Constructing PC Boards

Today if you need a printed circuit board (PCB) for prototyping, there is a good chance you will look up a quick-turn company like those found on the PCB Directory website like Bittelle, San Francisco Circuits, or a host of other providers. Costs can be a little as $40 to $50 for three, 3" x 3", 2-layer PCBs and can be delivered in a week or less. A 4-layer PCB of the same size would cost somewhere around $100. Considering how much circuitry can be squeezed into a 9 inch2 board these days, board with surface mounted components on both sides, that's a lot of board for a little money. If you are really in a hurry for your boards, the fabrication companies offer various levels of expedited service for more $$$. There are some people who for one reason or another still prefer to make their own PCBs. For them, this article from Popular Electronics magazine might be a good resource for how to go about it. All the necessary materials like ferric chloride and copper clad substrate material...

Crystal Diodes in Modern Electronics

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 cathode...

Simple Solid-State Circuits for the Experimenter

People are entering the field of electronics all the time and many want to learn not only circuit theory and troubleshooting, but design as well. With all the pre-packaged integrated circuits available that perform just about every function imaginable, there are still times when you either want or need to set about designing your own circuit. Interfaces between two circuits, or to displays and sensors are examples of the kinds of applications that might need a custom design. That applies not only for RF type circuits that require impedance matching, but also to low frequency analog and digital circuits. This article by Mr. Jim Huffman, which appeared in a 1972 issue of Popular Electronics, provides an introduction on how to methodically determine all necessary requirements and then actually design your circuit - in this case an audio amplifier. A technician I worked with in the early-to-mid 1980s who was an inspector at Westinghouse Oceanic Division...

Radar & Radio Engineering Crossword Puzzle for November 3

Each week, for the sake of all avid cruciverbalists amongst us, I create a new technology-themed crossword puzzle using only words from my custom-created lexicon related to engineering, science, mathematics, chemistry, physics, astronomy, etc. This one is for November 3, 2019. 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, see someone or something in the exclusion list who or that is directly related to this puzzle's theme, such as Hedy Lamarr or the Bikini Atoll, respectively. Enjoy...

Noise of Thermal Agitation

Admittedly, I did not do any follow-up research on this, but there is reason to believe that prior to this Radio News magazine article, there was not a general agreement on what formula to use for thermal noise in an electrical system. Here is a statement made by author S.J. Mallory, "At first, however, there was no general agreement concerning the magnitude of this basic Johnson noise power level. Some engineers used the quantity KTB, others used 2KTB and still others used 4KTB." We of course all use KTB nowadays for thermal noise power - aka Johnson noise. It's a good read on the subject of sources that determine the noise floor of a system. There's also this kind of Johnson noise...

After Class: Power Transformers & Electrostatic Speakers

Basic transformer circuits have not changed in the more than sixty years since this article was published in Popular Electronics magazine. The applications have definitely changed, though, since active circuits of the day required a relatively low voltage (step-down) for vacuum tube cathode heaters, and at least one relatively high voltage (step-up) for biasing the tube plate. Most transformers for today's consumer applications perform a single step-down operation for 3.3 V, 5 V, 12 V, etc. In many applications, transformers are done away with altogether in favor of solid state rectifiers and regulators. A 5-question quiz is provided at the end. There is also a short tutorial on electrostatic speakers and some analog and digital signal info. Digital circuits were still a relatively new (and scary) concept to most people at the time...

Receiving "Explorer's" Radio Signals

Amateur radio operators who engage in satellite communications by now are very familiar with needing to compensate for Doppler frequency shifts. Author D. Ripani writes in this May 1958 issue of Radio & TV News magazine how he was caught off guard by the need to compensate for relative motion between the satellite and his fixed receiver. He needed to continually readjust while tracking the Explorer 1 satellite. Nowadays, many (probably most) Hams use software to automatically track and tune transceivers based on readily available ephemeris data published on orbital paths. Due to elliptical orbits that vary in altitude above the Earth's surface, the Doppler shift is not a constant for any satellite. Mentioned is the calculated Doppler shift of ± 2,900 Hz based on Explorer's orbital speed of about 18,000 mph. The included screenshot is from my RF Cafe Calculator Workbook (free download) Doppler Shift calculator...

Simpson Electric Company Model 260 Advertisement

I was first introduced to the Simpson 260 volt-ohmmeter (VOM) in the radar shop where I was assigned un the USAF. Here is the modern version of that classic, the Simpson 260-8 VOM; it looks a lot like the original. Here is an advertisement that I scanned out of my copy of the July 1944 QST magazine. It highlights the precision to which its meter movement pivots are manufactured. "While Simpson Electric Company, chartered in 1934, is a firm with a distinguished past, it is just as importantly an organization with a dynamic present and a definite future." There is an entire website dedicated to the history of the Simpson 260. The famous 260 Volt-Ohm-Milliammeter put Simpson on the map and cemented a reputation for quality that still defines Simpson in the marketplace today." You can still buy a brand new Simpson 260 (-8) from Amazon, or grab a vintage...

Silicon Solar Cells

As with most technologies, solar cells have come a long way in the last half century. Fabrication processes and efficiencies have improved significantly, motivated highly in the last twenty years or so by the global push to replace fossil fuels with other forms of power*. This article from a 1973 issue of Popular Electronics magazine is a snapshot of state of the art solar cells at the time. In the 1970s, there were no large scale solar cell arrays that were a critical part of an electric power grid. Ditto for wind turbines. One of the most significant uses of solar cells then was for powering satellites that operated near enough to the sun to generate useable energy (out to about Mars' orbit). Due to the relatively low output capacity, nuclear power supplies provided electricity for higher demand nearby loads and for deep space probes. A radioisotope thermoelectric generator; i.e., nuclear, powered the lunar rovers for Apollo astronauts. Yep, we left plutonium 238 on the moon...

Electricity in Motion: Current,  Basic Navy Training Courses

One of the Notable Tech Quotes which has appeared on RF Cafe is, "The nice thing about standards is that you have so many to choose from," by computer scientist Andrew Tanenbaum. In the middle of the last century, a change in the fundamental understanding of current flow precipitated what has become a very large opportunity for people to misunderstand descriptions of current direction caused by a difference in voltage potential (voltage) - depending on the era a particular description was written. Beginning with Benjamin Franklin, electron current flow was assumed to be from positive to negative, ostensibly but incorrectly, because a positive thing must contain an excess of something (charge carriers - electrons) and a negative thing must have a deficiency. Hence, current flowed from an excess source to a deficient sink. We now know that negative things contain more electrons (relatively) than a positive thing. "Conventional current" is defined as charge carriers...

A 12,000 Tube Electron Brain

This Radio-Craft magazine article starts out stating, "A skilled mathematician with a desk calculator requires four years to do what the IBM Calculator does in eight hours." That was in 1948. Just last month a headline read, "Given the task of finding a pattern in a seemingly random series of numbers, Google's quantum computer produced an answer in 3 minutes and 20 seconds. It estimates that the Summit supercomputer here at the Oak Ridge National Laboratory in Tennessee would take 10,000 years to complete the task. The IBM 12,000 vacuum tube computer performed its calculation for an improvement factor of [(3 yr • 8760 hr/yr) + (1 yr • 8784 hr/yr)] ÷ 8 hr = 4383 (4.383 thousand). The Google quantum computer performed its calculation for an improvement factor of (10,000 yr • 31557600 s/yr) ÷ 200 s = 3.15776E11 s ÷ 200 s = 1.57788E9 (1.57788 billion -- or milliard)...

Standing Waves on Transmission Lines

In this article from a 1942 issue of QST magazine, author T.A. Gadwa employs a standing wave mechanism analogy that I don't recall having read before - that of a dam on a river. The river is the transmission line with a lake as the source (presumably) and then he imagines a dam load. The dam standing waves, per his description, have phase and amplitude characteristics that depend on how tall the dam wall is relative to the surface height of the dammed river. An extensive array of graphs is provided showing how the current of the dam standing waves react to the dam transmission line termination impedance. I always wonder when seeing electrical-mechanical parity examples whether, as with this case, there are any dam magazine articles out there that use an electrical transmission line to help fellow civil engineers...

Editorial - Engineering Enrollments Down Sharply

The origin of the phrase "Everything old is new again" is credited to everything from the Bible to Shakespeare to Mark Twain. It might be one of the most oft-repeated statements. The topic of this editorial from a 1972 issue of Popular Electronics is a prime example of why people like me invoke the aforementioned dictum. For as long as I have been aware of the state of engineering and technology, opinion writers (aka "journalists"), have lamented the sorry state of education in that it cannot motivate and produce a qualified new crop of replacement engineers, scientists, technicians, doctors, nurses, chemists, and other white collar workers (I can't recall ever hearing of lawyer shortage, unfortunately). Looking back at how the "shortages" have been handled...

Electronic Component Checking (L, C, and R)

When this article on component (resistor, capacitor, and inductor) measurement appeared in a 1957 issue of Radio& TV News magazine, readily available, inexpensive multimeters were not in existence. For about $20 you can now buy a brand new handheld DMM that will make very accurate resistance measurements and reasonably good capacitance measurements at frequencies up to a few MHz, where lead inductance starts to be significant (test frequency is usually only a few kHz). Finding an affordable, accurate inductance meter is another story. Cheap LCR meters can be purchased on Amazon for around $35-$50, and the quality is supposedly...

Engineering the Integrated Communications System

As a follow-on to the "Planning Integrated Signal Communications" story, this article is the next step in the U.S. Army Signal Corps' implementation of ubiquitous communications systems. Along with powerful transmitters and super-sensitive receivers at command communications hubs are the many hand-held, back-pack, and vehicular radios needed to complete strategic and tactical operations across the face of the Earth. It wasn't just wireless systems that Signal Corps engineers and technicians were responsible for, but also all the wired equipment and interconnecting cabling. The possibility of software configuration for network switches, radios, modems, telephones, antennas, and ancillary components had never been thought of in 1950 (by very few, anyway). Everything was set up with patch panels...