More spark today. I really liked how Robert Dalby demonstrated spark transmission and reception. He used a simple Piezoelectric flame starter (like the one that many of us have in our shacks) as the transmitter, with a homebrew coherer connected to an LED and some batteries as the receiver. Ingenious. As with CuriousMarcs video of yesterday, you can see how Marconi's system really worked. Brilliant.
This demo also shows how many devices can generate part of the noise we hear in our receivers. We see and hear the noise generated by a nearby electric fence, and the noise made by a simple electric motor. Many new builders have trouble accepting the reality of noise. Noise happens.
The entire YouTube channel is very interesting. Check it out here:
It is based on the amazing collection of Dieter Beikirch (I think he is DJ5RS) and is presented by Robert Dalby. Here is how they describe the channel:
German avionics in the era of the vacuum tube.
Join us as we investigate the most critical period in the rapid development of electronics, especially airborne electronics, from the first spark-gap radios of WW1 to the advances in radar technology in WW2.
CuriousMarc provides a good demonstration of how spark transmitters work with coherer detectors. His measurements are really illuminating. His device just needed a "tapper" to de-cohere the metallic filings. We see the tapper in this wonderful "Secret Life" video by Tim Hunkin:
On December 1st 1924, the 20kW Alexanderson Alternator with the call sign "SAQ" was put into commercial operation with telegram traffic from Sweden to the United States. 101 years later, the transmitter is the only remaining electro-mechanical transmitter from this era and is still in running condition. On Christmas Eve morning, Wednesday December 24th 2025, the transmitter is scheduled* to spread the traditional Christmas message to the whole World, on 17.2 kHz CW.
You can listen to the CW from Ciprian's setup above. I listened to it carefully and clearly heard the "KW ALTERNATOR" words at around the 3:30 mark in Ciprian's video. I wondered if this was in fact the SAQ Alternator (but then again, who else would be on 17.2 kHz on Christmas Eve?). I looked at the video from Sweden (below) at around the 49.37 mark we see the operator send "200 KW ALTERNATOR." Through Ciprian's video, I copied "KW ALTERNATOR." So Ciprian's operation was a success. Congratulations Ciprian!
That is a question we get fairly regularly when we tell the other fellow that our rig is homebrew. I often get the feeling that the question stems from a certain insecurity -- the guy who asks it may feel a bit insecure because the "rig" he is running is completely commercial and his only role in its production was to flash a credit card number.
But lately I have been reading through Jim Williams' wonderful book "Analog Circuit Design -- Art, Science, and Personalities" and I can see that there may be something to this question.
It was the chapter by Barrie Gilbert that made me think more about this. Barrie is the legendary designer for whom the Gilbert Cell is named. This circuit is at the heart of the NE602 chip that many of us used to build our first "Neophyte" receivers and other homebrew rigs. Barrie's chapter is entitled "Where do Little Circuits Come From." Uh oh.
Barrie grew up in the post-war United Kingdom. He father had been killed in a German bombing raid. As a kid, he built crystal radios and, with his brother, "shortwave sets" on softwood bases. He used a TRF receiver that employed Manhattan-style construction. Barrie, it seemed, was one of us.
But then, he suddenly seemed more advanced. He wrote:
"Later, I began to build some receivers of my own but stubbornly refused to use circuits published in the top magazines of the day, Practical Wireless and Wireless World. Whether they worked as well or not they had to be "originals" otherwise, where was the satisfaction? I learned by my mistakes but grew to trust what I acquiered in this way: it was 100% mine, not a replication or mere validation of someone else's inventiveness."
Wow, that is certainly hardcore. I will note, however, that in getting back to the the question about whether I have "designed" the rig myself, I have NEVER had the questioner come back to say that HIS rig was homebrewed from HIS OWN original design. Never. Not once.
And I will note that building a rig from the schematic is an enormous challenge. It is not easy. It is not the mere replication of someone else's inventiveness. Anyone who thinks it is easy should try to homebrew a simple direct conversion receiver. They will discover that it is NOT easy.
I guess this comes down to what we mean by "homebrew." I prefer to stick to the old ham radio meaning of the term: It is homebrew if it was built at home, even if it is built from a schematic done by someone else. When Jean Shepherd built his Heising Modulator, was he working off a schematic from a ham radio magazine? He almost certainly was. But he gathered the parts, laid out the chassis, and put the circuit together. Most importantly, when trouble cropped up, he was able to step in and make the needed corrections. Was his modulator "homebrew?" Of course it was. Did he design it himself? No, his name was not Heising!
More than 100 people built our SolderSmoke Direct Conversion Receiver. We resisted pressure to turn this project into a kit. The folks who built it worked off schematics that we had prepared. They gathered the parts and built their own circuit boards, Manhattan style. They struggled to get the whole thing to work, to make sure the VFO was on the right frequency and at the right level, that the AF amplifier was not oscillating. Were these receivers "homebrew?" Of course they were.
Jim Williams warned that Analog Circuit Design was "A wierd book." He strongly discouraged collaboration between the authors, and noted that this would probably result in "a somewhat discordant book." We see that discord in the hardcore position taken by Barrie Gilbert. Many of the other designers seem to take a more flexible, less austere position. Some even seem to downplay the role of mathematics.
I think Barrie had a right to be proud of his fundamentalism. But not all of us are capable of that. Writing in Jim Williams' book, Samuel Wilensky sums it up nicely:
"I classify analog designers into one of two categories. There are those who do truly original work, and these I consider the artists of our profession. These individuals, as in most fields, are very rare. Then there are the rest of us, who are indeed creative, but do it by building on the present base of knowledge."
First off, what a great name. It is a real ham radio name. Grote Reber. And he was indeed a ham: W9GFZ. We don't have names like that anymore. But we should.
Second, Grote Reber's mother was also the teacher of Edwin Hubble. Hubble was the guy who discovered that there were OTHER GALAXIES in the universe, and that they were all moving away from each other. That was a BIG discovery! Later, Grote's mom also had her son in her class. Both students were from Wheaton, Illinois.
Lest there be any doubt about Grote's dedication to radio, consider the following. (Much of the following comes from Wikipedia. https://en.wikipedia.org/wiki/Grote_Reber)
When he learned of Karl Jansky's work in 1933,[5][6][7] Grote Reber decided this was the field he wanted to work in, and applied to Bell Labs, where Jansky was working.
In the summer of 1937, Reber decided to build his own radio telescope in his back yard in Wheaton, Illinois. Reber's radio telescope was considerably more advanced than Jansky's, and consisted of a parabolic sheet metal dish 9 meters in diameter, focusing to a radio receiver 8 meters above the dish. The entire assembly was mounted on a tilting stand, allowing it to be pointed in various directions, though not turned. The telescope was completed in September 1937.[8][9]
Here is a really great article from Sky and Telescope magazine (July 1988) about Reber's homebrew radio telescope:
He was limited by the size of locally available 2X4 lumber. Neighbors thought he was trying to control the weather or to bring down enemy aircraft. Between Wheaton and the NRAO site in West Virginia, Reber's telescope spent some time at the National Bureau of Standards site in Sterling, Virginia. I was in Sterling just yesterday. I wonder if there is a plaque or something noting the telesccope's stay in that town. I note that at age 15, Reber had built a ham radio transceiver.
AND THEN HE MOVED TO TASMANIA
He did this because of propagation and low noise conditions. (This reminds me of how we sometimes said that very few people have actually said the words, "And then we moved to the Azores.")
Starting in 1951, he received generous support from the Research Corporation in New York, and moved to Hawaii.[12] In the 1950s, he wanted to return to active studies but much of the field was already filled with very large and expensive instruments. Instead he turned to a field that was being largely ignored, that of medium frequency (hectometre) radio signals in the 0.5–3 MHz range, around the AM broadcast bands. However, signals with frequencies below 30 MHz are reflected by an ionized layer in the Earth's atmosphere called the ionosphere. In 1954, Reber moved to Tasmania,[12] the southernmost state of Australia, where he worked with Bill Ellis at the University of Tasmania.[13] There, on very cold, long, winter nights the ionosphere would, after many hours shielded from the Sun's radiation by the bulk of the Earth, 'quieten' and de-ionize, allowing the longer radio waves into his antenna array. Reber described this as being a "fortuitous situation". Tasmania also offered low levels of man-made radio noise, which permitted reception of the faint signals from outer space.
His Homebrew House in Tasmania
In the 1960s, he had an array of dipoles set up on the sheep grazing property of Dennistoun, about 7.5 km (5 miles) northeast of the town of Bothwell, Tasmania, where he lived in a house of his own design and construction he decided to build after he purchased a job lot of coach bolts at a local auction. He imported 4x8 douglas fir beams directly from a sawmill in Oregon, and then high technology double glazed window panes, also from the US. The bolts held the house together. The window panes formed a north facing passive solar wall, heating mat black painted, dimpled copper sheets, from which the warmed air rose by convection. The interior walls were lined with reflective rippled aluminium foil. The house was so well thermally insulated that the oven in the kitchen was nearly unusable because the heat from it, unable to escape, would raise the temperature of the room to over 50 °C (120 °F). His house was never completely finished. It was meant to have a passive heat storage device, in the form of a thermally insulated pit full of dolerite rocks, underneath, but although his mind was sharp, his body started to fail him in his later years, and he was never able to move the rocks. He was fascinated by mirrors and had at least one in every room.
To Canada -- And a Rejection of the Big Bang
The same July 1988 issue of Sky and Telescope magazine has a good historical vignette of Reber, with a focus on his actvities in Canada late in life (click on the image below). Reber had big doubts about the big bang. Unfortunately this seemed to spill over into scorn and ridicule for those who -- well -- believed in the big bang. We see this at the end of the article. Oh well, even great people sometimes get cranky.
Three cheers for Grote Reber.
I had trouble making the WayBack Machine links to work on my blog. But they seem to work on the Wiki page. So to see them, go to https://en.wikipedia.org/wiki/Grote_Reber Then go to the Reference section and take a look at the second and third items.
This book is kind of weird, but give it a chance. The author seems too prone to describe the physical attributes of his colleagues, especially female colleagues. But he was born in 1910 -- he was an old guy when he wrote this book, so perhaps we should cut him some slack. And there is one memorable episode where he defends a female applicant. In spite of the shortcomings, there are many real gems in there, often hidden among the descriptions of 1930's era Kleenex machines and refrigerators. I picked up the book a long time ago and only read it recently.
Some highlights:
-- Crystal Radios in the 1920s.
-- Working Australia from Michigan on 40 CW in 1927. And waking up his parents to tell them. (Decades later, I did the same thing after a ZL contact).
-- Doing a radio propagation survey using the 5 meter band (FMLA!)
-- Jansky's discovery of an extraterrestrial hiss in 1932. (It seems like that was the big discovery, So why did Penzias get the Nobel prize?)
-- A youthful trip to Nazi Germany and the Soviet Union.
-- A regular ham band schedule from Ann Arbor to Berkeley that featured Ernest Lawrence and Robert Oppenheimer.
-- Lots of mention of Fred Terman, Grote Reber, and Karl Jansky,
-- Some discussion of how Jansky was turned down for a job. And about how being a radio amateur actually hurt chances for employment; there are a few lines about anti-ham prejudice.
-- Lots of people known to us show up in the book: Joe Taylor, Shoemaker and Levy of Shoemaker-Levy 9 fame, Arthur C. Clarke, Maarten Schmidt of "First Light," and many others.
-- And of course, the WOW signal (that has recently been explained as probably having a natural origin).
-- Kraus tells of how the Latin words "Ad Astra per Aspera" (to the stars, with difficulty) were engraved above their radio telescope receiving room. He goes on to (correctly) criticize those who write about radio telescopes, without having ever built one. Remarkinig on one such critic, John Bolton, a revered Austialian radio astronomer and radio telescope builder, wrote, "If the writer had built a radio telescope his story of radio astronomy would be a different story."
Here is a good review of Kraus's "Big Ear Two" book:
Earlier this month I had stumbled across a 1964 QST article entitled "A Sideband Transceiver, VU2 Style." I forwarded the link to Pete N6QW, Grayson KJ7UM, and to Farhan VU2ESE. Last night Farhan sent me this insider look at early SSB in India. It is really great. The battle for preeminence among early SSB homebrewers in India reminds me a bit of Jean Shepherd's descriptions of homebrew radio in Hammond, Indiana. Farhan's description of the early rigs being "all over the place, in about 3 or 4 boxes... with a whole lot of wires running all over" really resonated with me -- yes, even today, that is true homebrew. Thank you Farhan for sharing this with us.
Farhan writes:
VU2NR, Raju was a legend! Quirky, brilliant and liked to be by himself. He lived to a very old age of 100 or so. He was the first ham to get on SSB from India. Therein hangs a story of espionage, stolen secrets, cold war, politics and kleptomania. Most of the actors are now dead, so it can be told now.
I never met VU2NR, he rarely travelled. One evening at Paddy's shack, I was shooting the breeze with VU2RM, Ram, about my own SSB efforts. Ram was probably the most knowledgeable ham on SSB in India and his RM96 was widely duplicated. Paddy and Ram were trying to empty out a bottle of the Old Monk and I casually mentioned how we had to scrounge around for SSB lattice filters until Wes showed us how to build them ourselves. At that point, Ram unloaded this story to us:
VU2NR joined the Allies and worked as a radio mechanic with the RAF. After the war, he joined the ICAO (International Civil Aviation Organization) and then finally the United Nations as a comms expert, he was in Aden for a while. He understood the radios well and he became a well known homebrewer. His most brilliant work was the NR60 (it is an SSB radio built around four CA3028 kind of mixers). It was the first SSB radio that I had built (and it worked!) but we are getting ahead of ourselves.
Back in the 50s, ham shacks of India consisted of World War II surplus receivers and a self-built 807 transmitter driven by a VFO. There was a fair amount of buzz on the bands about SSB. The hams could occasionally pick up DX that was on SSB and easily resolved by the BC-348s and the HROs but there was no way to build one. The QST was difficult to get your hands on but Raju had become a subscriber of the QST during his RAF days.
A QST sailed on a slow boat from the USA and landed up at the port on the east coast of India, Vizag and made its way to Raju's doorstep. Over weeks, he gathered parts and in the summer of 1955 he quietly came on 40 meters on SSB! This blew everyone away. Until now, one had only heard stories of SSB transmitters told by sailors of Sandra Maria Gracia after a few drinks to a bunch of hams clutching onto their 807s. It was as if Jesus had materialized!
VU2RM, Ram was not amused. He was a homebrewer with pride and honour. He could never be bested. He spent the next evening tuning on Raju's SSB up and down to note that the other sideband was missing and the carrier was gone. It sank into him that Raju had indeed beaten him to SSB. Ram worked at the Kakinada port, about 100 miles further down south on the east coast as the port radio engineer. He didn't sleep well. At 5 am, he got up, walked out and took a bus to Vizag where Raju lived. He was at Raju's door at 9 am. Raju was amused at the young guy and invited him in. They knew each other as rival homebrewers. There was tension in the air. Raju showed off his SSB transmitter in the front hall of his home. It was all over the place in about 3 or 4 boxes. There was the power supply, the PA, the ssb generator using a 2Q4 (a passive RC phasing network), a separate VFO box and a whole lot with wires running all over. In a corner was his stack of QSTs.
Raju's XYL called out for coffee and snacks (called 'Tiffin' in south Indian English) and Raju sauntered off to the kitchen to fetch his celebratory feast...
With alacrity and swiftness that only comes once in a lifetime, Ram, VU2RM, sprang to action. He darted to the QST collections, quickly found the one with the SSB transmitter on the cover, turned the pages to discover VU2NR's dog eared pages. He was staring at the circuit trying to memorize it. He realized that 2Q4's internal diagram had really odd values that he could never remember. So he did what James Bond, Bertie Wooster and Louvre thieves would have done. He rolled it up and slipped it into his pocket! (In those days, QST could be rolled and slipped into your trouser pockets, leading to wider dissemination of knowledge). He called out to Raju asking him to forget the refreshments as his bus was due back home. He legged it out and didn't stop until the bus stop. He hid around the bus yard hoping to not be caught by Raju. In the meantime, Raju, cursing the young upstart, drank both the filter coffee cups and left for work. Raju was unaware that the royal jewels were stolen.
VU2RM, Ram, started to work on his SSB radio over the next few days. He stopped going to work. At first, he figured out how to null the carrier using a twin triode modulator. Next, he fabricated the 2Q4 circuit. He sand papered lower value resistors until they read as close to the value as he could manage on his analog volt-ohm meter. He gave up on the exact capacitances and just soldered a bunch of the closest together. He had a crude 2Q4 equivalent. This, he dropped into his rat next circuit and an 'Almost' SSB signal emerged. He was probably having a sideband suppression of less than 15 dB at this point. It was suppressed and the carrier was nulled. He declared victory.
In the morning, Ram was on the band strutting off his SSB transmitter to the local gang. Graciously accepting the accolades from his fan club and extolling virtues of life on SSB to the lesser mortals. The news quickly spread over CW and AM of VU2RM as the second SSB station from India.
In the meantime, the atmosphere at VU2NR was tense. You could cut the air with a toggle switch. Raju had no idea how Ram had gotten the SSB. He carefully tuned around on his signal. He could pick up faint traces of the opposite sideband. Ram's carrier was also leaky. He decided that Ram was probably passing off his AM transmitter as a SSB. He said as much on air to his own devotees. Ram, ever watchful of his own reputation, heard this criticism and broke in, challenging Raju to prove that his was indeed not SSB. Raju's reaction was mixed. Now he wasn't sure.
It was now Raju's turn to have a sleepless night. After his breakfast, he had had enough of confusion and he hauled his old scope and himself into the 8 am bus to Kakinada and showed up at Ram's doorstep! "Show me your radio" he said crisply.
For Ram it was his moment of crowning glory. He had brought Raju down to his shack! Raju plugged his scope into Ram's transmitter. He sniffed around the transmitter which was laid all over the table. "Where is your 2Q4?" he asked. Ram pointed to bunch of resistors and capacitors and Raju realized Ram's dog headed brilliance. He sat down, traced to the balancing pots (there would be two of them as this was a phasing transmitter). At this time, he decided to show Ram his greater prowess. He reached out to the carrier nulling pots, and tweaked them to minimum carrier (Ram was watching the oscilloscope with his mouth wide open). He told Ram that he had now fixed the carrier and then showed him how to adjust the RF phasing control for minimum by tuning to the opposite sideband on Ram's Bc 348. Having proved to Ram that he was a better homebrewer, he declared that now, Ram's transmitter was indeed SSB and not semi-AM. Raju retrieved his honor by being gracious and "mentoring" Ram.
They had coffee and snacks and it was time for Raju to leave, as Ram was showing Raju to the door, Raju's eye caught a QST on the shelf... he pulled it out and stared down at the QST with his own address neatly stickered on the QST's cover. He glared at Ram for a long time and turned away and left in a huff. Ram called after him down the street but Raju was gone.
VU2NR's last radio was built when he turned 90. It was the NR90 and it was built using NE612 chips. His hamming came to an abrupt end when one day his son dropped in unannounced only to find him perched on his tower of 30 feet height, fixing a fallen element of his self-made log periodic. The son was so horrified that he took away all the radios to save him from self-harm (this part of the story is unconfirmed).
My friend Sasi, VU2XZ, was close to him and he got the family to donate his callsign to a repeater that has been established in his memory. VU2NR lives on.
- f
------------------------
Here is the link to the 1964 QST article. VU2NR's article appears on page 19:
I surfed over today to Soldersmoke and noticed you had put up a very nice film from the 1960s made by MIT "Science Reporter" on the DSKY design for the Apollo Guidance Computer.
In the same vein, you might enjoy viewing something from the same era on the Haystack 37m telescope / radar in its early mid 1960s days:
Herb built the observatory for its original ballistic missile radar / satellite imaging mission and was involved in early MIT microwave radar development.
"Growing up in Elizabeth, New Jersey, Herb liked gadgetry. As a teenager, he became a ham radio operator and built a primitive television set at the same time NBC was trying to get its first signal on the air. His shop teacher was so impressed by Herb’s genius that he contacted MIT, which invited Herb to attend the college.
He spent the bulk of his career developing radar when there was none in the United States. He joined the Radiation Lab at MIT, which was just being established to support the war effort during World War II, designing radars for ships and aircraft. In 1942, when England was in the throes of its air war with the Nazis, Herb went to England and installed radar in planes with a novel navigation system that he and a team had designed for the Royal Air Force. He later spent three years at the Los Alamos, New Mexico, laboratory improving instruments for the A-bomb. After seeing the need for a continental defense network against the Soviet missile threat, he returned to MIT to build it. If not for Herb, there also likely would be no MIT Haystack Observatory, a pioneering radio science and research facility."
Okay. I was born in New Jersey, and my first acquaintance with electronics was about the age of 12 or 13. We had a battery-operated radio, which didn't work, and I asked around about what do we do about it. They referred me to a man two blocks away, who was a radio ham it turned out. So I carried this monster with the big horn and, I guess, the dog sitting on the speaker to his house. We went down in the basement, and I was just fascinated. I was hooked right then and there. A year later I became a radio ham at the age of 13, 14 and literally have been in the field ever since, until I retired. I was fortunate enough to go to MIT as an undergraduate, and most of the people I ran into of that vintage didn't really have a hands-on feeling for electronics. By the time I got to MIT, I had built all kinds of things, including a TV set. Then it turned out that NBC was just trying to get their TV set on the air in New York on top of the Empire State Building."
First, thanks to Ashish Derhwagen N6ASD for alerting me to this video. You should all check out his blog.
This is a really important video. It is the best I have seen about the history of electricity and electronics. It is from 2011, but it is still very good. Jim Al-Khalili travels through the world and displays the actual devices developed by the likes of Heinrick Herz, Guglielmo Marconi, and Jagadish Chandra Bose. There is great discussion of Benjamin Franklin, Volta and Galvani. The role of electricity in The Enlightment is discussed.
Jim talks about the early transatlantic cables, and why some of them didn't work.
We see Jagadish Chandra Bose developing early point-contact semiconductors (because the iron filings of coherers tended to rust in the humid climate of Calcutta!)
There is a video of Oliver Lodge making a speech. There is a flip card video of William Crookes (one of the inventors of the cathode ray tube and the originator of the Crooke's cross).
We see actual coherers.
There is simply too much in this video for me to adequately summarize here. Watch the series. Watch it in chunks if you must. But watch it. It is really great.
In the early years of amateur radio, long before factory-built gear was easily available, hams built their own transmitting and receiving equipment, known as homebrewing.[2]In the 1930s, 40s, and 50s, hams handcrafted reasonable-qualityvacuum tube-based transmitters and receivers which were often housed in their basements, and it was common for a well-built "homebrew rig" to cover all thehigh frequencybands (1.8 to 30 MHz). After WWII ended, surplus material (transmitters/receivers, etc.), was readily available, providing previously unavailable material at costs low enough for amateur experimental use.[3]
Homebrewing was often encouraged by amateur radio publications. In 1950, CQ Amateur Radio Magazine announced a ‘‘$1000 Cash Prize ‘Home Brew’ Contest’’ and called independently-built equipment ‘‘the type of gear which has helped to make amateur radio our greatest reservoir of technical proficiency.’’ The magazine tried to steer hams back into building by sponsoring such competitions and by publishing more construction plans, saying that homebrewing imparted a powerful technical mastery to hams. In 1958, a CQ editorial opined that if ham radio lost status as a technical activity, it might also lose the privilege of operating on the public airwaves, saying, ‘‘As our ranks of home constructors thin we also fall to a lower technical level as a group’’.[4]
I began writing this book when I realized that my homebuilt station seemed to be almost
unique on the air. For me, the education and fun of building radios is one of the best parts of ham
radio. It appeared to me that homebrewing was rapidly disappearing, so I wrote articles about it
for my local radio club newsletter. My ham friends liked the articles, but they rarely built
anything. I realized that most modern hams lack the basic skills and knowledge to build radios
usable on the air today. My articles were too brief to help them, but perhaps a detailed guide
might help revive homebuilding. I have tried to write the book that I wish had been available
when I was a novice operator back in 1957. I knew that rejuvenating homebuilding was probably
unrealistic, but I enjoy writing. This project has been satisfying and extremely educational for me.
I hope you'll find the book useful...
...My personal definition of “homebuilding” is that I build my own equipment starting from
simple components that (I hope) I understand. I try not to buy equipment or subassemblies
specifically designed for amateur radio. I am proud to be the bane of most of the advertisers in
ham radio magazines. I still buy individual electrical components, of course. I just pretend that
the electronics industry never got around to inventing radio communications.
An irony of our hobby is that, when the few remaining homebrewers retire from their day
jobs, they often build and sell ham radio equipment. These industrious guys manufacture and sell
every imaginable ham gizmo. I doubt any of them have noticed that, by making everything readily
available, they have discouraged homebuilding.
My only quibble is that it kind of left unclear the differences between JFETs and MOSFETs. After all, we still use both. Note our beloved J310 JFET. And the IRF510 is a MOSFET.
Google's AI explains:
A JFET (Junction Field-Effect Transistor) and a MOSFET (Metal Oxide Semiconductor Field-Effect Transistor) are both types of field-effect transistors, but the key difference is that in a JFET, the channel conductivity is controlled by a reverse-biased PN junction, while in a MOSFET, it's controlled by an electric field across an insulating layer between the gate and the channel, allowing for a much higher input impedance and greater design flexibility in MOSFETs; essentially, MOSFETs are considered a more advanced version of JFETs with superior performance in many applications like high-speed switching and integration into complex circuits.
This is a really OLD video, but there is a lot of great material here:
-- Tubes. (Valves or Thermatrons)
-- Coax.
-- Frequency Division Multiplexing.
-- Negative Feedback and the fight against distortion.
-- Transistors and early experiments with semiconductors.
-- Fiber optics and Masers.
-- Satellite communications.
-- Early hopes for video communications.
The video is, by today's standards, extremely misogynist. And the sound experiment with the poor woman wearing a male head was just weird. But still, an interesting film.
Thanks to Mark KM4GML for reminding us of this wonderful Bell Labs (AT&T) video archive.
Brace yourselves. This is just too much, too much radio history, too much cool stuff. We are into ham radio sensory overload territory here. The rigs, the radios, the radioactive stuff (including tubes!). Lots of Whermact stuff. A Chinese receiver. Tesla coils and Faraday shields. Much more.
Thanks to Helge LA6NCA for alerting us to this and for shooting these videos. And thanks to Jens OZ1GEO for putting this magnificent collection together. I hope they find sometplace to keep this all together so that future generations can benefit from it.
George WB5OYP points out there is more from Jens here:
Such a beautiful article. Ramakrishnan VU2JXN sent it to me. It reminded me of how puzzeled we were when we found "Schenectady" on old shortwave receiver dials, amidst truly exotic locations. Rangoon! Peking! Cape Town! Schenectady? Obviously this was due to General Electric's location in that New York State city. But reading this article, I am thinking that the presence of Charles Proteus Steinmetz had something to do with it. His informal title (The Wizard of Schenectady) confirmed that we have been right in awarding similar titles to impressive homebrewers.
Here is the Smithsonian article that Ramakrishnan sent.
My journey into the world of amateur radio began in a very primitive way. My first "rig" comprised of a spark-gap transmitter and a coherer based receiver. A coherer is a primitive radio signal detector that consists of iron filings placed between two electrodes. It was popular in the early days of wireless telegraphy.
Spark transmitter (using a car's ignition coil to generate high-voltage sparks):
Coherer based receiver (using a doorbell for the "decoherer" mechanism):
When I keyed the transmitter, a high voltage arc would appear at the spark-gap and this produced (noisy) radio waves. The signal would be received by the iron-filings coherer on the other side of the room. A coherer is (usually) a one-shot receiver. You have to physically hit it to shake the filings and bring the detector back to its original state. That's what the doorbell hammer did. It would hit the coherer every time it received a signal. It amazed me to no end. A spark created in one room of my house could make the hammer move in another room. Magic!
Soon after this project, I started experimenting with *slightly more refined* crystal detectors and crystal radio circuits. As most of you would know, these amazing radios don't require any batteries and work by harnessing energy from radio waves. I guess these simple experiments instilled a sense of awe and wonder regarding electromagnetic waves, and eventually, this brought me into the world of amateur radio in 2015.
My main HF rig is an old ICOM IC-735. The only modification on this is radio is that it uses LED backlights (instead of bulbs):
With space at a premium in San Francisco, the antenna that I have settled for is an inverted vee installed in my backyard (and it just barely fits). I made the mast by lashing together wooden planks. For this city dweller, it works FB:
I have recently gotten into CW, and it has definitely become my mode of choice.
I'm a self-taught electronics enthusiast and I love homebrewing radio circuits. I'll be sharing more info about them soon.
Thanks for checking out my page. I hope to meet you on the air!
