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 This article explains the six most common
two-port network matrix descriptions used in circuit theory, RF/microwave engineering,
filter design, amplifier design, and transmission-line analysis: Z-parameters, Y-parameters,
h-parameters, ABCD-parameters, S-parameters, and scattering-transfer T-parameters.
Each representation describes the same linear two-port network, but each chooses
a different set of independent and dependent variables. Because of that choice,
some matrix types are natural for low-frequency circuit analysis, some for cascade
calculations, and some for high-frequency measurement where direct open- and short-circuit
tests become impractical. The most important...
 Each week, for the sake of all avid cruciverbalists
amongst us, I create a new
technology-themed crossword puzzle using only words 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,
see someone or something in the exclusion list who or that is directly related to
this puzzle's theme, such as Hedy Lamarr or the Bikini Atoll, respectively.
Enjoy!...
 There are lots of audiophiles in the RF
Cafe audience who might appreciate this article on the characteristics of human
hearing and ways in which stereo hi-fi equipment attempts to reproduce realistic
sound, as if from a live performance. A handy-dandy chart is provided that shows
the characteristics of various audible frequency ranges, and the
kinds of speakers best suited for reproducing the sound. It was
published in a 1955 issue of Popular Electronics magazine when stereo hi-fi
system building was a major pastime, but still should be applicable today. If you
do a search on RF Cafe, you will find many articles covering stereo hi-fi equipment...
 The other day a song entitled "Western
Union" played on my local over-the-air oldies radio station. It was released
by the group, The Five Americans, in 1967. The full lyrics of "Western Union" can
be found at the bottom of the page, but notice the "Dah-Dit-Dah-Dit-Dah" repeats
in the refrain. My lack of a Morse code deciphering ability required that I rely
on an online translator for considering what the code might be. Depending on how
you separate the dits and dahs, the string of characters can be interpreted as TETET
(- . - . -), TAA (- .- .-), KA (-.- .-), NK (-. -.-), CT (-.-. -) or other combinations.
RF Cafe visitor
Alan
Dewey has provided new insight on the characters...
 Listen to the
RF Cafe Podcast! Hugo Gernsback, a name familiar to anyone who has been reading
some of the vintage electronics articles posted here on RF Cafe over the years,
was never short on ideas - both serious and fanciful. In 1947, when this editorial
appeared in his very popular Radio-Craft magazine, radio had become ubiquitous
in the commercial and consumer worlds, but he laments that the appliance had not
yet received its due compliment of
ancillary devices. Telephone, which had been around even longer
that radio, had a fair market of add-ons like a shoulder rest for the handset, an
amplifier for the hard-of-hearing, remote ringers, etc. There was not yet a selection...
 Windfreak Technologies designs, manufactures,
tests and sells high value USB powered and controlled radio frequency products such as
RF signal generators, RF synthesizers, RF power detectors, mixers, up / downconverters,
and a 15-band programmable filter (5 MHz-8 GHz). Since the conception
of WFT, we have introduced products that have been purchased by a wide range of
customers, from hobbyists to education facilities to government agencies. Worldwide
customers include Europe, Australia, and Asia. Please contact Windfreak today to
learn how they might help you with your current project.
 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.
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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.
 Engineers are entirely comfortable with numbers
multiplied by very large powers of 10; that is, with many trailing (or leading if
a decimal) zeros after the significant figures. A terahertz is 1 x 1012,
or 1 followed by twelve zeros, or
1,000,000,000,000 Hz. A picosecond is 1 x 10-12 s, or eleven
zeros between the decimal point and the one, or 0.000000000001 s. The mass
of the sun is approximately 1.9885×1030 kg, or 1,988,500,000,000,000,000,000,000,000,000 kg. The mass of an electron is approximately 9.10938×10-31 kg,
or 0.000000000000000000000000000000910938 kg. We don't even break a sweat when
punching those kinds of numbers into a calculator...
 This
passive
limiter is a simple combination of cascaded "T" type resistive attenuators that
are switched in and out of the circuit based on the power level in the line. The
design takes a bit of thinking due to needing to retain a reasonable impedance match
at the input and output throughout various stages' conduction states. Arriving at
an optimal value for resistors would require a circuit simulator with a mathematically
based optimizer, but, especially for amateur radio work, close is good enough. That
is not to say Hams are a bunch of slackers - they're not - it's just that component
and software resources are not as readily available (aka "prohibitively expensive")
for doing the analysis...
 Believe it or not, many countries did - and
some still do - charge people wanting to receive over-the-air (not cable or satellite)
commercial radio and/or television programming a
wireless license fee for the privilege. Yes, this is for receiving, not transmitting,
signals. If you dared to tune in a BBC program without a license, a fee could be
expected upon detection (pun intended). The Monthly Review feature in this 1946
issue of Radio-Craft magazine reported an increase in cost to the equivalent
of $29 in 2021 money (per the BLS Inflation Calculator). Also highlighted was a
method for printing radio circuits made with conductive inks on ceramic sheets -
known today as thick-film printing...
 By 1962, John T. Frye's techie troubleshooting
teenagers
Carl and Jerry had graduated from high school and were attending Parvoo University
(PU?) as electrical engineering students. It was a natural progression. Unlike many
of the company names and products - like the Delco DN278 transistor mentioned here
- that appeared in the Popular Science series, the college's name is fictional.
Maybe author Frye had a connection to Porvoo, Finland, and Anglicized the name.
Per RF Cafe visitor Jim P., "The stadium in the story is Moss-Ade stadium.
The stadium at Purdue University is Ross-Ade stadium. I would guess that Parvoo
comes from Purdue." According to a search I did to determine whether..."
 As mentioned in the past, most things you
might want to find from the present or past can be found eventually on eBay. Such
is the case with the Webster Electric Model 205 Tape Recorder mentioned in this
Mac's Radio Service Shop episode which appeared in a1954 issue of Radio &
Television News magazine. Here, Mac McGregor schools sidekick electronics technician
Barney Jameson on the workings of a high quality tape recorder, including some of
the ingenious methods devised for test and alignment. I especially like the magnetic
tape specifically prepared for head alignment by the Toogood Recording Company of
Chicago (yes, it was a real company, named after Mr. Louis S. Toogood)...
 Here is an advertisement for
Hytron Corporation that I scanned from page 83 of my copy of the June 1944
QST magazine. Hytron was a manufacturer of electron tubes. "So Many Owe
So Much To So Few," reds the title line. That is a paraphrase of Winston Churchill's
famous statement during World War II, "Never in the field of human conflict
was so much owed by so many to so few." That was in August 21, 1940, more than a
year before the U.S. entered the war. Perhaps of greater interest to RF Cafe visitors
are the next lines: "In peace, the Nation's debt to the radio amateur was great.
During hurricanes, floods, and other disasters, he sprang forward with emergency
communications. His endless...
 This 1952-era promotion for Bell Telephone
Laboratories describes what is essentially an early
Supervisory Control and Data Acquisition (SCADA) system; it's just that the
term had not been coined yet. SCADA systems uses sensors of various types to monitor
the status of critical parameters and report it back to a remote location via telephone,
cable, or radio links. It reduces or eliminates the need for personnel to be present
unless immediate human interaction is required to handle an adverse situation. Electrical
distribution stations, gas and oil lines, telephone switching installations, etc.
SCADA systems are typically monitored by computers and in most cases log events
and initiate required actions...
 As with on my Airplane and Rockets
hobby website, a big part of my motivation for scanning and posting these vintage
electronics magazine articles has been two-fold. The primary purpose is to provide
access to historical documents for research and educational reasons. The second
reason is to have the names of people and places published in text format (everything
OCRed) so that someone doing a Web search for himself, a relative, or a friend,
might run across it here. I receive e-mails occasionally from readers who are
thrilled to find those names in an old article, especially when the person
discovered has passed on and it serves as a fond remembrance. Features such
as...
 This
Technology Theme Crossword Puzzle for April 25th has many words and clues related
to RF, microwave, and mm-wave engineering, optics, mathematics, chemistry, physics,
and other technical subjects. As always, this crossword contains no names of politicians,
mountain ranges, exotic foods or plants, movie stars, or anything of the sort unless
it/he/she is related to this puzzle's technology theme (e.g., Reginald Denny or
the Tunguska event in Siberia). The technically inclined cruciverbalists amongst
us will appreciate the effort. Enjoy!
 Judging by some of the letters written to
magazines by their readers,
obtaining parts referenced in many construction articles proved difficult or
impossible to procure. Ziff-Davis, a major publisher in 1940 as well as today, ran
this notice in a 1940 issue of its Radio News magazine offering advice
as to how one might go about getting everything needed. Unlike nowadays where nearly
every available source worldwide can be found on the World Wide Web, back then searching
could be - and too often was - a long, slow process. Just finding a phone number
or mailing address for a potential supplier presented a major obstacle to anyone
without a collection of catalogs and magazines - or at least...
 Electronic mail did not start out as we know
it today, whereby anyone with access to an Internet-connected device can compose
and send a typed message to a similarly equipped receiver. The first electronic
mail message was sent (and received) on November 1, 1960, between post offices in
Washington, D.C., and Chicago, Illinois. This article from Popular Electronics
magazine takes you on a step-by-step tour of how the
Speed Mail system worked, including its dedicated shortwave radio links between
participating cities. Great care was taken in an attempt to assure message confidentiality
by having the letter opened and scanned automatically inside a sealed machine on
the transmit end ...
 After having read many articles about Dr. Lee
de Forest, it seems the poor guy was besieged his entire life by envious and/or
belligerent electronic communications compatriots who sought to defame him and/or
deny him of monetary rewards. This January 1947 issue of Radio-Craft
magazine includes a dozen or so pieces written by friends and colleagues who
recognized the momentous struggles and achievements of Dr. de Forest. Such
burdens of fame are borne by many - if not all - persons of similar celebrity.
Dogged persistence is the order of the day for experimenters and
breakers-through of assumedly impenetrable walls. Guys like de Forest lived by
the old adage recommending that "if at first you don't succeed...
 Here is a little electronics hobbyist humor
in the form a comic series titled "Hobnobbing with Harbaugh," compliments of
Popular Electronics magazine. Dave Harbaugh drew many comics for technical
magazines. For the non-Ham, QSL is the Q-code for "'I confirm that I received your
transmission." You don't need to be an amateur radio operator to appreciate these
comic strips, though. Note that with it being 1963, the husband and wife are shown
sleeping in separate beds - just like in the TV shows of the era like The Dick Van
Dyke Show and I Love Lucy. BTW, the kid in the crib is spelling out -..(d) .-(a)
-..(d) -..(d) -.--(y).
 It was a lot of work, but I finally finished
a version of the "RF &
Electronics Schematic & Block Diagram Symbols"" that works well with
Microsoft Office™ programs Word™, Excel™, and Power Point™. This is an
equivalent of the extensive set of amplifier, mixer, filter, switch, connector,
waveguide, digital, analog, antenna, and other commonly used symbols for system
block diagrams and schematics created for Visio™. Each of the 1,000+ symbols was
exported individually from Visio in the EMF file format, then imported into Word
on a Drawing Canvas. The EMF format allows an image to be scaled up or down
without becoming pixelated, so all the shapes can be resized in a document...
 Here are a couple more
electronics-themed comics from a 1940-era issue of Radio News magazine.
The scenarios depicted in these old comics are often based on the real-life experiences
of radio and electronics servicemen. No doubt many guys got clobbered by high voltage
or deafening audio when a customer decided to power up a television or radio while
being worked on in the home. When this comic with the police car radio appeared
in 1940, it had only been a decade since the first 2-way radios were being installed
in patrol cars (see "A New Arm of the Law"). A huge list of technology-themed comics
is listed at the bottom of the page. Enjoy! |
