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 Joe Cahak, owner of Sunshine Design Engineering
Services, has submitted another fine article for posting here. Joe has many years
of automated RF testing experience to leverage when writing this paper on making
measurements with scattering parameters (S-parameters) involved. He begins, "In many RF and Microwave
measurements the S-Parameters are typically expressed in dB (decibels) Magnitude
units and Degrees in the polar coordinate system. Network and Vector Network
Analyzers and Spectrum Analyzers all measure with voltage ratio measurements, so
to convert to dB in terms of volts we must use the following equation. The
Spectrum Analyzer is a frequency discriminating detector that detects the
voltage for the signal. It will give the amplitude of signal as a function of
frequency. It is scalar in measurement dimension magnitude...
 Sam Benzacar, of Anatech Electronics, an
RF and microwave filter company, has published his June 2026 Newsletter that, along
with timely news items, features his short op-ed titled "Millimeter-wave
5G: Physics Didn't Get the Memo." In it, Sam discusses how the wireless industry's
present-day talk regarding millimeter-wave 5G operating above 24 GHz sounds
a lot like the big plans it had for ubiquitous gigabit connectivity with micro base
stations located on every street corner that would assure continuous coverage. It
never materialized. The physics issues with above-24-Ghz path loss, shadowing, handset
(i.e., phone) construction, etc., will greatly affect the service's usefulness.
New items include SpaceX telling the FCC to scrap its Rural...
 The world's first electric wristwatch
went on sale on January 3, 1957 - the Ventura model, by Hamilton Electric, and it
retailed for $200. I use the event as the theme of the RF Cafe logo for that day
in history. Unlike today's electric watches which use a crystal for timing,
the early watches used a pulsed motor to energize the balance wheel coil, in place
of a mainspring and an escapement mechanism. Some "atomic" wristwatches today like
the Casio Waveceptor (<$40) use the WWV signals from Boulder, Colorado, to synchronize
the time with world standards. The watch shown in this article from the February
1958 edition of Radio-Electronics magazine is a model 500, which you can find more
detail about on the Unique Watch Guide website...
 RF Cafe visitor Mike M. sent this very
interesting note after reading this "Frequency Modulation Fundamentals" article: Again, you hit it
out of the ballpark, Kirt! Great article out of QST magazine. Absolutely
accurate to credit "The Old Man" Edwin Armstrong for the invention/development of
FM and much more, plus the work of Dan Noble, who worked with the Connecticut State
Police and Motorola as Director of Research. Also many, many others. Some that have
never been properly credited. Guys like Bob Morris, W2LV and Frank Gunther, W2ALS.
They were both interviewed by Ken Burns for "Empire of the Air". I was fortunate
enough to talk to both of these guys after I got my Tech license in 1970. My immediate
supervisor/mentor from 1972 until he retired in ~1990...
 Today has been a busy day, so a couple
electronics-themed comics from issues of vintage Radio &
Television News magazines help to relieve the stress a bit. I could never figure
out why these comics were buried deep inside most issues at the ends of article
continuations. These two were on pages 88 and 93. The top one is meant to demonstrate
just how obsessed the public was with the relatively new television phenomenon -
just look at what they chose to ignore on the display TV in order to get a peek
at the inside workings of a television set. The other comic, while clever in its
intent, would never pass editorial muster in today's world because of the great
hazard it represents...
 Do you remember your first calculator -
electronic, that is (slide rules and abacuses don't count - actually they do, right?)?
Mine was acquired sometime in the fall of 1976 during my first attempt at secondary
education at Anne Arundel Community College in Maryland, where eventually, in 1987,
I was awarded an Associate's degree in Engineering (which constituted the first
two years of my eventual BSEE at UVM in 1989, on whose notable alumni list I am
not). My name is not in AACC's list of notable alumni, either. But I digress. My
calculator was a Texas Instruments model SR-50 that had a small red LED display.
It cost about $100 ($445 in today's inflated money...
 You genius types might not be able to relate
to the rest of us who read articles like this one entitled "Fundamentals of Color TV: The NTSC System" and are in awe of minds
that conjure such things as the NTSC System and then build, refine, and perfect
working hardware. Making the system backward-compatible with existing black and
white (B&W) signals added to the complexity and cleverness of the solution -
akin but more sophisticated than compatibility of stereo with original mono radio
transmissions. When catchy marketing slogans like the familiar (to old folks) RCA
television advertisement claim of "Before you see the color ... Your ColorTrak System
grabs it, aligns it, defines it, sharpens it, tones it ... and locks the color on
track," what it actually means is that a very smart bunch of engineers and scientists
spent a lot of time and money designing...
 San Francisco Circuits, a leading printed
circuit board fabrication and assembly supplier serving commercial and defense markets,
describes how
Military-grade printed circuit boards (PCBs) are designed for environments where
failure is not an option. Standards like MIL-PRF-31032, MIL-PRF-55110, and MIL-PRF-50884
define stringent requirements for materials, fabrication, testing, and traceability,
ensuring boards perform reliably in extreme conditions. These specifications guide
engineers and manufacturers in creating PCBs that withstand temperature extremes,
vibration, shock, and humidity far beyond commercial standards. MIL-PRF-31032 serves
as the modern umbrella specification, covering rigid, flexible...
 Welcome to the
RF Coaxial Connectors
Quiz, an essential module for any engineer or radio hobbyist focused on maintaining
interconnect integrity across their signal chain. Whether you are standardizing
your station hardware, troubleshooting high-frequency signal leakage, or verifying
the physical port interfaces for your test bench equipment, a thorough understanding
of coaxial connector characteristics - from the rugged reliability of the Type N
to the precision of the SMA - is vital. This assessment challenges your proficiency
in connector selection, exploring the differences in mating mechanisms, cutoff frequencies,
constant-impedance geometries, and the practical environmental...
 This could be one of the earliest reports
of
mobile communications between a private automobile and a home
base station. Using a personally designed and installed 5-meter transceiver both
at home and in his car, Mr. Wallace is able to talk to his 12-year-old son
on the way from work. My guess is that in 1935 there were not too many traffic jams,
even in Long Beach, California, so it is doubtful that was the cause for his announced
expected later-than-normal arrival home. The article states the automobile power
supply needed to produce 300 mA of current at 525 V, which is ~160 W
per Ohm's law, which seems unlikely considering car batteries were 6 V
at the time, and that would work out to ~26 A. My question is whether little
Billy possessed a license permitting him to talk back to dear old dad from the home
station...
 Prior to the International Geophysical Year
(aka IGY, which ended up running for a year and a half), spanning from July 1, 1957,
through December 31, 1958, not a lot was known about the upper atmosphere. May 1946,
when this article appeared in Popular Science magazine, was less than a
year after the end of World War II. During the war a lot was learned about
long distance wireless (radio) communications between and across continents and
ship to shore. Scientists theorized about the phenomenon of
charged particles at high altitudes which, being electrically conductive, could
reflect electromagnetic signals so that over the horizon signals could be exchanged.
Coincidence with sunspot activity and aurorae had already been established, but
more knowledge was needed. Rocket...
 This photo of Bell Telephone Labs' three
scientists, G.L. Pearson, D.M. Chapin, and C.S. Fuller, inventors
of the "Bell Solar Battery," reminds me of the very familiar shot of John
Bardeen, Walter Brattain, and William Shockley huddled over their point contact
transistor in December of 1948. The "battery" terminology is an interesting
choice since we normally think of a battery as a charge storage device, but in fact
a battery is fundamentally a charge creation device. A secondary battery may be
recharged by reversing the depleted chemical (or other) process that generated the
initial charge, but it first created the potential via a basic charge separation
process. What we today refer to as a solar cell is a form of primary battery that
is not rechargeable. Just as some chemical batteries (cells) are reactivated by
replenishing the electrolyte, the solar cell is replenished by photons giving up
their energy to the semiconductor substrate...
 Here is the final installation of a 22 part
series entitled "The Saga of the Vacuum Tube," by Gerald Tyne, that appeared in
Radio News magazine in 1946. Part 1 was printed in March 1943. The collective
contents, which covered the development of the vacuum tube from its conception to
the end of World War I, could have been published as a stand-alone book. Author
Gerald F. J. Tyne presented the series to trace the development which
took place up to the end of World War I along a particular branch of the network
of roads which led to the modern radio tube. He traced the evolution from studies
of the interactions between heat and electricity as pursued by the early philosophers
and by the physicists who followed them (Lee de Forest, et al). These limitations
have been...
 There are many online
Fresnel Zone calculators.
Most do the basic calculation for the maximum radius of the Fresnel Zone for a given
frequency and separation between antennas. Some allow you to enter an obstacle's
distance from one of the antennas, and its height, then lets you know if the obstacle
falls within the Fresnel Zone. Very few plot the shape of the Fresnel Zone, and
even less include an obstacle positioned on the plot. Most rare are calculators
which take the curvature of the Earth into account. RF Cafe's new online Fresnel
Zone calculator handles all those parameters. Check it out...
 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...
 It has been a long time since I heard this
saying: "Well, they always say that if you want to find out the best and easiest
way of doing something, just put a lazy man at the job." Mac McGregor offered that
line to his service shop technician Barney - in jest of course - when Barney explains
his million dollar invention idea for a
fool-proof vacuum tube tester that can be used by just about anyone.
Mac's Radio Service Shop creator John Frye often used the monthly techno-drama
to introduce some good ideas for new inventions and/or new methods for troubleshooting
problems. Somewhere along the line I think I have seen an advertisement for a tube
tester that used the automation concept dreamed up by Barney...
 I tend to be a traditionalist for most things,
but do not go out of my way to make trouble for other people who don't appreciate
the way things are and have been... as long as, per Thomas Jefferson, "It neither
picks my pocket nor breaks my leg." In other words, if your actions cause me no
financial or physical harm, I'm not likely to oppose your actions - unless they're
illegal. Many older Hams are greatly offended at the FCC for having removed the
Morse code requirement in 2005 for obtaining an amateur radio
operator's license. They see it as a way to separate the wheat from the chaff,
so to speak; that is to say, to maintain a barrier that keeps non-serious aspirants
from gaining entry into the ranks of the elite group...
 For more than a decade, I have been posting
these
Radio Service Data Sheets for radios and various other audio and
visual electronics sets that appeared in vintage electronics magazines. This one
for the Atwater Kent Model 649 all-wave, 9 metal tube, superheterodyne console radio
set was published in the November 1935 issue of Radio Craft. "All-Wave"
radios were popular at the time because they provided access to shortwave bands
so listeners could tune in foreign broadband stations - often with the rudimentary
built-in antenna. Short Wave Listening was actually a worldwide sport that had its
own cadre of enthusiastic participants, including a dedicated magazine entitled
Short Wave Listener...
 We read a lot about the
early
radar system that was in operation at Pearl Harbor in December 1941 when the
surprise attack by Japanese naval airplanes decimated the fleet with a 3-hour-long
raid beginning at around 8:00 on that sleepy Sunday morning. According to "The Untold
Pearl Harbor Radar Story," by C.P. West, the SCR-270B (Signal Corps radio #270,
rev B) radar system had a range of 250 miles at an altitude of 50,000 feet. Westinghouse
built the system in 1940 following a development contract issued by the Army Signal
Corps in 1936. Historical documents report of the three systems on the island, two
had been shut down and that with the remaining system, operators Joseph Lockard
and George Elliot detected a formation of aircraft about 137 miles out to sea. They
were told it was a squadron of B-17s and to not worry about it...
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Loading history...
The RF Cafe Homepage
Archive is a comprehensive collection of every item appearing daily on this
website since 2008 - and many from earlier years. Many thousands of pages of unique
content have been added since then.
 Heathkit's claim to fame was that it was
able to offer user-assembled kits of high quality electronic products at a price
lower than what equivalent factory assembled equivalents would cost. While that
is probably generally the case, it is difficult to gauge what the relative quality
really is. Some of the kits were easy to assemble for even people with little experience,
but a good portion of them required familiarity with soldering and how electronics
were put together. The instructions provided were very thorough, complete with photos
and drawings of how each step should look. In fact, according to a 1972 installment
of Mac's Service Shop entitled "Philosophy of a Kit Manufacturer," every Heathkit
kit instruction booklet goes through a rigorous cycle of writing, testing, and rewriting
before being released for production...
 One very satisfying aspect of 'rolling your
own'
audio frequency coils (aka chokes, aka inductors), is how well the simple inductance
equations match measured end results. Unless you really manage to mangle the job,
if you use the right equation and are reasonably careful to observe wire size, spacing
(including insulation), and core diameter, you will be amazed at how close practice
matches theory. Although strictly speaking audio frequencies run from a few Hertz
up to maybe 15 kHz for people with really good hearing. My experience is that
similar success can be had even into the low MHz realm with just a little tuning
required. It's not until you get into the realm of self-resonance that everything
starts falling apart with basic equations...
 This "Electronic
Crossword" appeared in the September 1958 issue of Radio & TV News magazine.
Its creator, John Gill, designed specialty theme crossword puzzles for many other
editions of Radio & TV News and Electronics World (see the big list at the bottom
of the page). He considered this crossword to be a "fooler" because he claims
to include many "unusual definitions and a number of obscure words which you will
have to work around if your vocabulary of 'exotic words' is rusty." It really doesn't
seem so difficult to me, and anyone used to working my custom RF Cafe Crosswords
will have no problem with it.
 When someone with the first name of "True"
writes an article about transmission line feeds for short-wave antennas, you should
probably take note. This very topic has been covered in detail many times since
the use of impedance-matched transmission lines have been in use (more than a century),
but since there are always people new to the concept, it is good to keep introducing
the topic on a regular basis."Transmission-Line
Feed for Short-Wave Antennas" appeared in a 1932 issue of QST magazine.
Even in this era of prefabricated everything, it still often comes down to winding
coils and adjusting cable lengths to get optimal impedance matches between transceivers
and antennas.
 The word prefix "para" can mean "above and
beyond" or "resembling" or "abnormal or incorrect." Ward Products probably preferred
first two be inferred by potential customers when naming their
PARA-CON television antenna, although it actually is a shortening of "parabolic."
The "con" part is a shortening of "conical." After reading the text of this full-page
advertisement from a 1951 issue of Radio & Television News magazine, I'm inclined
to assign the third prefix meaning of "para" to it. Then, add in the "con" part
where "con" can take on either the noun form meaning of "disadvantage" or the verb
form definition of "to trick or defraud," and you get what this antenna truly represented
in terms of achieving superior performance. At best the PARA-CON exhibited the characteristics
of a phased pseudo-[bi]conical antenna. The allusion to a parabolic antenna...
 Not everyone who visits websites like RF
Cafe is a seasoned electronics veteran. While I and most likely you, too, can do
series and parallel circuit analysis (and series/parallel for that matter, possibly
using Fourier or La Place transforms for reactive AC circuits) in our sleep,
many are recently getting into the wonderful world of electronics who are just coming
of age or have suddenly at a later point in life developed a passion for the craft.
Accordingly, this article from Radio News magazine provides yet another
tutorial on the fundamentals of series and parallel circuit analysis. Only resistors
and basic Ohms law are covered...
 Here are a couple more
tech-themed comics from a vintage electronics magazine (Popular Electronics).
The one from page 101 reminds me again about how different the world of retail sales
is today compared to just two short decades ago. Prior to the advent of online marketing
and sales, you either walked into a brick and mortar (a term rarely heard before
the Internet era) type store and walked out with your purchased product, or you
thumbed through a catalog and placed an order either by mail or telephone. Most
people opted to pay for a postage stamp rather than pay the long distance phone
charge (a term rarely heard today). Free overnight or 2-day shipping from many e-stores
makes online shopping nearly as instantaneous as walking into a store. People under
20 years old have never known much different, but some old-timers still find the
paradigm change strange. The way things are going...
 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 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. Incidentally, the 1952 presidential election
was between Dwight D. Eisenhower and Adlai Stevenson. You might wonder how many
U.S. presidents were/are Amateur Radio operators. Answer...
 August 9th's custom
Amateur
Radio crossword puzzle contains many words particular to Amateur Radio (labeled
with an asterisk *). 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...
 Just as the title of this installment of
Mac's Service Shop, "A Typical Day in the Shop," suggests, the story is a
recollection of the kinds of scenarios that would found in an ordinary shift in
an electronics service business in the mid 1950's. Vacuum tubes were the norm of
the day, as were discrete leaded components and a rat's nest of wires running
from solder lug to solder lug. Printed circuit boards were beginning to appear
in commercial products, but mostly existed in specialty defense and aerospace
applications. You might wonder how many different ways could there be for simple
circuits like biasing and heater element lighting, but some pretty imaginative
variations made their way into radios, television, record players, and tape
decks, and often times that made a serviceman's life heck. Such was the case
here as über-owner-technician Mac admonishes sidekick Barney for not taking
time...
 The old adage about a picture being worth
a thousand words is still true today, even in the Information Age in which we live.
A lot of people, especially those new to the field of electronics, struggle with
the
concept of decibels as applied to power and voltage (and to a lesser degree
current). A plethora of computer, browser, and phone app programs are available
to make individual, specific conversions, but what has been learned about the fundamental
relationship? A nomograph is still one of the best tools both for teaching and performing
conversions. This article that discusses properly matching impedances of amplification
stages includes a nice nomograph...
 If you have never read the story of
Lee de Forest's journey from initial experiments to finally achieving success
with his amplifying vacuum tube, the Audion, then you might want to take a few minutes
to look over this article. It was published in a 1947 issue of Radio-Craft
magazine as part of the 40th anniversary of the invention that changed the electronics
world. With so many other things which are nowadays very commonplace, we tend to
not think about or appreciate the ingenuity and effort that went into them. It is
one thing to make incremental improvements in an existing technology, but to conceive
of and created an entirely new realm of science is quite another. As with Albert
Einstein's relativity and Robert Goddard's liquid-fueled rockets, and the Wright
brothers' powered aeroplane...
 This "Carl and Jerry" episode entitled "Extracurricular
Education" is a bit far-fetched compared to the typical storyline, but it does
illustrate how when you are desperate to get out a distress signal, a little technical
knowledge and having a knack for improvisation can save the day. Back then there
were probably a lot more people sitting around their radios or TVs who might have
heard the SOS message and actually know what it was. I am no Morse code master,
but anytime I hear the familiar di-di-dit dah-dah-dah di-di-dit (··· --- ···) cadence
in a movie or anywhere else, my attention tunes into it like a mother recognizes
her baby's cry in a noisy room. Interestingly, seat belts are mentioned in this
1963 issue of Popular Electronics magazine. Ford began installing them in 1955 as
an option...
 This
Analog & RF
Filter Basics Quiz targets those of you who are relative newcomers to the world
of radio frequency (RF) electronics, but seasoned vets are welcome to give it a
go as well. It addresses frequency response and physical construction. Images were
obtained from Anatech Electronics documents entitled "Guideline for Choosing RF
and Microwave Products" and "Understanding Filter Types and Their Characteristics."
API Technologies' "RF & Microwave Filters," is also referenced...
 When I think back at the
engineering labs
from my days in school, I wonder how much things have really changed from then until
now. It is hard to believe that freshman and sophomore labs are not still consumed
with radial lead resistors, inductors, and capacitors, solderless breadboards, and
a variety of light bulbs, motors, transformers, relays, and rheostats. By the time
you move into the junior year, labs have gotten a bit more intense with microprocessor
controls (mine used an 8088 CPU with machine language programming for the serial
port), some high voltage apparati[sic], digital logic circuits, and a chance to
lay out/fabricate/populate a PCB. On-hand test equipment consists of 2nd or 3rd
generation oscilloscopes, signal generators, and power supplies. I did a search
for photos of labs from back in the early to mid 1900s to see if much had changed
from then until the time I was in college... |
