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 According to this full-page advertisement
in the June 1955 issue of Radio & Television News magazine, Bell Telephone
Laboratories was responsible for designing and fielding "waveguide pipe," aka flexible circular waveguides. According to
other historical sources, both George Southworth of Bell Telephone Laboratories
and Wilmer Barrow of the Massachusetts Institute of Technology (M.I.T.) independently
and simultaneously developed circular waveguide, but the early devices were rigid
pipe rather than being fabricated from tightly wrapped, insulated wire that permitted
it to be bent rather than requiring separate corner and offset pieces. Insertion
loss and VSWR is typically not as good as with rigid waveguide, but the ease of
installation in many situations justifies the poorer electrical performance. Bell
Telephone Laboratories was responsible...
 Having recently struggled a little with
re-stringing the dial cord on a vintage Realistic (Radio Shack) Patrolman-50
Radio, it really became apparent why the
Sams Photofact Folders were of such value to electronics servicemen.
Unlike the tangled mess of dial cord shown in the ad, I had the advantage of being
able to carefully open the chassis and photograph the routing and wrapping of the
broken dial cord around pulleys and shafts. Even so, a lack of experience required
some trial and error to get the tensioning correct. No doubt many unqualified radio
owners attempted to fix their own broken dial cords prior to breaking down and committing
to spending a few bucks to have a pro do it correctly. The tight quarters in my
portable radio had me using tweezers to do some of the routing...
 My mother loved
Norman Rockwell paintings for their ability to get to the heart of Americana.
She was an avid collector of books on Rockwell and decorated plates for display
- as avid as one can be on my newspaper classified ad manager father's feeble
salary, anyway. I, too, have a great appreciation for Rockwell's great talent
to choose his subject matter and models and to, when fitting, include a nearly photographic
level of detail within. The Saturday Evening Post magazine featured many of his
works spanning from 1916 until 1971 - from the middle of World War I and on
through World War II, Korea, and Vietnam. Summer, spring, fall, and winter;
Christmas, Easter, Veteran's Day, President's Day, Mother's Day, New
Year's, and other annual events; experiences of love, happiness, joy, surprise,
sadness, and a host of other emotions...
 Time to put on the thinking cap again for
three more "What's
Your EQ?" circuit challenges, compliments of Radio-Electronics magazine
in May 1962. The first is a classic "black box" type problem which, from reading
its description, involves some sort of resonant circuit. that's all I'll say on
that. The next, called "An Easy One?" should, by the way it is drawn, be a clue
that it might be easier to solve if you re-draw it to make a familiar-looking circuit.
Hint: Summons the spirit of Sir Charles Wheatstone. Just the name of the last one,
"Iterative Network," is enough to induce a cold sweat. As with most of these "What's
Your EQ?" problems, successful completion of a first year college circuits course
is plenty to get through them. A few are better attempted by people with hands-on
experience troubleshooting circuits, but don't let that scare you off...
 KR Electronics has been designing and manufacturing custom filters
for military and commercial radio, radar, medical, and communications since 1973.
KR Electronics' line of filters includes lowpass, highpass, bandpass, bandstop,
equalizer, duplexer, diplexer, and individually synthesized filters for special
applications - both commercial and military. State-of-the-art computer synthesis,
analysis, and test methods are used to meet the most challenging specifications.
All common connector types and package form factors are available. Update: KR Electronics
has been acquired by NIC, where KR Electronics'
legacy of quality and innovation will continue to thrive, offering the same trusted
products and services under NIC's leadership. For over three decades, NIC has delivered
high-quality component performance and reliability, ensuring the successful deployment
and operation of our clients' mission-critical solutions. Designed and manufactured
in the USA. Please visit NIC today to see how
we might be of assistance.
 Roger McCraw sent me these photos from his
assignement in U-Tapao, Thailand, cicra 1973. I submitted a couple of the images
to AI for colorization - amazing! Says Roger, "The pictures were taken at U-Tapao,
Thailand and are dated April 1973. I was there from Jan 73 till Jan 74
and was a 30351 in the 1985th Comm Squadron. Since I was the newbie I was selected
to change the light bulbs so I decided to give a Nixon peace sign for the photographer.
The MPN was on a turntable so it could service both approaches to the runway. The
ATC displays were in a trailer that was attached to a building, it was just to right
of truck in picture. I only remember the name of one person because his name is
listed on TWS website. He bought a four function calculator...
 This installment of the After Class series
in the December 1957 edition of Popular Electronics deals with inductors.
It is a beginner-level introduction to how
reactive components behave in circuits. For some reason the concept
of magnetism's influence on electrical current (present with inductors but not
capacitors) seems to be more difficult to comprehend than that of electrons, even
though James Clerk Maxwell shows in the mid 1800s that the two phenomena are interrelated.
I am tempted to say that back in the 1950s when this article appeared, people were
less familiar with the relatively new concept of electronics, but in thinking about
it, your typical 2019 reader is probably even less likely to know anything at all
about electronics or the way basic components work. I would bet that maybe 1% could
even tell you the difference between AC and DC current...
 Not very long ago I mentioned
Jean Shepherd (original assignee of W9QWN and later K2ORS call
signs) as being one of my favorite old-time radio broadcasters (1960s-1970s). Jean
was famous for recounting stories of his own life and for reporting news of the
time in a way that could hold you in rapt attention from beginning to end. His humor,
wit, and command of the English language was acknowledged by his contemporaries.
If you listen to enough of his broadcasts you will notice the frequent mention of
electronics and his experiences as a licensed amateur radio operator beginning at
a tender young age. Just recently I listened to him recount his first day in high
school when a SNAFU in the computer-generated (must have been a UNIVAC) class schedule
mistakenly had him reporting to the girls' swimming pool...
 I was born in the era of screw-in glass
fuses in household electric service panels. There was always a supply of replacements
in the cabinet above the stove. Sometime around 1978, prior to enlisting in the
USAF, I replaced the fuse panel with a Square D circuit breaker panel - a skill
learned through four years of electrical work. In the Air Force, I worked on a 1950s
era air traffic control radar system which consisted of many chassis assemblies
having fuse holders on their front panels. The racks themselves had a circuit breaker
panel, but it was a retrofit from sometime in the early 1970s. That was my introduction
into the wide variety of cylindrical glass fuses - high and low voltage, normal-,
slow- and fast-blow, time delay, etc. I learned of the reason why circuit designers
employed each type, and always used exact replacements when possible. Later, as
a circuit and systems design engineer myself, I always was careful to specify the
most
appropriate fuse type. This 1960 article in Radio-Electronics magazine
is a good primer on fuse handling...
 Being that this
Circuit Quiz appeared in a 1966 issue of Radio-Electronics magazine,
the amplifier components shown are transistors, rather than vacuum tubes. I have
to admit to not doing very well on it. One of the challenges is first determining
what the intended function of the circuit is supposed to be, then you figure out
what is wrong with it. Spoiler alert: I'm going to use circuit A as an example.
It is declared to be a voltage regulator circuit, and the deficiency is the lack
of a stable voltage reference. The architecture is typical of a voltage regulator
with the common base setup used to increase the current supply. However, there is
no reason to necessarily assume the DC IN is not itself already regulated, and the
function if merely to increase the current supply capacity. If that is the case,
then the circuit seems sufficient as shown. Maybe the fact that there is no problem
otherwise should tell you make an assumption about the designer's intention and
look for something that would be suspect under that condition. Anyway, that's my
excuse and I'm sticking with it ;-)
 This rather extensive article from a 1947
issue of QST magazine describes the method used by author Philip Erhorn
to experimentally determine optimum
spacing for the parasitic elements of his antenna. Unless you
have electromagnetic field simulation software available for designing antennas,
the procedure typically involves beginning with published formulas for element length
and spacing, then resorting to a cut-and-test method of finding a combination that
works best for your installation and goals. Almost certainly no two Hams end up
with identical configurations because differences in terrain...
 Since this is a presidential election year,
I figured it would be a good time to post a tongue-in-cheek- story that appeared
in the November 1952 issue of QST magazine about a fictional American president
J. Willoughby Winkelspoof. The American Radio Relay League
(ARRL) always has been and still is apolitical, so don't take seriously anything
you read here. If you are an astute follower of politics, you might pick up on the
nuances woven into the story, and might even marvel on how much the political landscape
has changed in the half century since Pres. Winkelspoof graced the Oval Office...
 This is Part II of a 3-part series of articles
on
magnetostriction devices. At audio and low IF frequencies, the
use of ferrite elements to construct relatively high-Q resonant circuits for filtering
was a big deal in the middle of the last century. Although not presented in this
article, design formulas and tables were published to implement the familiar Butterworth,
constant-k, Chebyshev, Gaussian, and other types. Tuning, particularly for higher
order filters, could be a chore since it involved a cut--and-try method on the ferrite
rods. However, that is what was available in the day, and it evidently worked well
enough to be worth the trouble for desired...
 Electronics World magazine often published
electronics-themed crossword puzzles. Unlike RF Cafe engineering crosswords
I created for two decades that use only technical words and clues, this one does
include some unrelated words. A couple clues I was surprised to see pertain to radar;
e.g., 32A: Small visible mark on a radar or scope screen, and 44A: Identification
Friend or Foe. Some words require a familiarity with technology of the era, but
you shouldn't have much trouble. You'll need to print this out on paper to work
it..
 Advances in
transformer technology are driven by the need for miniaturization and efficiency,
particularly in airborne and high-frequency military equipment. By optimizing core
materials and fabrication, engineers can significantly reduce the weight and physical
dimensions of transformers. A major technical milestone highlighted in this 1964
Electronics World magazine article, was the development of grain-oriented
silicon steel, which, through precise crystal alignment, offers superior magnetic
properties and reduced energy losses compared to traditional soft iron. Modern design
further mitigates power loss from hysteresis and eddy currents by employing thin,
insulated laminations...
 It didn't take much in the early days of
radio to capture the curiosity of consumers with buzz phrases like a "Mystic Hand"
to keep the radio tuned properly - really just AFC control, and a "Phantom Conductor"
circuit that boosted the volume of high level audio (a nonlinear amplifier). Here
are 4 more Radio Service Data Sheets from Radio-Craft magazine.
Crosley Model 1316 Radio Service Data Sheet,
Westinghouse Model WR 207 & WR 208 5-Tube Dual-Band Superheterodyne
Radio Service Data Sheet,
RCA Victor "High-Fidelity Electrola," Model R-99 Radio Service
Data Sheet...
 Back in the days when I built a lot of prototype
electronic gear, project enclosures were generically referred as a "Bud
Box." Lab stock rooms always had a good variety of sizes and configurations
of the soft aluminum and sometimes plastic boxes that were easily drilled, punched,
filed, and painted to make professional looking equipment. Not all the project boxes
were made by Bud Industries, but just as everyone knows you're talking about
a cola when you say "Coke," it was understood that a "Bud Box" was a chassis for
a home-brewed circuit. They are still seen in construction articles of electronics
hobby magazines today. I have even seen test equipment and utility items for sale
that are obviously in a Bud Box type of chassis. This full-page advertisement for
Bud Radio appeared in a 1930 issue of Radio Craft magazine - a mere two years after
opening their doors...
 This week's crossword puzzle sports a radar
and radio theme. All RF Cafe crossword puzzles are custom made by me, Kirt Blattenberger,
and have only words and clues related to RF, microwave, and mm-wave engineering,
optics, mathematics, chemistry, physics, and other technical subjects. As always,
this crossword contains no names of politicians, mountain ranges, exotic foods or
plants, movie stars, or anything of the sort unless it/he/she is related to this
puzzle's technology theme...
 The
traveling-wave tube (TWT), invented by Dr. Rudolph Kompfner during World War
II, revolutionized microwave amplification by providing exceptional bandwidth without
the limitations of traditional resonant cavities. By utilizing an electron gun,
a precision-wound helix, and a magnetic focusing circuit, the TWT transfers energy
from an electron beam to a propagating signal wave. This design enables high-gain,
low-noise performance essential for radar, missile guidance, and high-capacity telecommunications
systems like the TH radio-relay. Although early production faced challenges regarding
reliability and manufacturing complexity, ongoing engineering refinements achieved
the stability necessary for critical applications, including the Telstar communications
satellite...
 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)...
 An old electrician's saying goes "Ground is ground the world around," implying that every point
on Earth's surface is at the same potential - specifically 0 volts. We know, of
course, that it is not so. Maybe on average such a claim could be made, but just
as "sea level" is not the same at all points on the ocean's surface (hence we speak
of "mean sea level"), neither is the voltage potential the same everywhere. Further,
just as the salinity of all points on the ocean surface do not have the same salinity
(and thereby conductivity), the conductivity of various places on dry land vary
- often significantly. Electric power systems are very concerned with soil electrical
conductivity in the vicinity of power generation installations...
 Byron Goodman published a very thorough
diode
modulator article in a 1953 issue of QST magazine. It was one of the
first of such articles that used the very recently available semiconductor diodes
rather than the previously used vacuum tubes. Single-balanced bridge and ring modulator
circuits are presented, along with the theory behind their operation. It would be
a few years more before double balanced mixers with their abilities to reject even
intermodulation products, and triple balanced mixers with very high overall spurious
product rejection, would become commonplace...
 Back in the 1960s, Electronics Illustrated
magazine ran a series of monthly Q&A columns titled "Electronic
Brain," where readers wrote in to query the staff on particular quandaries.
Even if you have been in the electronics game for decades, there were plenty of
questions that probably invoked the "I'm sure I could have answered that at some
point, but it's been so long that I couldn't say for sure," thought. The magnetomotive
force topic in this set of three items did it for me. I knew there was a magnetic
flux equivalent of electric current flow, but I probably would not have been able
to write the equation using the precise...
 We are accustomed these days with stores
having "no questions asked" return policies for just about anything. I once watched
a guy successfully return a 4" PVC plumbing fitting that had clearly been smeared
with glue in the coupling areas. Another time a guy returned a painting drop cloth
that was full of paint, declaring that it wasn't what he wanted. The return counter
bins of Walmart and other stores are always chock full of stuff. Such was not always
the case, though. This episode of
Mac's Radio Service Shop, mentions, among other thing, how busy
he and sidekick Barney had been right after Christmas doing troubleshooting and
repair on various electronic equipment that had been received as gifts. Imagine
receiving...
 San Francisco Circuits, a leading printed
circuit board fabrication and assembly supplier serving commercial and defense markets,
today announced that it has achieved Final
Cybersecurity Maturity Model Certification (CMMC) Level 2 Certification
status following a successful independent assessment by an accredited Certified
Third-Party Assessment Organization (C3PAO). San Francisco Circuits Achieves CMMC
Level 2 Certification The certification confirms that San Francisco Circuits'
enterprise information systems meet the cybersecurity requirements outlined in NIST
SP 800-171 Revision 2, as codified in 32 CFR Part 170, for the protection
of Controlled Unclassified Information (CUI)...
|
 • Skyworks
Reports Nearly $1B in Q2 Revenue
• Price
Rises for Analog, Discrete and Passive Devices
• Apple-Intel Foundry Could
Reshape U.S. Chip Manufacturing
• China Loses Monopoly over
Rarest of Rare Earths
• Samsung
Memory Chip Worker Union Strike Averted
 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.
 As with many areas of electronics communications,
much of both the initial and continued research in
atmospheric scattering of electromagnetic signals was/is done by amateur radio
operators. The phenomenon is routinely used for accomplishing long distance communications
(DX, in Ham terms) by exploiting the reflection property of ionized layers when
radio signals impinge at a certain angle. The portion of the signal that returns
to the transmitter location, when monitored, can provide information to the sender
about the height, distance, and frequency range of the reflecting atmospheric layer.
Some of the first indications of backscattering were noticed by radar operators
who would receive echo returns from "phantom" targets that were really atmospheric
reflections...
 I don't know about you, but I really miss
the hard-wired POTS (Plain
Ordinary Telephone System) days of remote communications. Unless the conversation
was with an overseas telco system, there was never a noticeable delay where both
parties were constantly either "stepping" on each other's words or having to consciously
wait before speaking to make sure the other guy has finished. Whether it be cellphone-to-cellphone
or cellphone-to-VoIP, nearly every conversation is annoying. Sometimes when one
party is on the POTS line with either a cell or Internet connection it can go well,
but if you want a hassle-free conversation (assuming the person you're talking to
is not a PiTA), you need a hard-wired connection on both ends. People loved to hate
Bell Telephone back in the day...
 Amateur radio operators - and all electromagnetic
spectrum users for that matter - have always lamented
crowded bands
and interference (QRM and QRN). That goes for licensed and unlicensed bands.
In 1976 when this editorial was printed in the ARRL's QST magazine, spectrum
occupation within allocated bands was defined by commonplace analog AM and FM methods.
Co-existence was generally not possible for operation within a common frequency
range. Spread spectrum modulation / demodulation changed all that beginning in the
1990s, but prior to then such schemes were largely the exclusive domain of military
communications, as were many other spectrum-saving methods which are commonplace
today. A big part of the reason is the significant advances in digital processing
hardware and software, along with declassification of some of the algorithms that
eventually found their way into cellphone, WiFi, and other commercial applications.
Given that many of the professional engineers...
 Way...... back in 1992, RF Design
magazine ran a software contest. Those were the days when most engineers and hobbyists
wrote software in either Basic or Fortran. I happened to use Turbo Pascal, by Borland.
At the time, I was working as an RF engineer for Comsat, in Germantown, MD. Having
done a lot of frequency conversion designs in my previous work at General Electric,
and even more there at Comsat, I had already written a crude program to calculate
mixer spurious
products, so this challenge gave me the excuse I needed to refine the user interface
and add some creature comfort features like loadable mixer spur files and detection
of spectral inversion if present. Although I did not win the grand prize, I did
win the runner-up prize (along with, I think, a couple other people). The prizes
included having the following article published...
 July 26th's custom
Radio Engineering crossword puzzle contains some words particular to radio,
radar, analog and digital circuits, components, and other tech-themed words and
clues. Each week for two decades I have created a new technology-themed crossword
puzzle using only words (1,000s of them) from my custom-created lexicon related
to engineering, science, mathematics, chemistry, physics, astronomy, etc. You will
never find among the words names of politicians, mountain ranges, exotic foods or
plants, movie stars, or anything of the sort. You might, however, find someone or
something in the otherwise excluded list directly related to this puzzle's technology
theme, such as Hedy Lamarr or the Bikini Atoll, respectively. Avid cruciverbalists
amongst us: the gauntlet has been thrown down.
 To be honest, I don't know whether
military electronics training commands the respect in private industry that
it did back in 1982 when I separated from the U.S. Air Force. If you left the military
within the last 20 years or so and care to share your experience with seeking civilian
employment, I'll be glad to add it here as a side note. Many of the electronics
technicians I worked with both as a tech myself and then as an engineer (after earning
a BSEE) got their initial classroom training in either the Air Force or the Navy.
There were probably some from the Marines and Army, but I don't recall any off-hand.
I hate to admit it, but I think the Navy vets were even more highly sought after
than we Air Force types. This 1969 issue of Electronics Illustrated...
 Cruciverbalists rejoice! Here is another
tech-related crossword puzzle to try your technical prowess. Unlike the weekly
RF Cafe crossword puzzle that contains only engineering, science, mathematics and
other tech words, this one from Electronics World does have a few unrelated
words. The big difference between making crosswords then and now is Mrs. Le Fevre
had to construct the grid of words manually, whereas I just create a huge file of
words and definitions, draw the grid outline, and then click a button to have software
put it all together. I'm guessing it took a couple hours to make this puzzle...
 These "Radio
Term Illustrated" comics from vintage Radio-Craft magazines are some
of my favorite tech-themed comics. Most were drawn by Frank Beaven in response to
suggestions / requests by magazine readers. The one here from page 80 entitled "Crystal
Gazing" was done by Franklin Folger. If you didn't know that it appeared in a 1947
edition, you might assume it depicts a Steam Punk themed LCD computer monitor mounted
atop a Morse code straight key, but of course it is not. At the time, cathode ray
tubes (CRTs) were the only form of video display, and while small like the one in
the drawing (and round, unlike the drawing), they were far from flat. Little did
the artist suspect that his "Crystal Gazing" idea meant to imply a type of mystic's
medium for seeing...
 Benjamin Franklin is famous for his kite-flying
experiment whereby he 'discovered' not electricity (as many people believe), but
that
lightning is a form of electricity (most people thought it was a jet of gas).
A lesser known fact about Mr. Franklin is that he invented the lightning rod
after realizing the electrical nature of lightning. His understanding of electric
fields facilitated an implementation whereby hefty iron cabling interconnected a
tall, pointed rod installed at the tallest point on a building and a spike driven
into the ground. Lightning typically strikes the object that is the shortest distance
(in terms of electrical field strength) from it because the discharge can begin
at the lowest voltage. The presence of the grounded lightning rod above the highest
point on a structure effectively brings that point all the way down to ground level...
 Prior to seeing this new tidbit in a 1976
issue of QST magazine, I had no idea that the wife of Peanuts comic strip
creator Charles Schulz was an airplane pilot - and that is with having been a huge
Peanuts fan for decades. Other than one of Snoopy's alter egos being that of a World
War I flying ace, there is no other theme of airplanes in the strip, although
according to this article, there was a 1975 Sunday comic strip with Peppermint Patty
and Marcie flying atop Snoopy's doghouse, from California to Michigan. The Straits
Area Radio Club (W8GQN) provided communications for the Powder Puff
Derby, aka the Women's Air Derby, race in which Mrs. Jean Clyde Schulz
took part in 1970, 1971, and 1975. It was a very long course - more than 2,000 miles
as the crow flies...
 The big graphic with Figures 1 through 17
reminds me of the kinds of study sheets I used to make when cramming for exams in
my college circuits courses. Did I ever tell you about the wise guy instructor I
had for my first Circuits class at the University of Vermont? Anyway, this article
provides an introductory level treatment of using
negative feedback in amplifier circuits. Lots of illustration and formulas are
included. Frequencies are at baseband, so you won't learn any secrets for high frequency
amplifier stabilization, but then even RF and microwave circuits eventually need
to convert down to baseband at some point for sampling or for use as audio or video...
 Joe Cahak, owner of Sunshine Design Engineering
Services in Ramona, California, has written a white paper entitled, "Measuring
Semiconductor Device Input Parameters with Vector Analysis." This article covers
a recent test experience that utilized some thinking about the test fixture, the
bias requirements and the device mounting and special calibration offsets needed
to de-embed the test fixture response from the device response within the test fixture.
The device also had to have bias on several ports simultaneously. We had to establish
a "reference plane" within the fixture, from which we can use the Vector Network
Analyzer's Port Extension or Phase Offset to dial out the distance from our 1 port
calibration reference plane to the point of short reference within the fixture.
With this phase offset compensation we can then measure...
 How far do you commute each day for
the privilege of doing your part to push back the frontiers of technical ignorance
and to boldly go where no engineer - or technician - has gone before. Do you
know what the cost equates for you each year? This handy-dandy infographic
lays out some
gruesome
numbers. Those with a weak stomach probably should pass on viewing this
one. Here's a hint at what you will see: See that big $795 in the thumbnail
image? That's the average cost per year for commuting -- per mile! Yessiree,
if you live just 10 miles from work, you're losing nearly $8,000 per year,
depending on you automobile type, on gas, tires, maintenance, devaluation,
and loss of your personal time (which is valuable, after all). Back in the
early 1990s I drove about 45 miles each way to Comsat, which took about 65
minutes due to miserable traffic, which is 130 minutes round-trip, or 2 hours
and 10 minutes (about the run time of an average movie) each day. Figuring
two weeks vacation and 10 holidays, that leave 48 weeks x 5 days/week = 240
days per year of commuting. 240 days x 130 minutes = 31,200 minutes =
520 hours per year. That's a fourth of a man-year (2,080 hours) on the road.
It was a great job, but combined with working 60-70 hours per week... |
