Destiny and Geomagnetism

If you read the physics and geographic news of the day, most likely you have seen articles on the rapidly increasing migration rate of the geomagnetic "north pole" over the past few decades. Magnetic north has never exactly lined up with geometric north (as borne out in geological samples of rocks), and neither has it ever been uniformly distributed across the globe. Ancient explorers on terra firma and at sea knew that a magnetic compass needle did not align with the same stars, moon, or sun position for every location, after accounting for difference in longitude. That is because the earth's magnetic field is very nonuniform in strength and does not follow straight lines from pole to pole as they more generally do from outer space. A correction factor must be applied to any magnetic north indication based...

The Amazing Surface Barrier Transistor

According to the Transistor Museum website, "The Philco Surface Barrier Transistor (SBT) was the 'hottest' transistor around until the late 1950s. This device performed very well at high frequencies and was used extensively in radio and computer circuits. Hobbyists were delighted to find such an inexpensive high frequency device... [Edwin] Bohr authored many well-remembered transistor construction projects in the 1950s/60s." Many of Bohr's construction articles featuring SBTs were published in Radio Electronics magazine, and this was one of them from 1957. The manufacturing process is described where jet streams of an electrolyte were shot at both sides of the germanium crystal to etch it as required - Neanderthal in nature...

ABC's of Transistors

Sylvania was yet another bedrock American technology innovation company that in the last few decades has been bought by foreign concerns*, while retaining at least some semblance of its original identity - mostly for brand loyalty purposes. Along with pioneering lighting products, Sylvania produced vacuum tubes and semiconductors for use in its line of radios and televisions. Sylvania engineers published a lot of articles in electronics magazines introducing transistors and early integrated circuits to laymen, hobbyists, and professionals, some of whom were fledglings to the field and others who were transitioning tubes types. This particular article suggests methods for verifying operation of PNP and NPN bipolar junction transistors (BJTs) and for troubleshooting basic circuits...

Electronics Crossword Puzzle, April 1967 QST

QST, the monthly publication of the American Radio Relay League (ARRL), occasionally ran a crossword puzzle with an electronics theme. This one appeared in the April 1967 edition. Unlike the weekly RF Cafe crossword puzzles, this one does have a few words that are not strictly technology and science themed. However, many of the clues and words require some familiarity with Ham radio subjects and lingo...

Bell Telephone Laboratories Waveguide Isolators

This full-page advertisement by Bell Telephone Laboratories in the June 1956 issue of Radio & television News seems to imply that their Dr. S. Weisbaum and/or his contemporaries was/were the original developer/s of the waveguide isolator. If so, it would be no surprise since Bell Labs was responsible for many technology innovations during its history - RF, microwaves, telephony, switching, transmission lines, test and measurement, and much more. Other information available on the Internet assigns credit to Bell Labs in the same timeframe. From the ad: "This isolator is a slab of ferrite which is mounted inside the waveguide, and is kept magnetized by a permanent magnet strapped to the outside. The magnetized ferrite..."

Engineering & Science Crossword Puzzle for June 2

This week's crossword puzzle contains the full name of our industry's big show in Boston. Since 2000, I have been creating custom engineering- and science-themed crossword puzzles for the brain-exercising benefit and pleasure of RF Cafe visitors who are fellow cruciverbalists. The jury is out on whether or not this type of mental challenge helps keep your gray matter from atrophying in old age, but it certainly helps maintain your vocabulary and cognitive skills at all ages. A database of thousands of words has been built up over the years and contains only clues and terms associated with engineering, science, physical, astronomy, mathematics, chemistry, etc. You will never find a word taxing your knowledge of a numbnut soap opera star or the name of some obscure village...

The Iconoscope

An iconoscope was an early form of television image capturing tube. Some amateur radio operators were experimenting with slow scan TV even back when the technology was relatively new to the world. When this article was written in 1944, there were still large portions of the United States that did not have television broadcast coverage. Of course I would argue that at the time of my growing up in the 1960s and early 1970s a lot of areas - even suburbs - were still not covered by TV signals, based on how cruddy the reception at my parents' house was. But I digress. The article mentions that because of the lack of TV coverage, many amateurs did not even have television receivers (TV sets) in their homes to use along with experimental television transmitters...

Motorola PNP & NPN Oxide-Passivated Silicon Annular Transistors

Everything is relative... just ask Albert Einstein. The use of terms like "contemporary," "modern," etc., in the titles of books has always annoyed me. They would be okay if the titles also included the year or at least the decade to which the claim applies. Not quite as nefarious is the claim of "high frequency" when describing electronics components since it is safe to assume that most readers understand the era to which it applies. To a lesser extent that goes for "high voltage" and "high current." This 1964 advertisement for Motorola's Oxide-Passivated Silicon Annular Transistors appeared in Electronics magazine touting the high frequency capability...

Sentinel Model 217-P Portable Radio Set Radio Service Data Sheet

Many months have passed since I last posted one of the Radio Service Data Sheets for vintage radio sets. This one for the Sentinel Model 217-P portable appeared in the August 1940 issue of Radio-Craft magazine. Hobbyists and professional electronics service shops relied on these back in the day because obtaining the information from manufacturers could be difficult or even impossible. Some companies would not provide service information for alignment and troubleshooting to businesses that were not officially endorsed to do so. That left some of the smaller shops and most do-it-yourselfers without a means to work on sets. Once places like SAMS Photofacts came along with information packets that could be purchased...

Carl & Jerry: Abetting or Not?

Carl and Jerry found the appearance and construction of 2,400 megacycle transmitters and receivers to be quite odd compared to the equipment they were used to dealing with. It's sometimes hard to believe such an attitude of wonder when our world today is utterly filled with wireless devices operating in the 2.4 GHz ISM band. Author John T. Frye could never have imagined that such a reality would would exist half a century after his story of the pair of teenage electronics sleuths. Unlike our postage stamp size integrated assemblies that cost a few dollars, they speak of "special ultra-high-frequency 'light-house' tubes with a cavity resonator clamped on top of them." Back to the story, though... Did you know that police were using radar guns as far back as 1963?...

Lesson from Europe

In the light of having just marked the 75th anniversary of the D-Day (Operation Overlord, June 6, 1944), which marked the beginning of the end of Hitler's ruthless siege on all of Europe, please note how Electronics magazine editor Lewis Young cites, in 1964, the continued rebuilding of Europe as the reason many - maybe most - companies there are still, two decades later, concentrating engineering and financial resources on getting back on a solid footing rather than chasing after the latest and greatest in nonessential technologies. It was probably an accurate assessment of the situation. However, I do take issue with his admonishment to American companies to emulate Europe's "practical approach" to innovation and manufacturing. There was absolutely no reason to dissuade and throttle activity here...

Commercial Aspects of Single-Sideband

Prior to phasing-based single sideband generation circuits, a brute force filtering of the unwanted sideband and carrier signals was required. Depending on how well the carrier was suppressed, more than half the total signal power could be lost. According to author Jack Brown in this "Commercial Aspects of Single-Sideband" article from a 1956 issue of Radio & Television News magazine, it had only been since the mid 1940s that wide-band audio-frequency phase-shift networks were even feasible. An ideal implementation of a single-sideband suppressed-carrier modulator (SSB-SC) would result in 100% efficiency, but typical results are in the 80% range...

USAF Recruitment Advertisement - Precision Approach Radar

This is cool. I saw a U.S. Air Force recruitment advertisement in a 1960 edition of Popular Electronics pitching careers as radar operators (air traffic control) and technicians (maintenance). The picture has the dual-display glide path and elevation sweeps from the MPN/13/14 radar system that I worked on in the late 1970s - early 1980s. A photo I took circa 1980 of our unit based at Robins AFB, Georgia, is shown below. The precision approach radar (PAR) operated at x-band (10 GHz) with an operational range of 10 nautical miles. The azimuth and elevation antennas were mechanically swept with motors that changed the geometry of a waveguide having dipole stubs along its length. The entire PAR system...

Engineering & Science Crossword for June 9

Since 2000, I have been creating custom engineering- and science-themed crossword puzzles for the brain-exercising benefit and pleasure of RF Cafe visitors who are fellow cruciverbalists. The jury is out on whether or not this type of mental challenge helps keep your gray matter from atrophying in old age, but it certainly helps maintain your vocabulary and cognitive skills at all ages. A database of thousands of words has been built up over the years and contains only clues and terms associated with engineering, science, physical, astronomy, mathematics, chemistry, etc. You will never find a word taxing your knowledge of a numbnut soap opera star or the name of some obscure village...

Radar-Tracking Accuracy Increased

The many idiosyncrasies of atmospheric phenomena that affect long distance communications are certainly more well known and understood today than they were in the early days of radio. Ionization, temperature and pressure gradients, suspended particulate contamination, and other factors have been extensively studied, measured, and modeled. Daily and seasonal patterns are somewhat predictable and exploitable for purposes of general use, but short term variability that affects long distance radar measures of distance, altitude, and speed requires near instantaneous, pulse by pulse analysis of atmospheric conditions. Research and development of methods for accommodating short term variations that skew measurements are an ongoing science. An extreme example of atmospheric variation...