|
 A lot of the guys I knew from my time in
the U.S. Air Force as an Air Traffic Control Radar Repairman (AFCS 303x1) went to
work for the government or defense contractors after separation. Many were retirees,
so they were (are) collecting military retirement pay on top of really good pay
doing field service work. At this point, probably most of those guys are now doubly-retired,
and collecting Social Security. They're living pretty well these days, probably
with nice homes paid off long ago. 1957, the year this solicitation for
field engineers appeared in Popular Electronics magazine, was right
at the end of the Korean War, and only a decade after World War II. A lot of
new equipment was designed and delivered...
 While working as an electronics technician
at the Oceanic Division of Westinghouse in Annapolis, MD, in the 1980s, I received
a vintage 1941 Crosley model 03CB console style radio for Christmas from Melanie.
It was in poor condition, having spent the previous few decades sitting in a barn
on the Eastern Shore of Maryland. Due to the era of manufacture, vacuum tubes rather
than transistors provided all the necessary amplification. One of the engineers
I worked for at Westinghouse (Mr. Jim Wilson, engineer extraordinaire)
was a Ham radio operator and had been from boyhood in Pittsburgh, PA. After learning
of my Crosley, he gave me his
B&K Dyna-Quik Model 650 tube tester for use in restoring the
radio. The Model 650 was a rather high-end portable tube...
 "Firefly Aerospace's Blue Ghost Mission
2 with the LuSEE-Night radio
telescope aboard will attempt to become the third successful mission to land
there. The moon's far side is the perfect place for such a telescope. The same RF
waves that carried images of Neil Armstrong setting foot on the lunar surface, Roger
Waters's voice, and hundreds of Ned Potter's space and science segments for the
U.S. broadcast networks CBS and ABC interfere with terrestrial radio telescopes.
If your goal is to detect the extremely faint and heavily redshifted signals of
neutral hydrogen from the cosmic Dark Ages, you just can't do it from Earth..."
 In the early days of television, what we
today refer to as cathode ray tubes were called
kinescopes. The kinescope on the receiving end displayed images generated
by a tube called an iconoscope on the transmission end. Kinescopes had round faces
onto which a rectangular picture was electronically drawn. Once manufacturing technology
evolved sufficiently, it became possible to make them rectangular in order to save
on material and to fit a larger picture in a smaller area. The real story as told
in this 1947 Radio News magazine article from my perspective is appreciating the
ingenuity of the manufacturing engineers for an ability to develop machines that
handle very complex operations. They were wonders of electromechanical manipulation.
Oh, and I learned a new word - "lehr"...
 This Radio Service Data Sheet for the
Sparton Model 40 6-Tube T.R.F. Automotive Receiver is an example
of the dozens of similar schematic and alignment instruction sheets that have been
posted on RF Cafe over the years. Obtaining technical information on most things,
even readily available items, prior to the Internet era was often very difficult
- if not impossible. Service centers had what was need provided by manufacturers
and distributors, but if you wanted to find a part number or service data on a refrigerator,
radio, lawn mower, garage door opener...
 Here is a great primer on the operation
of
traveling wave tubes (TWT). A controversy exists over who first invented the
TWT - Bell Telephone Labs' Dr. Rudolf Kompfner, or Andrei Haeff while at the Kellogg
Radiation Laboratory at Caltech. Regardless of its provenance, the device was a
major advancement in the development of high power microwaves. A TWT amplifies broadband
microwaves continuously: an electron gun emits a high-speed beam through a vacuum
tube, interacting with the weak input signal propagating along a helical slow-wave
structure. The helix slows the signal's phase velocity to sync...
 Take a break from workaday drudgery by trying
your hand at this week's
Amateur Radio crossword puzzle. Every word in the RF Cafe crossword
puzzle contains the usual collection of science, math, and engineering terms, and
also includes special words related to Amateur Radio (clues labeled with asterisk
*). There are no generic backfill words like many other puzzles give you, so you'll
never see a clue asking for the name of a movie star or a mountain on the Russia-China
border. 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. Enjoy.
 "Advanced threats lead to open architecture
approaches and new
analysis of electronic countermeasures. Over the past decade, preeminent countries
involved in major military conflicts mainly focused on asymmetrical warfare - surprise
attacks by small groups armed with modern, high-tech weaponry. During that same
period, however, near-peer adversaries began attaining impressive electronic warfare
(EW) capabilities. As a result, a plethora of new, dynamic threats flooded the EW
spectrum, pushing threat detection and analysis to keep pace. Large military forces
must now engage in ongoing..."
 Here are a couple more electronics-themed
comics from Electronics World magazine, good for winding down the week.
They appeared in the January 1963 issue. The page 86 comic reminds me of the professor
I had for solid state circuit design. He was supposedly the first person to successfully
use gallium arsenide (GaAs) as a semiconductor, although he also did pioneering
work with silicon. Anyway, Prof. Anderson would say he takes at least one "business"
trip each year to Portugal in order to search for higher quality raw semiconductor
material in sand on the beaches. He spoke Portuguese, BTW. The page 89 comic is
reminiscent of the pre-GPS days of navigation. Raise you hand if you ever drove
around utterly lost while looking for an off-the-beaten-path location...
 In the mid 1930s, hand-assembled products
were by far the rule rather than the exception for most products be they electronics,
furniture, appliances, automobiles, or toys. Many people lament - even curse - the
advent of machine automation in production, but the fact is for the vast majority
of things the consistency and quality of the finished component is typically much
greater. Toiling at the same task, in the same location, day after day, gets unbearable
very quickly for someone like me who likes to accomplish a particular job and then
move on to something new - even if "new" is defined as the same type of endeavor
but with different materials. There are many people, thankfully...
 At Parvoo University, amid relentless November
rain, H-3 dormmates Carl and Jerry pursue H-2's prank: a stolen bronze trophy plaque
hurled into a half-mile muddy stretch of river. Cold, turbid waters bar preclude
dives for a search; non-magnetic bronze defies current-day metal detectors. Jerry
repurposes his cousin's boat depth-finder as an
enhanced sonar, exploiting echo signatures. A motor rotates a neon tube across
a depth-calibrated dial; at zero, contacts trigger a 200-kc ultrasonic pulse from
the transducer in transmit (speaker) mode, flashing initial glow. Bottom echo reflects
to transducer in receive (microphone) mode, amplifying...
 The announcement and public demonstration
of Senatore Guglielmo Marconi's "death ray" device was the coming true of some of the worst fears
of science fiction aficionados. Application of these newly created centimeter wave
"beams" could roast the flesh of man or beast when generated with great enough power.
The diminutive wavelength not only would heat liquids, but also provided a means
of detecting and measuring energy reflected off of "targets" such as aircraft and
boats. It applications were endless. Although not called so, one of the article's
diagrams looks to be an example of a bistatic radar system. The early magnetron
implementation is quite different...
 The Federal Communications Commission (FCC)
is looking for qualified applicants for
Field Agents in seven Enforcement
Bureau (EB) offices across the United States: Atlanta, GA; Boston, MA; Chicago,
IL; Dallas, TX; New Orleans, LA; New York, NY, and Portland, OR. Incumbents will
resolve Radio Frequency (RF) interference, educate users, and enforce regulations.
The GS levels for this position have been expanded to GS 7, opening the opportunity
for new college graduates. One year of work experience is not required for this
position. Closing date is March 2, 2026...
 If you are from a family of electronics
hobbyists and/or professionals, then there is a good chance your grandfather and
possibly even your father kept a handy-dandy list of common
circuit design formulas handy. Part 2 of the list appeared here in a 1930 issue
of Radio-Craft magazine. All the formulas on this page dealt primarily
with vacuum tubes, the schematics for which were presented in Part 1 of the series.
There are still lots of hobbyists who restore and/or modify vintage sets, so the
equations are still worth publishing. There was not an "app for that" back in those
days. Prior to a smartphone in every pocket, notes were pinned to a lab wall or
kept in a hand-written notebook...
 The name
Frank Conrad probably does not sound familiar to most people in
the electronics communications field today, but at one time he was the assistant
chief engineer to the Westinghouse Company. Back when voice radio (as opposed to
Morse code, aka CW) was being pioneered, Mr. Conrad was widely known for his efforts
in commissioning the country's first commercial broadcast installation - KDKA in
Pittsburgh, Pennsylvania. His arranging for live coverage of election night results
in 1920 is credited for launching a huge interest by consumers in purchasing radio
sets for their homes (Warren Harding beat James Cox that night, BTW). Toward the
end of his career, Conrad was active in helping develop...
 Copper Mountain Technologies develops innovative
and robust RF test and measurement solutions for engineers all over the world. Copper
Mountain's extensive line of unique form factor
Vector Network Analyzers
include an RF measurement module and a software application which runs on any Windows
PC, laptop or tablet, connecting to the measurement hardware via USB interface.
The result is a lower cost, faster, more effective test process that fits into the
modern workspace in lab, production, field and secure testing environments. 50 Ω
and 75 Ω models are available, along with a full line of precision calibration
and connector adaptors.
 Details of ancient Parthian
electrochemical batteries unearthed near Baghdad by archaeologist Wilhelm Konig,
dating over 2,000 years, was reported in this 1964 Popular Electronics
magazine article. Housed in earthenware jars sealed with asphaltum (bitumen), they
featured a copper cylinder soldered with 60/40 tin-lead alloy - identical to modern
electronics, prior to PB-free mandates - encasing a corroded iron rod for electrodes,
enabling electroplating of gold, silver, and antimony via electrolytes like copper
sulphate, ferrocyanides, or lye. GE engineer Willard F.M. Gray replicated them successfully
for Pittsfield's Berkshire Museum, using iron rods for series connections. More
cells surfaced in a Seleucia magician's hut and Berlin Museum...
 It seems most of the articles we see on
the subject of attenuator pads are based on signal reduction in terms of decibels
for units of power. Although it is a simple matter to convert power decibels to
voltage decibels, it would be more convenient if you are working with voltage to
have formulas and tables of values based on voltage ratios. This article does just
that. As a reminder, the decibel representation of a ratio is always 10 * log10 (x).
If you have a voltage ratio of V1/V2 = 0.5, then
10 * log10 (0.5) = -3.01 dB. If you have
a power ratio of P1/P2 = 0.5, then 10 * log10 (0.5) = -3.01 dB.
Does that mean that -3.01 dB of voltage attenuation is the same as 3.01 dB
of power attenuation...
 This might be a perfect application for
QuentComm. "Researchers led at the University
of Science and Technology of China (USTC), have achieved a major milestone in quantum
communication. For the first time, they demonstrated a key component required for
scalable quantum repeaters, which later allowed them to carry out device-independent
quantum key distribution (DI-QKD) across 100 kilometers. The results, published
in Nature and in Science, represent important progress toward building a functional
quantum internet. The work also reinforces China's position at the forefront of
quantum research and technology..."
 This Radio Service Data Sheet for the Clarion
"Replacement" Chassis, Model AC-160 A.V.C. Superhet is an example of the dozens
of similar schematic and alignment instruction sheets that have been posted on RF
Cafe over the years. Obtaining technical information on most things, even readily
available items, prior to the Internet era was often very difficult - if not impossible.
Service centers had what was need provided by manufacturers and distributors, but
if you wanted to find a part number or service data on a refrigerator, radio, lawn
mower, garage door opener...
 Remember the test patterns that used to
be broadcast by over-the-air broadcast stations that were used to align the electron
beam defection circuitry in CRT-based televisions? That pattern of squares, circles,
parallel and radial lines was generated by a special tube called a "Monoscope" on the transmitter end. Focus, 4:3 picture aspect ratio,
linearity, frequency response, and contrast and brightness were all tweaked to optimize
the pattern on the TV receiver circuitry. Of course not all sets were capable of
obtaining a perfect alignment due to inferior design and/or a scheme by the manufacturer
to provide a lower cost model with the tradeoff being a poorer picture - that it
the type of TV we always had in our household as...
 Anritsu has been a global provider of innovative
communications test and measurement solutions for more than 120 years. Anritsu manufactures
a full line of innovative components and accessories for
RF and Microwave Test and Measurement
Equipment including attenuators & terminations; coaxial cables, connectors &
adapters; o-scopes; power meters & sensors; signal generators; antenna, signal,
spectrum, & vector network analyzers (VNAs); calibration kits; Bluetooth &
WLAN testers; PIM testers; amplifiers; power dividers; antennas. "We've Got You
Covered."
 Dave Harbaugh created a great many electronics-themed
comics back in the 1960s for magazines like Popular Electronics, QST,
"73", and others. His "Hobnobbing
with Harbaugh" series usually depicted hobbyists and technicians in a state
of surprise and/or dismay over some event while in the act of pursuing his passion
(electronics, that is, not a woman). Although I have never run across any evidence
of it, I wonder how many of the scenarios are derived from personal experience.
Many do not have captions. I have to admit to being stumped at what he is trying
to convey in the comic where the guy is staring into the back of the TV while his
wife...
 Competition amongst countries and businesses
existed long before the advent of radio receivers. Here is an interesting story
which demonstrates how international politics and corporate policies has been part
of the electronics industry since its inception. In order to circumvent what were
considered to be outlandish patent licensing fees, Danish engineer Carl Arne Scheimann
Jensen developed a new "gridless" type of vacuum tube (aka valve) which was called
the "Renode." Rather than using a screen grid in the path between the
cathode and plate, the Renode employed two sets of beam concentrator and deflector
plates on either side of the electron beam's path to modulate the conduction. According
to measurements it provided a slight improvement in both linearity and selectivity...
 "Sixth-generation wireless networks, or
6G, are expected to achieve terabit-per-second speeds using terahertz frequencies.
However, to harness the terahertz spectrum, complicated device designs are typically
needed to establish multiple high-speed connections. Now research suggests that
advanced topological materials may ultimately help to achieve such links. The experimental
device the researchers have made, in fact, achieved 72 gigabits-per-second data
rates, and reached more than 75% of the three-dimensional space around it. Current
solutions typically achieve only one or two of these features at a time and often
rely on complex
antenna arrays or mechanical steering..."
 This week's
RF & Microwave Companies crossword puzzle includes the names
of all my current advertisers and a few others that will be familiar to many of
you. These kinds of puzzles take a particularly long time to create because of needing
to force words into certain positions. That leaves the software with fewer options
for fitting the other words. All the words in RF Cafe crossword puzzles are relevant
to engineering, science, mathematics, etc., stored in a hand-built (over more than
two decades) lexicon of thousands of terms and clues. Enjoy...
|
 • U.S.
Manufacturing Sector Returns to Growth
• ARRL
Student Coding Contest $25k Award
• Shielding
Electronics Supply Chain from Cyberthreats
• Fund Opens
Defence Contracts to UK Startups
• Global
Trade Holds Its Ground
• FCC
"Supercharge" Wi-Fi in 6 GHz Band
 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.
 The
General Electric (GE) Model 250 portable radio was considered a "suitcase" style
because it looked kind of like - guess what? - a suitcase. It ran on either 120
volts AC or an internal 2.1 volt battery. A charging circuit was provided for the
battery, which was a nice feature so the owner didn't have to keep buying new batteries.
Fortunately, there seems to be many of these GE 250 radios available in various
states of reconditioning. eBay* currently has four listed ranging in price from
$40 to $150. One listing has very nice photos of the internal workings and of the
Willard model RADIO-25-2 wet storage cell battery (see below, right). Click on the
thumbnails for larger images. The nomenclature label for the radio is fully legible.
This Radio Service Data Sheet for the GE 250 radio appeared in the August 1946 issue
of Radio-Craft magazine...
 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 and still look good. The imported symbols can also
be UnGrouped into their original constituent parts for editing...
 In the days before people were so easily
offended by light-hearted poking, it was not uncommon to find magazine articles
written by the wives of hobbyist husbands lamenting the habits and proclivities
of their matrimonial mates. Over the years I have read many such treatises in model
and full-scale airplane, electronics, and Ham radio publications. As with "A
Radioman's Wife Puts in a Good Word" from a 1951 issue of Radio-Electronics,
they typically start by expressing frustration of having lost their once-doting
husbands to alternative loves in the form of hobbies (I once saw a boat named "The
Other Woman"). Determined to win back the devotion of their sweethearts, they make
a sincere attempt to learn about and be part of whatever hobby or hobbies is/are
the cause of abandonment of wife and children. It usually doesn't take long for
Friend Wife, as Popular Electronics' Carl Kohler addresses his better half, to decide
that try as she may, engendering a sufficient...
 When Arthur C. Clarke talks, people
listen (to paraphrase the old E.F. Hutton commercial). Mr. Clarke
wrote many books and papers about space technology and was a popular commentator
on space-related issues. He also made several predictions about the future of technology
that proved to be remarkably accurate, such as the use of geostationary satellites
for telecommunications. Clarke famously published his "Extra-Terrestrial Relays:
Can Rocket Stations Give World-Wide Radio Coverage?" in a 1945 issue of Wireless
World magazine. Nearly a decade later he penned this "The
Resonant Sky" article for the August 1963 edition of Radio-Electronics
magazine. The former essay predated the 1957-1958 International Geophysical Year
(IGY) atmospheric studies which laid the groundwork for space exploitation, while
the latter followed on the successful orbiting of a few satellites. Basically, everything
Clarke presents here has come to fruition, albeit a bit later than he thought it
might take...
 This Radio Service Data Sheet covers the
Ford-Philco radio model FT9, 6-tube auto-radio receiver. It appeared in a 1936
issue of Radio-Craft magazine. 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. Thumbnail photos at the left came
from a Ford-Philco FT9 radio on eBay. A large list is included at the bottom of
the page of similar documents from vintage receiver schematics, troubleshooting
tips, and alignment procedures. They were originally published in magazines like
this one, Radio and Television News, Radio News, etc. I scan and
post them...
 Banner Ads are rotated in all locations
on the page! RF Cafe typically receives 8,000-15,000 visits each
weekday. RF Cafe
is a favorite of engineers, technicians, hobbyists, and students all over the world.
With more than 17,000 pages in the Google search index, RF Cafe returns in
favorable positions on many types of key searches, both for text and images.
Your Banner Ads are displayed on average 225,000 times per year! New content
is added on a daily basis, which keeps the major search engines interested enough
to spider it multiple times each day. Items added on the homepage often can be found
in a Google search within a few hours of being posted. If you need your company
news to be seen, RF Cafe is the place to be...
 The U.S. Army's Signal Corps was set up to
"exercise supervision over signal communications literally from the Pentagon to
the foxhole." Created in 1860 at the suggestion of a military doctor, the
Signal Corps originally used a system of flag waving for messaging dubbed
"wigwag" and graduated to overseeing the nationwide telegraph network six years
later. By 1870, members were tasked with establishing and operating a weather
forecasting service, so in 1907 when they created an aeronautical division it
was just in time for facilitating the nation's rapidly growing cadre of aircraft
pioneers (recall the Wright brothers had flown four years earlier at Kitty Hawk)
by providing en route weather information. Having already mastered the state of
the art that was radio and telephone...
 This is the
electronics market prediction for Belgium, 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. Military systems for NATO and television
sets were a big part of the picture. Unless you can find a news story on the state
of the industry, detailed reports must be purchased from research companies like
Statista. Their website has a lot of charts on Belgium's current electronics market
showing revenue in the consumer electronics segment amounts of US$2,995M in 2023.
Reports for other countries - Japan, the UK, France, Russia, and more - are also
provided...
 At the end of the last century (the 20th),
aside from the impending total collapse of the world's electrical infrastructure
due to Y2K computer date issues, technovisionaries (a word I just made up)
predicted the near-term demise of local over-the-air (OTA) broadcasting of both
commercial radio and television. Cable and satellite was going to supplant it
all. For a short while things seemed to be going that way, particularly as both
forms of media (radio and TV) began being available via smartphones. The FCC
(Federal Communications Commission) was so sure OTA television was dead that it
wanted to reallocate unused spectrum (white space) for other uses. It also
mandated a conversion of all TV broadcasting to be done in digital form. The
plan forced either trashing of existing television sets and purchase of new
models or the purchase of analog-to-digital conversion boxes. The compliant
public folded like a cheap suit...
 You're not going to find much information
about the "Futuramic
Antenna" by doing an Internet search. I had never head of such an antenna before
seeing this article about it in the October 1952 issue of Radio-Electronics magazine.
Although it was the trade name of a design by Channel Master, the authors (company
engineers) claim it is a variation of a Yagi antenna which provides a much wider
bandwidth by stacking multiple antennas and phase adjusting them in a combiner.
The story takes place in the era shortly after the FCC ended a freeze on new television
broadcast station licenses (1948) because channel assignments in the spectrum were
being changed and UHF channels added, rendering some older equipment in need of
modification or replacement. The effort was a model of bureaucratic chaos...
 Do you think any tool company would publish
an advertisement like this in today's hypersensitive environment? When Weller ran
the ad shown below in the May 1952 issue of Radio & Television News
magazine, nobody anywhere could have conceived of a world six decades later where
the mere sight or mention of a gun would send snowflake types running for the nearest
safe space (which, sadly, has a special symbol
 a la a nuclear fallout
shelter). It is a little surprising that Weller still markets the tool as a soldering
gun rather than, say a heavy-duty, finger-operated, palm-conforming, graspable soldering
implement ;-( Does anyone know whether soldering guns are allowed in
schools these days? Zero Tolerance policies would require...
 There is a twofer on this page - a feature
article and a couple related
electronics-themed comics. Point-to-point wiring of electronics
assemblies is rarely seen these days. For that matter, the use of leaded components
is rarely seen these days. The advent of printed circuit boards was a real breakthrough
concept when they became commercially viable in the 1950s. As the comic at the bottom
of the page suggests, many people did not even know what a printed circuit board
was. The air traffic control radar unit that I worked on in the USAF had all point-to-point
wiring in a trailer-full of chassis. Terminal strips and bus strips, bifurcated
terminals, tube socket terminals, and studs from relays and switches were the connection
points...
 Something happened at work that reminded
me of a funny event from way back during my time at Westinghouse Oceanic Division
(now part of Northrop Grumman), in Annapolis, MD. There is a moral to this story.
During my electronics technician days there, I spent the first couple years building
PCBs, wiring harnesses, and system-level assemblies for
Navy
sonar systems. We had some really slick stuff like towed vehicles with transducer
arrays along the sides, nose cones for smart torpedoes, flow sensors, proximity
fuse elements, etc. The exposure to all that, and the super-smart people that designed
it, fuelled my desire to go to the trouble of earning an engineering degree. One
of my tasks for a while was to build the transducer arrays, which entailed building
the hundreds of tiny transducer elements. The assemblies were made of a machined
aluminum base plate (about 1-inch square), onto which a precisely cut low density
foam block was attached. On the top of that was a set of two machined aluminum plates
that sat on either side of a piezoelectric ceramic transducer element...
 Although not specifically stated, some of
the technology reported in this August 1945 issue of Radio-Craft magazine
was not so long before classified technology developed during World War II.
The
Radiotype system of wireless teletype developed by General Electric
was an early attempt to provide a mobile means of sending and receiving hard copy
messages. It was a rather complex scheme that used a typewriter to drive a tape
punching apparatus, which was fed into a radio transmitter to send coded tones (as
opposed to CW pulses) for a receiver to then decipher and drive an Electromatic
typewriter. The demonstration used a police car to carry remote equipment. In related
news, RCA's wireless 488 word-per-minute (wpm) telegraph multiplexer using time
division multiplexing (TDM) Also featured was the FCC's decision to move the commercial
broadcast FM band from 54-88 MHz up to 88-106 MHz (now up to 108 MHz...
 Prior to the availability of high speed semiconductor
circuitry, there was not enough computational power available - particularly in
airborne platforms - to perform a significant amount of real-time signal processing
in
radar systems. Analog methods were available to do things like
stationary target cancellation (moving target indication, MTI) and noise reduction
to eliminate clutter on the plan position indicator (PPI, aka radar scope), range
and azimuth blanking of selected regions of the scan, signal discriminators and
integrators, and false target elimination via pulse repetition rate (PRR) and pulse
repetition interval (PRI). There was nothing, really, in the older vacuum tube based
systems to derive a target profile based on radar cross section (RCS) and signal
vector (amplitude and phase) processing. This 1971 article reported on what was
at the time information about very new technology that was just being...
 The term "drone"
these days for most invokes the image of a little plastic spider-looking thing with
propellers mounted at the ends of the arms - usually with a toothless bumpkin at
the controls. Those same people often think drones are relatively new devices. People
with a just a little more information automatically classify all radio control (R/C)
models, be they traditional fixed-wing aircraft or helicopters, as drones. Pilots
of the aforementioned models are even likely, per observers, to have all their teeth
and bathe regularly. I happen to be one of the latter type R/C modelers and while
I no longer possess all 32 teeth I had at birth, I do bathe regularly. Drones have
been around since World War I where they were used for target practice by ground-based
marksmen. Once radio remote control became practical, adopting it for use in pilotless
aerial platforms was a natural evolution. I have written in the past about what
a large contribution hobbyists have made to "drone" technology both through their
technical prowess and flying ability...
 In this article from a 1942 issue of QST
magazine, author T.A. Gadwa employs a
standing wave mechanism analogy that I don't recall having read before - that
of a dam on a river. The river is the transmission line with a lake as the source
(presumably) and then he imagines a dam load. The dam standing waves, per his description,
have phase and amplitude characteristics that depend on how tall the dam wall is
relative to the surface height of the dammed river. An extensive array of graphs
is provided showing how the current of the dam standing waves react to the dam transmission
line termination impedance. I always wonder when seeing electrical-mechanical parity
examples whether, as with this case, there are any dam magazine articles out there
that use an electrical transmission line to help fellow civil engineers...
 Prior to phasing-based single sideband generation
circuits, a brute force filtering of the unwanted sideband and carrier signals was
required. Depending on how well the carrier was suppressed, more than half the total
signal power could be lost. According to author Jack Brown in this "Commercial
Aspects of Single-Sideband" article from a 1956 issue of Radio & Television
News magazine, it had only been since the mid 1940s that wide-band audio-frequency
phase-shift networks were even feasible. An ideal implementation of a single-sideband
suppressed-carrier modulator (SSB-SC) would result in 100% efficiency, but typical
results are in the 80% range... |
