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 Resistance
is the fundamental property of a material to oppose the flow of electric current,
converting electrical energy into heat. From the high-conductivity copper traces
on a PCB to the specialized carbon-film or metal-film resistors that define voltage
levels and bias currents, resistance is the "control valve" of every electronic
circuit. While Ohm's Law provides the basic relationship between voltage, current,
and resistance, physical reality introduces complexities such as temperature coefficients,
power ratings, tolerance variation, and the unavoidable skin effect at high frequencies.
Resistors are not just passive elements; they are precision tools used for limiting
current, dividing voltages...
 The
unijunction transistor (UJT), invented in 1953, was originally
known as a "double-base diode" and explains why to this day the terminals are labeled
"E," "B1,' and B2." It is commonly modeled as a diode connected between two
resistors, with one resistor being variable. As the name implies, unlike a bipolar
junction transistor (BJT) that is more familiar to most people and has two semiconductor
junctions connected to the base, a UJT has just one junction. As is explained in
detail in this 1970 Popular Electronics article, the net effect of the UJT's
arrangement is a region of negative resistance which makes it good for use as an
oscillator. In fact, the relaxation oscillator...
 Proficiency in Morse code is no longer required
as part of obtaining an Amateur Radio license. A proposal to drop the 5 wpm requirement
was first floated by the FCC in 2005. It was actually at the request of the ARRL;
to wit, "In 2004, the League called on the FCC to create a new entry-level license,
reduce the number of actual license classes to three and drop the Morse code testing
requirement for all classes except for Amateur Extra." ARLB018 FCC Proposes Dropping
Morse Code Requirement Entirely Now, there is no code requirement for any license
class, not even the Amateur Extra. A lot of Hams are not happy about it, but times
have changed and the need for code...
 After getting out of the U.S. Air Force
in 1982, I was fortunate to get a job at the Oceanic Division of Westinghouse Electric
Corporation in Annapolis, Maryland. Most of the guys who worked in the area with
me were former electronics technicians from the armed forces. We spent most of our
days (and often evenings) building small quantity specialty systems for the U.S. Navy.
The facility was fairly small and was not set up for high volume production; that
was the purview of the much larger operation based adjacent to the Baltimore / Washington
International Airport (BWI), which built ground-based and airborne radar systems.
Whilst there, I did a lot of
wire-wrap assemblies that went...
 This first installment in a multi-part series
on magnetism appeared in the October 1947 issue of Radio-Craft magazine.
At the time, there was great interest in
magnetic tape and even magnetic wire recorders. Lots of articles
were published on the electronics and mechanics of recorders, but relatively few
discussed the physics of magnetics. Although the title says it is about permanent
magnetic theory, there is also a lot of information on electromagnets. Terms such
as reluctivity, magnetomotive force, magnetic flux, conductivity of electrical and
magnetic circuits, conductance, B-H curves, maxwells, oersteds, and gilberts are
introduced, along with some simple equations...
 Capacitance - the ability of a system to
store an electrical charge - is a cornerstone of electronics, enabling everything
from simple filtering and coupling to complex energy storage and timing circuits.
While the ideal model of two parallel plates is easy to visualize, real-world capacitors
involve a diverse array of materials, geometries, and limitations. Whether dealing
with electrolytic, ceramic, film, or tantalum types, each component introduces specific
characteristics like Equivalent Series Resistance (ESR), dielectric absorption,
and voltage coefficients that can define the success or failure of a design. As
frequencies rise, parasitic inductance and resistive losses often become...
 The dichotomy between the customer who is
worried about the service
shop owner ripping him off and the service shop owner who is worried
about the customer ripping him off is an old one. Given how even normally honest
people allow themselves a "white lie" here and there to consummate a business deal
or pacify the whims of an acquaintance, it is understandable how such suspicions
come to be. In this 1958 issue of Radio & TV News, Mac McGregor and
trusty sidekick Barney Jameson discuss how to handle customers who imply the desire
for or outright request (even demand) special consideration on repair services and/or
replacement parts. The steadfast policy of Mac's...
 This is the
electronics market prediction for Sweden, circa 1966. It was part
of a comprehensive assessment by the editors of Electronics magazine of
the state of commercial, military, and consumer electronics at the end of 1965.
Among Sweden's modern-day most recognizable electronics and related manufacturers
are Ericsson, Saab Group and Electrolux, in existence in one form or another since
1965. Automotive company Volvo is also among the largest manufacturers there, although
not specifically of electronics. A number of contemporary resources are available
for obtaining reports (at a cost) on the electronics industry in almost every country
on Earth. Among them are...
 Here is a bit of "outside-the-box" thinking
from the vacuum tube era that is essentially a form of integrated circuit, where
the active and passive components are discrete rather than semiconductor. The concept
was to provide an assembly that could be plugged directly into a signal gain path
tube socket and provide an additional amount of amplification without needing to
do any special wiring or mounting of components to the chassis. The cost of $9.95
in 1951 is the equivalent of $128 in 2026 money, so it wasn't a cheap upgrade
- and that did not include the cost of an additional tube (about another $13 in
today's money). Given typical electronics service shop rates of just a couple
bucks...
 Anatech Electronics offers the industry's
largest portfolio of high-performance standard and customized
RF and microwave filters and filter-related products for military, commercial,
aerospace and defense, and industrial applications up to 40 GHz. Three new
models have been added to the product line in July, including a 30 MHz LC lowpass
filter with 1 dB insertion loss, a 5 MHz LC bandpass filter with a 3-7 MHz
passband, and a 5000 MHz cavity bandpass filter with an insertion loss of just
0.8 dB. Custom RF power filter and directional couplers designs can be designed...
 X-parameters are a frequency-domain behavioral
modeling framework for nonlinear RF and microwave components. They were introduced
commercially by Agilent Technologies, now Keysight Technologies, as an extension
of the earlier Polyharmonic Distortion, or PHD, modeling theory developed by Jan
Verspecht, David Root, and collaborators. X-parameters are often described as the
nonlinear equivalent of S-parameters, but that phrase must be understood carefully:
X-parameters generalize the wave-based, port-oriented language of S-parameters to
large-signal, harmonic-rich, nonlinear operating conditions, but they are not a
universal, exact, global description of every possible...
 Radio-Electronics magazines'
"Service Digest" column regularly reported on issues relevant to the electronics
servicemen who repaired radios, television sets, phonographs, recorders, and similar
items - often in the customers' homes. Then, as now, professionalism and courteous
behavior was often rewarded with word-of-mouth referrals to friends and relatives,
resulting in new business opportunities. An interesting topic also included was
the need to observe extreme caution when working around TV tubes (CRT's) not
just because of the lethally high voltages present, but because of the
danger of tube implosion and the resulting scattering of glass
shards. An example given is that due...
 Prior to the advent of
FET-input multimeters, obtaining a very high input impedance meter
required the use of a vacuum tube circuit that used a buffer stage to isolate the
measured signal from the loading effects of the meter movement. As most people reading
this article already know, the voltage value indicated by a non-buffered meter can
be greatly affected by the meter's loading of the device under test (DUT) if
the meter's impedance is not many times greater than the DUT's impedance.
The voltmeter is used in parallel with the circuit under test, so for example if
the impedance of the DUT is 100 kΩ and the meter's impedance is also 100 kΩ,
the meter will display a value as if the DUT...
 RF Cafe visitor Brad B. just provided
the following
Watkins-Johnson Tech Notes for the collection: v5-3, v5-4, v5-5,
v5-6, v6-2, v6-3, v6-4, v6-5, v6-6, v8-1, v8-4, v9-1, v9-2, v9-3, v9-4, v9-5, v10-2,
v10-5, v10-6. They run the gamut from Solid State Limiting Amplifiers and Antenna
Polarizations to Digital Signal Processing for Multichannel Receiving Systems. Many
old-timers consider the W-J Tech Notes to be some of the best sources of circuit
and systems design guides ever written, especially for military, defense, and aerospace
applications. Waaaaay back in the 1970s and 1980s when I was new to the electronics
design world, offices, cubicles, laboratories, company...
 I'm not sure how much
mechanical filters are used in circuit design these days due to
their somewhat large size and complexity. They typically exhibit a high "Q" with
a relatively flat passband (with some ripple) and very sharp cutoff in the skirts,
and the insertion loss is low compared to lumped element equivalents (for comparative
out-of-band cutoff). Operational frequencies were limited to a few hundred kilohertz,
so they are useful only at intermediate and baseband frequencies. This article,
appeared in a 1953 issue of Radio-Electronics magazine, describes the basics of
mechanical filter design and construction. Mechanical filters from aircraft radio
manufacturer Collins and other can be...
 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.
 The most effective method for
isolating DC power traces, low-frequency analog signal traces, high-frequency analog
signal traces, and digital signal traces on a multi-layer printed circuit board
is not simply to "separate everything with gaps." The best-practice method is functional
partitioning combined with continuous, carefully assigned reference planes, controlled
return-current paths, localized power distribution, and layer stackup planning.
In practical PCB design, signals do not travel only in copper traces. Every signal
current has a corresponding return current, and at higher frequencies that return
current follows the path of lowest impedance, usually directly under...
 In this episode of John T. Frye's
"Carl & Jerry" series, the intrepid pair of teenage electronics hobbyists and
Ham radio operators are experimenting with an audio amplifier rig that uses a parabolic
dish for concentrating sound waves at a focal point where they have a microphone
mounted. Aside from picking up bird noises and a neighbor lady scolding her husband
for not properly washing the windows during a round of Spring cleaning, Carl imposes
upon Jerry for a lesson in
feedback techniques - both positive and negative - and the reasons
one is preferred over the other. The story winds up with a clever double entendre
comment referring to osculation...
 We all know that for the most part television
stinks. Back in 1951 when this article appeared in Radio-Electronics magazine,
the technology was very new and it was considered a miracle not to be wasted on
inane programming. Newscasts actually presented news and not opinion, movies and
sitcoms cast the nuclear family, law enforcement, the military, religion, and patriotism
in a positive light rather than as the purveyors of evil in the world. By the end
of the 1960s to early 1970s a lot of that had changed. Political and social agendas
weaseled their way into nearly all programming to the extent that terms like "boob
tube" and even, yes, "smellivision," became common monikers for television...
 "Are we killing the broadcasting goose, layer of many golden eggs?"
Dr. Lee de Forest asked in his inaugural address, upon his election to the presidency
of the Institute of Radio Engineers. So went the opening editorial in a 1930 edition
of Radio News magazine. It was directed at the question of whether excessive,
"gratuitous" advertising was going to be so offensive to listeners that they would
turn off the set and go back to their former silent worlds. Remember that many,
if not most, households, and certainly not automobiles, even had radios at the time.
Building an audience was essential to nurturing the new phenomenon of radio, and
to saturate the listeners with commercials would surely doom...
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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.
 "A transistorized i.f. stage for a TV set
can be built today to fit into a match box. But
molecular electronics has made possible the production of a device
that contains two such stages and is only a fraction of the size of a single transistor!"
Nobody talks of molecular electronics today, but that really is an accurate term
for what we have when compound semiconductors like GaAs, GaN, or any of the many-atomed
exotic photovoltaic substrates are being discussed. When referring to pure elements
like silicon that are being doped with impurities, I'm not sure those structures
are considered molecules which, according to Dictionary.com, are "the smallest physical
unit of an element or compound, consisting of one or more like atoms in an element
and two or more different atoms in a compound..."
 This week's custom RF Cafe crossword
puzzle contains some words particular to amateur radio, along with other tech-themed
words and clues. Each week for 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...
 "It is hard for one to believe that there
is room for
further reduction in size and weight from what we are accustomed
to today." So wrote Radio & TV News magazine editor William Stocklin
in 1958. It was a decade after invention of the transistor (1948), and the first
integrated circuit had not yet been developed (Robert Noyce, 1959), but even so
it seems fairly short-sighted for a major electronics magazine editor. While being
amazed at the shirt-pocket-size transistorized radio and hearing aid, he still found
hope for the future of miniaturization of vacuum tubes, such as diodes recently
released by General Electric that would "fit into the shell of a standard type of
transistor." Sure, it is easy in hindsight...
 This is the third and final installment
of Hy Levy's series on
attenuators, line filters, and matching transformers as published in Radio-Craft
magazine. Audio and low IF frequencies are used in the examples, but the formulas
and principles can be extended to higher frequencies. Bifilar windings are covered
as a method of minimizing self-inductance in wire-wound resistors. Although inductance
is not desired in resistors, bifilar windings can also be connected to have current
in both wires flowing in the same direction, thereby increasing the magnetic field
rather than canceling it. You will probably want to read the previous two parts
to work up to this point...
 "Do you think that F.C.C. would be engaged
in the present terrific expense and effort of getting our fingerprints and citizenship
histories if there were intention of shutting us down shortly?" That statement was
printed by the QST magazine editor in the issue that preceded the December
7, 1941, attack on Pearl Harbor by thirteen months. A few things about it are troubling.
First, the
FCC was collecting fingerprints of licensed amateur radio operators.
Second, the FCC was assimilating information about licensed amateur radio operators'
citizenship histories. Third, a combination of short-sightedness and apparent naiveté
concerning the FCC's willingness to shut down amateur radio operations once
America had been inevitably drawn into World War II...
 From about the middle of the 1950s through
the 1990s,
stereo systems were a pretty big deal amongst music listeners.
A lot of the interest was driven by rapid improvements in technology in sound recording
and reproduction equipment. An economical boom in the post Korean War years combined
with a process developed by Emory Cook to cut dual channels of stereophonic sound
onto vinyl records enabled a fad fueled by teenagers of building the best home sound
systems possible with available funds. Audiophiliac adults, of course, were also
prime motivators of the technology since they had deeper pockets and could afford
higher-end equipment and larger collections of records. Magnetic tape was also a
bit part of the craze, but the big money was in vinyl. If you peruse the vintage
electronics magazines like this Radio & TV News, Popular Electronics, Electronics
World, et al, you will notice the pages were filled with technical articles on and
advertisements for stereo music reproduction gear...
 Here is a quick course on how to
point antennas for over-the-horizon (DX) reception, and, if you
also happen to have a license to transmit, for broadcasting. It covers how to determine
the shortest straight-line path by stretching a string around a globe (remember
those spherical maps that used to be a mainstay of every household and schoolroom?)
and using a protractor (a what?) to get the angle. Radio signals unless refracted
or reflected take a great circle route from point A to point B. Long distance airline
flights take the same routes, which explains why flights from London to Los Angeles
fly over Greenland enroute. Author Edward Noll uses a simple 1/2-wave dipole antenna
radiation pattern as an example of how directivity is affected by frequency (relative
to the fundamental)...
 Ever heard of the revolutionary
Graphechon
Tube, by RCA? Neither had I, until I saw it mentioned in an ad for RCA televisions
in a 1950 edition of The Saturday Evening Post. My curiosity was piqued enough to
do some research. First, here is the text of the ad: "Scientists at RCA Laboratories
work with split-seconds of time too infinitesimal for most of us to imagine. Their
new electron tube, the Graphechon, makes it possible. For instance, in atomic research,
a burst of nuclear energy may flare up and vanish in as little as a hundred-millionth
of a second. The Graphechon tube oscillograph, taking the pattern of this burst
from an electronic circuit, "remembers" what happened - and re-creates it in a slow
motion image which can last for a minute and a half. Scientists may then observe
the pattern...
 Raytheon is another of the stalwart early
American electronics and technology manufacturing company. It began operations in
Cambridge, Massachusetts in 1922 under the name of the American Appliance Company.
The name was changed to
Raytheon in 1925 to reflect its growing vacuum tube business.
Did you know the name Raytheon means "light from the gods?" In this case, the light
refers to the orange glow from the tube heater filament. If you have ever had the
privilege of seeing in a darkened room vacuum tubes glowing inside a vintage radio,
you will understand the relationship to a godly sight. Not too many years ago, there
were still a few companies like Tesslor...
 This might be my oldest copy of QST,
being Vol. XIII, Number 6. Up until a few decades ago, authors commonly
appropriated themes and characters from familiar fairy tales and fables for use
in articles of instructional nature. Some publications even used comic book
style formats for teaching to beginners. The term "wabbulation" (aka "wobbulation" and "wobulation")
is spoken to Uncle Jimmy by the fabled Piper, and I have to admit not being familiar
with the term. According to W2PA's story, 1920s era QST technical editor Robert
Kruse coined the word to describe inadvertent modulation of the carrier frequency
during CW or phone operation. Per the Wikipedia entry, "wobulation" is Hewlett-Packard's
term...
 July 19th's custom
Electrical Engineering crossword puzzle contains some words particular
to radio, radar, analog and digital circuits, components, and other tech-themed
words and clues. Each week for 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.
 Here is the Radio Data Sheet for
Zenith radio models 8H032, 8H033, 8H050, 8H052, 8H061 as published
in a 1947 issue of Radio-Craft magazine. Some of the electronics magazines
used to include this type of high level documentation so that hobbyists and even
service shops with budgets too small to afford cabinets full of SAMS data packets
could work on the radios. Most of the radio manufacturers would not even sell factory-prepared
documentation to anyone who was not an "authorized" service center. The RadioMuseum
website has nice examples of restored versions of both the Zenith 8H032 and the
Zenith 8H034 tabletop radios. The electronics are similar but the chassis designs
are completely different...
 Long before their college days at Parvoo
U., our two amateur electronics sleuthing buddies were on the job tracking down
and trapping bad guys by using their combined knowledge of circuits and physics.
In this episode,
Carl and Jerry are tasked with helping a hobby store owner stop
a rash of thefts that always seems to occur during a busy time right after school
lets out for the day. Their first inclination was to devise a system like the big
department stores were installing that used passive tags on items that would trigger
an indicator when passed through the detector at the exit door. That was in 1958
when the anti-theft tags were first being utilized...
 Not everyone who visits RF Cafe is a seasoned
engineer or technician. Some are just getting into electronics as part of a career
path and/or hobby endeavor and appreciate the availability of entry-level information.
As an oft-quoted sage-type person famously said, "A journey of a thousand miles
begins with the first step." Accordingly, here is a short article explaining the
basic physics and application of the of
backward diode, which is akin to a Zener diode and tunnel diode
in that it is meant to operate in the reverse bias region. National Semiconductor,
Texas Instruments (TI), and Raytheon were the manufacturers in 1958 when this article
appeared in Radio-Electronics magazine. National Semiconductor was swallowed up
by Texas instruments in 2011...
 Proper soldering is almost as much of an
art form as it is a technical skill. Having been through numerous soldering classes
in my career, starting with electrical vocational courses in high school, then again
in USAF technical school, and other times while working as a technician and engineer,
I always exercise care in
making solder joints. Proper preparation - including both tinning
of mating surfaces and a means to prevent the joint members from moving during cool-down
- is of utmost importance for assuring a nice, smooth, shiny joint with just the
right amount of solder. Lead-free solders do not tend to produce the level of shininess
as do the good old 60-40 type tin-lead solders...
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