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 I remember hearing a long time ago about
"The Thing"
- a passive bugging device discovered within a wooden Great Seal gifted to the U.S.
Embassy in Moscow. This 1962 Electronics Illustrated magazine feature explores
the ingenious, battery-less Soviet listening device. Far from a conventional electronic
bug, this passive device utilized a specialized resonant cavity and a diaphragm
that modulated an external 1600 MHz radio beam, essentially acting as an echo-based
microphone that was incredibly difficult to detect. While the article highlights
the device's diabolical simplicity and sensitivity, it contains no mention of the
U-2 incident or Gary Powers; notably, historical records clarify that Ambassador
Lodge displayed the device in 1960 to expose Soviet espionage...
 Based on beleaguered wife Sylvia Kohler's
mention of GE's Electronics Park in this story (surely a fable... or not), she and
unintentional antagonist, superheterodyne hubby (aka "Happy Boy," but we know him
as Popular Electronics cartoonist
Carl Kohler) probably lived in the Syracuse, NY, area. Electronics
Park existed during the hey days of General Electric when the sprawling campus ,
just north of I-90, designed and manufactured a plethora of both household and military
electronics products. GE's Electronics Laboratory ("E-Labs") was the company's pride
and joy. Today, a tiny portion of Electronics Park is still occupied by Lockheed
Martin, who bought that GE division in the 1990s, and the rest belongs the city.
But I digress... enjoy the story (her reason for referring to hubby as a Superheterodyne
is highlighted)...
 Multielement quad antennas are as popular
today as they were in 1967 when this article appeared in the ARRL's QST
magazine. That is not to say they are common. This particular design is for the
10-, 15-, and 20-meters bands, all three
of which are still in use today. If you build a multielement quad as shown here,
you might want to find a substitute for the bamboo frame members; aluminum tubing
is pretty cheap, but if you use metal, you'll need to use insulators at the connection
points. Formulas are provided for determining element lengths and director and reflector...
 This Radio Service Data Sheet from a 1932
issue of Radio-Craft magazine provides schematics and parts lists for
Silver-Marshall Model 727-DC Battery-Operated Superheterodyne
receiver. Most - if not all - electronics servicemen had subscriptions to these
magazines because they were a ready source of not just these service sheets, but
because of the extensive articles offering advice on servicing radios and televisions.
In fact, many electronics manufacturers had a policy of supplying service data only
to bona fide shops. A large list is included at the bottom of the page of similar
documents from vintage receiver schematics, troubleshooting tips, and alignment
procedures...
 There is something about these proposed
shorthand circuit symbols that reminds me of the IEEE digital
logic symbols using the distinctive shape (the traditional format) versus the newer
rectangular shape format. The set is quite extensive when all the different flavors
of combinatorial blocks - flip-flops, timers, counters, shift registers, encoders,
decoders, etc. - are included. My personal preference, you might guess, is the original
format with distinctive shapes. Although I do not do a lot of digital work, it is
easier for me to follow the signal flow and mentally perform the logic operations
with the distinctive shapes. But I digress. This article from a 1947 issue of
QST magazine introduces...
 Anritsu has been a global provider of innovative
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a full line of innovative components and accessories for
RF and Microwave Test and Measurement
Equipment including attenuators & terminations; coaxial cables, connectors &
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spectrum, & vector network analyzers (VNAs); calibration kits; Bluetooth &
WLAN testers; PIM testers; amplifiers; power dividers; antennas. "We've Got You
Covered."
 Mac's young technician sidekick Barney decides
to one-up the
do-it-yourself television repair books that were flooding magazine
pages those days by writing a series of do-it-yourself surgery books. He figures
if the other guys can get rich by convincing Joe Sixpack that he can easily fix
problems in his TV set - where potentially lethal voltages lurk in every corner
- in as little as five minutes while saving hundreds of dollars from those rascally
shop owners, then surely those same people might buy his books for removing your
own appendix or tonsils. Deny the greedy doctors...
 This week's
Science & Engineering Crossword Puzzle has a special message
included that has to do with why you might be off work on Monday for a holiday.
Oh, and it also happens to be the world's most revered religious time of commemoration,
which to the delight of some and to the sorrow of others, is rapidly fading into
the shadows of time. The colorful "no-letter" squares were inspired by the type
of candy I am eating as I make the puzzle. As always all the other words are from
a hand assembled file of thousands of terms from science, engineering, mathematics,
chemistry, astronomy, etc. 7 Across + 15 Across to all...
 It really was not all that long ago when
wiring images for news stories literally meant
transmitting photographs over a twisted pair of telephone lines
either to a fax machine or to a computer on standby waiting for incoming files.
Videocasts were being regularly performed via satellite of ground relay microwave
stations since the 1960s, but most still shots were sent via phone lines. For the
last decade and a half, both still shots and videos have been transmitted as a routine
matter via camera-equipped cellphones, and as with most technologies we have quickly
become so accustomed to the convenience that memories of the old ways are quickly
(even thankfully) forgotten. This article from a 1936 edition of Radio-Craft
magazine describes one of the really early systems. Notice that coupling to the
telephone line is...
 On
sale through the end of June! Werbel's new
WM3PD-6-18-S, 3-way Wilkinson divider that operates from 6 to 18 GHz.
It is part of Werbel Microwave's catalog of splitters that offer a wide range of
port count and frequency ranges. Its compact aluminum enclosure measures 1.57 x
1.57 x 0.38 inches. The device is RoHS compliant, however it may be specially
ordered with lead solder. Return loss 14 dB typical input, 15 dB typical
output. Insertion loss above 4.8 dB is 0.3 dB typical. Isolation 23 dB
typical. Phase balance 3.4° typical. Designed and assembled in the USA. "No Worries
with Werbel!"
 Velocity modulation, aka deflection modulation,
of electronic images was evidently considered by some engineers to be potentially
disruptive technology when this article was published in a 1951 issue of Radio &
Television News magazine. You can see from the pictures that the result is
an image that today's digital software would render with an "emboss'" technique.
More vertical relief seems to be generated with the analog velocity modulation technique
compared to what my graphics program does when embossing the original photo. At
the bottom of the page is a velocity modulation video demonstration found on YouTube...
 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.
 Fortunately, there is a constant flow of
people newly interested in electronics who are seeking information on basic principles.
Some will find an article this one on
Ohm's law fundamentals and decide maybe being just a user of electronics
is good enough. Others will, as did you and I, read this kind of material and be
amazed at how ultimately predictable electrical circuit parameters are. If he or
she continues and launches into a career in electronics or electrical engineering,
it won't be long before he or she will, as do you...
 Whilst reading this Carl Kohler technodrama
entitled "Thin Air My Foot!," I happened upon this word new to me: "din,"
as in "It was dinned into me." OK, maybe you already knew that, but surely I should
have been aware of its alternate meaning other than being a loud noise ("the agitated
cat made quite a din."). Fortunately, I am not subject to a household of people
who refuse to put things back in their respective places when through with them,
but this tale of woe tells what might be a familiar scenario to you. To be honest,
this could have been written about me as a boy - before the U.S. Air Force taught
me a thing or two about organization and neatness - since I continually frustrated
my father by leaving his tools (and hardware and lumber and paint) scattered in
forgotten places around the house and yard...
 Antenna radiation (beam) patterns published
by manufacturers are obtained under ideal - or close to ideal - conditions with
a carefully prepared and calibrated open air test site (OATS) or an enclosed anechoic
chamber. Multipath, imperfect earth ground, obstacles both manmade and natural,
misshapen elements, poor VSWR, antenna orientation (in both azimuth and elevation)
are among the many factors which produce real-world operational results that do
not jive with a manufacturer's datasheet. Without employing some far field 3-dimensional
field strength scheme see
Drone-Based Field Measurement System™), there is no way to obtain
a complete picture of how your antenna performs in all directions...
 It has been quite a while since posting
a
Carl & Jerry adventure tale. The teenage-neighbors-cum-Ham-radio-operators-cum-electronics-hobbyists-cum-amateur-detectives-cum-pranksters
are the creation of John T. Frye. He published a monthly episode in Popular
Electronics magazine. Mr. Frye is also the author of the
Mac's Radio Service Shop series of instructional stories
that ran in Radio & Television News magazine. This adventure is quite
a digression from the typical storyline in that the boys actually engage in a bit
of deceit in order to save face based on a bet...
 Exodus Advanced Communications is a multinational
RF communication equipment and engineering service company serving both commercial
and government entities and their affiliates worldwide. Power amplifiers ranging
from 10 kHz to 51 GHz with various output power levels and noise figure
ranges, we fully support custom designs and manufacturing requirements for both
small and large volume levels. decades of combined experience in the RF field for
numerous applications including military jamming, communications, radar, EMI/EMC
and various commercial projects with all designing and manufacturing of our HPA,
MPA, and LNA products in-house.
 Is
the
BOMARC an airplane or a rocket? If it is an airplane, then it is the pilotless
type (aka "drone"). If it is a rocket, then it is the ultimate in controlled trajectory
hardware - at least in its day. The DoD referred to it as a surface-to-air guided
missile. The name is a combination of "BOeing Airplane Company"
and "Michigan Aeronautical Research
Center." Clever, non? If memory serves me correctly (it's been
30+ years), the AN/TPX-42 IFF (Identification Friend or Foe) secondary radar system
(built by Gilfillan) I maintained as an air traffic control radar technician reserved
a special "X" bit in its data packet to designate the BOMARC - and maybe other guided
missiles. That might have been a military secret at the time...
 "Israel's Iron Beam laser weapon that can
destroy drones for a few dollars 'a pop' are being developed and introduced into
combat service. The Chinese
Hurricane 3000 system is another new weapon developed to tackle the growing
use of drones in combat. However, unlike the laser-based Israeli system, the Hurricane
3000 system uses microwaves to disable drones and drone swarms at ranges exceeding
3 kilometers (1.9 miles). This is a similar weapon to the US Army's Leonidas microwave
weapon, although China claims that the 3000's reported three-kilometer-plus range
is over a kilometer more than the Leonidas system...
 This is interesting. The title for the
General Motors S1B radio says it is a 25-cycle model, as compared
to the S1A, 60-cycle model. According to an IEEE Xplore paper, "At 8:53 PM on 12
October 2006, a 66-kV circuit breaker tripped and locked out at the Harper Substation
in Niagara Falls, New York, due to downed transmission conductors near Buffalo,
New York. That event marked the end of over 111 years of 25-Hz alternating current
(ac) electric power service on the American side of the Niagara Frontier." 25 Hz
was considered a good, low frequency for...
 Here is a good
quiz that tests your knowledge of classifications of science fields.
It appeared in a 1949 edition of The Saturday Evening Post magazine. Even
if you do not particularly know the relationships, you should be able to get most
if not all twelve correct with a combination of surety, recognition of word roots,
and a process of elimination. Good luck...
 ConductRF is continually innovating and
developing advanced solutions for RF cable assembly and various RF through millimeterwave
interconnect requirements. We'll be posting their latest RF cables and technical
articles here at RFcafe.com, but to stay abreast, you're encouraged to visit their
Updates section at https://www.conductrf.com/blog
and sign up for their monthly news releases.
 During the early 1960s, Short-Wave Listening
(SWL) was a remarkably popular era-defining hobby, as enthusiasts worldwide competed
to pull in distant broadcasts from London, Moscow, or Hong Kong. "How
to DX Satellites" challenged these listeners to advance beyond Earth-bound stations
to the ultimate frontier: intercepting signals from orbiting spacecraft. While skeptics
dismissed satellite DXing as impossible due to extreme distances, low power, and
elusive verification, the author maintained it was achievable for those with the
right patience and gear. Successful monitoring required sensitive communications
receivers, crystal calibrators...
 Radio Shack,
like so many of America's original great companies, was born and lived long and
prospered during its glory days, then eventually waned into insignificance and obsolescence
within the last decade or so. It is not always simply an unwillingness to adapt
to new technologies and methods that dooms them. The forces behind those life cycles
are often beyond their control because start-ups vying for market share do not carry
the burden of and have to deal with established investments in people, facilities,
and infrastructure...
 Although obviously (but getting less so)
before my time, the mention of this airborne radar surveillance system having been
built by
General Electric, in Utica, New York, struck a chord since that
is where I had my first engineering job after having graduated from the University
of Vermont with a BSEE degree. It seems to me the work at the time was all done
in the converted textile complex on Broad Street. They were the glory days of GE,
Westinghouse, Collins, Raytheon, and other electronics titans whose engineers, technicians,
assemblers, and program managers...
 The June 1949 issue of Radio & Television
News had four
television-themed comics. Television at that time was a relatively
new home appliance, so there was a huge amount of interest in the technology. It
hadn't really been all that long since the public got used to hearing sound (i.e.,
'talkies') in the movie theater, so the mystique that surrounded television made
it the subject of a lot of puns and jokes. 1949 was a mere four years after the
end of World War II, and the post-war economic boom was primed by a surplus
of left-over electronic components along with lots of available talent both in the
areas of design and assembly...
 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.
 Both my father and grandfather were
stamp collectors - philatelists is the technical word - who dabbled
in a recreational way with commemoratives from foreign countries. Nearly all were
canceled (used) stamps that today, as back in their
day, have no real value other than to someone interested in history. Of course none
are the rare types. I now possess many of those stamps in an album that was painstakingly
hand-illustrated and assembled to arrange each stamp according to its country and
issue date. At one time I, too, dabbled in the hobby, having collected many plate
blocks and special issue U.S. stamps in the 1970s and 1980s, along with purchasing
a few designs of special purpose such as those with aerospace and communications
themes...
|
 • FCC
Approves Charter's $34.5B Acquisition of Cox
• Amazon
Might Buy Globalstar
• AI Could End
Online Anonymity (or falsely identify)
• How
Test and Measurement Will Evolve in 2026
• AI
and Geopolitics Forge Memory Market Crisis
 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.
 Waveform shaping is essential in today's
crowded communications spectrum. Spectral masks are precisely defined in order to
prevent "spreading" beyond the allocated frequency ranges at defined power levels.
Whenever anything other than a continuous sinewave is being broadcast, there is
spectral content generated in addition to the fundamental frequency. A Fourier transform
of the waveform reveals which frequencies at what power levels comprise the waveform.
The CW signal used by Morse code operators is a pure sinewave (or nearly so), but
there is a spectral problem with it every time the signal turns on or off because
of the square-ish edges involved during switching. RC networks are used in the transmitter
circuits to tame the edges so that they do not turn on and off so quickly and in
doing so reduce the extraneous frequency content. Author George Grammer argues that
even though the signal could theoretically be made "clickless" (aka "chirpless"),
there is an auditory benefit to the clicks or chirps that aids operators listening
to high speed code transmissions...
 Here are a couple more
tech-themed comics from a vintage electronics magazine (Popular Electronics).
The one from page 101 reminds me again about how different the world of retail sales
is today compared to just two short decades ago. Prior to the advent of online marketing
and sales, you either walked into a brick and mortar (a term rarely heard before
the Internet era) type store and walked out with your purchased product, or you
thumbed through a catalog and placed an order either by mail or telephone. Most
people opted to pay for a postage stamp rather than pay the long distance phone
charge (a term rarely heard today). Free overnight or 2-day shipping from many e-stores
makes online shopping nearly as instantaneous as walking into a store. People under
20 years old have never known much different, but some old-timers still find the
paradigm change strange. The way things are going...
 Windfreak Technologies is proud to announces
the availability of our
FT108, an innovative
programmable bidirectional filter bank spanning a frequency range of 5 MHz
to 8 GHz in 15 bands. Band selection can be controlled through USB, UART or
at high speeds through powerful triggering modes. Each unit is factory tested via
network analyzer with unique data stored in the device to help with its use. Crossover
frequencies are stored so the user can send a frequency command and the FT108 will
utilizes Intelligent Band Selection logic to automatically toggle the optimal
filter path based on minimum insertion loss. Readback of FT108 insertion loss at
any frequency between crossover points allows for easy amplitude leveling...
 A more common configuration for
transistor amplifiers is the common-emitter configuration. Positive feedback
is a little more difficult with this configuration because the input and output
signals are 180º out of phase. Positive feedback can be accomplished by feeding
a portion of the output signal of the second stage back to the input of the first
stage. This arrangement is shown in figure 1-19. The figure shows that each stage
of amplification has a 180º phase shift. This means that the output signal of Q2
will be in phase with the input signal to Q1. a portion of the output signal of
Q2 is coupled back to the input of Q1 through the feedback network of C3 and R3.
R3 should have a large resistance to limit the amount of signal through the feedback
network...
 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...
 Back in the 1970s and 80s when I was a regular
reader of magazines like Popular Science, Mechanix Illustrated,
Popular Mechanics, et al, it never occurred to me that there were so many
stories and news tidbits related to electronics and communications. Now, half a
century later as I read through many of them, I am amazed to see just how much content
there is for posting on RF Cafe. Of course I was nowhere near as familiar with the
topics at the time, so the stories did not have the draw they do now. Just as with
the contemporary magazines I peruse each month, I typically go through them from
cover to cover, reading much of what is there, including the advertisements. This
1949 report is on the National Bureau of Standards' (NBS, now National Institute
of Standards and Technology, NIST) frequency and timing standard signals from their
original location near Washington, D.C., call sign
WWV. Details on the various continually broadcasted signals are covered within,
along with some of the equipment used to accomplish the feat. You will need to visit
the current WWV website to compare with today's signals...
 "Those who cannot remember the past are condemned
to repeat it." That line from George Santayana's The Life of Reason: Reason in Common
Sense always comes to mind whenever I see articles from vintage publications about
how people at the time were being forced to defend their ways of life from maniacal
would-be dictators who marshaled armies of like-minded crazies to invade and attempt
to subdue other countries and/or citizens within their own borders. It seems after
a generation or two of comfortable, relatively safe existence, the collective guard
is lowered and the hard-lessons from history are forgotten or subversively erased
from memories. This particular 1944 Radio News magazine article tells the
story of women of European Allied nations - in particular Polish women - taking
up arms against Axis powers (Germany and Italy) during World War II. Part of
the survival effort included learning to
operate and service communications equipment in order to provide surveillance
and security both on the battlefield and in helping countrymen escape the incursion.
Some were captured...
 On the May 13, 2005 episode of The Tonight
Show, Jay Leno held a Morse code vs. SMS speed contest between two Ham Radio operators
using Morse code and two Millennials using their smartphones for texting (SMS).
At least one member of the audience thought texting would win. Watch the video to
see if she was right. Mr. Chip Margelli (K7JA) did the sending. He declares, "Let
me assure you that we never saw that message before I flipped the blue card over.
Each message, in rehearsal, was different. The character count was the same as the
one during dress rehearsal, though, to account for the time slot. And they put the
card on the table "upside down" creative to how I flipped it, as you can see on
the video." Mr. Ken Miller (K6CTW) did the receiving...
 Is there such as thing as too many articles
on
transmission lines? I think not, at least for most visitors to RF Cafe. Since
the fundamentals of transmission lines have not changed in the last century, it
really doesn't matter when an article was written. This one covers the basics of
impedance and wavelength, and then delves briefly into the subjects of antenna feeder
transmission lines and using transmission lines as impedance transformers. As with
most topics these days, there are many software programs available that will calculate
parameters for you, but successful setup and operation requires a solid understanding
of what is happening with your electronic gear, antennas, and the transmission lines
that provide the interfaces...
 Being a repairman of any sort has always
resulted in a wide variety of customer responses. Of course poor technicians deserve
all the derision they receive, but
good technicians often catch a boatload of grief whether or not their efforts
result in success. Nobody wants to pay more money than he has to, but too often
the owner of a property who is in desperate need of knowledgeable help has a sudden
change from gratitude for the technician's willingness to take on the challenge
to maniacal repulsion when informed of the cost. I have always endeavored to perform
as much needed labor myself as possible, whether it be car repairs, home maintenance,
appliance fixing, electronics troubleshooting, etc. However, there are some things
you simply cannot do for yourself either because of a lack of knowledge, lack of
necessary equipment, or government licensing. On those occasions, I try to remember
be as polite and gracious as possible, even after being presented with a bill including
$90 per hour for a car mechanic...
 Many topics of the
electronics-themed comics which appeared in Radio-Craft were suggested by the
magazine's readers. Staff artists like Frank Beaven turned those suggestions into
cartoons. For a while there was a special feature called "Radio Term Illustrated"
where, as the name suggests, terms like "Signal Generator" and "High Potential"
are rendered in farcical form. These four comics, two of each type, appeared in
a May 1947 issue of Radio-Craft. I have to admit that even with my familiarity with
vintage electronics memes I do not get the Television "Organ" comic (yes, I understand
the organ grinder, but not how it applies to TV).
 Most digital and
analog multimeters rely on precision resistors for scaling the input voltage
or current to keep it within the safe operational range of the meter movement or
analog-to-digital converter circuit. Resistance value selection is a relatively
simple matter of series and/or parallel combinations and their resulting divisions
of voltages and/or currents. When this article appeared in a 1931 issue of Radio-Craft
magazine, the whole concept of electrical circuit design was entirely new to most
people, including shunts and multipliers for meter scales. The International Rectifier
Company (IRC) article gives a handy rule of thumb for setting resistor values when
considering the resistance of the meter movement coil. There is a nice table of
resistor values provided, but I was a little disappointed to find that not a single
equation is given for calculating custom values...
 Author William Blair lamented in a 1958 issue
of Radio & TV News magazine that helix (aka helical) antennas had not
yet been widely adopted by amateur radio operators despite the advantages they can
provide. Helix antennas are used for transmitting and receiving circularly polarized
electromagnetic waves. An advantage of using a
circularly polarized antenna for receiving is that it is able to make use of
wavefronts arriving at any polarization angle along the propagation axis,
thereby accommodating transmissions at any polarization angle. Theoretically, an
ideal antenna with a particular polarization would not receive a signal arriving
at an angle perpendicular to it, and the strength of any signal would be
proportional to the cosine of the angle of impingement...
 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...
 In this 1953 QST magazine article, Authors
Cohen and Hessinger warn about the need to consider the
capacitive loading effects of shielded and closely-space test leads when measuring
other than direct current or very low audio or line frequencies. Lead capacitance
is especially likely to affect measured values when the frequency is high and/or
the source and load impedances are high. As was common in the day, capacitance units
of μμfd (micro-micro farads = 10-6 x 10-6 = 10-12 F) are cited, which is equivalent
to units of pF (10-12 F)...
 The term "modern" in the title of any book
or article never has set right with me because it is utterly ambiguous about the
era to which "modern" refers. Sure, it sounds good at the time, but when applied
to this 1966 QST magazinearticle, "modern" should be replaced with "four-decade-old."
However, in this case the content is still relevant even thought it was written
so long ago (or else I would not be reproducing it here). It may well have been
most people's first exposure to
elliptical (Cauer) filters. As you might expect, the rigorous, headache-inducing
mathematics is omitted, but the article does give an example of implementing an
audio frequency bandpass filter by cascading a lowpass filter and a highpass filter.
If you are familiar with filter design, you know that because of phasing and inband...
 This is another example of a multi-part article
of which I happen to have discovered only one of installments - Part 9. As is often
the case, each article is pretty much stand-alone and does not require that you
have already seen the previous sections. In 1951, computers were still mostly analog;
digital circuits were just beginning to get serious research thanks to the recent
advent of solid state devices. Boolean algebra, truth tables, and combinational
logic were just beginning to be taught in engineering courses.
ENIAC (Electronic Numerical Integrator and Computer), first used in 1945 at
the end of World War II, was the world's first general purpose digital computer,
and its active elements were vacuum tubes - about 20,000 of them. As you might expect,
there was a lot of excitement in the electronics, scientific, and finance world
about digital computers that would be inexpensive enough that individual corporations...
 Homodyne reception, although we don't often
refer to it today using that term, involves mixing the modulated signal with a local
oscillator that is tuned to the same frequency so that the demodulated signal is
at baseband. In other words, the result of a homodyne nonlinear mixing process is
a sum frequency of 2x the signal input and the difference frequency is DC (at the
low end of the modulation). That is a simplistic explanation, and this 1942
Radio-Craft magazine article goes into a little more detail about methods,
advantages, and disadvantages. Why not just make things simple and make every receiver
a homodyne circuit? The answer is that with homodyne operation every theoretically
possible mixer spurious product will fall inband without any means of filtering
them out. Sometimes it doesn't matter, but especially in today's crowded radio spectrum
it just is not workable because the interference level would be too intolerable...
 Author Lawrence Sharpe pointed in 1955
in this Radio & Television News article the potential for confusion
when reading columns and advertisements written by our brothers from Across the
Pond when they appeared in American electronics magazines. Most of us are familiar
with valve vs vacuum tube, bonnet vs. hood (car), football vs. soccer, fag vs. cigarette,
holiday vs. vacation, nappy vs. diaper, petrol vs. gasoline, torch vs. flashlight,
flat vs. apartment. There are many more, but those come to mind. Read through this
short list of purely electronics terms and learn that
"earthed" is the same as our "grounded." One thing that surprised me was how
the Brits had already adopted pico (e.g. pF) for the numerical unit of 10-12
while we were still using micromicro (10-6 x 10-6 = 10-12,
e.g., μμF). Note how I omitted a comma... |
