking ordinary cellphones directly to orbiting satellites. Companies
like SpaceX with its Starlink system, AST SpaceMobile, and others are racing to
deploy constellations that can serve standard smartphones without specialized hardware.
The technology relies on large phased-array antennas in space, advanced beamforming,
and new spectrum-sharing arrangements with terrestrial carriers. Proponents argue
D2D will bring emergency communications and basic connectivity to remote areas worldwide.
Critics raise serious concerns...
 During my electronics technician days at
the Westinghouse
Electric Company's Oceanic Division in Annapolis, Maryland, I spent the
first couple years building printed circuit boards, wiring harnesses, and system-level
assemblies for U.S. Navy sonar systems. We had some really slick stuff like towed
vehicles with transducer arrays along the sides, nose cones for smart torpedoes,
flow sensors, proximity fuse elements, etc. Exposure to all that, and the super-smart
people that designed it, fuelled my desire to go to the trouble of earning an engineering
degree. One of my tasks for a while was to build the transducer arrays, which entailed
building the hundreds of tiny transducer elements. One of the phased...
 With the extreme volatility of today's
stock market, I thought this might be a good time to re-post an article I wrote
back in 2012 entitled "Arbitrage via Microwaves." The ±200 point daily swings
of a mere 8 years ago seem paltry compared to ±1,000 of late. The original page
on the IEEE Spectrum magazine website is dead now, so I had to change the
hyperlink to an archived page on The Wayback Machine - a great resource for you to remember if
you ever need to retrieve a webpage that has been disappeared [sic]. My piece begins:
"If you have wondered why the world's stock markets behave the way they do,
why the DJIA falls 150 points on one day on news of Greece leaving the euro...
 You wouldn't know it from the lineup
of
Crosley Corporation radios and turntables appearing in department
stores, but the company also manufactures dishwashers, ranges and freezers, clothes
washers and dryers, and air conditioners. That is still a small chunk of what Crosley,
based in Cincinnati, Ohio, made back in the middle of the last century, including
cars and trucks, a small private airplane (the Moonbeam), television sets and even
had a television broadcast station, as well as other items that were part of the
mainstream of American life. Take a look at their About Crosley webpage for more
insight. Amazingly, along with the extensive line of retro radios and turntables,
they still also...
 What got my attention in this 1955 Radio &
Television News magazine article was the "picture-on-the-wall" concept being predicted by General Electric
(G-E) engineers, based on its light-amplifying phosphor invention. Determining exactly
how the device works is difficult based on the information given, but it appears
that the ultraviolet light source which is being amplified is projected onto the
surface of the amplifying substrate, and then an exact duplicate of the image is
reemitted toward the viewer. The conceptual drawing of a large screen hanging on
the wall is most likely driven by a UV projector located near the ceiling, akin
to how the large screen home theaters popular in the early...
 When most people are asked to name
prolific inventors, people like Thomas Edison and George Westinghouse,
with 1084 and 361 each, respectively, come to mind - at least for the United States.
As of this writing, Kangguo Cheng of IBM holds the record with 2039 U.S. patents
assigned. Nikola Tesla had about 300 patents. Lee de Forest, the subject of
this 1937 Radio-Craft article, had a little over 180 patents. That still
qualifies as prolific by my estimation. However, there is more to ranking a person's
inventive worth than the number of patents awarded - like how profoundly his or
her invention(s) impacted the world. For instance, Alexander Graham Bell had a mere
18 patents...
 Development of the
cavity magnetron during World War II helped change the destiny
of Allied forces through using high frequency radar with enough power to detect
distant targets while using frequencies which were out of the normal detection bands
of Axis forces' receivers. Most equipment at the time could not operate efficiently
(or at all) above a few hundred MHz. It was considered a top-level secret with great
concern that the technology not fall into the hands of German and Japanese scientists.
According to this early post-war advertisement in a 1945 issue of Radio News,
Bell Labs was totally consumed by the development of magnetrons, and was relieved
to finally be able to boast of its...
 Exodus Advanced Communications presents
the
AMP20162, a high-power, solid-state amplifier designed for low frequency applications,
including radiated susceptibility (RS103), EMI/RFI lab and general broadband testing.
Covering 10 kHz to 250 MHz, this wideband system ensures signal integrity
and flat response, making it a reliable choice for demanding environments. The AMP20162
provides between 2500 and 3000 W, typical, across the frequency range and boasts
a P1dB of 1700 W. Utilizing a Class A/AB design, the AMP20162 supports all
modulation types and 64 dB gain while maintaining harmonic performance around...
 While
FM broadcasting (frequency modulation) began in the United States
in the late 1930s, it was not until after World War II and even the Korean
War, in the 1950s, that the major shift to FM took place. It took even longer for
FM to get a foothold in Europe mainly due to the emphasis on rebuilding essential
infrastructure and manufacturing destroyed by the war. As this article points out,
the newer FM radio features allowed it to thwart some of the propaganda efforts
of the Soviets in East Germany who would be stuck in technologies that lag two or
more decades behind the free world even to this day (ain't Communism / Socialism
great?). The "medium-wave band" referenced...
 Welcome to the RF Cafe
Frequency Mixers
Quiz, a technical assessment focused on the critical non-linear components that
enable frequency translation in transceivers and test equipment. Whether you are
designing heterodyne receivers, analyzing local oscillator (LO) leakage, or striving
to minimize spurious intermodulation products in your signal chain, a deep understanding
of mixer dynamics is indispensable for high-performance RF design. This quiz covers
the core principles of frequency conversion, exploring topics such as conversion
loss, isolation, port-to-port feedthrough, and the generation of mixing products.
By testing your grasp of these essential concepts, you refine your ability to optimize
your system's dynamic range...
 Way back in the 1980s while working at Westinghouse
Oceanic Davison in Annapolis, Maryland, an engineer who knew I had recently obtained
a 1941 Crosley Model 03CB console style radio generously gave me his
B&K Dyna-Quik Model 650 Vacuum Tube Tester. It is a very comprehensive
portable tester used by many professional radio and television servicemen. My tester
also had the Model 510 Accessory Socket Panel that added an ability to test 50%
more tube types. One indication that it is one of the later model tube testers is
the inclusion of a transistor testing socket. Unlike testing vacuum tubes, all of
which plugged into sockets to make them easily replaceable, testing a transistor...
 Punch cards have been used in computer systems
since the very early days of digital programming. They were probably the first form
of read-only memory (ROM), come to think of it. I hate to have to admit it, but
the meager computer used in my high school computer lab (circa early-mid 1970s)
used
punched cards. I never took the class, but stories abounded of
how pranksters would shuffle a stack of punch cards while the student programmer
wasn't watching and then get a good laugh when nothing worked. There are also
plenty of cases where a stack was inadvertently knocked onto the floor and had to
be laboriously re-ordered. IBM is the brand that comes to most people's minds
when thinking...
 As with my hundreds of previous
science and engineering-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 the name of a movie star like Hedy Lamarr or a geographical
location like Tunguska, Russia, for...
 Despite all the prefabricated, relatively
inexpensive products available these days, there are still many people who like
to build their own projects. Whether electrical or mechanical - or both - some sort
of
enclosure is usually involved. Often, you can cannibalize an existing,
retired project to use its chassis or find a product at Walmart or a home improvement
store that does not cost too much that you can buy just to get its enclosure. Buying
a pre-formed chassis for your project can get expensive, so there are times when
the best option is to obtain a piece of sheet metal (which can also be expensive)
and bend it yourself. If you have never attempted such an endeavor, believe me it
can be...
 Einstein's theories of relativity revolutionized
our understanding of space, time, and gravity. Special Relativity (1905) rests on
two postulates: the laws of physics are the same in all inertial frames, and the
speed of light in vacuum is constant for all observers. From these flow time dilation,
length contraction, relativistic mass, and the famous equation E=mc². General Relativity
(1915) extends these ideas to include acceleration and gravity by treating gravity
not as a force but as the curvature of spacetime caused by mass and energy. The
equivalence principle - that gravitational acceleration is locally indistinguishable
from inertial acceleration - is its cornerstone. Importantly, General Relativity
fully subsumes Special Relativity: in regions where gravity is negligible (flat
spacetime)...
 Naval communications and their communicators
have always been held in high regard. Operating and maintaining sophisticated electronics
equipment is difficult enough on solid ground, but doing it on the ocean with winds
and waves tossing the platform (ship) relentlessly can exacerbate the problem tremendously.
It is a wonder that radar systems can even be useful with the antenna constantly
rotating about pitch, roll, and yaw axes while simultaneously shifting in the x,
y and z axes. Sure, airborne platforms have the same sort of challenge, but their
perturbations are not typically as violent, as great in magnitude, or as prolonged
as a naval vessel in rough seas. For the record, I'm a former USAF radar...
 After previously presenting the permanent
magnet, chapter 12 of the NAVPERS series of courses takes a look at the
electromagnet. It is like a natural or artificial magnet in its
attraction but unlike in its control. Its attraction is tremendous-it can hold tons
of iron. But because this magnet is powered by an electric current, the magnetism
can be turned on and off with the flick of a switch. Electrically-powered magnets
are called electromagnets. Electromagnets come in all sizes and shapes - and do
all kinds of jobs. All electromagnets use a coil of wire and a core of iron to produce
their magnetism. The coil furnishes the magnetic flux and the iron concentrates
it. To understand how it...
 A few days ago I mentioned that a popular
early form of radio detector circuit involved the used of a flame - yes, the flame
of a fire, not a romantic significant other. The subject arose in a couple articles
in the January 1947 issue of Radio-Craft magazine that celebrated the 40th
anniversary of
Lee de Forest's Audion vacuum tube invention. This particular
piece was authored by de Forest himself, who was a personal friend of Radio-Craft
editor Hugo Gernsback. It is a very interesting autobiographical account of the
early days of experimentation and the evolution of what eventually became the world's
first mass producible signal amplifying device. You will also read that de Forest
created the designation...
 Here is the electromagnetic wave section
of the "Wireless Networking in the Developing World," book (open source). "Wireless
communications make use of
electromagnetic
waves to send signals across long distances. From a user's perspective,
wireless connections are not particularly different from any other network connection:
your web browser, email, and other applications all work as you would expect. But
radio waves have some unexpected properties compared to Ethernet cable. For example,
it's very easy to see the path that an Ethernet cable takes: locate the plug
sticking out of your computer, follow the cable to the other end, and you've
found it..."
 Many topics of the
electronics-themed comics which appeared in Radio-Craft were suggested
by the magazine's readers. Staff artists like Frank Beaven turned those suggestions
into cartoons. For a while there was a special feature called "Radio Term Illustrated"
where, as the name suggests, terms like "Signal Generator" and "High Potential"
are rendered in farcical form. These four comics, two of each type, appeared in
a May 1947 issue of Radio-Craft. I have to admit that even with my familiarity with
vintage electronics memes I do not get the Television "Organ" comic (yes, I understand
the organ grinder, but not how it applies to TV)...
|
Loading history...
The RF Cafe Homepage
Archive is a comprehensive collection of every item appearing daily on this
website since 2008 - and many from earlier years. Many thousands of pages of unique
content have been added since then.
 This June 1945 issue of Radio News
magazine reported on the passing of President Franklin Delano Roosevelt; he
died on April 12th. While radio was building its presence as a relatively new form
of communication, Roosevelt exploited the technology often with radio speeches and
his well-known series of "Fireside Chats." At the outbreak of World War II,
many Americans first learned of the December 7th, 1941 ("a date which will live
in infamy") Pearl Harbor attack via the radio - before newspapers hit the stands.
Calvin Coolidge, Roosevelt's predecessor (and of Herbert Hoover's), actually made
the very first radio address. It also included some unwelcome news about the availability
of new radio receivers being delayed due to parts shortages. Unbeknownst to me prior
to reading...
 This vintage
Heathkit CR-1
Crystal Receiver kit is one the latest unbuilt Heathkit kits which appeared
on eBay, and can still be found there occasionally both in kit form and fully built
sets. I have been saving the images in order to preserve the history. The constantly
growing list is at the lower right. A PDF version of the Heathkit CR-1 Crystal Receiver
Manual can be found here, but I captured the pages (below) in case it disappears
someday. Note the information included on the operation of detectors and oscillators.
The copyright on the manual is 1956, and it appears in the 1958 Heathkit catalog
for $7.95 ($75.10 in 2021 money per the BLS). From the catalog page: "This crystal
radio is just...
 Here is a brief synopsis of radar (radio
detection and ranging). Today, most people who would be reading a magazine like
Radio-Craft would have at least a layman's level of knowledge of what radar
is and how it works. However, in late 1945 when the transition from a wartime society
to a "normal" existence was solidly underway, many new terms and types of inventions
previously withheld for defense security reasons were being released into the public
domain. I have mentioned previously that some people were vehemently against making
a lot of the stuff known, but government agencies wanted to get the information
out in order to promote innovation for improvement, to provide new technology...
 The Remington Rand "Univac" (UNIVersal
Automatic Computer) computer was delivered on March 31, 1951.
Its main memory consisted of liquid mercury delay lines arranged in 1000 words of
12 alphanumeric characters each. A Univac famously calculated the first presidential
race forecast - Eisenhower vs. Stevenson - and was correct! This 1957 report in
Radio & Television News magazine mentions how "giant electronic computers
no longer rank as laboratory curiosities or frightening science-fiction robots."
The Unisys company is today's descendant of Remington Rand...
 In 1957, only a top-of-the-line automobile
deserved a radio containing 13 discrete transistors and four crystal diodes. Only
buyers of such a top-of-the-line vehicle could afford the luxury offered by an electronic
marvel that promised instant-on music with superior sensitivity and selectivity
over the vacuum tube models that lesser humans endured. As shown in this 1957 issue
of Radio & TV News magazine,
Delco's Model 7268085 was up to the task as it populated the dashboards
of Cadillac's Eldorado Brougham. Modern day radios use a single IC for
performing all reception, filtering, amplification, and tuning functions, with
superior performance compared to the Delco without...
 Major Eugene Skinner (a mere Captain when
the previous two parts were written) wrote many articles about radar and microwave
technology for Radio-Craft magazine. In 1945 he provided a three-part series
entitled "Microwaves." This third part focuses on
antennas and radiators, including waveguides and feedhorns. The discussion is
high level covering the basic operation of basic circuit elements, so it is excellent
fodder for people new to the field - hobbyists, students, technicians, and engineers.
The previous two parts are also available if you want to start at the beginning...
 If you have not yet discovered the Engineering
and Technology History Wiki (ETHW) website, now would be a good time to surf on
over and take a look at the vast resources there - particularly the "Oral-History"
series of in-person interviews of our field's top scientists and engineers. Among
them are Dr. Harold Beverage, Dr. Ulrich L. Rohde (N1UL), Harold S.
Black, Harold A. Wheeler, Dr. Irwin Jacobs and Dr. Andrew Viterbi,
and of particular significance to me,
Dr. David B. Leeson (W6NL), founder of California Microwave and
Ham radio contesting champion. Many of the oral interviews were conducted in the
pre-Internet era and some of the people are no longer with us. A few days ago...
 Here is a million dollar idea for you to
consider. I hereby dub it the "Drone-Based Field
Measurement System™"(dB-FMS™). The concept came to me while reading a column
in QST magazine discussing the use of the EZNEC antenna radiation pattern prediction
software. As you know unless an antenna is situated in a perfect, unobstructed environment
like in the middle of a desert with a perfectly uniform ground or on a space-based
platform, physical obstacles and variations in surface conductivity can significantly
alter the 3-dimensional field distribution. Columnist Joel Hallas (W1ZR) is a master
at EZNEC and is routinely called upon to model antenna systems for people. As important...
 I frequently refer to magazine editor, inventor,
author, and futurist Hugo Gernsback as a genius who accomplished as much in his
lifetime as just about anyone has. He often noted in his magazines, including as
in the 1945 issue of Radio-Craft, where products, methods, and events he
predicted ended up coming true. It might seem like a case of "blowing his own horn,"
so to speak, but the fact is that then, as now, you have to publicize your successes
because competitors and those who wish to cause you harm will not do it for you.
Here, he had described a year previous a "Radio
Bomb" which had the capability of radio controlled guidance, including onboard
navigation for pinpointing targets...
 Long before digital communications was widely
adopted, there was a great need for stable frequency-determining devices / systems.
That is to say, low bit error rates (BER) for digital communications are not the
sole motivation for
oscillators with low short-term and long-term stability and low levels of jitter.
One obvious need for precise frequency control is radar, in order for accurate ranging
(the second "R" in radar) and in the case of Doppler systems, for accurate radial
velocity reporting and clutter cancellation. Those capabilities existed long before
digital systems came online. Aside from radar, precise frequency was needed in order
to reduce guard band width between assigned channel...
 Without warning, a couple days ago our hot
water heater became just a cold water storage tank.
Our A.O. Smith GCV 40 100 HWH had been functioning perfectly
since we acquired it with the house in 2008. Being a gas hot water heater, I had
a bit trepidation about messing with it since gas has a way of exploding at the
most inconvenient times - like when your face is staring into a burner chamber.
I attack electrical problems with near-reckless abandon from having dealt with AC
and DC supplies and controls for nearly five decades. Nevertheless, last December
when our Trane VX95 gas furnace decided it was time to be a cold air storage container,
I sought advice on the Internet for how to exact...
 Don Hoefler, widely credited for being the
first author to use the term "Silicon Valley" in print* to refer to the rapidly
building semiconductor region of the San Francisco Bay area, published a series
of articles in the 1944-1945 timeframe in Radio-Craft magazine about radio
and television broadcast equipment. This particular installment is part XII, covering
broadcast antenna towers. At the time, commercial installations were few and
far between as priority was given to scarce resources for military applications.
He discusses the tradeoffs involved in various vertical antenna designs, including
the tower structures: top-loading, center-loading, etc. When I first looked at the
traditional tapered...
 Anyone visiting RF Cafe (other than by accident)
almost certainly knows of
Drs. Bardeen, Brattain and Shockley fame for their transistor invention while
jointly working at the Bell Telephone Laboratories. The trio shared The Nobel Prize
in Physics in 1956. Bell was so proud of their employees' efforts that they ran
full page advertisements to boast of the accomplishment. This one appeared in the
February 1957 edition of Radio & Television News. Alas, Ma Bell's moment
of glory was a bit diminished by needing to add a footnote admitting that Drs. Bardeen
and Shockley no longer work there. Note that while the ad says the transistor was
announced in 1948, the first demonstration to Bell managers was in December of 1947...
RF Cascade Workbook is the next phase in the evolution of RF Cafe's long-running
series, RF Cascade Workbook. Chances are you have never used a spreadsheet
quite like this (click
here for screen capture). It is a full-featured RF system cascade parameter
and frequency planner that includes filters and mixers for a mere $45. Built in
MS Excel, using RF Cascade Workbook is a cinch and the format
is entirely customizable. It is significantly easier and faster than using a multi-thousand
dollar simulator when a high level system analysis is all that is needed...
 This
Physics & Science Theme crossword puzzle for August 1st, 2021, 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. Enjoy! |
