|
 This 1958 Popular Electronics magazine
article provides practical instructions for constructing high-gain antennas to receive
108 MHz satellite signals, detailing four designs ranging from simple folded
dipoles to complex Yagi arrays. The author emphasizes that success requires precise
impedance matching, careful orientation, and weatherproofing, often utilizing modified
television hardware to capture weak transmissions from early space vehicles. While
the fundamental RF physics of signal gain and directivity remain unchanged,
"listening" to satellites today has shifted from manual, labor-intensive construction
of metal arrays...
 The name
Ernst Frederick Werner Alexanderson (1878-1975) might not seem
overly familiar to you, but he is credited with designing the first high frequency
alternator for transmitting longwave audio modulation over long distances. His device
preceded the spark and arc type transmitters that infamously spewed harmonics and
noise all over the spectrum and were therefore a great nuisance when broadcast at
high power levels. It was a relatively (for the time) narrowband scheme that permitted
more stations to be co-located in a given service area. He went on the develop one
of the first successful television projectors as well. Read a short biography on
Mr. Alexanderson in the "Men Who...
 The
National Association for Amateur Radio® (ARRL) is
seeking talented individuals
to join our team and help advance the Amateur Radio Service. We are currently
hiring for several impactful positions: • RFI Lab Engineer Support ARRL's
mission to protect and enhance spectrum access by managing and resolving Radio
Frequency Interference (RFI) cases • W1AW Station Manager This is a rare opening and
exciting opportunity to lead operations at W1AW • Public Relations & Outreach Manager
• Awards Program Supervisor • Development Associate • IT Support Specialist • Logbook of The World Support Associate
• Membership
Manager...
 December is traditionally the issue for
magazines to sum up accomplishments of the ending year and make predictions for
the next year. Radio-Craft magazine was no exception, but in 1936 they
went ten steps farther and prognosticated a decade into the future - all the way
to 1946! It is actually a tongue-in-cheek reprint from Pathe News magazine.
However, note the drawing of "professor teaches 2 million pupils," where he is instructing
via television and the railroad company boss checking in on the conductors en route
via
wireless teleconferencing. It might have seemed like a pipe dream
in 1936, but now it is commonplace. Not only do we now have live classroom broadcasts,
but millions of YouTube videos of instruction for performing...
 Once transistorized computers made desktop-sized
systems a reality, the sure eventuality of
humans being replaced by their electronic equivalents became a
popular theme of media pundits. News reports and "special features" on TV at the
same time scared citizens concerned for their jobs and assured them that by the
year 2000, humans wouldn't need to work anymore anyway because computers and robots
would be doing everything for them. The millennium crossover occurred a quarter
of a century and a half ago, and looking back it is true that computers and robots
have usurped a lot of what used to be done manually, but, as Mac presciently predicts
in this story...
 You have been warned not to believe anything
you see, hear, or read anymore, because of the ability of AI (artificial intelligence)
to alter and/or create just about anything. I offer in support of that thesis the
two photos shown here. The black and white image was scanned from a 1958 issue of
Popular Electronics magazine. I fed it exactly as shown to
Gemini 2.5 Flash, along with these simple instructions: "Please clean up
the 1958 magazine photo to remove noise, sharpen, and colorize it." You see the
result. The AI beast not only perfected the picture, but interpreted its content
(an amateur cyclotron, per the article) as a science laboratory scenario and added
the appropriate background. Yikes!
 Writing about "outdated" methods of radio-based
facsimile machine implementation in 1934 seems a bit incredible considering how
relatively new both technologies were at the time. Nevertheless, Radio-Craft
magazine editor Hugo Gernsback reported on the new era of
fax machines that were on display at the 1933 World's Fair in
Chicago. Of course fax machines of that time were not exactly desktop models that
could be located in a corner of your office or cubicle (not that cubicles were common).
If you substitute transistors for vacuum tubes, stepper motors for simple DC motors
and solenoids, and solid state lasers and LEDs for incandescent light sources, the
fundamentals have not...
 "It's not too early to gear up and get ready
for ARRL
Field Day! Field Day 2026 takes place June 27 – 28 and will bring together more
than 30,000 amateur radio operators for one of the most popular on-the-air events
in the US and Canada. This year's Field Day theme is 'Amateur Radio: A National
Resource.' Combined with the ARRL Year of the Club, it provides the perfect opportunity
for radio clubs to set up stations in public places to demonstrate ham radio's science,
skill, and service to our communities and our nation. All of the information you
need to get started..."
 New York City has forever, it seems, been
the place to be for street vending. A famously large pedestrian populace creates
an ideal venue for hacking goods of all sorts to passers-by. A phenomenon in radio
was created in the early 1930s with the rapid advances in technology and high volume
manufacturing techniques, coupled with increasingly efficient transportation of
goods on interconnecting roadways and delivery trucks. The photos included in this
Radio-Craft magazine story illustrate the level of enthusiasm by the public for
radio. A plethora of
replacement components for repairing malfunctioning sets and for
scratch-built sets at fantastically low prices helped fuel the fire. An offer of
"aluminum chassis" with pre-punched and drilled holes was really surprising not
because of the holes, but for...
 This week's
Wireless Engineering crossword puzzle contains the usual collection of science,
math, and engineering terms. Also included are a couple topics that have been in
the technical news headlines lately and the names of two new companies advertising
on RF Cafe. 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...
 Once again, the undaunted, indefatigable
husband of "friend-wife" - maybe even the alter ego of story-teller and artist Carl
Kohler - embarks on another
grand and glorious electromechanical project, always meeting with near - but
never total - success. This time around, the subject of his passion is a giant radio-controlled
model cruiser. In the 1950s and 1960s, the great size of such a boat was perfect
for the great sizes of model engines and model R/C systems. Vacuum tubes and rather
large, leaded resistors and capacitors comprised the electronics of both transmitters
and receivers, and at least two batteries were required for power...
 While working on vacuum tube based USAF
air traffic control radar and radio systems, and having seen many tube television
and radio sets I never recall seeing one of these form-fitting
metal shields. All the ones I've seen are simple cylinders that
slide over the tube and either twist into a receiving rim slot or they have spring
metal fingers that grab the glass envelope. As you might guess, utilizing a metal
shield around a tube for anything other than a low frequency application like an
audio amplifier or poser supply requires circuit design that takes into account
the capacitive effects of the large metal plates...
 "Venus
is often described as Earth's twin, but that comparison quickly falls apart at the
surface. With temperatures hot enough to melt lead and pressures that rival the
deep ocean, Venus's harsh environment has required NASA and other space agencies
to orbit the planet, studying it remotely while sustained surface exploration has
remained elusive. If NASA intends to deploy landers capable of operating for days
or even weeks on Venus, it must rely on a fundamentally different class of sensing
and control systems. Exploration would require
high-temperature ceramic sensors built from wide-bandgap materials and advanced
structural ceramics..."
 As with so many topics, the basics of topics
like
harmonic distortion (and other forms of distortion) in an amplifier circuit
has not changed much - if at all - over the decades. Test equipment and circuits
being measured get more advanced, but, especially if you are new to the concept,
articles like this one on audio-frequency distortion from a 1941 edition of
Radio-Craft magazine are as useful today as it was when it was written. When
studying, in particular, harmonic distortion, having a knowledge of the Fourier
series for common waveforms like triangle waves, sawtooth waves, square waves, and
even a semi-circle- shaped wave is especially enlightening since it explains a lot
of waveform shapes where harmonics are present...
 A
vertical antenna can have a significant advantage over a horizontal
antenna from a maintenance perspective, since, depending on how high the antenna
is mounted off the ground, the "business end" where electrical connections are made
are more accessible. The configuration shown here would be difficult to implement
if a mast rotator is to be used because of the stabilizing guy wires on the lower
frame. Although it should be possible to achieve the necessary rigidity without
guys by using an aluminum or fiberglass tubing frame rather than wood, preventing
weathervaning in strong winds could prove difficult. A nifty feature of this "reversible
beam" antenna is that reciprocal directivity is implemented simply by swapping out
a short...
 A 1958 report in the Russian journal Radio
detailed early scientific findings from Sputnik I and II, marking a significant
advancement in space-based electronics. Analysis of Sputnik I's radio transmissions
revealed
complex propagation patterns, including refraction and reflection off the ionosphere's
F2 layer, which allowed signals to travel far beyond direct visibility and occasionally
produce a round-the-world echo. These observations provided researchers with critical
data regarding how radio waves behave in relation to atmospheric layers and satellite
positioning. Furthermore, the article discussed findings from Sputnik II concerning
solar radiation intensity beyond the earth’s atmosphere. The researchers utilized
actinometry - the science of measuring electromagnetic radiation, particularly solar
radiation...
 As
I have written in a couple articles recently, there was a huge push in the mid 1930s
to adopt the revolutionary new
metal-encased vacuum tubes over established glass-encased tubes.
Today, interest in vacuum tube amplifiers is building among audio enthusiasts both
from a nostalgic perspective and from a long-perpetuated belief that sound from
vacuum tube circuits have a distinctively richer quality than that of solid state
devices. I post this stuff for the benefit of those who otherwise might not be able
to find the information otherwise. Your patience indulgence is appreciated...
 "In the fictional nation of Beryllia, the
2026 World Chalice Games were set to begin as the country faced an unrelenting heat
wave. The grid, already under strain from the circumstances, was dealt a further
blow when a coordinated set of attacks including vandalism, drone, and ballistic
attacks by an adversary, Crimsonia,
crippled the
grid's physical infrastructure. This scenario, inspired by the upcoming 2026
World Cup and the 2028 Olympic Games in Los Angeles, was an exercise in studying
how utilities can prevent and mitigate, among other dangers, physical attacks on
power grids..."
 Werbel Microwave began as a consulting firm,
specializing in RF components design, with the ability to rapidly spin low volume
prototypes, and has quickly grown into a major designer and manufacturer. The
WMC-2-18-15dB-S is a directional coupler that covers 2-18 GHz with a flat
response over the band. Features 15 dB coupling response with broadband flat
coupling response, high directivity, and excellent return loss performance. Coupling
flatness ±0.35 dB typical. Insertion loss 0.8 dB typical. Directivity
17 dB typical. "No Worries with Werbel!"
 The saga continues... Please bear with me
even if you have no interest in the much-hyped (at the time) history of the advent
of
all-metal vacuum tubes in the mid 1930s. They were predicted to
make glass-encased tubes obsolete. It never happened. Believe it or not, there are
a few folks out there (like moi) who like reading about the history. Posting this
on the RF Cafe homepage helps the search engines find and register it faster. If
you also happen to care, then you might be interested to know this article was...
 World War II was the "necessity" that
elicited the "mother of invention" activity responsible for many huge leaps in technology
- not the least of which was electronic verbal and non-verbal communications. Along
with radio and radar, Loran had become a major means of ocean and air navigation.
A fair description of the operational details, including timing diagrams, is included
in the text. Loran-A, the original system as it came to be known, was fully decommissioned
in 1980, thereafter supplanted by
Loran-C. With the advent of GPS, Galileo, and Glonass navigation
systems and their low and their low equipment and installation costs...
 In this 1960 Popular Electronics
magazine adventure, teenage inventors / hobbyists Carl and Jerry explore the mechanics
of
Space Inertial Reference Equipment (SPIRE), a sophisticated navigation system
using gyroscopes, pendulums, and clocks to track position autonomously. Inspired
by a television program featuring Dr. Charles S. Draper, Jerry demonstrates how
a gyro-stabilized platform maintains spatial orientation regardless of external
movement. The duo soon applies this scientific knowledge to a practical mystery
when a local factory manager seeks their help in catching an employee stealing expensive
alternators. By placing a timer-controlled, battery-operated gyroscope inside a
bait package, they successfully trap the thief. As the culprit exits the factory,
the activated gyroscope creates unexpected torque during a turn, causing the lunch
box to move erratically and reveal the stolen goods. The story concludes with the
boys reclaiming their device, leaving the factory manager delighted by his opportunity
to experiment with the powerful "toy." This plot is a lot like "The Hot Hot Meter"
story.
 This week's
Microwave and RF Engineering crossword puzzle contains the usual
collection of science, math, and engineering terms. Each week for more than two
decades I have created a new technology-themed crossword puzzle using only words
(1,000s of them) from my custom-created lexicon related to engineering, science,
mathematics, chemistry, physics, astronomy, etc. You will never find among the words
names of politicians, mountain ranges, exotic foods or plants, movie stars, or anything
of the sort. You might, however, find someone or something in the otherwise excluded
list directly related to this puzzle's technology theme, such as Hedy Lamarr or
the Bikini Atoll, respectively. Avid cruciverbalists amongst us: the gauntlet has
been thrown down.
 "Researchers based in Singapore and Belgium
have reported record high peak power-added efficiency (PAE), of more than 60%, for
moderately scaled gallium nitride (GaN) on silicon (Si) high-electron-mobility transistors
(HEMTs) at 30 GHz operation. At the same time, the devices perform with state-of-the-art
noise figures (NFs) as low as 1.1 dB. 'These results suggest that moderate
scaling could deliver competitive
GaN-on-Si HEMT technology, when combined with optimized epitaxial structure
and process..."
 Designing resistive
impedance-matched signal splitting networks is nowadays mostly
done with the assistance of computer software. In fact, odds are pretty high that
the designer either has no idea what the formulas behind the "magic" are, or at
least it has been a very long time since working them with pencil and paper. There's
no shame in that, though, just as there is no reason to expect someone using a cellphone
must know the intricacies of the internal circuits or the network to which it is
connected. We've moved past that. For those of us who still appreciate a refresher
on the behind-the-scenes calculations being performed at lightning speed...
 During and immediately following World War II,
the "Monitoring Service" of the British Broadcasting Corporation (BBC) relentlessly
listened to radio broadcasts from all over the world in order to be able to break
headline news and, if appropriate, pass strategic military information on to Allied
command centers (who were simultaneously doing their own monitoring). This article
tells of some of the more significant messages intercepted and how the facility
was a highly guarded secret in order to prevent sabotage and infiltration. At the
height of activity, 32 languages were being transcribed into English daily, consisting
of more than...
|
 • 6G Coming
- with
Connectivity & AI
• 5G
Americas Dissolves in 2026
• Taiwan
Exports to U.S. More Than China
• FCC Requires
FRN Contact Information Change Within 10 Days
• India Targets
1B 5G Subscribers
by 2031
• 6G Coming - with
Connectivity & AI
 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.
 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 about the old punched
card computer systems, but other companies like NCR (National Cash Register), HP
(Hewlett-Packard), DEC (Digital Equipment Corporation), and plenty of others others...
 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...
 When the concept
of
radio-refrigerators was presented in a 1933 edition of Radio-News,
it was not quite what has become reality today. At the time, the Radio Electrical
Exposition had recently been held in Madison Square Garden and the world was just
getting used to the miracle of radio waves - and refrigerators for that matter.
Radio-refrigerators never did make their way into the consumer market. Fast-forward
80 years and now we're seeing the advent of radio-refrigerators re-emerge, only
in a completely different format. This time, rather than playing shows from local
commercial broadcast stations, these appliances are communicating with Wi-Fi routers
to allow owners to check on status and contents from remote locations. In other
news, the editors report on a scheme to use a remote-controlled airplane, signaled
by a
Tesla spark gap transmitter, to drop bombs inside tornados in
order to break up and stop their...
 The first mathematical rules taught to entry
level electrical and electronics students are those of
Ohm's Law. Georg Simon Ohm was a German mathematician and physicist
who discovered during his experimentations that the current through a conductor
was directly proportional the the voltage potential applied across the conductor.
From there, he deduced the familiar V=I/R relationship that is the foundation to
all of what has followed in the field of electricity. The standard unit of resistance
- the ohm - bears his name. Watt, the standard unit of electrical power, was similarly
named after Scottish engineer James Watt, and the ampere standard unit of current
was named in honor of André-Marie Ampère. The standard unit of electrical potential
- the volt - was named after Italian physicist Alessandro Volta. Sure, most of your
know - or knew - all this...
 Here are the schematics and parts list for
the
Garod model 5A1 "Ensign" tabletop radio. They appeared in the September 1947
issue of Radio News magazine. Unlike with a lot of these service data sheets,
there was no textual description of the circuit functions or an alignment procedure.
A nicely restored example of the Garod 5A1 "Ensign" Tabletop radio can be seen on
the RadioMuseum.org website. 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. That makes today's situation similar to what existed
back in the era where such information was difficult to obtain without having an
inside line to the manufacturer. I keep a running list of all data sheets to facilitate
a search...
 When I saw this first
electronics-themed comic in the May 1959 issue of Electronics
World, my first thought was how most people today probably cannot relate to
the task of installing and adjusting a rooftop antenna for televisions. Ditto for
FM antennas. Most people who still watch TV use cable, although some have satellite
TV. Then I thought about how Ham radio operators are the last vestige of civilians
who rely on antennas and over-the-air radio communications (other than the world's
4.5 billion cellphone users who don't realize their phones are radios). Television
antenna design and installation was never a high-tech sport for typical homeowners
as it is for Amateurs; it was just a necessary nuisance. Finally, it occurred to
me than for a growing number of Hams...
 Simpson Electric is a name most RF Cafe
visitors are probably familiar with as being the maker of high quality analog multimeters,
with the Simpson 260 line being the most famous (it is still manufactured today).
Not as many people, however, know that Simpson also used to make oscilloscopes.
This article from a 1957 issue of Radio & TV News magazine was written
by a Simpson Electric engineer whose job was, in part, to respond to questions asked
by users. It covers basic operations like how to calibrate the display, adjust the
horizontal time base and vertical amplitude scales, and how to synchronize the display
with the input signal. Some explanation of
how to interpret periodic and pulse type waveforms is provided as well as tips
on how to avoid overloading and possibly damaging the instrument...
 This vintage
Heathkit
SA-5010 μMatic Memory Keyer kit is one the latest unbuilt Heathkit kits which
appeared on eBay. I have been saving the images in order to preserve the history.
The constantly growing list is at the lower right. The first instance I could find
for SA-5010 being offered for sale was in the Christmas 1982 Heathkit catalog, at
a cost of $99.95 ($250.40 in 2021 money per the BLS). It went to model number SA-5010A
sometime around 1985. Zenith bought Heathkit in 1979 (and kept the Heathkit name),
so that explains whey their name appears on the errata sheet in the photo. Heathkit
SA-5010 μMatic Memory Keyers can still be found on eBay fairly often, both in unassembled
kit form and completed units...
 Do you know what a soroban is? I have to
admit ignorance prior to reading this 1963 "Carl and Jerry" adventure in Popular
Electronics. As with many of these stories, real equipment, people, and companies
were referenced; this time it was the Pastoriza Personal Analog Computer, a modular
electronics system for calculating differential equations. The cost was around $300
(~$2,700 in c2021 money per BLS Inflation Calculator). Analog Devices bought the
company from James Pastoriza in 1969. What does the Pastoriza computer have to do
with the story, you might ask? Nothing, really; it was mentioned in a discussion
Carl and Jerry had when accepting a calculating speed challenge from obnoxious dormitory
mate, Bruce. Jerry would add a series of numbers on his soroban while Bruce would
add them with a pencil and paper. The winner got bragging rights...
 A news story with a title about a boat and reverse
current is more likely to be referring to water flow in a river or stream than about
electrical current in a conductor. Having grown up in a neighborhood next to a tributary
of the Chesapeake Bay, I spent quite a bit of time around boats, both large and small.
Salt water is particularly destructive to metal hulls due to
cathodic corrosion, exacerbated by the salt water's conductivity. While working as
an electrician in the 1970s, I installed electrical supplies for a few dockside cathodic
protection system that probably functioned like the one described in this 1965 issue
of Popular Electronics magazine. The principle is fairly simple whereby
anodes are placed in the water around the hull and a counter-current is
induced...
 Achieving what we consider relatively simple
results with electronics indicators used to be cutting edge technology. This
6AL7-GT
Electron-Ray Indicator Tube by Ken-Rad (a division of General Electric) provided
a dual-channel electrofluorescent (i.e., cathode ray) display of relative signal
strength or tuning the new-fangled FM radio stations. It was promoted in this 1947
issue of Radio News magazine. The tube could also be used, of course, for
many other applications where signal strength from any measured process: fuel level,
voltage, temperature, stock price, phase angle, sound volume, speed, etc., needed
to be measured. Today, we have electrochemical indicators so cheap that they are
built into off-the-shelf batteries at Walmart...
 Just in time for Christmas - a
yuletide crossword puzzle for you to work in the last moments of work while
waiting for the boss to give the order to leave early for the lone holiday weekend.
For the sake of avid cruciverbalists amongst us, each week I create a new crossword
puzzle that has a theme related to engineering, mathematics, chemistry, physics,
and other technical words. The clues with asterisks (*) are particular to this December
20th Christmas-themed crossword puzzle. As always, it 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...
 Oscillators were
never my forte. My biggest exposure to oscillators was unintentional
oscillations in amplifier circuits ;-( . This
Oscillator Quiz, published in the November 1962 issue of Popular
Electronics magazine, would
embarrass me if I attempted to complete it. Therefore, I will simply state
that I highly regard your oscillator prowess if you do better than 50% on it. I
guessed correctly at a couple of the more familiar circuits, but cannot even
make an educated guess at most of them. Don't let the presence of vacuum tubes
scare you off; mentally replace them with a FET and move on...
 Grammar and formatting standards have changed
over time. As technology evolves and society devolves, things like abbreviations,
use of capital letters, the "verbization*" of
nouns, interchanging of homophones (e.g., "their" and "there"), and the growingly
popular offense of eliminating the space between a number and its associated unit
(e.g., "914MHz" vs. "914 MHz") are becoming more prevalent. Look at nearly
any press release or datasheet from a component manufacturer in the past few years
and you will notice the number-unit change (I correct many of the ones I post on
RF Cafe). Some publishers (NPR) are particularly offensive at taking liberties
(aka laziness) and others (New York Times) are stalwart standard bearers
(good for them). I see many examples during my daily search for technical headlines.
We have gotten accustomed to many changes, and some have been around so long that
most people have never seen the former usage. Since I post a lot of articles from
vintage editions of the ARRL's QST magazine, I though it might be instructive
to include this list of common abbreviations used in the 1930s through 1960s (the
years I post). Most notable is the use of periods between letters and lower case
vs. upper case letters as with "a.m." (AM), "db" (dB), and "r.f." (RF)...
 Inductor-capacitor (LC) series and parallel combinations
comprised the first lumped element electrical filters for frequency discrimination. Below
a few MHz, with a little judicial placement of components and treatment of lead lengths,
building a successful
LC filter is not hard, and the measured response physical result looks very much
like the predicted response - provided the circuit model is sufficiently accurate. Above
50 MHz or so, very careful attention must be paid to parasitic elements (inter-turn
capacitance, lead inductance, cross-coupling) to get a good response. The advent of surface
mount components has made higher frequency LC filter...
 If you have ever placed a
fixed resistor in parallel with a potentiometer to reduce the total resistance,
then you are familiar with how you also convert a linear relationship of the wiper
movement with resistance to one that is nonlinear. That is because the equation
changes from Rtotal = Rx:potentiometer (where x is the potentiometer
position) to Rtotal = (Rx:potentiometer * Rparallel) / (Rx:potentiometer +
Rparallel). The graph of it looks like one of the curves in this chart.
Since the total parallel resistance is always smaller than the lowest value of the
two resistances, the greater the ratio of the two is, the more dominant the smaller
resistance value becomes. That means as the potentiometer wiper approaches the minimum
resistance end of its travel, the parallel resistor attached across it has virtually
no effect. Since parallel-connected inductors and series-connected capacitors scale
in the same manner as parallel-connected resistors, this chart is useful for those
circuits as well. Series-connected resistors and inductors, and parallel-connected
capacitors are simply the sums of their individual values...
 The
Barkhausen-Kurz (B-K) oscillator is credited as being the first
high power microwave generator that exploited the electron transit time effect.
It was developed in 1920 by German physicists Heinrich Georg Barkhausen and Karl
Kurz. As this article's author points out, the vacuum tube and supporting circuits
were difficult to produce and were not very well understood theoretically. Shortly
thereafter, the magnetron and klystron tubes came along and dominated the high power
microwave generation realm. Included in Part II of "Microwave - Generation
of Microwaves" is a good, brief explanation of the operation of both B-K and
magnetron circuits...
 While not many people are likely to build
this
R-C bridge circuit with vacuum tubes for use during design and troubleshooting,
this 1947 Radio News magazine article has a good basic description of operation
of any calibrated bridge circuit used to measure an unknown value. Interestingly,
a "magic eye" or "cat's eye" tube is used in lieu of a meter movement to give a
visual indication of an open, short, intermittence, poor power factor, and low "Q,"
as well as when the selected switch position correctly identifies the value of the
resistor or capacitor under test. Note that in that era μfd = μF and μμfd = pF... |
