|
 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...
 Mystery stories were broadcast on radio
stations in the days before television - and for quite a while after TV was available
for that matter. Families gathered around the living room radio set in excited anticipation
of the next adventure of shows like "The Shadow," "Amos 'n' Andy," "Tales of the
Texas Rangers," "Dragnet," and "The Green Hornet." During that era, it was common
also for electronics magazines, which focused largely on radio communications, to
experiment with printed dramas that had a radio-centric theme. Here is the first
of a series tried by Radio-Craft magazine in the late 1930s. A couple decades
later the Carl & Jerry adventures were run in Popular Electronics,
but other than that I don't recall seeing a lot of these things...
 Diode characteristics and their applications
have not changed fundamentally since this article was published in 1952. Sure, the
die are smaller, power handling and frequency range has increased, package styles
are greatly expanded, and the cost per unit is way down, but if you are looking
for some basic diode information, you will find it here in this 4th installment
of a multi-part series in Radio & Television News magazine. Don't let
the vacuum tubes in schematics scare you off and think that it makes the story irrelevant
for today's circuits. For purposes of illustration substitute a transistor's collector
(or drain) for the tube's plate, a transistor's base (or gate) for the tube's screen
grid, and a transistor's emitter (or source) for the tube's...
 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
mark...
 "If you have dark eyes and blonde hair.
and are under 30, you're due for some easy squeezing. Milligan's Appliance Center,
84 Main Street, is giving every girl between 16 and 30 who has these striking features
a newly patented orange squeezer, to introduce the new item ... Note: Any traces
of recent peroxide rinse will disqualify applicants." That is advertising copy offered
as an example effective promotional material in a 1947 edition of
Radio News. My first reaction was to think how something
like that would never fly today, but then I wasn't so sure. It seems there must
be anti-discrimination laws in this "offend nobody" climate today...
 Imagine having a serviceman of any sort
arrive at your house, fix your problem, and present you with a bill of $6 - parts
included. He would walk away satisfied that he had done a good job and was well
compensated for the work considering the effort invested in training and qualification.
$6 in 1932, per the Bureau of Labor Statistics'
Inflation Calculator is worth $135.97 in 2015 money - that's a
cheap service call even in today's economy. Further, the $14 stated as a day's earnings
is $317.26 in 2025, which equates to 50 (work weeks/year) x 5 (days/week) x $243.86
(/day) = $79,315 (/year) - not too shabby. Just between you and me, that's more
than I'm currently making per year running RF Cafe...
 Aegis Power Systems is a leading supplier
of AC-DC and DC-DC power supplies
for custom and special applications. Aegis has been designing and building highly
reliable custom power supplies since 1995. They offer a complete line of switch
mode power supplies and power converters for a variety of markets including defense,
industrial, aircraft, VME, and telecom. Supports military, aircraft, EV, telecom,
and embedded computing applications. Design and manufacture of custom power supply
solutions to meet each customer's exacting specifications. Please visit Aegis Power
Systems today. Manufactured in the USA.
 Oscillators were never my forte. My biggest
exposure to oscillators was unintentional oscillations in amplifier circuits ;-(
. This
Oscillator Quiz, published in the November 1962 issue of Popular Electronics
magazine, would embarrass me if I attempted to complete it. Therefore, I will simply
state that I highly regard your oscillator prowess if you do better than 50% on
it. I guessed correctly at a couple of the more familiar circuits, but cannot even
make an educated guess at most of them. Don't let the presence of vacuum tubes scare
you off; mentally replace them with a FET and move on...
 These letters represent an unfriendly exchange
between The Electrical Experimenter editor Hugo Gernsback and Dr. K.G.
Frank, of the Telefunken System of Wireless Technology, of Germany. Gernsback correctly
accused Dr. Frank of engaging in espionage for Germany and against the United
States of America, during World War I at a time we were not officially at war
with the Axis powers. He was arrested and interred for the duration of the war for
sending out "unneutral
messages" from the broadcast station at Sayville, Long Island, New York. See
"Radiobotage" in this month's (September 1941) editorial...
 "There's an interesting development in amateur
ballooning: using so-called
superpressure
balloons, which float high in the atmosphere indefinitely rather than simply
going up and up and then popping like a normal weather balloon. Superpressure balloons
can last for months and travel long distances, potentially circumnavigating the
globe, all the while reporting their position. You might imagine that an undertaking
like this would be immensely difficult and cost thousands of dollars. In fact, you
can build and launch such a balloon for about the cost of a fancy dinner out. You
just have to think small! That's why amateur balloonists call them pico balloons.
The payload of a pico balloon is so light..."
 Many of the words in this week's
crossword puzzle pertain to radar engineering. All the rest of
the words are related to technology, engineering, science, mathematics, aeronautics,
ham radio, chemistry, etc. There are no names of Hollywierd actors, shoe designers,
or romance novel titles. I will be glad to create a special edition crossword for
your newspaper, newsletter, etc. Enjoy...
 It's time to gather 'round for another story
about fictional radio service shop owner
Mac McGregor and his trusted sidekick technician, Barney. In this
episode, an errantly wired bypass capacitor on a chassis from one of the old AC/DC
radio sets caused Mac to get a 300-volt wakeup call when his hand brushed against
it. After explaining the situation to Barney and apprising him of the danger it
poses to an owner who unwittingly sticks his/her hand into the back of the cabinet,
Mac lists a few other common dangers to watch for. Radios that ran on either AC
or DC power were very common back in the early days because there were homes and
businesses that had both type systems wired in to the premises - in part due to
the famous battle between Thomas Edison's preferred DC electrical distribution system
and Nikola Tesla's preferred AC electrical distribution system. Another reason for
DC compatibility was that prior to the
Rural Electrification Act of 1936, many...
 An incredibly glaring example of the famous
admonishment* that those who ignore history are condemned to repeat it, Radio-Craft
editor Hugo Gernsback wrote in May of 1941, a full half year before the United States
of America officially entered World War II, about how current conditions regarding
domestic commercial radio broadcast stations were likely being used by German agents
to send coded messages to offshore vessels (ships, submarines, and aircraft).
In example, he cited, amazingly, an article he himself published in 1915 in
The Electrical Experimenter accusing Dr. K. G. Frank, of the German Telefunken
company, of conducting spy operations from the Sayville, NY, station on Long Island...
 Considering that not much more than a year
before this article was written that the transistor had been invented, it is impressive
that already Raytheon was producing a commercially available
CK703 "crystal triode." That nomenclature was a natural extension
of the preceding crystal diode already being widely adapted in circuit design. If
you have wondered how the transistor schematic symbol came to be as it is, you will
learn why here where the emitter and collector symbols actually both have arrows
on the ends that contact the base, indicating the "point contact" physical arrangement
of the semiconductor junctions. Shortly thereafter the arrow on the collector port
was eliminated, primarily, I suppose to avoid confusion when the E, B, and C labels
are not present...
 "CDimension recently unveiled a technology
that enables conventional semiconductor fabs to use ultra-thin semiconductor materials
to manufacture vertically integrated arrays of extremely small, fast, and efficient
"2D" transistors. It has the potential to change what's possible for both digital
and power devices. According to the company, it's already helping several chipmakers
explore how to apply their technology to produce digital and analog ICs that offer
dramatically higher logic densities, operating speeds, and energy efficiency..."
 Here are three more Radio Service Data Sheets
added to the online archive. As mentioned many times in the past, I post these for
the benefit of hobbyists looking for information to assist in repairing or restoring
vintage communication equipment. These particular radio models -
Emerson Model 20A and 25A,
Pilot Model B-2,
General Electric Model K-40-A - were featured in a 1933 edition
of
Radio-Craft magazine...
 A lot of RF Cafe visitors might not be familiar
with some of the electronic waveforms presented in this
Oscilloscope Quiz by Popular Electronics magazine's ultimate quizmaster, Robert
Balin. The shapes are recognizable to anyone who has done a lot of design, troubleshooting,
testing, or alignments on analog circuits. Electronics repairmen were intimately
familiar with these - and much more complex - waveforms. Modulation of the z-axis
is especially cool as it varies the intensity of the waveform. I always roll my
eyes when, back in the day, a laboratory or medical facility in movies or on TV
had an oscilloscope display with a Lissajous pattern writhing on the display...
|
 • Fund Opens
Defence Contracts to UK Startups
• Global
Trade Holds Its Ground
• FCC
"Supercharge" Wi-Fi in 6 GHz Band
• Legacy
Memory (DDR2, 3, 4) in Demand but Scarce
• 2026 is
Year of 6G Slop
• FCC to
Exempt Amateurs from Foreign Adversary Reporting
 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.
 This is another Radio Service Data Sheet
that appeared in the March 1936 edition of Radio-Craft magazine. I post
this schematic and functional description of the Crosley Model 515 (Fiver) 5-Tube
2-Band Superhet radio manufacturers' publications for the benefit of hobbyists
and archivists who might be searching for such information either in a effort to
restore a radio to working condition, or to collect archival information. An extensive
list of similar radio service data sheets from many different electronics magazines
of the day is at the bottom of the page...
 Admittedly, the only thing I remember about
Gray Code (aka reflected binary) from college courses is that successive count
values change only one bit per increment, saving power in some digital circuits.
The power savings comes from the fact that, especially for CMOS circuits, current
only flows during the transition of a state change from "0" to "1" or from "1" to
"0." Shaft position encoders were and still are a primary application of Gray Code
switching. If the encoder output digital code is going to be used in a binary computation
system, then there is an advantage in generating a direct binary ("natural") count
that does not require a Gray-Code-to-Binary conversion circuit (or software routine).
When the Wayne-George Corporation introduced its paradigm-changing "Natural Code
Non-Ambiguous Optical Encoder" in 1964, those conversion circuits were probably
not simple, compact, inexpensive semiconductor IC's, but more likely vacuum tube
behemoths. Even if IC's were used, the conversion circuit would have been comprised
of quad packs of AND's, OR's, NAND's, and NOR's, not even a single application...
 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 Frye ever attended
Purdue, "Remarkably enough, he never attended Purdue University..."
 Electrocution has always been - and always
should be - a hot topic (pun intended) in the realm of electrical and electronics
servicing and usage. Trade and hobby magazines have dedicated many column inches
to it over the years. A lot of people are deathly (there I go with the puns again)
afraid of being anywhere in the proximity of an exposed electrical connection. My
father, a newspaper classified advertising manager, was one of those people. He
would cringe when I took the cover off the fuse panel in the house to work on it.
He could barely bring himself to replace a blown fuse, which was not a completely
unjustified fear given the low standards of older electrical wiring. Those screw-in
fuses had a threaded metal perimeter around the bottom portion with a button connection
at the bottom center. Theoretically, that threaded metal perimeter is at ground
potential...
 A few weeks ago I posted a two-part article
on the Taylor
super-modulation principle published in Radio & Television News
magazine in 1948. It was a newly announced technology at the time and was written
by its inventor, Robert Taylor. This piece entitled "Understanding Super-Modulation"
appeared a couple years later by another author, John McCord, where he describes
how it works , how to tune super-modulation circuits, and how it compares to other
modulation methods - all conveniently in "Ham language." Super-modulation is a form
of amplitude modulation (AM) that makes use of carrier and/or sideband suppression
to achieve greater efficiency. A panadaptor - aka pan-adapter, aka panadapter, aka
radio spectrum scope, aka panoramic adapter - is used to view the RF spectrum across
a wide band. Essentially it is a low budget spectrum analyzer...
 Magazines usually provided at least a brief
description on the circuit functionality for each of the radio models presented
in schematic format. The January 1947 issue of Radio News published schematics
and parts lists for six sets, including this for the United models 980744 and 980745
"Sonomatic,"
but not a word about any of them accompanied it - just the schematic and PL. These
are AM radios designed for Buick automobiles, and the series ran for more than a
decade. One thumbnail image is the SAMS Photofact from an eBay auction, and the
photo thumbnail is from an eBay auction. I post this type of information as part
of my ongoing effort to make the information available to those who repair and/or
restore vintage vacuum tube radio sets...
RF Cascade Workbook is the next phase in the evolution of RF Cafe's long-running
series, RF Cascade Workbook. Chances are you have never used a spreadsheet
quite like this (click
here for screen capture). It is a full-featured RF system cascade parameter
and frequency planner that includes filters and mixers for a mere $45. Built in
MS Excel, using RF Cascade Workbook is a cinch and the format
is entirely customizable. It is significantly easier and faster than using a multi-thousand
dollar simulator when a high level system analysis is all that is needed...
 One of the nice things about these "What's
Your EQ?" challenges that appeared in Radio-Electronics magazine is
that they tax your ability to recall basic electronics circuit theory. The first
one in the June 1964 issue requires you (spoiler here) to apply Thévenin's theorem
in order to arrive at the solution. You also need to know about maximum power transfer
which (another spoiler) requires the load impedance to be the complex conjugate
of the source impedance. "No Volts" will make you very appreciative of today's high
input impedance voltmeters; the problem statement itself made my head hurt. Being
aware of such issues often meant the difference between success and failure when
assessing television and radio circuits. "Music-Intercom Trouble" almost certainly
was inspired by a 1960 Electronics World episode of "Mac's Radio Service
Shop," entitled "Technician or Consulting Engineer?." Have at it...
 Homepage
Archives for July 2023. Items on the RF Cafe homepage come and go at a pretty
fast rate. In order to facilitate fast page loading, I keep the size reasonable - under a megabyte (ebay, Amazon, NY Times, etc., are multiple
megabytes). New items are added at the top of the content area, and within a few
days they shift off the bottom. If you recall seeing something on the homepage
but now it is gone, fret not because many years I have maintained
Homepage Archives.
 This is the second and final installment
of an article on the topic of
frequency modulation (FM) that began with Part 1 in the July 1941 edition
of Radio-Craft magazine. Author Raymond Guy, a radio facilities engineer at the
National Broadcasting Company (NBC), covers all the fundamentals of FM (a relatively
new concept at the time, invented by Major Edwin Armstrong) not just from a functional
circuits perspective but also pointing out a broadcaster's concern for channel spacing
and broadcasting ranges. Transmitter pre-emphasis, receiver de-emphasis, noise thresholds,
and adjacent channel and co-channel broadcasting strategies are discussed here...
 Here's a little more
electronics humor from the November 1961 issue of Popular Electronics
magazine. This time the topic is stereo equipment, which was a big deal in the era.
Most equipment was still of the vacuum tube variety, and the country was still enjoying
the post-Korean war and low inflation economy, so there was disposable income to
be spent on creature comforts. Hobby and home improvement magazines od the day were
filled with reviews and recommendations on receivers, speakers, phonographs, tape
players, tone arms, stylus types, cables, antennas, and all the support equipment.
Articles on room design for optimized acoustic properties included sound absorbing
ceilings, walls, and floors, speaker placement, furniture location for the best
stereo (and quadrophonic) experience, etc...
 Have you heard of an electronic musical instrument
called a Theremin? You can still buy from Moog today the same sort of Theremin that
was described in this
Carl & Jerry episode from a 1961 issue of Popular Electronics magazine.
Ever the early adopters of breaking technology, the teenagers exploit the motion-sensitive
feature of the Theremin in hopes of improving Carl's basketball game. As usual the
boys, in mock dialog, describe the Theremin's operational theory for the benefit
of readers not familiar with the musical instrument. They do not, however, mention
that the device is named after its Russian inventor, Léon Theremin, who patented
the device in 1928. Read on to discover how a Theremin strapped to Jerry's back
was used to help Carl be a better free-thrower...
 In your rare few minutes of the workweek,
try your hand at this "Electronics
Helix Puzzle," provided by Mr. James Kimsey in a 1971 issue of Radio-Electronics
magazine. It it not as much of a challenge as a classical crossword puzzle, but
is still worth attempting. In some ways, though, if you get stuck on a word there
is more help available with a standard crossword because there are more than just
two (the first and last letter in this case) intersecting letters available to help.
If after completing this Electronics Helix Puzzle you would like to try your hand
at one of those traditional type crossword puzzles, consider working one (or more)
of my weekly...
 "My God, man! Drilling holes in his head
isn't the answer! Now put away your butcher knives and let me save this patient
before it's too late!" Those classic words were uttered by Dr. McCoy in "Star Trek
IV: The Voyage Home," after Lt. Chekov (promoted from Ensign after the TV series)
sustained brain damage as a result of falling from a "nuclear wessel" when 20th
century naval surgeons were about to open his skull to relieve pressure from swelling.
Look at these images from a 1932 article on using radio waves "to
produce
protective fever in killing germs of a number of diseases." 10 to 30 meters
was a popular wavelength band at a power of about 500 watts. The patient's body
part to be treated is placed between the plates to act "as a dielectric" while the
liquids are heated via induced oscillations similar to how a microwave oven works.
How did the doctors know when the treat...
 "Technically, panoramic reception is defined
as the simultaneous visual reception of a multiplicity of radio signals over a broad
band of frequencies. In addition,
panoramic
reception provides an indication of the frequency, type and strength of signals
picked up by the receiver. Deflections or 'peaks' appearing as inverted 'V's on
the screen of a cathode-ray tube." It is the kind of display that radar operators
at Pearl Harbor were using when they mistook wave of incoming Japanese bombers for
a squadron of B-17s from the mainland. The panoramic receiver is not a wartime development,
experimental models having been produced just prior to the outbreak of war. However,
the many uses to which it has been put have demonstrated that the panoramic idea,
particularly in the form of adaptors which may be connected to any receiver, is
going to be very important and useful in the ham station of the future. In simple
language this article reviews the general principles upon which the panoramic system
is based and includes also a picture of the many ways...
 For many years I have been scanning and posting
"Radio Service Data Sheets" like this one featuring the International
Kadette Model 1019 A.C. Superhet Radio in graphical format, and also include
some textual content to serve as search engine keyword targets. There are still
many people who restore and service these vintage radios, and often it can be difficult
or impossible to find schematics and/or tuning information. As shown in the thumbnail
image, you can still find many of these old radios in condition ranging from disaster
to fully restored. I will keep a running list of all data sheets to facilitate a
search...
 This "Radio Service Data Sheet" for the
Knight (Allied Radio Corporation) model E10716 Battery Portable radio appeared
in a 1939 issue of Radio-Craft magazine. A Web search for Knight radios
does not turn up very many results, so maybe they were not all that popular. Knight
competed with Heathkit for many years in the 1950s through 1970s with their line
of build-it-yourself kits. There are still many people who restore and service these
vintage radios, and often it can be difficult or impossible to find schematics and/or
tuning information, so for that reason I will continue to post these Radio Service
Data Sheets and keep a running list (below) of all of them to facilitate a search
on RF Cafe...
 We "Baby Boomers" remember a time when cell
towers did not present a ubiquitous (and, frankly, ugly) presence across the landscape.
Microwave relay towers for television and telephone links could be spotted sitting
atop hilltops and mountain ridges in some areas, and giant television and radio
station towers sat behind broadcast stations, and multi-element antennas dotted
house rooftops everywhere. Our grandparents (Millennials' great grandparents) remember
when even microwave relay towers were missing. This 1936 article reports on the
first microwave links spanning the English Channel to replace expensive and trouble-prone
submerged cable. Part of the impetus, not mentioned within, was the building inevitability
of war with Germany and the vulnerability of those communications links to being
compromised by Nazi submarines and divers... |
