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 Welcome to the
RFCafe
Isolators & Circulators Quiz, a technical overview focused on non-reciprocal
microwave components. These specialized devices are the primary tools used to
protect sensitive signal sources from reflected power and to route signal flow
in multi-stage RF systems. Whether you are isolating a high-power transmitter
from a high-VSWR antenna, developing duplexers, or optimizing the signal
isolation between cascaded amplifiers in a precision measurement setup, a solid
grasp of circulator and isolator physics is essential. This assessment addresses
the fundamental properties of ferrite-based non-reciprocal hardware, including
insertion loss, port-to-port isolation, power...
 How far do you commute each day for
the privilege of doing your part to push back the frontiers of technical ignorance
and to boldly go where no engineer - or technician - has gone before. Do you
know what the cost equates for you each year? This handy-dandy infographic
lays out some
gruesome
numbers. Those with a weak stomach probably should pass on viewing this
one. Here's a hint at what you will see: See that big $795 in the thumbnail
image? That's the average cost per year for commuting -- per mile! Yessiree,
if you live just 10 miles from work, you're losing nearly $8,000 per year,
depending on you automobile type, on gas, tires, maintenance, devaluation,
and loss of your personal time (which is valuable, after all). Back in the
early 1990s I drove about 45 miles each way...
 Joe Cahak, owner of Sunshine Design Engineering
Services in Ramona, California, has written a white paper entitled, "Measuring
Semiconductor Device Input Parameters with Vector Analysis." This article covers
a recent test experience that utilized some thinking about the test fixture, the
bias requirements and the device mounting and special calibration offsets needed
to de-embed the test fixture response from the device response within the test fixture.
The device also had to have bias on several ports simultaneously. We had to establish
a "reference plane" within the fixture, from which we can use the Vector Network
Analyzer's Port Extension or Phase Offset to dial out the distance from our 1 port
calibration reference plane to the point of short reference within the fixture.
With this phase offset compensation we can then measure...
 Author Howard Wright takes the opportunity
here to distill the
concept of modulation down to its basic operation while dispensing
with the garbled mix of "graphs, formulas, charts, vectors, diagrams, and Greek
letters which often enter into various discussions of modulation". Wright describes
how to the uninitiated radio dial spinner, the culmination of events occurring behind
the scenes in an AM reception is akin to knowing "that, to be reproduced, the picture
[in a magazine] was broken down into its primary colors, if all we had to go by
was the original print and the magazine?" That is a very apt comparison...
 Alliance Test Equipment sells
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equipment and offers short- and long-term rentals. They also offer repair, maintenance
and calibration. Prices discounted up to 80% off list price. Agilent/HP, Tektronix,
Anritsu, Fluke, R&S and other major brands. A global organization with ability
to source hard to find equipment through our network of suppliers. Alliance Test
will purchase your excess test equipment in large or small lots. Blog posts offer
advice on application and use of a wide range of test equipment. Please visit Allied
Test Equipment today to see how they can help your project.
 Benjamin Franklin is famous for his kite-flying
experiment whereby he "discovered" not electricity (as many people believe), but
that
lightning is a form of electricity (most people thought it was
a jet of gas). A lesser known fact about Mr. Franklin is that he invented the
lightning rod after realizing the electrical nature of lightning. His understanding
of electric fields facilitated an implementation whereby hefty iron cabling interconnected
a tall, pointed rod installed at the tallest point on a building and a spike driven
into the ground. Lightning typically strikes the object that is the shortest distance
(in terms of electrical field strength) from it because the discharge can begin
at the lowest voltage. The presence of the grounded lightning rod above the highest
point on a structure effectively brings that point all the way down to ground level...
 These "Radio Term Illustrated" comics from vintage Radio-Craft
magazines are some of my favorite tech-themed comics. Most were drawn by Frank Beaven
in response to suggestions / requests by magazine readers. The one here from page
80 entitled "Crystal Gazing" was done by Franklin Folger. If you didn't know
that it appeared in a 1947 edition, you might assume it depicts a Steam Punk themed
LCD computer monitor mounted atop a Morse code straight key, but of course it is
not. At the time, cathode ray tubes (CRTs) were the only form of video display,
and while small like the one in the drawing (and round, unlike the drawing), they
were far from flat. Little did the artist suspect that his "Crystal Gazing" idea
meant to imply a type of mystic's medium for seeing...
 The big graphic with Figures 1 through 17
reminds me of the kinds of study sheets I used to make when cramming for exams in
my college circuits courses. Did I ever tell you about the wise guy instructor I
had for my first Circuits class at the University of Vermont? Anyway, this article
provides an introductory level treatment of using
negative feedback in amplifier circuits. Lots of illustration
and formulas are included. Frequencies are at baseband, so you won't learn any
secrets for high frequency amplifier stabilization, but then even RF and microwave
circuits eventually need to convert down to baseband at some point for sampling
or for use as audio or video...
 Prior to seeing this new tidbit in a 1976
issue of QST magazine, I had no idea that the wife of Peanuts comic strip
creator Charles Schulz was an airplane pilot - and that is with having been a huge
Peanuts fan for decades. Other than one of Snoopy's alter egos being that of
a World War I flying ace, there is no other theme of airplanes in the strip,
although according to this article, there was a 1975 Sunday comic strip with Peppermint
Patty and Marcie flying atop Snoopy's doghouse, from California to Michigan.
The Straits Area Radio Club (W8GQN) provided communications for the Powder
Puff Derby, aka the Women's Air Derby, race in which Mrs. Jean Clyde Schulz
took part in 1970, 1971, and 1975. It was a very long course - more than 2,000 miles
as the crow flies...
 Way...... back in 1992, RF Design
magazine ran a software contest. Those were the days when most engineers and hobbyists
wrote software in either Basic or Fortran. I happened to use Turbo Pascal, by Borland.
At the time, I was working as an RF engineer for Comsat, in Germantown, MD. Having
done a lot of frequency conversion designs in my previous work at General Electric,
and even more there at Comsat, I had already written a crude program to calculate
mixer
spurious products, so this challenge gave me the excuse I needed to refine the
user interface and add some creature comfort features like...
 Amateur radio operators - and all electromagnetic
spectrum users for that matter - have always lamented
crowded
bands and interference (QRM and QRN). That goes for licensed and unlicensed
bands. In 1976 when this editorial was printed in the ARRL's QST magazine,
spectrum occupation within allocated bands was defined by commonplace analog AM
and FM methods. Co-existence was generally not possible for operation within a common
frequency range. Spread spectrum modulation / demodulation changed all that beginning
in the 1990s, but prior to then such schemes were largely the exclusive domain of
military communications, as were many other spectrum-saving methods which are commonplace
today. A big part of the reason is the significant advances in digital processing
hardware and software, along with declassification of some of the algorithms that
eventually found their way into cellphone, WiFi, and other commercial applications.
Given that many of the professional engineers...
 As with many areas of electronics communications,
much of both the initial and continued research in
atmospheric scattering of electromagnetic signals was/is done
by amateur radio operators. The phenomenon is routinely used for accomplishing long
distance communications (DX, in Ham terms) by exploiting the reflection property
of ionized layers when radio signals impinge at a certain angle. The portion of
the signal that returns to the transmitter location, when monitored, can provide
information to the sender about the height, distance, and frequency range of the
reflecting atmospheric layer. Some of the first indications of backscattering were
noticed by radar operators who would receive echo returns from "phantom" targets
that were really atmospheric reflections...
 For many years I have been scanning and
posting Radio Service Data Sheets like this one featuring the
Admiral "Aeroscope" 161-5L, 162-5L, and 163-5L Midget Set models which appeared
in a 1939 issue of Radio-Craft magazine. There are still many people who restore
and service these vintage radios, and often it can be difficult or impossible to
find schematics and/or tuning information. Some websites offer to sell this information,
but often what is shown here is enough to get an old radio working again since most
times both schematics and alignment steps are included. I keep a running list of
all data sheets to facilitate a search...
 I'm probably one of the few people remaining
who fairly regularly recite the World War II (WWII) era slogan of "Use
it up. Wear it out. Make it do, or Do without." One of the primary killers of
economies has been inflation, whatever the cause - usually deficit spending by government
and/or printing of fiat money. Wartime typically produces high inflation levels
due to the need to produce the equipment necessary to wage a battle. Supply and
demand are another cause of inflation. If the demand is greater than the supply,
prices go up because owners want to maximize profits. If the need for skilled labor
is greater than what is available, workers demand higher pay, and the price goes
up. During WWII, as the chart to the upper left shows, inflation rates were sky
high, and the government propagandists called on the citizens to "do their part"
to keep prices under control by not creating a higher demand then the supply chain
could accommodate...
 SF Circuits' specialty is in the complex,
advanced technology of PCB
fabrication and assembly, producing high quality multi-layered PCBs from elaborate
layouts. With them, you receive unparalleled technical expertise at competitive
prices as well as the most progressive solutions available. Their customers request
PCB production that is outside the capabilities of normal circuit board providers.
Please take a moment to visit San Francisco Circuits today. "Printed Circuit Fabrication &
Assembly with No Limit on Technology or Quantity."
 Welcome to the
RF Cafe Antenna Theory
Quiz, a specialized assessment designed to test your knowledge of the radiating
structures that define the success of any RF communications system. From fundamental
dipole operation and feedpoint impedance to the critical nuances of gain, polarization,
and pattern formation, a deep understanding of antenna physics is essential for
any serious radio enthusiast or professional engineer. This quiz challenges you
on key concepts, including the characteristics of Yagi-Uda arrays, the significance
of front-to-back ratios, the dynamics of ground planes, and the practical challenges
of matching networks. By evaluating your grasp of these essential antenna principles...
 Each autumn I used to anxiously await the
appearance of the newest edition of
The Old
Farmer's Almanac on the store shelf, and such was the case with this 1981
issue. It is not that I was/am an avid farmer, just that I enjoy reading the anecdotes,
tales, and interesting historical tidbits included amongst the pages along with
tables of high and low tides, moon and sun rising and setting times, astronomical
events, and weather patterns expected for the year that lay ahead. Most of all,
I liked working the puzzles and riddles. Over the years the difficulty levels gradually
got lower and lower (aka dumbed down), to the point where for the last decade or
so I have not even bothered buying the OFA. Now it is full of numbnut stuff...
 This is a great
electronics-themed comic from a February 1972 issue of Popular
Electronics. It encompasses the essence of the stereotypical salesman ruse,
especially in that era when people were sure that electronics repair services were
out to rip them off by selling unneeded services and replacement parts. Aspiring
TV technicians who couldn't grasp the technology moved on to working as mechanics
in a garage, poking tiny holes in brake lines to scare owners into paying for complete
braking system rebuilds. I usually like to post multiple comics on each page, but
at the moment only this one is available...
 As with your school and college days where
once there was no longer any reason to memorize physical constants, conversion formulas,
and names of people, places, and things, much of the noggin's gray matter was
repurposed to remember topics of more immediate need. You can always look up what
you have forgotten. While studying for your Ham radio or FCC license, being able
to be able to quickly convert between wavelength and frequency is essential. Recalling
on demand
frequency-wavelength pairs is a real time saver on a timed exam.
Even being able to perform the conversion on a calculator during the test takes
up valuable time that could be better used on other tasks. This handy-dandy chart
for converting...
 IMS 2026 (IEEE MTT-S International Microwave
Symposium) is the world's premier RF and microwave conference, bringing together
thousands of industry professionals from around the globe to explore the latest
technologies, tools, and technical developments. IMS2026 will feature the RFIC Symposium,
the new RFSA and RFTT Symposia, and conclude with the ARFTG Microwave Measurement
Conference. everything RF
website's medai team is providing full coverage of the event. Stop by Booth 24048
to meet the crew.
 In
1961, the United States Navy commemorated the fiftieth anniversary of the A-1 Triad,
the service's first aircraft. This milestone honored
Glenn Hammond Curtiss, the father of naval aviation, who designed the versatile
machine capable of operating on land, water, and air. Born in Hammondsport, New
York, in 1878, Curtiss possessed an innate obsession with speed and mechanical ingenuity.
Before revolutionizing aviation, he dominated motorcycle racing, famously earning
the title of the fastest man on Earth. His transition to flight led to landmark
achievements, including winning the Gordon Bennett trophy in France and executing
the first successful U.S. intercity flight...
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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.
 Lee de Forest, upon whom was conferred
the honorary title "Father
of Radio" by Radio-Craft editor Hugo Gernsback (and others), exemplifies
personal traits of most great inventors: high intelligence, stick-to-itiveness,
courage, passion for his subject, determination, and a willingness to endure a lot
of personal and financial abuse. The January 1947 issue of Radio-Craft
magazine celebrated the 40-year anniversary of Mr. de Forest's invention
of the Audion vacuum tube by including a large number of articles by various authors
who knew him personally and attest to his greatness. I will be posting a few of
those pieces, and you will probably be shocked at some of the shenanigans that went
on by conniving people and naysayers who tried to deny de Forest due credit.
For example, based on his work to make more sensitive receivers a judge in a lawsuit
brought by Marconi strictly enjoined him "to forever desist from the manufacture,
sale or operation of any system of wireless telegraph...
 The
thyratron is not necessarily a familiar type of vacuum tube to most RF and microwave
electronics practitioners unless they happen to be involved in radar, imaging (x-ray),
particle accelerators, etc.† It is basically a high speed, high current switch used
in pulse forming networks for firing magnetrons (via a high-voltage transformer).
Both the S-band airport surveillance radar and the X-band precision approach radar
I worked on in the USAF employed thyratrons. The X-band radar had been modified
by the time I came on the scene to use a solid state thyratron (one of the earliest
adaptations), but the S-band radar still used its original vacuum tube thyratron.
While I don't recall for certain, I believe the thyratron in the thumbnail image
is the one it used. The accompanying ruler...
 This Popular Electronics article
by at-the-time editor Oliver Ferrell offers recommendations on how to spot a good
deal in
grab-bag assortments of electronics components when shopping for good deals,
whether it be at a retail outlet, flea market, or Hamfest. The advice is a useful
today as it was then. Little did anyone know that half a century later there would
be another source for cheap parts that would dwarf what had previously been available
- the Internet, and in particular, eBay. Mr. Ferrell mentions the term "radio
row," which was a downtown area in many cities where surplus equipment dealers peddled
their wares. In the 1950's and 60's, a lot of it was left over from wars, and included
not just electronics parts but also mechanical gear. Two of the more famous "radio
row" areas were in New York City and Tokyo, which were covered in two other articles
entitled "Radio a la Cortlandt Street!," and "Akihabara Tokyo's 'Radio Row'," respectively...
 Multipath signal interference is as prevalent
today as it was at the beginning of radio communications - maybe more so since there
are typically more reflective obstacles between the transmitter and the receiver.
The evidence of multipath with digital communications, be it voice, Internet page
viewing, or movies, is slowness in transmission as opposed to the analog case where
garbled speech on radio and ghosting pictures on television are the evidence. High
data rates with digital transmissions typically mask the packet errors and their
necessary re-transmission; it all happens before the buffered information is presented
to the listener / viewer. However, there is no such buffering of over-the-air radio
or TV transmissions so evidence of multipath is immediately noticeable. I remember
how sometimes...
 "Micro" as applied to electronics is relative,
depending on which decade you reference. In the 1940s, a micro-size electronic assembly
might have included "peanut" vacuum tubes and even some sort of printed circuit
board. That was a huge step down in size from standard size tubes with point-to-point
wiring between tube sockets and solder lugs on switches, potentiometers, variable
capacitors, etc. Fixed value leaded resistors, capacitors, and inductors, and transformer
wires connected to those lugs as well as to many terminal strips installed specifically
for making connections. Once transistors came on the scene in the 1950s, a new round
of
miniaturization took place based on not just a significantly smaller size of
solid state transistors and diodes, but their lower voltage and current requirements
meant ancillary components could be made smaller as well due to lower voltage...
 Well, this might get some dander up amongst
the believers that Sir Robert Watson-Watt is "the
Father of Radar." In the December 1957 edition of Popular Electronics magazine,
Colonel William R. Blair was given that honored designation based on his work on
a pulse-echo method of direction finding in the 1920s. The Wikipedia entry for Col.
Blair refers to him more specifically as the "Father of American Radar." William
R. Blair was awarded U.S. patent #2,803,819, titled "Object Locating System," on
August 20, 1957 - a full 13 years after the patent application was submitted. Watson-Watt
was issued a patent in 1935 on a radio device for detecting and locating an aircraft.
His research was born out of an investigation into a "death ray" which had reportedly
been invented by the Germans.
 Less than a year had passed since the surprise
attack on Pearl Harbor by the
Japanese
navy when this article was published in QST. America had sprung into
high gear to help the war effort - both as civilians and as military members. A
vital part of the strategy was to educate as many people as possible regarding the
tactics and habits of the enemy. Media of all sorts were used to help get the word
out. QST did its part, probably more so than most forms of media, by appealing
to those people capable and willing to contribute to the vitally important task
of communications. How many hobbies could be directly applied to the needs of the
military and homeland defense? Precious few, other than radio design, assembling,
testing, and operation. I suppose to be fair I would have to mention a few other
hobbies like vehicular maintenance, firearms marksmanship, and model building...
 As with my hundreds of previous
science and engineering-themed crossword puzzles, this one for February 9, 2020,
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 reasons which, if you don't already know, might
surprise you.
 In 1971 the International Telecommunications
Union (ITU), convened a meeting dubbed the World
Administrative Radio Conference for Space Telecommunications (WARC-ST). The
ITU was a specialized agency of the United Nations for telecommunications, with
a membership of 140 nations. Satellite communications was barely a decade old, but
already the need for international agreements on spectrum usage had become very
apparent. Prior to the 1971 meeting, there was the 1963 Extraordinary Administrative
Radio Conference held in Geneva, Switzerland. Amateur radio had its presence in
the game acknowledged with further allocations for its members' OSCAR birds; six
had been flown already. As of this writing there are about 20 OSCAR satellites still
in operation. Amateur satellites take many forms these days, including the newest
trend in CubeSat platforms with a well-defined set of specifications on dimensions
and mass per cube. Launches are provided on a space available basis at a substantially
discounted cost...
 QST did a regular series of articles
titled "Hams in
Combat" during World War II. This story is unique in nature in that it tells
of a newspaperman-turned-soldier who, in the story writer's mind, would have been
the most suited for the job of author. It tells a far different story of the South
Pacific than we were treated to in weekly episodes of McHale's Navy! "Had this story
been written by the man who should have written it - Capt. William H. Graham, W9BNC
- it would have been one of the greatest "Hams in Combat" yarns ever told in these
pages. But Bill Graham never got around to writing his story. He was too intensely
occupied with the living of it - too keenly aware of the new paragraph... Note the
letter I received from Capt. Graham's great grandson.
 Some of what you and I consider common knowledge
is largely unrealized by most people. Call me a geek, but I take pleasure in pointing
out to people that the
Fahrenheit and Centigrade scales are equal at -40°, and I especially enjoy working
out the simple proof for them. Most people appreciated the effort and are amazed,
claiming to have never seen that before. When I read the following in Smithsonian
magazine, "Winter temperatures here, some 250 miles northeast of St. Petersburg,
sometimes plunge to minus 40 degrees Fahrenheit," I wondered whether the author
knew that -40°F = -40°C. Maybe he just didn't want to confuse his readers by omitting
the redundant superfluous 'F' or 'C,' and it couldn't be 'K' because there are no
negative Kelvin degrees. It could also be that he knew but figured most people do
not...
 This article describes a method for
tuning beam antennas from the ground rather than needing to experiment with
matching capacitors and/or inductors at the antenna end of the transmission line.
The scheme uses a separate length of transmission line attached to the reflector
element at a length an integer number of half-wavelengths as required to reach the
ground. That way, tuning elements can be installed and adjusted for one or more
bands without needing to climb up to the antenna. The method can be used for any
number of elements, but of course it could get a bit messy with more than a couple.
The author, Major Charles E. Spitz (W7JHS), describes using a field strength meter
to verify tuning correctness. Having read many QST magazine articles on
antennas over the past decade or so...
 Motivated by the series of articles about
Lee de Forest in the January 1947 issue of Radio-Craft magazine, I did a search
of U.S. newspapers from 1905 through 1947 looking for news items on him. In particular,
I was hoping to find something about the
lawsuit levied by the Marconi Company against Lee de Forest wherein the
judge was reported to have told him, "...to forever desist from the manufacture,
sale or operation of any system of wireless telegraph." Alas no such information
was discovered, but the search will continue. I did find this piece and many other
interesting items that will be posted as time permits. Here, Mr. de Forest
sued, with the assistance of the U.S. Government, an investment company for defrauding
investors in regard to company stock sales, using a charge of mail fraud to assist
in prosecution. Mail fraud, tax evasion, interstate commerce and other such non-state
related charges were (and still are) routinely used by the Feds...
 Try as I did, I could not find any instance
of the Ness Clocks all-digital liquid crystal display (LCD) desktop clock which
appeared in this 1973 Popular Electronics article. There must not have
been many produced. LCDs had only been commercially available for a year or so when
this went on sale. Of the relatively few digital display clocks and watches available
in the 1970s, the vast majority used light-emitting diodes (LEDs), and most sold
for north of $100 (~$600 in today's money). Portable devices with digital displays
really began to flourish with the advent of both
CMOS circuitry and LCD displays; i.e., low current devices that extended battery
life. Wrist watches, which could only accommodate very small batteries with limited
energy storage capacity, were amongst the greatest beneficiary...
 I usually try to post something a little
less serious and technical on Fridays to help everyone wind down from the long week
just passed. It could be a Carl & Jerry or a Mac's Radio Service Shop story,
an electronics quiz, or even something I found out on the Internet. This time it
is a "believe-it-or-not" type feature entitled "Curiosa
in Radio," about radio manufacturing, operating, and infrastructure. One factoid
claims "Only 1.1% of set manufacturers in business in 1924 are building sets today."
It could due to being in the middle of the Depression Era so almost nobody was making
/ buying radios, but more likely it reflects the reality of the many people who
jumped into the fledgling radio industry early on and then could not gain market
share. Enjoy. |
