David Sarnoff, Howard Armstrong & the Superheterodyne Receiver

What is the superheterodyne method and how did it usher in the era of broadcast radio? This is the story of Howard Armstrong who invented the superhet receiver in a WW1 bombing raid and David Sarnoff who fought his way from poverty to controlling an empire. Check it out!
Also, if you want to see some amazing pictures of Armstrong and his history check out users.erols.com/oldradio
Armstrong/WJZ photos from the Harry Houck Collection or Columbia University's Armstrong Collection
Finally, as usual, the music is from the fabulous Kim Nalley

[@Kathy_Loves_Physics]

CORRECTION: I implied that the superheterodyne system used signal *addition* like playing two guitar strings at the same time, but I have been corrected and it is a signal multiplication not addition. Sorry for the confusion.

[@davidhaworth1802]

In a sense you are also correct in that the envelope of the combined guitar string output contains the difference frequency. However, in practice, schemes that produce multiplication and suppress the local oscillator are preferred. Great channel BTW.

[@raymundhofmann7661]

"Mixer" is a unlucky name, as it implies addition. On the other side if it has a non linear transfer function, which at some point nearly everything has, it creates the new frequencies of multiplication and more. Mixer is just a sloppy name coined in the beginning of a non linear amplifier stage "mixing" the local oscillator and the rf input.

[@raymundhofmann7661]

@@davidhaworth1802 The "beat frequency" effect is a illusion due to the finite time interval our ear and brain analyzes the spectrum with, it perceives two close frequencies as one modulated frequency. Our ear and brain in effect is a non linear frequency analyzer, similar to what you get with the magnitude value of a frequecy spectrum from a discrete fourier transform of a time interval. Taking the magnitude of a complex frequeny bin is the non linear function similar to the ear where certain nerves detect vibration strength of tuned vibrating hairs.

[@richardcallahan8698]

Sum and difference resultants of algebraic combination, like a piano makes beats. You are correct.

[@rayoflight62]

When you beat two frequencies F1 and F2 in a mixer (non-linear component like a diode or a triode), you obtain two more frequencies, F1+F2 and F1-F2. The IF stages (usually two or three of them) do filter out the F1+F2 component, while the F1-F2 corresponds to the IF frequency of the radio, and is successively amplified and detected.

[@proudsnowtiger]

Armstrong deserves a Hollywood biopic... tragic tech hero of the 20th century.

[@Kathy_Loves_Physics]

proudsnowtiger he sooooo does. I would pay big bucks for that.

[@proudsnowtiger]

Biting my tongue over the FM/Sarnoff story to come - no spoilers! But love that you're covering the commercial shenanigans as much as the technology. Anyone who thinks today's IP wars are something new knows nothing about Marconi, de Forest, Sarnoff et al. Oh, that great shot of Edwin and Marion on the beach with the first portable superhet - I didn't know until just now that it still exists and is in the Henry Ford museum. kzbin.info/www/bejne/hoC0pKmJisRld9U

[@Kathy_Loves_Physics]

proudsnowtiger It’s certainly changes your view of Sarnoff’s complaint when Armstrong climbed to the top of the tower doesn’t it?

[@dahawk8574]

Lee de Forest got a nice tribute with Dr McCoy of Star Trek fame. Credit to his parents, considering that baby Kelly was born in 1920. And you can say that Armstrong got his tribute in space as well, considering how the first to land on the Moon were EDWIN Aldrin & Neil ARMSTRONG. The tie actually runs deeper, because one year prior to the historic mission, Aldrin's mother committed suicide. Her family name was Moon. Her father, another Moon, also ended his own life. Now while a lot of current attention has been given to Neil Armstrong in recent months, this is not the first movie made about that mission. Back in the 70s, a movie was made about Buzz called Return To Earth, with Cliff Robertson playing the lead. Aldrin's depression ran deep and he too came close to ending his own life. Now we have excellent movies made about people like Steve Jobs. It would be great if today's generation got to learn about the tech heroes of yesteryear. A movie about Sarnoff, de Forest & Armstrong. I agree that would be excellent. De Forest has a star on the Hollywood Walk of Fame. Howard Armstrong deserves far more recognition. Ask someone who invented radio. If they have a guess, they might say Marconi. But his invention was nothing like the radio that revolutionized the world. That happened because of de Forest's vacuum tubes and Armstrong's receiver. THESE deserve to be household names. THANK YOU Kathy, for such an excellent video!

[@anthonyarmstrong4701]

Another Armstrong inventor What about the one who invented the system that most deep oil platforms use

[@erin19030]

We had a big party in1970 when Sarnoff retired. However we didn’t invite him. He was a real Party pooper.

[@NemonicanatLarge]

I have to admit, your videos are amazing. First time I noticed, that your videos were probably boring and probably not worth my time but I decided to check one out. For the most part I thought that they were worth m my time so I started watching. This one was awesome. The research and presentation I was impressed. I started my career in electronics and computers. Now, after over 50 years (I'm 68) in these fields, even tho I managed to hamstring my future.I've managed to talk my way into some fantastic jobs. These included DEC, Compac, and others, I feel I have, in many ways, succeeded . It all started with repairing a radio that had been thru a fire. I was 14 and I was hooked. Seeing the true history of RCA, I am beyond impressed. Thank you.

[@PabSungenis]

I’m a broadcaster, so Armstrong has always been my hero.

[@user-bo8eq7ki5w]

What is especially wonderful is that the principle of superheterodyne reception invented by Edwin Armstrong is the basis for the operation of all transceiver devices today ! Long life great," the right " invention ! (and of course , even Mr. Edwin is the inventor of regenerative radio and FM radio) I certainly do not know English, but many words from radio engineering I understand. There are very few videos on KZbin about this great inventor , and you have new precious historical photos. That's great ! It's terribly interesting ! Thank you ! 73 !

[@Kathy_Loves_Physics]

I'm so glad you enjoyed it.

[@josephstratti52]

This is the most interesting series on KZbin that I have ever come across.My utmost praise for Kathy and her content.Just fantastic and enlightening!

[@Kathy_Loves_Physics]

Aww thanks

[@tomstrum6259]

Hi Kathy !! ....You should stand with your original "Uncorrected" Beat frequency signal conversion explanation illustration....Anyone familiar with reading U. S. patents, will frequently encounter inventor applicant claims so repeatedly "micro-detailed" exaggerated to point of functional fantasy !! But yet, in Armstrong's 1920 original Patent # 1,342,885 ... No mention of voodoo,, Algebraic--Trigonometric, "Multiplication" signal conversion is found.... Just the simple but new (for 1918) radio "Reception" application principle of Beat frequency conversion to "Lower" frequency Amplification stages... Your original 1920 radio vintage "Invention Breakthrough" style explanation is most appreciated !!! Keep your great informative content coming & forget the techno nitpickers !! .....

[@ebayscopeman]

One of the great things about the superheterodyne that makes the design so great is the concept of the IF amplifier. It is the design of the IF amplifier that makes these designs so sensitive and work so well. The main reason: it is easier to make a high gain, lower noise amplifier using several narrowband cascaded sections than trying to make a single stage wideband amplifer as used in prior tuned RF designs. Howard Armstrong was a true genius and his principle of the superheterodyne method used in the 1920's are still widely used today in receivers and test and measurement equipment to this day. It is sad that he passed in the way that he did, and it seems that few people even know anything about this great man. As a side note I read the book I got from you at PCB Carolina last year. I could hardly put it down. I am looking forward to your next one!

[@zubershaikh7663]

The knowledge u spreading is priceless.. very nice .. i am watching u from india 🇮🇳

[@ralphburns6659]

HEY MR. ARMSTRONG THANK YOU FOR ALL YOUR GREAT INVENTIONS MY FRIEND!

[@Kathy_Loves_Physics]

Definitely, love Armstrong

[@7c3c72602f7054696b]

Thank you Major Armstrong, and thanks for the video!

[@ocpud2999]

I consider Armstrong as one of my childhood heros. My dad was an engineer. And saw how his inventions changed the world. It's sad he is not known more

[@jonkzak]

What a wonderful professor you must be. Your definition of AM radio finally penetrated my thick skull and the Light bulb of understand blinded me. Oh how I wish I had heard this in my youth. Thank you for the wonderful video. Be safe and keep sharing.

[@acmefixer1]

Thanks for giving viewers the real, often sad history of radio. Sarnoff did eventually get to be a General. But he was a mean guy. Most AM radios used a local oscillator frequency that was above the station's frequency, so the IF was the *difference* between the station frequency and the local oscillator frequency.

[@flagmichael]

If it were on the low side, the oscillator in AM radios would have gone below 100 kc! (Hey - we are talking about history; we didn't have any stinkin' kHz in those days!)

[@Steve-GM0HUU]

@@flagmichael Yes, back in the day it was kay-sees and em-sees.

[@jamesmulcare5321]

Sarnoff never served a day in the military. He was given a Brigadier General rank because of his work on General Eisenhower's communications staff. He stole basically stole Farnsworth's television patents and screwed him out of a 1 million dollar infringement judgement by never paying it. He was more than mean, he was a ruthless scumbag...hope it's nice and hot where he is now

[@mariofilippi3539]

I enjoyed you video very much, thanks. Sarnoff was the proverbial guy who pulled himself up by his own bootstraps.

[@garbo8962]

Believed the old superheterodynes only used 5 tubes. A 35W12 rectifier tube, 50C5, 12AU6 and 2 others. Learned about them back in the 1960's. Have an old tube radio in my garage that I still use. Interesting vid. Ashamed very few young kids get interested in electronics or turning wrenches. Learned how to solder and use my dads model 260 Simpson meter before I learned how to drive. Put together a radio, tube & transistor tester, and 25" Heath kit color TV.

[@flagmichael]

The "All-American Five" came in two versions: one with octal base tubes and one with miniature tubes. Those were the miniature tubes. I think RCA had the original patent but when that expired everybody made them virtually the same. For years the RCA tube manual had a schematic of that version in the back. I believe transistors displaced even those tubes when transistors became cheaper than tube sockets. The miniature tube radios came on printed circuit boards near the end but the economics just shifted too far too fast. RIP to the AA5. In this history channel, I would be negligent if I didn't mention that the book, "SONET/SDH Demystified" has a few pages about the birth of the transistor. In short, the post-WW2 boom brought high expectations, including private instead of party telephone lines. That required more copper, which was being snarfed up by the housing boom. The solution was multiplexing, but vacuum tubes had heat and energy problems. That is why the transistor came out of Bell Labs.

[@johnstone7697]

The AA5 lineup was 12BE6 mixer, 12BA6 IF. 12AV6 detector/af amp 50C5 audio output and 35W4 rectifier.

[@8546Ken]

You're referring to the small "AC-DC" table radios. The large console radios may have had more tubes and a power transformer. With a transformer, all the tubes had 6.3V heaters The tube numbers were often just 2 digits. They usually had shortwave bands.

[@Raymond_duck]

Brilliant!!! Absolutely loving these videos.

[@Robinzano]

I used to live in Somerset, New Jersey, right down the street from Radio Court. About a mile away is Marconi Park. I've heard that Marconi Park is where his antenna was, and Radio Court is where the transmitter was. I'd love to see a video with the history of that, especially since I lived right around the corner, I'm an amateur radio operator, and my full time job is a radio communication specialist.

[@anguscampbell2302]

Absolutely love your tuition. Right at my level . Less is more. Thankyou

[@atomicdmt8763]

LOVE these 10min clip- format!

[@jamespowell1442]

This is a great channel,keep up the good work!!

[@Kathy_Loves_Physics]

So glad you liked it.

[@sammyk7024]

This video brings me back wonderful memories, as my very first "serious" electronics project was indeed a superheterodyne radio receiver, some 40 years ago. It was a helluva lot of fun, as I had my siblings, my mother and my grandpa help me build a ridiculously huge dipole antenna to test the dang thing.

[@goodmaro]

A Beveridge?

[@sammyk7024]

@@goodmaro it ended up as a Beverage, indeed. a half wave one, although my original plan was to set up an actual full wave dipole. details are fuzzy, but I'd guess I ran out of copper wire.

[@amtsgedicht]

thank you - you're the first person that makes me understand the superhet system and I tried many before!

[@CharlesAustin]

We take radio for granted: not now ..!! Love the history you give !!

[@dennisfahey2379]

I love the line "Think Fiddler on the Roof, but with a painter". That is absolutely priceless.

[@steveperry1344]

i really enjoyed your story of some of the history of radio. i was trained as a ground radio repairman when i was in the air force 50 yrs ago and worked on very large radio transmitters.

[@jackbronsky]

Kathy, you are simply the greatest.

[@AnbroBR]

Nice video, Kathy! I have read two books that covered the life of Armstrong - the first was written by Tom Lewis and the title was "Empire of the Air." It was the book on which PBS' home video, "Empire of the Air: The Men Who Made Radio" was based. The second book was written by Lawrence Lessing and its title was "Man of High Fidelity: Edwin Howard Armstrong." Having read both of those books and having watched PBS' video numerous times, it is my opinion that it was Sarnoff's ruthless quest for the almighty dollar that drove Armstrong to suicide. The worst part about it is that they were at one time very close friends. This coming December 18th (2020), and continuing on through December 20th, I am going to be using my ham radio station to operate a "special event" in honor of Armstrong's birth and his accomplishments. I will be primarily using the "20 meter" (14 MHz.) and the "40 meter" (7 MHz.) ham bands for my operation. I will also be checking out conditions on the "15 meter" (21 MHz.), the "80 meter" (3.5 MHz.) and the "160 meter" (1.8 MHz) bands. The bulk of the operation will be on the 20 meter and the 40 meter bands - the 20 meter band being a "day-time band" and the 40 meter band being a "night-time band." My special event operation will only use "CW" - ham radio jargon for Morse code. I am quite sure that I will be able to put a good signal into Europe, Asia and also "down under," in Australia and New Zealand. I plan on having a lot of fun in putting this on and it will be my way of expressing my appreciation to Armstrong, without whose inventions radio, television and cell phones would not be like they are today! 73, Brad Anbro, N9EN

[@Kathy_Loves_Physics]

Brad, I also enjoyed both books very much (and, of course the PBS video was very well done). I love your idea to honor Armstrong and I like to think he would like it too. Cheers, Kathy

[@bombadeer8231]

Love your channel Kathy 👍

[@charlesharkin2165]

Lovely presentation

[@giovafra61]

I've just discovered your channel and so I have to congratulate with you. I'm watching the series dedicated to the radio, from the 1st valve, Fleming, De Forest, Armstrong and so on. Very clear explanations. That's a good way to learn. Thank you and...GO AHEAD IN THIS WAY!

[@Kathy_Loves_Physics]

So glad you liked it.

[@johngough2958]

Great story - have to keep watching!

[@JamesWHurst]

A most stupendous telling - of a story rarely told. Thank you for creating and sharing this.

[@Kathy_Loves_Physics]

Glad you liked it

[@bobblacka918]

Love your channel. There is nothing quite like it for drama and accuracy.

[@amramjose]

That was great! I have always been a fan of radio, specially vintage radio. Let's go to the rest of the FMstory!

[@denvrital]

Hi Kathy... Love your program.. just found it by accident. I am now hooked. You are a very good commentator. I worked for RCA in their tube division in Avenel, New Jersey in my teens. I loved the energy in that factory. It was an interesting place to work. In my youth, I built many kits using tube technology such as EICO and Heathkits and I still have most of them today. My VTVM and RF oscillator still work after all these years too. Thanks again for the great story and I look forward to many more. Lenny from Denver

[@9487087496]

Highly informative and motivating. Thank you.

[@joeretired4552]

Great video. Great history.

[@usmale4915]

Great channel. You're the best. I like how you go into great detail...it's refreshing, to say the least! I thoroughly enjoyed this particular video. And I also just subscribed! Thank you for sharing, you are one very knowledgeable individual!

[@USNavySeabee]

My father worked along Edwing Armstrong until his death at the Alpine Tower in New Jersey.

[@Kathy_Loves_Physics]

That is amazing. I hope I described Armstrong accurately. Did your dad have any personal stories about Armstrong? I would love to hear more. Feel free to email me (my email is in the about section but if I add it in my comment my comment gets flagged!)

[@ralphburns6659]

WOW, WHAT AN HONOR, JUST WOW!!!!

[@curtvincent3728]

OMG! You are amazing! That is the best description of the circuit on all of youtube! Well done! And you did a good job of putting Armstrong in the proper light. Sad ending.

[@Kathy_Loves_Physics]

Thank you I’m so glad you liked it. And poor Armstrong, still makes me sad to think of it

[@davidatrakchi2707]

You have an amazing way of presenting these facts

[@dr.mikeybee]

You're such a great vlogger. I really love these.

[@choxxxieful]

Well done, my dear!!! Keep up the fabulous work!!!

[@Kathy_Loves_Physics]

Charles Harding thanks Charles, glad you liked it.

[@Alkoluegenial]

Just wanted to say that I really enjoy your videos and have already recommended them to several people, who also love them. Have a nice day.

[@Kathy_Loves_Physics]

Alkoluegenial thank you so much! You have made my day.

[@mattgraves3709]

These are great videos, thanks so much!! Subbed up also

[@davidepperson2376]

Great video and great explanations - thanks for sharing!

[@budokai6706]

Very cool stuff! Thank you...

[@gregnewberry4813]

Empire of the Air is a very interesting documentary of early radio. Nice video!

[@Kathy_Loves_Physics]

Great book and documentary

[@bobwferguson]

I got a degree in mass communication and I’ve seen your videos for the past week and learned more from them than college

[@prabhakarv4193]

Very nice and informative. Thank you

[@AdamosDad]

The first receivers I worked on in the Navy, back in the 60's had BFO controls on the front panel.

[@grzesiek1x]

based on Armstrong schematics I have just built a receiver, finally I got and understood how it works and what it is even more important how to make it work or adjust. principle is quite simple but there are a lot of things to consider and check...

[@johnpeterson7264]

Great video for enthusiasts of radio !

[@randydireen3566]

Just found your channel! You deserve millions of subscribers. Very happy. I love this stuff.

[@robhtp3817]

Okay I’ve seriously been binge watching your videos, today I’ve watched 8 of your very informative, educational, & entertaining videos. Thank you so much. I almost want to go out and invent something. 😆 or at least maybe buy a DIY radio kit to show my 9yr & 11yr old daughters how a radio works.

[@Kathy_Loves_Physics]

RobHTP what a fantastic idea! to be honest I have never made a DIY radio and I so want to.

[@microdesigns2000]

Did you ever build a DIY radio? I built a crystal radio as a kid and TDA7000 radio as a teen. Nowadays I am an automation and controls engineer. I am thankful to my parents who purchased an electronics kit when I was young. So I hope you built a radio with your kids. 📻

[@ronwisman1767]

Just discovered your shows. Love this

[@0dbm]

Thank you , I Learned so much , I am hooked

[@dysfunctional_vet]

i started working with radio seriously as a career in the 1970's. the vac tube R390's (surplus) WW2 radios were amazing for their versatility, you could close the band pass down to .1 hertz, meaning you could hear individual signals in sideband. I could listen to stations from south africa, china, russia, south america and other places all using a 330 foot dipole about 40 feet hung in trees. working with the two i had, was pure joy and the BFO made the un-intelligible crystal clear for listening. good program

[@WarpFactor999]

Kathy, having been a ham for some 60 years, and working in radio, radar, general electronics, and computers since, I find your content wonderful! Well done! I too share a strong interest in the history of electronics. You could do segments on the early days of amateur radio, rotary spark gaps, coffin kilowatts, etc. The ARRL has some wonderful source material. Sadly, amateur radio is dying out as it's now simple to talk around the globe over the internet. But how many people know that many of the early radio improvements came from hams? Hams even had their own satellite in orbit as a radio and data repeater system.

[@flagmichael]

Hey! I remember when disaster communications in the first minutes and hours was often through ham radio. (Former WA6TDG - I let my license lapse when I started working in avionics. One night I wondered, "who is paying me to do this?")

[@WarpFactor999]

@@flagmichael LOL! Indeed. Hams did it as a service to the public and to justify their use of the ham radio bands. I've kept my ticket but am not active anymore. Not many of us left on the air anymore. The FCC has tried very hard to get more people interested in ham radio, but it is just fading away like us old farts.

[@ricsanders69]

Fantastic video...I'm going to suggest to new Ham Radio Operators to watch your videos...these are very informative. I've built a few radio kits and a couple were Superheterodyne aka Superhet! 73 de KN4FTT

[@kennynickell9883]

No questions, just CUDOS for great vids..

[@lcmd7833]

This information is fascinating! With a technical education and background, these are things I should know ... but I never was exposed to the historical knowledge, which puts everything in context.

[@cranegantry868]

Fascinating, loved this. Subbed too.

[@qkitselectronics5415]

Great video. this should have many more likes, come on people show some love for all the research and great pictures Kathy has put together. Have a great day everyone, if you can't play a sport, be one.

[@wakomatic5402]

Great storytelling

[@cat637d]

Outstanding work!

[@cat637d]

Armstrong was an independent thinking master engineer! Possibly not a genius as he has been styled but certainly a very competent and capable technician in his field. Had Sarnoff not been such a narcissist....brilliant, but still a narcissist, RCA might still be in existence due to Armstrong's later developments. Many of his developments in the radar field were still classified just a few years ago!

[@markrowland1366]

Thankyou for this simple explanation of a wonderful gift to mankind. At twelve I won a Philips constructo set, on which I assembled a three transistor radio receiver, winning it as a prize. I was manager of the largest Neon sign shop in Australia and edited the new handbook on neon shop practice. We used 18 kV transformers at over one amp. kHz radio transmitters in creating plasma for desktop signs. When upward lightning was reported and it's colour described, I was able to introduce it's finders to Neon equipment pervayers, who produced the associated vacuum, and were observing the colours when testing product. I hope that confirmed what was maybe still conjecture.

[@marzymarrz5172]

The Sarnoff Marconi connection is amazing. It’s as if the universe opened a door.

[@yahyaqarshaee9764]

I am truly honored Kathy for meeting you 💜

[@Kathy_Loves_Physics]

Why thank you. The honor is all mine.

[@PaulHigginbothamSr]

I really liked your gift of super heterodyning. What you do not mention is Armstrong in France and finding two radios in one room interfering with one another during Ww1. In your previous video of the vacuum tube I had no idea these people from the past didn't really understand how triode tubes work. I just assumed they knew from the get go it was electron flux not ions. So as usual it was an accident not a blazing certainty and here you show 3 knobs on these difficult to manage receiver dials. So the same position on the dial was always changing but you could mark the stations on two dials to reach the station you wanted.

[@karthick86c]

Good video Kathy dwelling into the history of superheterodyne and how it came to be what it is today. Keep up the good work and you are bound to get a large audience here on youtube in no time.

[@Kathy_Loves_Physics]

Thanks so much! If you feel like sharing on social media that would be awesome. Cheers, Kathy

[@karthick86c]

@@Kathy_Loves_Physics Sure Kathy. Will do. Thanks.

[@rosswarren436]

Looking forward to your book! We need a cast of characters map...LOL...

[@russbellew6378]

Excellent and accurate presentation.

[@Kathy_Loves_Physics]

Thank you I try my best

[@georgekoerner6591]

Great job

[@captainernest4307]

You are amazing.

[@LaurenceRonayne]

Ok I'm hooked on your videos now.

[@Kathy_Loves_Physics]

Bwa ha ha!

[@Steve-GM0HUU]

Very interesting - thanks👍. Definitely interested to see more videos on various pioneers of radio. Marconi was certainly an interesting character. Although, as a Scot, your thoughts on James Clark Mawell would be interesting.

[@keacoq]

Just so interesting, thank you

[@richlaue]

I understand how it works, and having built, from scratch, several radios, I understand what the advantages are. In addition, my grandfather had a, non superheterodyne radio that required the user to individually tune each stage of the receivers amplification. This radio also needed 3 batteries of different voltages

[@galaxysam1375]

Very nice!

[@jeffharrison1090]

Another GREAT and all so interesting production! Are you surprised by the twist and turns that ppl lives take profes- sionally and personal for their success? Published are the great highlights, triumphs and accomplishments, but not the sometimes tragedies that later follows like here and in other tales like Vail and Morse with the telegraph? Friends splitting because of greed or wanted top billing. Others becoming depressed and sought isolation! Funny, how we tend to always have the happily ever after image in our minds...I like happily ever after....lol!!!

[@thomashardin911]

You look awesome! ⚡️💃🏻🤘

[@GrahamC-eg6ln]

The AR-812 is a reflex design with the first vacuum tube being both the RF amplifier and the first IF amplifier. The very low intermediate frequency of 40 Khz is so that the RF and IF signals can be kept separate by simple filters.

[@GrahamC-eg6ln]

The low intermediate frequency would require the IF transformers to be quite bulky - but the cost saving of reducing the tube count would more than offset any increase in IF transformer manufacturing cost. Reducing the tube count would also extend battery life.

[@TheEvertw]

The heterodyne design is one of the key breakthroughs of the century. It is amazingly elegant! The key technical benefit is that a highly optimized filter can be used to convert the intermediate frequency to audio. Without the heterodyne principle, this filter would need to be variable, making it much less optimized, resulting in far worse selectivity for the radio. This would have meant much more bandwith would have to be allocated for each radio station, and far worse audio quality. And it would have made it almost impossible to mix color information and audio in with TV signals: these are transmitted in tiny bits of bandwidth that require very selective filters to reconstruct. Later radio's combined the two variable capacitors into a single device where one knob changes both capacitors, so the antenna filter and the internal oscillator change frequency in harmony.

[@flagmichael]

Ages ago I acquired a Bosch console radio made in 1928. It was a TRF (Tuned Radio Frequency) receiver with a 3 or 4 gang - I forget which - tuning capacitor and a tuning dial that ranged from 0-100. It actually worked fairly well for local stations - other than not having Automatic Gain Control - but not so much for distant stations.

[@karlroebling3316]

Wonderful!

[@blipco5]

Great story. Subscribed. 👍

[@rachelcarre9468]

Fab video!

[@carllafrance5510]

Excellent video just found your channel d subscribed !

[@BernardS4]

great job you have put this history together. There is part of the RCA story that I have read or heard about. didnt the Navy have a part in founding RCA out of the American arm of Maconi with partnership with Westinghouse, GE. United Fruit

[@smiggo1481]

It was long believed to have been invented by US engineer Edwin Armstrong, but after some controversy the earliest patent for the invention is now credited to French radio engineer and radio manufacturer Lucien Lévy.[1] Virtually all modern radio receivers use the super heterodyne principle. Another example where we will never know who was the inventor for sure!

[@Boitaoutix]

From Wikipedia (Google translated): It is to Lucien Lévy, head of the laboratory of the Center radiotélégraphique militaire de Paris that we owe the implementation of the superheterodyne although the principle had been indicated by the German Alexander Meissner in 1914. The French Paul Laüt, of the same laboratory that Lévy would also have been a precursor in 1916. Lévy filed two patents on August 4, 1917 and October 1, 1918, and the priority of Lévy's patent over that of Edwin Armstrong will be recognized by the Court of Appeal of the district of Columbia in 1928. The German Schottky who had also filed a patent in June 1918 will recognize the anteriority of Lévy in 1926.

[@Sam_on_YouTube]

I don't see a video yet on Hedy Lamarr, the actress who invented frequency hopping, the technology behind cell phones. That would make a great addition to your catalog.

[@Kathy_Loves_Physics]

It’s coming, but it’ll take me a while to get there.

[@siyunguo8176]

Thank you!

[@titicoqui]

of course impossible to resist video

[@heribertohernandez8881]

Good job

[@jmguevarajordan]

Armstrong knew about the idea of the superheterodyne when he was in France. My guess is that the idea of the superheterodyne was known by many people, in fact Armstrong acknowledged it, but Armstrong took it, improved it, patented it and made it commercial. Armstrong was 'doer' and not just a 'thinker'. Unfortunately, he made a big mistake thinking that Sarnof(f) was his friend.in addition, Armstrong belonged to an 'era' in which inventors could become rich with their inventions, but that 'era' was over after ww2 and Armstrong did not realize it.

[@you8164tube]

thank you for your wonderful program. l wonder whether one can control the volume by changing the current thru the filament. usually it's done by changing the voltage amplitude to the grid.

[@davidkleinthefamousp]

Ty Kathy I would even listen to you read the phone book!

[@Kathy_Loves_Physics]

Thank you, but I think I would do one of the worst renditions of reading the phone book ever considering that I mispronounce words so often. 🤣

[@josealphonso2848]

Learn a lot more from you than my physics class

[@MISSIONCAT11]

When I was in school, one very interesting xperiment I was required to perform was to measure the mass of the electron. This was not done directly, rather by observing microscope bubbles moving in the air under an electric field, and then computing the "smallest common denominator" of the oil droplets velocity.

[@flagmichael]

The famous Millikan oil drop experiment. If not for that experiment we would not have the concept of wave/particle duality... electrons would only be known as waves and the atomic model would be radically different.

[@jmguevarajordan]

You went to a very nice high School, I only saw that experiment in the textbook.

[@johnneedy3164]

Super interesting 👌 👍

[@Kathy_Loves_Physics]

Thank you so much 🙂

[@dillydonovan]

just read Empire of the Air and i'm addicted! thank you for the video! what did you think of Oppenheimer? Nolan should do the story of radio next!

[@charlesmrader]

This video is quite personal to me, because of my family history. My father, Abraham L. Rader, was born in 1906, of immigrant parents, and when he was a teenager, he was interested in radio. In those days, radio for ordinary people was a crystal set, with all the problems of amplification and tuning that this video makes clear. But my father started a company to make and sell crystal radios. He also hired an engineer to try to solve some of those deficiencies. My father had no formal training in electronics, just hand-on experience. His engineer was a perfect fit, very bright but not entrepreneurial. That engineer invented the superheterodyne radio. My dad's company sold the first superheterodyne radios to ever reach the consumer market. Sadly, from our point of view, Sarnoff and RCA had the necessary patents and my father, who didn't even know what a patent was, found that he had to leave his business or be sued. He never talked to me about that part of his life, but of course my mother knew about it. When he died, I put together an obituary speech and that was when I learned about it.