My favorite is "The Cat Battery", originally published in Life Magazine in 1884 and republished in IEEE Spectrum in August 1984. Unfortunately, you have to fork over $13 (IEEE member rate) for a copy of something that's long been in the public domain. So much for the Internet.
Anyway, the article describes how when you put two cats together (especially male), you see electrical phenomena such as hair standing on end and if you wire the cats together in series by clipping on jumpers you see even more pronounced electrical effects. Most cats have a resistance of one home (pronounced "Ohm"), though some cats have more than one 'ome and some unfortunate cats are 'omeless.
The article has wonderful 19th century drawings of cats in both excited and quiescent states.
I was a sucker for an article in one of trade magazines in the 70's-80's, like Popular Electronics, or Electronics Illustrated
It was an article about an "In-Situ" solar panel using cookie trays and sand. I had no clue!
Still one of my favorites -- I believe it was in the EDN April Supplement sometime in the mid 80s -- was a pair of logarithmic amplifiers that used microprocessors as diodes in the feedback path of the op-amp by connecting VSS & VDD backwards. One circuit used an Intel processor and the other a Motorola processor, and as I recall, the article included test data and a discussion about which was the better chip to use for this application, Intel or Motorola.
The hilarious thing of course, was that these were functioning log amp circuits.
There's the 70's Wireless World article 'Dynamic Range Versus Ambient Noise' by George Izzard O'Veering, which can be found at:
I also remember a magazine called Elektor which had some spoof circuits in its April editions, like a 'Battery Eliminator', which was a dead short.
Remember when Bob Dobkin announced the Dark-Emitting Arsenide Diode (dead)?
.....or the technical paper that claims that light emitters are actually dark suckers: http://www.rogermwilcox.com/darksucker.html
Contra-polar energy... If you phase shift the current 180 degrees to the voltage, an ordinary lamp will be able to emit a beam of dark. They even had the math and a "photo" to prove it. Publish date: April 1, 1970-something, I think it was in a Popular Mechanics.
Or how about a 1980's QST magazine april 1st arrticle about injecting DYE in your coax and firing up your transmitter so you can see your yagi antennas pattern.
I had just pulled out some of my moms cloths DYE and was looking in her kitchen cabinets for a way to inject the DYE in the coax feed line when I glanced back and realized what month of QST magzine the article was in.
Of course without saying a word I then quietly put everything away all the time with my mom watching me with the typical expression on her face just about to ask me "what are you up to now?"
Back on the subject of the Write-only memory (WOM), when Signetcis announced the product I sent off for a free sample (yes, thay acutally offered samples of this part!!!). A few days later I received a package containing a chip with the number "25120-N-NFG" on it, a bumper sticker that said "Honk if you're WOMsome, and a pair of plastic sunglasses with a rubber nose and fake bushy eyebrows attached.
Now THAT's the way to roll out a product!
I seem to recall Compute magazine had a series of April Fools ads in the early 80's. In particular, I remember an auto eject system for floppy disks that at the slightest sign of a computer crash would eject your floppies at high speed. (Remember when a computer crash could zap files on your floppies)? Of course, this system did have a problem of injuring anyone in the path of the ejected floppy, or embedding the floppies in brick walls. :)
Elektor again :
ever had frozen car locks.
the elektor car lock defrost circuit. never be frozen out of your car again.
simply plug it into the cigar lighter socket of the car, and it instantly defrosts the mechanism.
The great thing, is it actualy would have worked, as it was a large transistor / diode bonded to a spareKey, which got hot.
Anybody remember usenet? Ever read alt.folklore.computers?
Back in 2005, someone (I'm not sure who) identifying himself as "Mike Rowe" claimed to have found about a dozen ADX 7300 computers in a warehouse, and was wondering whether they had any value, or if he should scap them for the gold in their connectors.
Talk about knowing your audience! If you didn't know that an ADX 7300 was a relabeled PDP-1, and that fewer than 50 PDP-1's were ever built, you probably wouldn't care. And if you did know that, you would easily believe it wasn't common knowledge (because it isn't). AFAIK, there are only three PDP-1's known to exist, and they are all in the hands of the Computer History Museum.
You can read the thread here:
Our special projects director once wired a circuit into the telecoms cabling duct in the managing director's office.
The circuit was deigned to start making a sound like a clucking chicken, 20 seconds into any incoming phone call.
It took the MD ages to find it because the device was totally silent until a customer phoned him, and then of course he was busy on the phone.
I worked for many years in the R&D labs of a huge now-defunct Canadian telecom manufacrurer.
The old timers once told me of an April Fools prank they pulled on a PhD whom they thought was too arrogant for his own good. They somehow rewired the guy's lab bench for half voltage, changed all the pilot lamps in his test equipment to compensate, then changed the shunts in his voltmeter so that it would read what all the voltages were supposed to be. Needless to say his prototype circuit and none of his test equipment operated correctly though there were signs of life, and the meter said everything was normal. Even his soldering iron got warm but not enough to be useful. This went on for a week until someone took pity on the guy and confessed.
ELEKTOR once had a rain predictor consisting of a resistor, an LED and a battery (no switch). When the LED was lit, it was raining. They predicted an accuracy of greater than 50%. They then went on to analyze the rainfall patterns in various parts of England and yes, the LED would be correct more than 50% of the time. LOL Brian
The "Anticipating timer". I believe it was an EDN design idea. It had a 555 timer with an op amp configured as a negative resistor. This negative RC time constant could then be used to drive some relay contacts. Set it to 10 hours, and if you got home and found you had left your air conditioner running all day, you could use the -10 hour time constant to turn off the air conditioner ten hours before you pushed the button.
I recall a data sheet for a Watkins Johnson limiter that had a family of graphs for AM-to-PM conversion (something you want to minimize when limiting a signal feeding a phase detector in a PLL). There were multiple traces on each chart for different frequencies and then there were several charts for different temperatures. The correct title for this would have been "AM-to-PM conversion vs. frequency vs. temperature" but the engineers got one past marketing by making it "AM-to-PM conversion vs. frequency vs. phase of the moon". Since both temperature and phase of the moon are in degrees, it was dimensionally correct.
I remember that WJ catalog with "vs. phase of the moon"! I think it was around '86 or '87. And yes, you could tell that the engineers definitely snuck that one past the tech pubs people, because it was the only example of humor in the entire catalog.
It was in the early-to-mid 80s, and I'm pretty sure it was in multiple editions, escaping the editors multiple times.
The editor of the rfcafe.com site has asked for someone to send him a graphic... here's the link
Waaaaaayyyyyy back when, Popular Electronics had a photo in a blurb announcing a new power transistor in a VERY LARGE TO-3 style case that dwarfed a Crescent (TM) wrench. They fessed up in the same issue; it was a miniature wrench about the size of a charm for a charm bracelet.
Would have been nice to have one of those babies in real life back in the CB Radio days ...
As to WOM, while reviewing a proposal many years ago, I seem to recall from the tech manual submitted in that procurement that the DEC PDP computer proposed had Write-Only Memory: it was a series of output ports mapped to memory locations. You could write to it to sent data to a peripheral, but nothing came back. (I don't recall, but they probably had ROM for input, also)
The machine wiring crew did pull a good one on me one April. After I had a machine started upm and fully debugged and I thought that I was ready for the customer to come in for an initial runoff trial, after lunch, some sections did not function quite right any more. And nobody was available to assist, they all seemed to be working on "other stuff" nearby. So I grabbed a multimeter and a set of prints and started the machine in the manual mode. In about five minutes I found a few connections to terminal blocks that had been insulated with heatshrink tubing over the bare copper conductor. I had it going in just a few more minutes, not in a very good mood. Then came the applause, it seems that I had proven my diagnostic skills. I probably should have been more amused.
I once heard a similar story about Ernie Kovacs back in the Dumont Network days of early USA television. The TV studio was at the top of a hill, near the transmitting tower, with a good view of the city. As a prank, sometime when they transmitted a late-night movie, they would turn down the master volume at the studio -- just a little. Everyone in TV land would then turn up their volume. A few minutes later, the studio would turn down the master volume again, and everyone in TV land would increase their volume again. After half an hour of this, the master volume would be way down and everyone of TV land would have their volume turned all the way up.
Then the studio would turn the master volume all the way up, and they'd run to the windows to watch lights turn on all over the city as thousands of unsuspecting victims suddenly had their TVs blaring and waking up their neighbors.
You'd lose your license trying something like that today, but things were unreliable enough back then that you could blame it on a technical malfunction and get away with it. Actually, it's a pretty good way to measure the size of your audience :-)
@Susan: Back in the days, Norwegian TV told viewers they were testing new color broadcasts. In order to see the colors all light bulbs in the house had to be turned off. Needless to say, Oslo went dark.
Brilliant!!! I'm laughing to myself just thinking about it :-)
Not engineering related -- but when I was a kid in England there was a TV program called "Blue Peter" for young viewers (it might still be running for all I know). I remember one April Fool's day episode where they did a "mockumentory" segment showing people in Italy harvesting the strands of spagetti dangling from the branches of the spagetti trees (LOL)