Mac's Radio Service Shop: Barney's Dog Show

Whether you are a DIY'er, tinkerer, hobbyist, experimenter, roustabout, odd-jobber, handyman, jack-of-all-trades, innovator, or any sort of electronics dilettante to any degree of adeptness from mere abecedarian to seasoned professional polymath, chances are you can learn something useful from just about all of John T. Frye's "Mac's Radio Service Shop" techno-drama stories. They appeared on a monthly basis in Radio & TV News magazine, and then continued when it became Electronics World in 1959. The varied collection of "dogs" that piled up on Barney's bench while Mac was on vacation provided a convenient excuse to touch on a wide variety of equipment types, from record players to radios, including sets that had fallen victim to "home-talentitis" at the hands of a not-so-capable owner...

Atomichron - World's Most Accurate Clock

The National Company, of Malden, Massachusetts, which made this cesium-based Atomichron in the mid-to-late 1950s, began life as a toy manufacturer. It had an output frequency at the nominal resonance frequency of cesium - 9192.631830 MHz - and was accurate to better than a second in 600 years. The unit was 7 feet tall and weighed 500 pounds. Modern cesium standards are more stable and are portable. As of January 2013, the NIST-F1 cesium fountain primary frequency standard is accurate to within one second every 100 million years! That's a tad better than the Atomichron, non?

Radio Data Sheet 346 General Electric Farm Radio Model 280 

For many years, I have been scanning and posting schematics & parts lists like this one that appeared in radio and electronics magazines in the middle of the last century. Most use vacuum tubes. This General Electric Model 280 Farm Radio "Radio Data Sheet" was in the May 1947 issue of Radio-Craft. The Radio Museum website has more information on the GE Model 280 Farm Radio. Farm radios were designed to work on storage batteries since until the Rural Electrification Act of 1936 was put into effect, most rural properties had no commercial AC electric power service. 11 years later, work was in progress to light up the entire country, but many locations had to wait while resources went to service war production needs. No actual example of the Farm Radio could be found online. There are still many people who restore and service these vintage radios...

Mr. Math Analog Computer

Back in the early 1990s, while working for a fine Midwestern company that made automated utility meter reading (AMR) equipment, an older gentleman was hired as a contractor to do some design work. He was an instant hit with everyone not just because of his engineering prowess, but because of his stories of the mechanical and analog electronic computers he worked on for the U.S. Navy. After being commissioned as an ensign at the U.S. Naval Academy in Annapolis, Maryland, he spent time studying, researching, and designing massive radar-directed gun pointing systems for battleships. Just as contraptions like Babbage's difference engine was a marvel of contemporary engineering, so, too, were those fantastic shipboard amalgamations of gears, switches, vacuum tubes, rheostats, flywheels, cams, and bearings. Calculations of azimuths and elevations were made using sum, difference, integrating, and multiplication circuits built of discrete analog components and electronic valves...

Comics with an Electronics Theme 

Here are a couple new-old tech-themed comics from vintage Popular Electronics magazines. Both have a Ham radio theme, so maybe you need to have been there to appreciate the scenario... or maybe not. It is possible that the presence of clothes pins on twin lead or ladder line could de-tune the line, and could crush the internal dielectric of a coaxial line. There is no metal on boxer shorts, but maybe the clothes pins are the type with a metal spring. For the other comic, you just need to know what ••• --- ••• is to get it. Enjoy

Zenith TV Ad, PCBs Not Inside

"PCBs? We ain't got no PCBs in our TV sets†... We don't have to give you no stinking PCBs." That is effectively what the Zenith television advertisement from a 1958 edition of Radio-Electronics told its potential customers. According to the Zenith communications department, even though their head R&D guy, Dr. Alexander Ellett, was "the daddy of printed circuit boards," they stuck with the traditional point-to-point wiring in all their TV chassis. I have to agree with them from a troubleshooting and component replacement perspective. There's nothing easier than heating a solder lug or terminal post to unwrap a leaded R, L, or C either to measure its value, isolate it from the rest of the circuit for making tests, or to replace it. There is no worry about solder splatter or bridges, overheating the PCB material to cause delamination, or lifting metal traces from the surface. There is also no issue with getting a component lead out of a plated-through hole. Yes, of course modern circuits need multilayer, high density circuit boards...

NanoVNA Portable Vector Network Analyzer

Phil Salas, AD5X, published an extensive review of the NanoVNA vector network analyzer in the May 2020 issue of the ARRL's QST magazine. Unfortunately, the article is not available to non-members, but if you are a member or know someone who is, it would be worth reading. He compared measurements by the NanoVNA with those obtained using an Array Solutions VNAuhf, which yielded very favorable results. There are many knock-offs of the NanoVNA available, which is typical since most of these low-cost, high-performance electronics devices are built using widely available block-level components that make replication relatively easy. Variations in the quality of coaxial connectors, internal batteries, switches, etc., can and often does make a big difference in the quality and ruggedness of the equipment you buy. Firmware and support software can vary significantly as well. It's a roll of the dice to some extent...

On the Very Highs

"Our first complete column devoted to the subject [of v.h.f. and u.h.f. signal variation], presenting material similar to that which follows, was withheld from publication at that time in compliance with censorship." That is an amazing statement from a time when almost any form of technical information that was not already public knowledge was withheld for the sake of the war effort. Nothing that might even remotely give the enemy an edge, and consequently possibly harm our troops, got past the government censors at the War Department. Most citizens and even media editors willingly complied. Compare that with today's 5th column traitors at most of the media outlets that not only can't wait to publish information that will aid and abet our country's enemies, but have been known to manufacture stories in order to make the U.S. look bad...

Early Digi-Key Advertisement

Waaaay back in the mid-1980s when I first became aware of Digi-Key, it was one of the relatively few electronics component suppliers that had a large on-hand stock of commonly used parts and provided fast shipping. Places like Newark Electronics and Allied Electronics also provided good service, but Digi-Key usually offered lower prices than the others. By the 1990s, I was placing orders at least weekly during circuit design projects. Digi-Key was founded in 1972 in Thief River Falls, Minnesota - the town that for many years often had the country's lowest recorded daily temperature. This 1/4-page advertisement appeared near the back of a 1974 issue of Popular Electronics magazine. By the mid-1990s, their multipage ads in electronics magazines were proliferating like today's Harbor Freight ads. Here's a bit of trivia I just learned: The company's name is a reference to the "Digi-Keyer Kit," a digital electronic keyer kit that founder Ronald Stordahl developed and marketed to amateur radio...

Japan Short-Wave Phone to America Open

"Tokyo is now a next-door neighbor-thanks to the magic of short-waves." That statement was made in a 1935 edition of Short Wave Craft magazine after the American Telephone and Telegraph (AT&T) company completed its wireless phone (voice) link between the U.S. and Japan; which is the first 'T' in AT&T. Most people today would probably have a hard time guessing that the second 'T' in AT&T stands for 'telegraph.' Its surprising that the name has not been changed to reflect the outdated-ness. Western Union sent its final telegraph in 2006. Another news headline a couple years ago reported on India sending its final official telegraph message...

Vintage Electronics-Themed Comics

Here are a couple more electronics-themed comics from vintage Radio-Craft magazines. Artist Frank Beaven, who created a huge number of comics and advertisements (e.g., Eveready batteries, Zippo lighters) for technical and other types of publications (Saturday Evening Post, New Yorker, Esquire), did both of them. Beaven must have a fan base since many examples of his drawings are offered for sale on eBay. Most of his comics credit reader suggestions as the basis for the subject. I have to admit to not really "getting" the gag in the top comic. Maybe Sinatra's voice strained the frequency response of simple tabletop radios of the day. The bottom comic is one of a series entitled "Radio Terms Illustrated," in this case "High Potential." I'll be posting a few others in the coming months...

Subminiature Magnetic Amplifiers

Magnetic amplifiers (aka "mag amps") use a property of saturated core inductors (saturable reactors) to obtain signal amplification via a transformer-type plus diode-assisted voltage multiplication. Magnetic amplifiers were preferred over vacuum tube amplifiers in some circuits because they do not require a high bias voltage, are generally smaller in size, are quite robust and are practically immune to microphonics. Their biggest limitation is bandwidth. The high number of turns in the core provides a lot of interwinding capacitance so the self-resonant frequency is in the low megahertz range. Additionally, the need for the magnetic amplifier reactor to operate in a saturated condition further imposed a limit on the frequency response. Even today, there are some critical applications that exploit the fool-proof and ultra high reliability nature of the magnetic amplifier. This article goes into the details of operation both as amplifiers and as bistable multivibrators...

Calvin's Father Explains...

This has always been one of my favorite Calvin & Hobbes comic strip episodes. Calvin's father, a patent attorney, is famous for providing zany explanations to Calvin's inquiries about physics, astronomy, and other science subjects which he knows nothing about. In this comic, Calvin is riding in the car over a bridge with "Weight Limit 10 Tons" on it. He asks his father how the limits are determined. His father, whose name has never been divulged (neither first name nor last name), replies with a typically hilarious version of what goes into the weight limit calculation. Read on for explanations on where babies come from, why old photographs are in black and white even though much older paintings are in color, the sunset, how a light bulb works, and even Relativity, amongst other things. Bill Watterson was truly a genius...

Radio & Radar Engineering Crossword Puzzle for April 19

April 19 commemorates a special birthday here at RF Cafe as explained in 39 and 74 Across. You can calculate her age by solving these two equations in two unknowns: Her Age = Her Year of Birth - 1902, and My Age = Her Year of Birth - 1900. Actually, you don't need to know my age to solve the first equation. This tech-themed crossword puzzle contains only clues and terms associated with engineering, science, physical, astronomy, mathematics, chemistry, etc., which I have personally built over nearly two decades. Many new words and company names have been added that had not even been created when I started in the year 2002. You will never find a word taxing your knowledge of a numbnut soap opera star or the name of some obscure village in the Andes mountains. You might, however, encounter the name of a movie star like Hedy Lamarr or a geographical location like Tunguska, Russia...

How to Break the 10-Words-Per-Minute Code Barrier

When you think about it, the speed at which a human being is able to accurately copy Morse code is limited by the same kinds of processes that limit the speed at which binary data can be sent between electronic transceivers (modems). Noise introduced into the signal at both the transmitting and receiving ends or in the transmission path connecting the two, degrades the ability of the receiver (electronic and human) to discern between a "1" and a "0." It can take the form of electrical or audio interference and distortion. Phase noise in the electronic realm is sort of the equivalent of an irregular sending human hand that cannot maintain equal dwell times for dits and dahs, thus making the recognition of characters error-prone. The operational speed of circuitry on an electronic assembly can also limit the speed at which Morse code can be copied similar to how a particular person's gray matter can limit his comprehension speed...