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Radar Reaches the Moon
"These pulses speed toward the moon at the
fantastic speed of light… through the ionosphere and on into the unknown void surrounding
the earth's atmosphere." Hard as it might be to imagine nowadays, in 1946 there
was no empirical data regarding the Earth's upper atmosphere other than the few
instrumented sounding rockets that had been launched for studies. Orbiting man-made
communications satellites were still a decade away when engineers at the Evans Signal
Corps Engineering Laboratory in New Jersey made the first
Earth-Moon-Earth (EME, aka "moon bounce") signal bounce using a massive radar
and antenna that blasted 10 MW EIRP pulse at the lunar surface. It was a big
deal then; it's no big deal today. Amateur radio hobbyists routinely conduct EME
communications from the comfort of their home-based Ham shacks, using equipment
vastly superior to and less expensive than the 1946 setup...
RCA Radiograms
Radio Corporation of America (RCA) was not
the inventor of the telegram, but it did decide that the status quo transmitting
and delivery services available like the Marconigram were in need of improvement.
Accordingly, in 1929 the company initiated its
RCA Radiogram, as promoted in this 1947 issue of Radio-Craft magazine. A promotional
brochure printed by RCA in 1950 entitled, "What it is - What it does," contrails
a lot of detail about the radiogram, including many photos of the operational offices.
RCA Radiograms initially could be sent from ship to shore, shore to shore, ship
to ship, or shore to ship. No mention was made of being able to send them to/from
aircraft. At the time, the cost was 21¢ per word. As with most things, authentic
RCA Radiograms...
Sylvania News Radio Service Edition
Once mobile and other high-vibration and
impact operational environments became the norm for communications, it became necessary
to design hardware so that electronic components would not work themselves loose
and cause intermittent or total failure. With vacuum tubes, placing locking shields
over them did the job, but that caused other issues such as increased cost, poor
cooling, and increased chassis size and weight. Some circuits with high power and/or
frequency benefited from shields, but most did not need them. Sylvania introduced
a scheme called "Lock-In" (trademark name of "Loktal")where
the center pin incorporated a circumferential groove that latched into a capturing
mechanism...
An Early Radiophone
The January 1947 issue of Radio-Craft
magazine was dedicated to editor Hugo Gernsback to articles celebrating the 40th
anniversary of his personal friend Lee de Forest's invention of the Audion
amplifying vacuum tube. Click on the Table of Contents link to access many of the
other articles - all of which are very insightful into the many amazing activities
of Mr. de Forest. Many of the articles were written by friends and business
associates of him. The "radiophone"
addresses here is actually one of the earliest mobile phone, being interconnected
by radio signals rather than a twisted pair of wires. Take note of the "flame audion"
mention, which believe it or not describes de Forest's earliest experiments
which used a pair of salted platinum plates embedded in an actual flame. Yes, that
actually constituted an amplifying element...
Kill Those Harmonics
Here is a short tutorial on how to construct
a
¼-wave stub "trap," or filter to attenuate even-order harmonics from transmission
lines. It applies whether the transmission line is feeding an antenna or is a section
of copper foil running on a microwave substrate. Author Kent Mitchell (W3WTO) discusses
both an open stub and a shorted stub. In case you are not familiar with how quarter-wave
transmission lines stub work, a short at the far end appears as an open circuit
where the stub connects to the main transmission line, and an open stub line appears
as a short circuit. That is because there is a 180° phase shift at the end of the
shorted stub and a 0° phase shift at the end of the open stub. Therefore, there
is a total of 360° (i.e., 90°+180°+90°=360°, equivalent to 0°) with the shorted
¼-wave stub so it has no effect where it attaches to the main transmission line.
The open stub experiences no phase shift...
Science & Engineering Crossword Puzzle for August 23rd
August 23rd's custom
Science & Engineering themed crossword puzzle contains only 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. The technically inclined cruciverbalists amongst
us will appreciate the effort.
Serviceman's Experiences
Whether or not this is a true story does
not matter- it is
both instructive and funny, especially if you catch the import of the closing
statement. Electronics magazines from the era of repairable entertainment electronics
devices like radios, television, and phonographs often carried stories of the woes
experienced by servicemen. Tales of in-home work were the most interesting, especially
when the homeowner tried to bilk the poor technician out of paying or accusing him
of purposely inflating the bill with unneeded parts and service charges. This 1941
issue of Radio News magazine is a good example of how frustrating the business
could be.
Science in Music
If you are not in the habit of listening
closely to the words of songs, you could easily miss the the fact that many make
passing mention of topics on
science and mathematics,
while others integrate it as the primary theme. There are a lot of songs written
and produced by people whose primary vocation is in the sciences; their songs are
a secondary "hobby" type of endeavor - often with a touch of humor. Don't miss Tom
Lehrer's incredible "Elements Song."
Other songs are created by mainstream popular groups and happen to integrate themes
of science, mathematics, engineering, etc. One of the earliest examples I can recall
noticing was produced by the Moody Blues - "The Word." At the time, I did not fully
appreciate the profoundness of the lyrics in terms of how they described the electromagnetic
spectrum in its entirety, but an examination of the lyrics (below) reveals the profundity
of the words...
Pearl Harbor Day Crossword Puzzle for December 7th
For the sake of avid cruciverbalists amongst
us, each week I create a new crossword puzzle that has a theme related to engineering,
mathematics, chemistry, physics, and other technical words. This December 7th
Pearl Harbor Day crossword puzzle has a few words and clues relating to the
surprise attack in 1941. As always, the crossword contains no names of politicians,
mountain ranges, exotic foods or plants, movie stars, or anything of the sort unless
it/he/she is related to this puzzle's technology theme (e.g., Hedy Lamarr or the
Bikini Atoll). The technically inclined cruciverbalists amongst us will appreciate
the effort. Enjoy!!!
Bell Telephone Laboratories - EDT Crystals
Occasionally when I post a Bell Telephone
Laboratories (aka Bell Labs) promotion from a vintage electronics magazine, someone
writes to challenge the claim being made by Bell Labs of having been the progenitor
of the idea. This full-page ad apparently claiming to have developed the process
needed to grow high purity crystals appeared in a 1947 issue of Radio-Craft
magazine. The huge
EDT (Ethylene Diamine Tartrate) crystal shown was created over a three-month
period. Its intended use was for filters in telephone communications circuits. Development
of the crystal growing process is yet another case of "necessity being the mother
of invention," given that the massive increase in demand for phone service across
the country left the company short on filter crystals. Bell Telephone Laboratories'
manufacturing arm, Western Electric...
AM/FM Under Siege
The
electromagnetic world sure is a noisy place and it is getting worse all the time
- in every region of the spectrum. Intentional radiation is not so much of a problem
because it usually falls within well-defined limits and is predictable, but sloppy
engineering and, honestly, ignorance, has made life harder for just about everyone.
Listeners to broadcast radio in both the
AM and FM bands
have really taken a hit. AM has always been prone to interference by its very nature,
so anyone listening expects the occasional pop or hiss from atmospheric phenomena
or a light switch being flipped on or off. Have someone in the house run a blender
or drill and you can forget hearing anything until the task is completed. It comes
with the territory, so to speak. FM was and is largely immune to most forms of interference,
but lately I have been noticing it coming from some of the most unusual places.
For as long as I can remember, I have preferred to have a radio on in the background
whilst whiling away at work and at play...
Elementary Radio Quiz
There is a good reason why Harold Glenn called
this an "Elementary Radio Quiz." It appeared in a 1947 issue of Radio-Craft
magazine. If you have been in the analog and RF electronics field for more than
a couple years and don't score 100%, it has to be due to a misreading of accidental
selecting of the wrong answer. I know what you're thinking - "The fool must have
screwed up and missed at least one and is making excuses." Not this time - although
I don't deny it could have happened. Anyway, it might be a fun quiz to pass out
in the break room or maybe present it to a Ph.D. candidate during an interview ;-)
"Bonne chance!," as Corporal Louis LeBeau might say...
Not Such A Smooth Operator
Something happened at work that reminded
me of a funny event from way back during my time at Westinghouse Oceanic Division
(now part of Northrop Grumman), in Annapolis, MD. There is a moral to this story.
During my electronics technician days there, I spent the first couple years building
PCBs, wiring harnesses, and system-level assemblies for
Navy
sonar systems. We had some really slick stuff like towed vehicles with transducer
arrays along the sides, nose cones for smart torpedoes, flow sensors, proximity
fuse elements, etc. The exposure to all that, and the super-smart people that designed
it, fuelled my desire to go to the trouble of earning an engineering degree. One
of my tasks for a while was to build the transducer arrays, which entailed building
the hundreds of tiny transducer elements. The assemblies were made of a machined
aluminum base plate (about 1-inch square), onto which a precisely cut low density
foam block was attached. On the top of that was a set of two machined aluminum plates
that sat on either side of a piezoelectric ceramic transducer element...
New Standards for TV Antennas
The RETMA referenced in this 1954 Radio &
Television News magazine article entitled "New
Standards for TV Antennas" was commonly known back in the day, but not many
would recognize it nowadays. RETMA, founded in 1953 at the dawn of the commercial
television age, was the Radio Electron[ics] Television Manufacturing Association.
It set standards for electronics components like resistors (e.g., the 1%, 2%, 5%,
10% series), capacitors, inductors, equipment racks, and antennas. After many name
iterations, what began as the Radio Manufacturers Association (RMA), it changed
to RETMA in 1953, then to Electronic Industries Association (EIA, well-known for
its 19" rack standards) in 1957, and today it is known as the Consumer Technology
Association (CTA). The cost of letterhead and promotional material changes over
the years must have been enormous ;-) Tracing the full history is difficult, but
between Wikipedia and the JEDEC websites you can get a pretty good picture. The
"Antenna Section" spoken of here is the area of the RETMA manual pertaining to antennas...
Tin Whiskers, Bell Telephone Laboratories
The famous words of Jorge Agustín Nicolás
Ruiz de Santayana y Borrás (aka George Santayana) immediately came to mind when
I saw this Bell Telephone Laboratories advertisement in a 1955 issue of Radio &
Television News magazine: "Those who cannot remember the past are condemned
to repeat it." Anyone involved in the electronics field at the beginning of the
lead-free (Pb-Free) craze in the early 2000's probably remembers the purportedly
unexpected phenomenon of
tin whiskers growing out of lead-free solder joints and wreaking havoc with
the short circuits caused when whiskers between adjacent elements made contact.
The problem appeared with closely spaced connector pins, fine pitch integrated circuit
packages, high density surface mount circuit board layouts, etc. Military and aerospace
engineers and scientists had fits initially trying to figure out what was going
on...
