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 These are the schematics and parts list
for vintage vacuum tube radios
Westinghouse Model H-133;
Arvin Models 150TC, 151TC; and
Admiral Model 7C63, Chassis 7C1 as they appeared in the December
1947 issue of Radio News magazine. I scan and post these for the benefit
of hobbyists and historians seeking such information. As time goes by, there is
less and less likelihood that records of these relics from yesteryear's archives
will be made available. As with all historical information, it takes someone with
a personal interest in preserving the memories in order to fulfill the mission...
 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. Designed and
manufactured in the USA. Please visit NIC today
to see how we might be of assistance.
 Here is another electronics quiz for you
to try. Intuition from experience goes a long way here, but if all else fails you
can work out the details of the rectifier circuits to determine
which lamp received the most current. Keep in mind that the diode
symbols are not LEDs; it is the "A," "B," and "C" symbols inside circles
that are the lamps whose brightnesses are being considered. LEDs did exist at the
time this quiz was created in 1969, but the circuits would perform differently if
in fact LEDs were used for double duty of rectification and illumination...
 The more things change, the more they stay
the same. That saying applies to many recreational activities. Pick up a copy of
QST magazine that was published in the last year and look at
reader comments and you will find laments about the dwindling
participation of youngsters, an increased degree of incivility and rule breaking
during engagement, the high cost of getting into the hobby, yadda yadda yadda. I
witness it regularly in the model aircraft world, too. That is not to say the issues
are not true or irrelevant, just that they are persistent. Each generation, it has
been said, tends to think...
 I have long-maintained that the vast majority
of electrical problems on consumer products can be attributed to bad connector or
switch contacts. Just yesterday, I restored a 1970's-era TI talking kids' toy to
working order just by cleaning the plug-in program module and mating motherboard
contacts. RF Cafe website visitor / contributor Bob Davis sent this suggestion for
curing intermittent or non-responsive front panel buttons on test equipment and
other electronic gear like radios, remote keypads, games, tools, vehicles, keyboards,
locks, etc. His problem was with a R&S spectrum analyzer. He found a solution
from ButtonWorx, who manufactures replacement
pressure contacts for a large range of products. Some are entire arrays to replace
original parts, and others are individual switches for custom requirements.
 You wouldn't know it from the schematic,
but this
Coronet
Model C-2 tabletop radio has a very unique feature: The tuning scale/pointer,
and volume and tuning knobs are on the top of the case, that is, the face of the
radio points upward when properly displayed. When searching for photos of the Coronet
C2, I found a few examples where the radio was sitting on a surface with the face
situated vertically like a standard model, but the feet are clearly on the side
opposite the face. The schematic and parts list for the Coronet C2 radio appeared
in the February 1947 issue of Radio News magazine. 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. I keep a running list
of all data sheets to facilitate a search...
 Have you noticed that every time a shooting
or other attack event occurs - especially pertaining to "R" targets - the quality
of the video looks like something from the 1970s, or of a UFO sighting? Most private
surveillance cameras in homes, cars, and businesses - even traffic cams - have resolution
and full color so good you can distinguish faces and even identify brands of clothing,
weapons, etc. This is a frame from the attempted assassination attempt this weekend
at the White House Correspondents Dinner. The perp, a celebrated "Teacher of the
Month" from California, rushed the security point with multiple weapons. Conceal
carry, do training, and watch your six.
 In the early 1950s, the U.S. Navy built
what was at the time the world's largest and most powerful radio broadcast transmitter
station at the
Jim Creek Naval Station on Wheeler Mountain in Washington state.
Its 1.2 MW, 24.8-to-35 kHz VLF transmitter (call sign NLK) can reach anywhere
in the world, even to submarines. A half wavelength at 24.8 kHz is 19,830 feet.
Photos indicate that the transmitter is located in the middle of a dipole arrangement.
"Catenary cables," if you are unfamiliar with the term, refers to the sagging shape
assumed by both the antenna cables and the tower support cables. "Catenary" stems
from the word "chain" since it is in the form...
 Carbon tetrachloride (CCl4) was
a common cleaning agent used commercially through about the early 1950s when it
began receiving a lot of bad press due to a linkage to severe kidney damage from
exposure even in vapor form. I notice that Mac mentions having read an article about
the potential danger of "carbon-tet" in an edition of Radio & Television
News magazine, not coincidentally the publication where the "Mac's Radio Service Shop" series appears. He also mentions a publication
called International Projectionist, which included instructions for cleaning
movie film with carbon tetrachloride, and had...
 It is amazing to me how many times I read
an article, whether in a vintage magazine like this 1947 issue of Radio News,
or a current edition of QST, how when discussing maximum power transfer
from a source to a load, the author states merely that the load impedance must equal
the source impedance. The fact of the matter is that the source and load impedances
must be the
complex conjugates of each other in order for maximum power transfer
to occur. That is to say that if the source has a complex impedance of R + jX, then
the load must have a complex impedance of R - jX (and vice versa)...
 Unlike today when resources of all types
seem to be endlessly available, during World War II countries needed to collect
and recycle much in the way of metal, rubber, cloth, and other basic materials for
re-purposing into products used in fighting the enemy. Media coverage of bottle,
metal, and tire drives showed children pulling Radio Flyer wagons loaded to overflowing
with such items gathered from trash piles and soliciting neighborhood residents
for anything that could be spared. Raw materials were not the only type of items
needed, however. "Use
it up, Wear it out, Make it do, or Do without" was the slogan. Finished goods
like electronic components - vacuum tubes, transmissions cable, transmitters and
receivers, tuning capacitors, d'Arsonval meter movements, and other parts -
were sorely needed by manufacturers both for building new equipment and for servicing
damaged gear. After the war was won, the War Assets Administration...
 Around the time when this "The
Great QSL Quarrel" appeared in a 1960 issue of Electronics Illustrated
magazine, there was a long-standing friction between amateur radio operators and
shortwave listeners regarding the exchange of QSL confirmation cards. Far from mere
paper, many hams view their custom-designed cards as valuable reflections of their
personal rigs and efforts. Consequently, they often discard subpar listener cards
that are illegible, aesthetically dull, or lacking meaningful data. To ensure their
reports are actually welcomed, shortwave listeners are urged to adopt higher standards:
utilizing professional printing or clear handwriting...
 A momentous development that changed the
field of radio communications warranted merely a half-page announcement in 1935
when
frequency modulation inventor Edwin Armstrong had his article
published in Radio-Craft magazine. It indisputably changed the world while causing
poor Mr. Armstrong much grief while defending his right to the invention. Spread
spectrum modulation / demodulation would be the next big communications advance
that began with the frequency hopping (FHSS) scheme dreamed up by Hollywood actress
Hedy Lamarr and pianist Antheil George during World War II. Direct sequence
spread spectrum (DSSS) followed in the digital age, and since then I do not know
of any fundamentally new communications technology in that time...
 Since 2005, San Francisco Circuits has been
a trusted U.S. provider of advanced PCB manufacturing and assembly solutions for
R&D innovators, prime contractors, and integration experts.
Flying Probe Testing (FPT) has long been a reliable method for validating PCB
designs, particularly for prototypes and low volume production. Unlike traditional
in circuit testing (ICT), which relies on custom built fixtures, flying probe systems
use movable probes to test electrical connections directly, eliminating the need
for dedicated hardware. Flying probe testing uses multiple programmable probes to
contact pads...
 The February 1947 issue of Radio News
only had two
electronics-themed comics. Many months have up to half a dozen
comics. Maybe the winter blues had set in with the magazine's illustrators. The
first comic is a tad bit prescient in that it depicts a robber running past a television
store and seeing a TV in the front display window showing a real-time video of the
cop chasing him. That was way before there was a video surveillance camera on every
street corner. I haven't discovered a vintage magazine yet with someone taking a
"selfie." There is a growing list...
 These are the schematics and parts list
for vintage
Emerson vacuum tube radio models 501, 502, and 504;
Crosley model 56TD-W; and
Arvin model 140P as they appeared in the November 1947 issue of
Radio News magazine. I scan and post these for the benefit of hobbyists
and historians seeking such information. As time goes by, there is less and less
likelihood that records of these relics from yesteryear's archives will be made
available. As with all historical information, it takes someone with a personal
interest in preserving the memories in order to fulfill the mission...
 John Comstock created many crossword puzzles
for Radio & TV News magazine, and a couple others, in the 1950s and
1960s. This one titled "Test
Equipment Teaser," appeared in the March 1959 issue. It is not a densely populated
grid with complex intersections of crossing words (unlike the RF Cafe crossword
puzzles, which do have them), but at least with this kind, all of the words and
clues are directly related to electronics and technology (like RF Cafe crosswords).
Anyway, it shouldn't take you too long to zip through this one. The only clue/word
that might give you trouble is 32 Across. Enjoy...
 Exodus Advanced Communications' representatives,
in discussions during last month's EMV (Elektromagnetische Verträglichkeit) show
in Cologne, had many attendees express interest in receiving an Exodus brochure
covering our RF amplifier solutions for
drone (UAS) applications. Exodus supports defense contractors with a family
of RF amplifier modules optimized for UAV, drone, mobile, and fixed Counter-UAS
platforms. At the center of this portfolio is the
AMP10008, an ultra-lightweight solid-state RF amplifier module
that demonstrates what is possible when SWaP is treated as a primary design driver
rather than a compromise...
 The cover of this month's Radio &
Television News magazine is part of the issue's story on performance testing
of resistors. The author was an engineer for
International Resistance Company (IRC), which is still in business
as part of TT Electronics. The massive ovens were used for load-life testing to
certify resistor products for both military and commercial uses. When required,
humidity enclosures subjected resistors to increased levels to test for insulation
breakdown at high voltage. As the article observes, since a 10-cent resistor can
take down a multi-thousand system, it is important to guarantee every component's
integrity...
 Werbel Microwave is a manufacturer of RF
directional and bidirectional couplers (6 dB to 50 dB) and RF power dividers
/ combiners (2- to 16-way) with select models operating up to 26.5 GHz and
100 W of CW power (3 kW peak). All are RoHS and REACH compliant and are
designed and manufactured in our Whippany, NJ, location. Custom products and private
label service available. Please take a couple minutes to visit their website and
see how Werbel Microwave can help you today.
 RF Cafe's spreadsheet-based engineering
and science calculator,
Espresso
Engineering Workbook™, is a collection of electrical engineering and physics
calculators for commonly needed design and problem solving work. The filter calculators
do not just amplitude, but also phase and group delay (hard to get outside of a
big $$$ simulator). It is an excellent tool for engineers, technicians, hobbyists,
and students. Equally excellent is that Espresso Engineering Workbook™ is provided
at no cost, compliments of my generous sponsors. 49 worksheets to date...
 Although the Japanese attack on Pearl Harbor
on December 7, 1941, was a complete surprise and shock to the nation, that fact
that the United States would eventually be drawn officially into World War II
was well known. The amateur radio community had begun talking about the potential
impact on radio communications hobbyists earlier in the year, as evidenced by articles
printed in QST and other magazines. Within a couple weeks of Congress declaring
war, all unauthorized transmissions from Ham stations were terminated in order to
prevent both intentionally and unintentionally conveyance of information that could
proves useful by the enemy. Along with being a patriotic bunch that were eager to
help defeat Axis powers, they also...
|
 • U.S.
Engineering
Ph.D. Programs Losing Students?
• What
Hormuz Exposed About Semi Supply Chain
• Broadband
Equipment Market Set for 2026 Rebound
• Foundry
Revenues to Grow 24.8% YoY
• U.S.
Manufacturing Sector Flexes Its Muscles
 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.
 Here is another trio of vintage electronics-themed
comics from Radio-Craft magazine. Two are part of illustrator Frank Beaven's
"Radio
Terms Illustrated" series, where readers would write in with suggestions and
Mr. Beaven would put the ideas in ink. These two are "Poor Reception, and "Regeneration."
If you look at the bottom of the page, you will find a big listing of other comics,
with many of the other "Radio Terms Illustrated" instances ("High Potential," "Signal
Generator," "Overload Capacity," "Amplitude," "Transmission Loss," etc.) labeled.
Enjoy!
 This article describing the "Auto-Sembly"
technique for fully automated processing of electronic assemblies appeared in the
1954 issue of Radio & Television News magazine. Auto-Sembly was developed by
the U.S. Army Signal Corps, and might have first appeared in print in the 1951 issue
of Electronics magazine. Single-sided printed circuit boards (PCBs) with components
mounted on the far side were hot-dipped in a solder bath. All components were through-hole
at the time since surface mount was not in the picture yet. The large mass (weight)
and relatively low adhesion strength of copper foil to the substrates would not
reliably hold the components in place under even normal use. PCBs were just entering
the electronics market, and as with many new technologies was enthusiastically embraced
and encouraged by proponents, or vehemently shunned by opponents. Given that transistors
had only been invented four years earlier, PCBs of the era incorporated vacuum tube
sockets...
 Windfreak Technologies is proud to announces
the availability of our
FT108, an innovative
programmable bidirectional filter bank spanning a frequency range of 5 MHz
to 8 GHz in 15 bands. Band selection can be controlled through USB, UART or
at high speeds through powerful triggering modes. Each unit is factory tested via
network analyzer with unique data stored in the device to help with its use. Crossover
frequencies are stored so the user can send a frequency command and the FT108 will
utilizes Intelligent Band Selection logic to automatically toggle the optimal
filter path based on minimum insertion loss. Readback of FT108 insertion loss at
any frequency between crossover points allows for easy amplitude leveling...
 With more than 1000
custom-built stencils, this has got to be the most comprehensive set of
Visio Stencils
available for RF, analog, and digital system and schematic drawings! Every stencil
symbol has been built to fit proportionally on the included A-, B-, and C-size drawing
page templates (or use your own page if preferred). Components are provided for
system block diagrams, conceptual drawings, schematics, test equipment, racks, and
more. Page templates are provided with a preset scale (changeable) for a good presentation
that can incorporate all provided symbols...
 This vintage
Heathkit HW-8
QRP Transceiver kit is one of the latest unbuilt Heathkit kits which appeared
today on eBay - a fitting subject for the "Why Key Clicks?" article below.. I have
been saving the images in order to preserve the history. The constantly growing
list is at the lower right. The HW-8 covers the 80-, 40-, 20-, and 15-meter bands
for CW. As you can see from the video at the bottom of the page, there were a lot
of parts in the kit to assemble. The first instance I could find for HW-8 being
offered for sale was in the Spring 1976 Heathkit catalog (p79), at a cost of $129.95
($623.56 in 2021 money per the BLS). From the Spring 1976 Heathkit catalog: "We've
made the world's most popular low-power CW transceiver even better! To the Heathkit
HW-7 - we have added more bands, more features and a super new receiver section
that's the best in its class. The famous HW-7 QRP Transceiver helped thousands of
hams work the world on a couple of watts - and on a budget. Now, in the same value
conscious tradition, Heath announces the HW-8...
 By the time most of us who even remember
cathode ray tubes (CRTs) were first introduced to them, the technology
and manufacturing processes had been pretty much perfected - especially for the
standard 525-line resolution type. The NTSC published a standard for B&W television
in 1941 and then for color in 1953. This "Picture Tubes" article in a 1955 issue
of Popular Electronics provides a look inside a CRT manufacturing plant
at General Electric. If you want one of the best explanations I have ever seen on
how a TV picture scan is implemented, check out this video. If you don't understand
raster scanning after watching it, you never will. You might be surprised to learn
that there were not actually 525 lines of picture information, but that only about
480 to 487 lines of picture were included - the rest were...
 Radio-Craft magazine's "Radio Term
Illustrated" feature of electronics-themed comics was very popular. Famous artist
Frank Beaven, who created illustrations for numerous publications at the time, took
ideas submitted by readers and turned them into clever word (or phrase) pictures.
You will need to consider some of them from the viewpoint of someone in the 1945
era in which they were made. I don't know if women Navy personnel are referred to
as WAVES (Women Accepted for Volunteer Emergency Service ) anymore - probably not.
Arcing from motor armature brushes was a common cause of radio interference in the
days of AM broadcasting, hence "brush discharge." Enjoy!
 Here are a couple more
electronics-themed comics from a 1940-era issue of Radio News magazine.
The scenarios depicted in these old comics are often based on the real-life experiences
of radio and electronics servicemen. No doubt many guys got clobbered by high voltage
or deafening audio when a customer decided to power up a television or radio while
being worked on in the home. When this comic with the police car radio appeared
in 1940, it had only been a decade since the first 2-way radios were being installed
in patrol cars (see "A New Arm of the Law"). A huge list of technology-themed comics
is listed at the bottom of the page. Enjoy!
 Here is
Zenith Models 5D011-5D027 schematic and parts list as featured in a 1947 edition
of Radio News magazine. Unlike with most of the Radio Service Data Sheets,
this came from group of three which also included the Bendix Models 636A, C, D and
the Coronet Model C-2, al three of which are tabletop models. As mentioned many
times in the past, I post these online for the benefit of hobbyists looking for
information to assist in repairing or restoring vintage communication equipment...
 Part 1 of this "All About IC's" trilogy titled,
"What Makes Them Tick," author Bob Hibberd introduced the concept of semiconductor physics
and doped PN junctions. In Part 2, he discusses methods used to
fabricate monolithic, integrated circuits (IC's) on silicon chips.
Transistors, diodes, resistor, capacitors, and to some extent, inductors, can be
built using a combination of variously doped junction regions, metallization,
and oxidation (insulators). Technology has come a long way since 1969, including
mask techniques, 3-D structures, doping gradients, feature size, dielectric
breakdown strength, current leakage, circuit density, mixed analog, RF, and
digital circuitry, and other things. Part 3, covered in the August issue, goes
into more detail about how passive components are realized in silicon...
 Nothing has change in the design and application
of
resistive attenuator pads since this article appeared in a 1959 issue of Electronics
World. It could be legitimately reproduced verbatim in the August 2018 issue of
any magazine. When you crank through the equations you will arrive at resistor values
slightly different from those presented here because the author chose the nearest standard
5% tolerance resistor values. For instance the 10 dB, T-type attenuator for 75 Ω
terminations shown in Figure 7 gives series branch resistors of 33 Ω and a parallel
branch resistor value of 51 Ω. The result is an attenuator that does not present
exactly the desired input and output impedances or the exact attenuation value. More
precise values are 39.0 Ω and 52.7...
 This story was posted sometime around 2009.
Since that time, research has been conducted by members of the
Harvard Wireless Club
regarding the veracity of the claim. RF Cafe visitor Fred Hopengarten, Esq. (K1VR),
wrote to apprise me of the situation. It concludes as follows: "Back in 1999, the
late K3UOC, who received his Ed.D. from the Harvard Graduate School of Education
and was very active with our club, wrote: Note: This legend has been published and
told by word-of-mouth countless times over the past 90 years. Unfortunately, it
isn't so. HWC members researched this story, even obtaining the copy of the Congressional
Record for the date in question. We could find no record of Mr. Hyman appearing
before congress. We have to admit, though, it's a very entertaining story!"
 There are a lot of audiophiles in the RF
Cafe audience, so this 10-question
Audio Quiz from Popular Electronics should prove useful.
It covers not just the physical aspects but also some simple electronics concepts,
like decibels of gain, crossover networks, push-pull amplifiers, etc. High fidelity
(hi-fi) stereophonic equipment was all the rage in the 1950s and 1960s. It was a
way for people to enjoy live concert quality music in their homes since the quality
of radio transmissions was not reliable, and stereo broadcasting was not a common
feature until the 1960s. Many articles were published educating beginners and veterans
on ways to optimize both equipment - receivers, turntables, speakers, equalizers,
etc. - and environmental parameters. Similarly, many stereo-themed comics (and here)
appeared in Popular Electronics and other magazines. Enjoy.
 Not everybody with a high temperature semiconductor
application in need of heat dissipation has access to a thermal management program
with a database of available commercial
heat sinks and/or an ability to analyze a custom-made heat sink. This article
from a 1965 issue of Electronics World magazine contains simple equations,
a handy chart, and instructions on how to use them to figure out what kind of heat
sink you need for your project. At the time TO-8 and TO-3 metal cans were a couple
of the most common sizes for which a large variety of heatsinks were available...
 Homepage
Archives for June 2024. 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.
 Decades before there were highly sensitive
CMOS-based light sensors and charge-coupled devices (CCDs), light detection for
image capturing was performed by vacuum tubes called
photomultiplier tubes (PMTs). They amplify light by releasing electrons in response
to a detector surface that answers to photon impingement. PMTs are still more sensitive
and of lower noise level than the silicon devices. In fact, super-sensitive elements
for many atom smashers and subterranean neutrino detectors still use photomultiplier
tubes for that reason. My first encounter with a PMT was as part of a video map
rendering system used on the airport surveillance radar (ASR) display that I worked
on in the USAF. Air traffic controllers etched an overlay map of the airport area
on a plate of coated glass. It was placed in a box that swept a light beam in synchronization...
 Most visitors to RF Cafe are either engineers,
technicians, or hobbyists who deal with watts in terms of
electrical power. This article from the January 1957 edition of Popular
Electronics deals primarily with watts in terms of acoustic power, but it also
addresses how obtaining acoustic watts relates to electrical watts. Audiophiles
will appreciate the table of speaker watts needed based on your room volume as well
as rules of thumb for selecting the amplifier power required to deliver that sound
effectively. You will note that back in the day the common abbreviation for decibels
was all lower case (db) ad opposed to how we do it today (dB). A tech-related comic
was on a page in the article so I included it as well...
 "Squegging" - Now there's a word you don't hear
every day. It is a shortened version of "self-quenching." As is often the case in these
"Mac's
Service Shop" sagas, we get a primer on certain circuit functions and how to
troubleshoot and resolve the issue. You can also usually count on learning more
than one lesson per reading. After replacing the failed component in Barney's
exasperatingly elusive receiver, Mac turns to record changer mechanisms and
their bewildering nature, but the real message being given is the value of
well-written troubleshooting guides from manufacturers. Even with today's
no-user-serviceable-parts-inside products, there are many times a
troubleshooting guide is included as part of the user's manual. That goes for
both electronic and mechanical products. You might laugh at the first step that
tells the owner to check to make sure the electric cord is plugged in or
batteries are installed with the proper polarity...
 Here are the schematic and parts list for
Zenith model 5R080 and 5R086 radio/phonograph combos, from a 1947 issue
of Radio News magazine. It must have been a fairly popular set because
many have been sold on eBay; in fact, that's where I got the photos shown here.
The schematic page from the Sam's Photofact also came from an eBay listing. Note
where it says that unless otherwise noted, all resistors values are ±20%. I suppose
when your phonograph turntable uses a metal chain drive mechanism, precision isn't
a huge concern. 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; that's why I keep a running list of all the data sheets I find to facilitate
searches... |
