Armstrong: the Tragic History and Physics of FM Radio

How Howard Armstrong created and detected frequency modulation (FM) radio and how it was so impressive that it actually caused his downfall!
Some links:
• Video
Very good video but, unfortunately, the methods that they described were not used by Armstrong. Still A+
• Video
OK video, not as detailed as the 1944 one.
The background music was from Kim Nalley and the "New Orleans Hop Scop Blues" which is by Jimmy Noone.
The theme song is by Kim Nalley and is a cover of "Electricity Electricity" from Schoolhouse Rock :)
• Electricity, Electric...

[@ntcrwler]

A simple and easy to understand explanation. Thank you! Edwin Howard Armstrong has always been one of my favorite inventors and inspirations. And what Sarnoff did to him was unforgivable!

[@moldyoldie7888]

They both made regrettable mistakes. Sad.

[@kirkp_nextguitar]

I got interested in electronics and electromagnetic waves by discovering my grandad’s 1922-23 radio textbooks and some old radios in the attic, and ended up in a related career. The history was part of the fascination. You’ve done a great job of presenting it.

[@gfriedman99]

Very cool.

[@JuanPab521]

Armstrong invented the receiver regenenative, heterodyne and the superheterodyne. He is the great radio inventor. Chapeau

[@robertewalt7789]

There is a radio tower called the Armstrong Tower, in northern NJ, across from NYC. First FM broadcast there.

[@ApartmentKing66]

@@robertewalt7789 Alpine, NJ, isn't it?

[@ApartmentKing66]

You do realize that "chapeau" is French for "hat?"

[@robertewalt7789]

@investorguy, yes the Armstrong Tower is in Alpine, just off 9W, not far from the Palisades Parkway.

[@billscow]

@@ApartmentKing66 He meant Chappaquiddick & something about a Kennedy getting away with a woman drowning in a car accident he caused by driving drunk because he did nothing to help or save her.

[@etmax1]

Well that was way more interesting than I thought it would be. Thank you very much. Interesting how complex the original discriminator was compared to the 60's when I got into the game. It also demonstrated what was (is) so seriously wrong with the US patent system. Sarnoff shouldn't have only been fined, he should have been jailed along with all of his lying engineers and anyone else that colluded.

[@lawrencedoliveiro9104]

Meanwhile, at around the same time, the Wright Brothers were busy using their patent on controlled flight to suppress all competition in the US aviation industry, letting the Europeans get an early lead.

[@spvillano]

@@lawrencedoliveiro9104 monopolies at their most efficient! :/ @etmax1, no Sarnoff should've been imprisoned and buried under the prison.

[@a64738]

The problem is really corruption and that rich power hungry psychopaths is running the world and has the power, it is now 1000 times worse then ever...

[@elmerexpress]

A very clear example that intelligence without wisdom can be a deadly weapon. Today this is visible all over the place...

[@kensmith5694]

Yes, Armstrong's method was far more complex than needed. This often happens with inventions. The "ratio detector" seems very obvious to us today.

[@timothystockman7533]

In order to get enough frequency deviation, Armstrong not only multiplied a low frequency signal many times, he took the resulting high frequency signal and heterodyned it back down so he could multiply it many more times, then he once again heterodyned it back down and multipiled it more. All of this multiplication finally gave him enough deviation. When I started high school around 1970, our school started an FM radio station WCNE, which is now community station WOBO. Our first transmitter was a CCA FM10D, which used a low frequency crystal oscillator driving phase modulator. Phase shift and frequency shift are essentially similar types of modulation. In order to get enough deviation for broadcast, the FM10D had several multiplier stages, similar to Armstrong's Columbia prototype. In fact, the de-emphasis network in the FM receiver, integrates the audio waveform above the knee of the de-emphasis curve with 6 dB per octave, essentially making high frequency audio compatible with a phase modulator. A phase modulated FM transmitter has what is called a pre-distortion network to adjust low frequency audio to be compatible with the de-emphasis curve. Note that the purpose of emphasis is to reduce high frequency noise, which is caused by the equal energy-per-octave response of the ear. It is just that de-emphasis can do double duty, both reducing the HF noise and integrating phase modulation. It seems this subtlety is missed by the amateur radio examination which wrongly asserts that the PURPOSE of de-emphasis is make an FM receiver compatible with a phase modulator; this is a byproduct, not the purpose. It is somewhat complex to generate a stereo signal using frequency multipliers, so as stereo took hold in the late 1960s, Gates developed the TE-3 direct FM stereo exciter. The problem was that a crystal oscillator could not be "pulled" far enough for wideband modulation, so the TE-3 had a complicated phase-locked-loop automatic frequency control system to loosely lock the FM oscillator to a crystal reference. The problem was that certain audio, particularly heavy bass, would cause the AFC to unlock and the station would drift. Disco music of the mid and late 1970s was the death of the TE-3. As the 1980s were getting started, Harris (who had bought Gates) came up with the MS-15 exciter, which was a direct FM unit with a much improved AFC system. My experience with the TE-3 was at WMRI and the MS-15 was at WKHY. So far as AM, broadcast could and did have good fidelity. When I worked at WBAA, our 5 kW Collins 21A transmitter had audio frequency response only 2 dB down at 15 kHz, which I measured. I had 2 different EE professors at Purdue tell me that AM broadcast stations must limit their audio to 5 kHz, which is completely incorrect. But a lot of people apparently believe this myth. In the early 1980s, the FCC started requiring stations to limit audio to 10 kHz (the NRSC emissions mask) so they could overpopulate the broadcast band. Wideband (10 kHz) c-quam stereo AM can sound amazingly good, but as time goes on modern electrical devices are raising the noise floor so that AM reception in cities may be too noisy. A couple years ago, during an extended power outage, I did some amazing AM broadcast DXing! I have found it sad that few people working in broadcast know the names Fessenden and Armstrong, radio pioneers who created their industry.

[@OsoMagna]

Thanks for that interesting comment. Wd4cxq

[@drwalker9093]

In 1979, when I took over as Technical Director of our college station, they had recently purchased a new FM transmitter, antenna, and stereo generator. (Also, Emergency Broadcast device, mixer, mics and turntables.) Previously, the station had been 10W (ERP 10W from a monopole). The TD before me had installed the audio equipment, the EBS device and the Orban stereo generator. My first major task was the technical portion a new license application for the 100W transmitter and 1.64 gain antenna. (They had spent the entire grant on hardware, and had nothing left to pay professionals to perform the license application. I _did_ get -a little- help from an alumnus EE to do setup and measuring/verifying the equipment performance. He worked for a company that let him borrow test & measurement equipment - he would drive 250 miles each way to help me on a few weekends.) The Orban Optimod stereo generator seemed magical - easy to configure, compression that did not intrude (though it would allow one to crank up the compression until it had near-zero dynamic range), and our audio quality was better than the commercial FM stations available locally. (They caught up. One of the broadcast engineers came an asked us about it, read the manuals and played with the settings...then got his station to go Optimod, too.) Others installed the new antenna before it was licensed. [I just went back and edited the station name out of the text above, to protect the innocent.] In High School, I read a biography of E. Howard Armstrong. Starting during Jr. High, I also constructed and experimented with my own outdoor antenna to DX AM at night.

[@kb9drh]

Howard Armstrong was a genius! His demise was tragic. Rest in peace Howard. Kathy nice job!!!!!!

[@aramboodakian9554]

This is truly a story with a tragic ending (very sadly) and not click bate like so many other KZbin posts. Thank you for the history.

[@SpeccyMan]

bait

[@Dave86229]

Your series of videos is really great. Please keep up the good work! Your subject may not appeal to everyone (I wish it did), but I am sure there is a small subset of viewers that really appreciate the work you have put into these videos!

[@disconer]

It appeals to me - a lifetime with electronics and a history buff - win-win

[@Mach7RadioIntercepts]

Great work, Kathy! Thanks for bringing us this great history of FM radio. Back when I was a flight instructor near NYC, we used the "Alpine Tower" as a visual landmark for flying up and down the Hudson. I never knew that tower's connection to FM broadcasting. Armstrong did so much for us who depend on radio.

[@erikziak1249]

Great series. KZbin should finally boost these videos, they are very valuable, as they tie together good explanation of how things work based on our knowledge of natural laws, the people who discovered them, and economy and politics together in a complete image. Everybody can learn something new from these videos. Truly great work. Hope your channel goes viral, it deserves it. The quality, precision and a good narrative communicated pleasantly and simply (yet not oversimplyfied) of your videos beats all those clickbait hype "tech", quantity content on KZbin. Other videos will be forgotten by history, but these are timeless.

[@erikziak1249]

@@sjb3460 I do not watch shorts at all. I hate vertical video and watch on PCs and in the rare cases when I watch on my phone, I always rotate it to its side. Shorts are perfect for the short attention span of the audience and KZbin makes it even worse and creates more and more "zombies" with an attention span of 30 seconds or less, just to forget what they just saw, as it gives literally zero new and memorable knowledge in the vast majority of cases. I really hate this trend.

[@trofaznimotor901]

​@@erikziak1249 jesi naš?Skip,if you dont understand,you very well descibe me,i lost probably hour of valuable time watching shorts,literally forgotting things i saw.

[@erikziak1249]

@@trofaznimotor901 Kathy má oveľa kvalitnejší content ako priblblé shorts, odporúčam. A niečo aj o polyfáze, ideálne pre trojfázový motor.

[@rollomaughfling380]

Ok, this is an instant sub. I'm a little upset KZbin's been sleeping on this channel in my reccs. Fantastic job, Kathy!

[@vartannazarian2437]

Thank you so much for such an informative video Kathy. You were able to include so much important information in just 12 min. For me, Armstrong is the greatest American engineer.

[@gregoryignatius4282]

Your channel is great. I love the straightforward and clear explanations of some very difficult material. You will probably never make as much as perhaps you should but from some of us who have lived through a lot of this, you have a great channel.

[@dell177]

Thank you for that great explanation. I still have the 1950's FM radio Tech Manual I filched from the army when I was working in communications in Korea. Your explanation makes a lot more sense than theirs did to someone new to the field.

[@sahhaf1234]

you are exactly doing the type of the program that I love most: history of electronics..

[@j.vonhogen9650]

Wow, what a sad story! I wasn't expecting such tragic ending. Thank you for your great videos!

[@sundog486]

You are a great presenter. Although I already know the technological details you present, the history you present and your enthusiasm make it a delight to watch.

[@srvr1007]

This is my new favorite channel. Thank you so much for making these videos.

[@Kathy_Loves_Physics]

srvr1007 thank you so much for thanking me so much (if that isn’t too meta)

[@dahawk8574]

SHOE! My new fav chan too! Kathy, you're brilliant. I hope to get fully caught up on your series here soon, and hopefully you've done a video sharing your own background. I'd love to hear the story on how you got so knowledgeable on the Big E. What you've done here should be required for anyone getting a degree in EE. At least, if I was running a school I would require it. Actually, this is great stuff to teach to kids in gradeschool! Maybe the next version of the $100 Bill will have a kite on it, helping to inspire many people toward a greater appreciation of this secret history of electricity.

[@drbinglederry9785]

And 2 years later I’m repeating what has been said, this is my new favorite channel.

[@dahawk8574]

@@Kathy_Loves_Physics, you know how physicists speak of The Big TOE. Well your channel provides the SHOE to slip over the Theory Of Everything.

[@notvalidcharacters]

THANKS for this, Armstrong is a hero of mine and it's always satisfying to see his story told as it deserves..

[@mr50sagain55]

Thank you, Kathy, for the indeed clear description of Armstrong’s FM. Had been looking for this and per your comment, couldn’t find anything but the tragic storyline. I sincerely admire your ability to produce these wonderful videos!

[@ravenclawavenger2170]

When I was in high school electric shop I learned about AM signals. When the audio is combined with the radio frequency the result is the carrier singal plus the audio (a sideband), the carrier minus the audio (another sideband) and the audio. The transmitter loses the audio and transmits the carrier and sidebands.. The radio receiver picks the signal through an antenna, converts it and the side band to an intermediate frequency, amplifies this and then puts it through a diode which regenerates the audio. The radio frequency (RF) is filtered out with a tiny capacitor. The audio is amplified to drive speaker (used to often be called a loud speaker) and that is how we hear it. If a limiter were used with the AM radio we would not hear anything. Because the difference between the the carrier and the side bands reflects the frequency of the sound the signal frequency is limited to the bandwidth of the carrier. This is set to 10kilohertz on either side of the carrier. FM does not have this limitation. However FM channels are 200kilohertz wide.

[@holton345]

Great video, ma'am. I'm glad the KZbin algorithm recommended this to me. I'll be watching more of your content. Have a good 2022!

[@Kathy_Loves_Physics]

Thanks

[@unclemarksdiyauto]

I stumbled onto your video, as youtube suggested it. Happy to say I loved this explanation of FM! I work in radio so this is even more reason to understand how it works. Looking forward to more of your videos Kathy.

[@gator1984atcomcast]

What a story! Thanks for telling it in such an interesting way. And in only 12 minutes.

[@veenarasika1778]

I recently came across your videos and have found all of them fascinating. Keep up the great work!

[@craiglarson2346]

Thanks for the presentation. These fellows were titans of industry. Tesla and Edison - same thing - warriors working against one another. Pity. Not even once did you mention the square root of negative one. You succeeded in delivering!

[@peterking299]

Well done for making the explanation of FM and Armstrong's Phase modulator, and his demise that was so tragic.

[@AnbroBR]

Very good video, Kathy! Major Armstrong truly WAS the "father" of radio, NOT de Forest. Armstrong took de Forest's Audion and actually figured out how it worked and why, de Forest really not having a clue as to its operation. Armstrong then developed circuitry which would amplify radio signals and also generate them. He went on and invented the regenerative, super-regenerative and superheterodyne circuitry, circuits which we still use today in all AM & FM radios, in television and in cell phones. Armstrong also, as this video explains, invented wide-band FM radio, which was truly "high fidelity" and also FM multiplexing. All this is explained in PBS' documentary "Empire of the Air: The Men Who Made Radio." As an amateur radio (ham radio) operator, for the past three years, I have put on a special event, using my ham radio station at my home, in honor of Major Armstrong. I have a special FCC call sign assigned to me and I try to make it a 3-day affair. I use Morse Code only and try to work as many other hams here in the USA and around the world as possible. This is my on-going effort to honor Major Edwin Howard Armstrong. Truly a great man! Thank you.

[@luisvergani2693]

Edwin Howard Armstrong was the greatest electronics engineer that ever lived. The world biggest profesional organization, IEEE, at the time IRE (Institute of Radio Engineers) also sanctioned him at Sarnoff's request... Every wireless device to date contains something Armstrong created. Thank you Kathy for this video.

[@Kathy_Loves_Physics]

no argument from me for the first statement.

[@quagmyer7230]

Thanks to FM radio, I’m an audiophile today, back in the early to mid 80’s, in Cuba my older brother an I, used to build these almost 5 meters long arrow shaped Yagi antennas with the rear pointing North to get stations from the US, we used to listen to the hit parades from back then the Super Q FM 108, in Stereo, from Miami, ( that was just one of many stations we picked up), we used to make mix tapes and loved it when that little Stereo Red indicator came on. I always said that when it comes to music, I was born in the right era , (1971) but in the wrong country.

[@davidroyer5049]

Very clear, concise discussion of FM radio and Armstrong's development of it, as well as the tragic outcome for Arnstrong. All of this was familiar material for me and I loved how you got right to the essentials.

[@chrisking4802]

Thanks for this series. The background about the people and the struggles of development of these technologies is fascinating

[@rickbartlett6419]

This was a very good video on broadcasting... I never knew the history of AM vs. FM, but in 1974 obtained an FCC 1st phone. Thanks for a great technical video.

[@peterjeffery8254]

You are an excellent educator. I love the way your passion for the subject shines through you.

[@denniswofford]

That's a nice summary of Armstrong's invention (FM radio) and the legal battles that followed. Thanks Kathy.

[@AMBER1BRANZ2]

I researched my grandfather Elman Borscht Myers and discovered that he introduced Armstrong to Marconi. It was in written in a book that I now can't find. I heard from family that Marconi stole vaccuum tubes and patents from my grandfather. Many fell victim to the rush to claim credit! Sadly great men lost fortunes and some like Armstrong died defeated. Any info you have about this meeting would be greatly appreciated

[@agostinhooliveira5781]

Wow 😯

[@jackd.ripper7613]

Excellent as usual. I wish you had more time and wherewithal to do these more often. Have you considered collaborations? Not with me, I mean someone with actual talent. 'The History Guy' here on KZbin comes to mind. Please keep going!

[@Kathy_Loves_Physics]

Jack D. Ripper I am hoping I will be back to doing one a week soon (a girl can dream). Feel like trying to collaborate would just take longer but I’ve never tried it. So glad u liked it and am soo happy to have survived radio

[@keacoq]

I think you do the videos very well. I think that with collaboration you get all those problems of 'design by commmittee'. I'd say keep going as you are, doubtless seeking input from others when you think you need it.

[@stephenpowstinger733]

I am not an engineer but I feel like I grew up during some of this epic struggle. We were stuck with AM radios until about the mid 60s when the excitement was all about FM and FM stereo. It was great. I went on to work for a two-way FM radio provider (selling mainly Motorola equipment and repeater services) before that market was destroyed by the advent of cellphones.

[@brucemccreary769]

Another very enjoyable piece of EE history, well presented. Thank you, Kathy!

[@Micetticat]

Armstrong is one of my heroes! Thanks for making this video and for also explaining his inventions in a clear and simple way! One thing that I heard from my professors when I learned about FM is that the RCA FM frequency allocations used narrower bandwidths than the ones proposed by Armstrong. That means that if we kept Armstrong original allocations we would have a higher fidelity FM radio than the one we listen to now.

[@rfvtgbzhn]

But also less FM radio stations.

[@electronicsinstructor4267]

Your videos are great! Understanding the history of how a technology came to be, helps to understand how it works. Thank You.

[@DucatiMTS1200]

Kathy - You are clever. A well measured and beautifully presented video.

[@howardkranz6679]

Hello Kathy, I'm a herretic electronic hobbyist when it comes to simple radio circuitry, TRF for pure AM radio receivers : I built a straight--forward 3 transistor set using 2 FETs and 1 bi--polar. My home--brew schematic is an FET comon--source for the first--stage, a bi--polar for the 2 nd--stage, and another FET comon--source for the 3 rd--stage. Even with a single 240 uH tuning coil and matching 365 pF varriable capacitor, its performance rivals my cheap superheterodyne store--bought radio for RF gain and selectivity ( not the best, but satisfactory for my liking ) !!! My detector--circuit is a pump--rectifier using two 1N34A germanium--diodes. You are an enjoyable fantastic lady !!! Howie from 02446

[@mrflashport]

Major Armstrong gave his life and didn't back down in the face of corruption. He wouldn't take a pay off and sell out his soul. The superhet and FM are two of the most important contributions to the world of RF, and yet many people don't know who he was. Like the Hidden Figures of the space program, Major Armstrong was left out of many history books. Sarnoff and RCA stole more than Armstrong's patents for FM, they stole his soul and his life. Major Armstrong, you will NEVER be forgotten and all of us who work with RF THANK YOU for what you gave us.

[@55mikeburns]

Well done. I'm an electrical engineer and your description is quite good while avoiding the more difficult math.

[@kfl611]

I wish she had been a teacher of mine in school, no I got stuck with teachers that put mold to sleep - boring. This was so well presented and so not boring...........Thank you for posting.

[@caesarespinosa3131]

Magnificent work Kathy, you are wonderful !! Thanks

[@Kathy_Loves_Physics]

Aww thanks

[@bobbymcgeorge]

Great video Kathy but what an incredibly tragic story, I am crying like a baby!

[@Kathy_Loves_Physics]

It’s so damn sad isn’t it? Sarnoff could be a real SOB when he wanted to.

[@ShlomoFriedman]

Kathy, you are amazing! I was a "pirate" radio ham in Israel back in the early sixties... at the age of 14. I built all my equipment from 2nd WW junk...

[@TigerBoyRS]

This series are pure gold. For any Radio or TV fan, Armstrong and Farnsworth forever will be our heros. 💫 Focusing on FM Stereo, introduced in the early 60s, turned in commercial success in the late 70s, it still is widely used in all it's glory and quality of sound, hi-fi standard (20-20K Hz). I belive the broadcast range is the only limitation of FM, when compared with AM, for a same amount of power. KZbin should really promote accessible and rigorous science videos like this. Kathy Inspires People, could also be the name of this channel. Thank you so much, please keep on the good work. Cheers from 🇵🇹

[@Ebooger]

Armstrong's original broadcast tower, in Alpine, New Jersey still stands tall and is used continuously. New York City TV transmitters were all relocated there quickly after than world trade center was destroyed in '01.

[@MarkusAudio]

You have an instant sub...just because I Love Physics and History too, and you teach it so beautifully!

[@amirnovini8386]

Kathy I am an IEEE and a ‘geek’ since childhood. I find your topics and your explanations fascinating! Thank you for all that you do!

[@Kathy_Loves_Physics]

So glad you like them

[@MikePerigo]

Great video as usual. It's a pity that the links in the description no longer work.

[@martinmalloy8119]

Thank you for another fantastic video, I have to watch 10 times to understand the genius of this man ....

[@chuckotto7021]

The clarity of your discussion is so much appreciated. Thank you.

[@Thestargazer56]

I recall reading the owner's manual for my grandparent's 1967 Dodge. It listed the radio as being an accessory (it was also the first car that I had ever ridden in that had power brakes, steering, and air conditioning). It said that they recommended AM radio, as they said the short distance range and line of sight signal made it impractical for automobiles.

[@raimondspadaro8211]

Facinating!! Can't wait to listen to all of your lectures

[@MichaelJGrant]

Colonel Armstrong invented the limiter to eliminate noise often present AM transmissions as the was no intelligence carried in amplitude variations on a FM transmission. He must have foreseen AM Talk Radio.

[@Kathy_Loves_Physics]

Ha! It took me like 10 minutes to get the joke, but when I did... hehehe.

[@echodelta9]

It's all right polarization circular modulation. Actually the limiter made FM the original digital radio as when limiting happens it is on or off hence digital mode just not PCM.

[@JoJoGunn1956]

Yeah, to have foreseen Err Amerika so far in advance....

[@edjohnson7855]

Thanks for the informative video on FM and Armstrong. I grew up in NE NJ and visited the Armstrong tower at Alpine as a youngster. I learned some of the history then. I became an electronics engineer and amateur radio operator. I worked on microwave FM radio equipment in mid 1960's through 1980's. The technical descriptions resonated well with my experience. I've watched many of your videos, enjoyable and informative.

[@pp-nk2et]

Really appreciate your videos will need more time to watch them all studied physics at private school in the UK but It was far more abstract your presentation is much more understandable.

[@wrightmf]

I remember reading a section of a textbook for college EE course about FM radio. It described how FM radio had obstacles as you mentioned, author wrote the FM broadcast band (88-108) was losing money in 1960s and there was consideration of reallocating that spectrum. PBS had a fascinating documentary about Sarnoff, Armstrong, and DeForest. It said DeForest managed to get himself labeled as inventor of tubes necessary for radio but IRE and others said Armstrong knows more and can describe principles better. Sarnoff described himself, "I don't get heartburns, I give them!" This documentary described how Sarnoff paid for Armstrong to work in static free radio system, all this was done on a floor in the Empire State building with a dedicated staff (imagine that, Silicon Valley like development in downtown NYC), when Armstrong and his team eventually demonstrated FM radio, "you can hear the difference between striking a wooden match from a paper match." I have read Armstrong was an abusive person, as a Army captain in WWI he hit a subordinate so hard it broke his jaw. Also Armstrong had zero fear of heights as in that other video of him dancing on the high tower. In WW2 Armstrong granted patent rights to the govt for them to use whatever needed for free. But then everyone knew of FM and will use it anyway. Example is the Germans utilized FM for tank radios during WW2, and FM is far better than AM for land mobile radio.

[@giovafra6158]

Magnificent! I've just finished to watch the videos from #30 to #36. A real amazing history from Edison valve until Armstrong death. Absolutely well done. Thank you, Kathy.

[@Kathy_Loves_Physics]

You are welcome- glad you liked them.

[@colvinator1611]

Kathy that video was an excellent piece of American history. I love your presentation style and easy watch graphics. Thanks a lot. They never told us about Armstrong when I was studying army radio techniques in the 70's !!

[@grizbizusa]

I love your content! And just started your book, "The Lightning Tamers." Thank you for the careful explanation in your videos.

[@Julian-tf8nj]

excellent video (and series), thanks! I'd love you to go deeper into the engineering, physics and math...

[@johnhoeper8803]

Wow , you're so good I just discovered your channel Very informative , thank you

[@daveinthailand]

Wow brilliant as a tv engineer in the UK in the 70s 80s i can now sit back and watch these fascinating facts Great presentation watching from Thailand Thank you

[@robertgloverjr]

Wish I could have watched these videos of yours way back when all they had in high school science classes to calculate was a slide rule. I would have consumed all your videos back then like popcorn at a 35 cent Saturday double feature. The only question now is how many times to watch and rewatch all your videos until everything you’ve taught is completely internalized. You have converted dull science into fascinating, exciting drama that builds a hunger for more understanding. I recall you are writing a book….hooray!!!

[@st.charlesstreet9876]

Thank You Kathy for the history of FM radio. I had no idea that Armstrong was friends with Sarnoff.🥺 Appreciate all of your posts. 🤓

[@garethonthetube]

Excellent video. I remember studying the theory of FM at university. The mathematics is truly mind-torturing!

[@kensmith5694]

It gets even worse when you add a bunch of sub-carriers. For those who don't know: There used to be these "office music" services that were carried on FM radio along with the main audio channel. The way it was done was: The music was converted from audio frequencies up to stuff you can't here. This high frequency stuff was then added to the normal audio going into the transmitter. A receiver would as a first step be a normal FM radio. The 2nd step was to pick off the frequencies above human hearing and decode that. The thing that made it a little extra mind bending was the fact that more sub carriers could be added carrying more information then at first you might think is possible with the humans listening not noticing the little bit of interaction that happened between the subcarrier programs.

[@ronjon7942]

I remember learning radio theory at an EET school and it just wasn’t registering with me. Fortunately the school pumped quite a few students through, so almost every day a different (sometimes not) instructor would have the same class lecture repeated four, sometimes five, times a day. Quite helpful to get so many different perspectives, but the guy that could make it just work with me firstly started with historical context. And it wasn’t always the originators; it could be history from any point on the contuim. It’s always a joy to take a look back and then get back to it at lightspeed so that future peoples can look back at us.

[@cmgeolo]

This is great. I had a few professors that took time to teach us the importance of the history behind great inventions and discoveries. I really appreciate this excellent video.

[@davidb7328]

Wow. Amazing story. I never knew that about Armstrong. I just discovered this channel this past week and love it!

[@edmondedwards6729]

i had an idea when i was a kid that a person could use a double detector in AM radio, a positive diode, and a negative one too. The diodes put out signals that should cancel each other out if combined, except for information (noise) that isn't in the original signal. Then a muting signal based upon an output from the differential matrix would blank our or reduce the noise in the first audio amp stage. I built something along those lines and it seemed to have some good effect, but didn't persue the matter. Later I thought the two signals could be used in a comparator circuit, and not passing anything that was not equal in both data streams, if the audio were to be digitized, thus an improved way perhaps of accomplishing at least a reduction of noise and perhaps complete elimination is the noise were below a certain level, but haven't gone any further with the idea to see if it is viable.

[@rayoflight62]

With two diodes you make a signal doubler. For AM in 2022, the true noise-killer detector is called "Syncronous detector", which use logic gates to separate the carrier from the modulation, remove the noise and replace the parts of the carrier which are missing. Widely used for commercial aircraft Comms - which use AM modulation on a VHF carrier.

[@jimlocke9320]

The National Institute of Standards and Technology (NIST) operates a radio station, WWVB, broadcasting encoded time of day information on a carrier frequency 60 kHz from Fort Collins, CO. There are probably millions of clocks and watches that receive the signal and set themselves automatically. These timepieces use an envelope detector to recover the pulse width modulated (PWM) time data. In many locations, the signal is very weak and timepieces don't recover the data. In 2012, WWVB began broadcasting time data simultaneously on the same 60 kHz carrier in a phase modulated (PM) format. The reference carrier phase was unchanged for a 0 and shifted 180° for a 1. A synchronous demodulator is used to recover the PM data. Timepieces that recover PM can operate under more adverse reception conditions (weaker signal and more noise) than those that recover just the PWM data with an envelope detector. The LaCrosse UltrAtomic clocks recover the PM data. Timepieces that recover the PWM data using envelope detectors are not made obsolete. They continue to work where reception is good enough.

[@TheHansoost]

Very interesting and informative. Thank you.

[@bacontrees]

I cover AM and FM and basic wireless in my college classes, but I will now show them this excellent presentation to discuss.

[@rbk2745]

Hey, this channel is a gift. I am learning history, electronics and english. Thank you.😃

[@gristlevonraben]

great video. Did you know that a Lee DeForest also felt that he had been the father of radio. He too had sued and won patent cases. Your videos are very fascinating!

[@Kathy_Loves_Physics]

Gristle Von Raben I have a bunch of videos about de Forest. Very interesting fellow (for example he wanted his third wife to write a book titled “I married a genius”).

[@gristlevonraben]

@@Kathy_Loves_Physics wow, hilarious. I will check them out. Have a pretty week.

[@hewitc]

De Forest was over rated. By himself.

[@quistador7]

Idk how it took me so long to find your channel but it makes me so happy 😁. I wish you were my teacher when I was in school you have an awesome ability to teach

[@tomsayen9295]

Thank you for this awesome video, Kathy. I wish you had been my teacher when I took college communications courses 50 years ago.

[@harrydelange1821]

Very nice to watch and very interesting channel. Thank you Cathy!

[@markrowland1366]

Truely, I might watch again all your work. I managed the biggest Neon shop in the southern hemisphere. My insight into the colours, observed with increasing vacuum, to explain Sprites.

[@goodun2974]

The "magic eye" tube at 8:40, used as an aid in radio tuning, was the forerunner of the cathode ray tube at at 10:55. RCA bought the patent for the magic eye tube from Dumont; if Dumont had hung onto that patent, the history of television (and oscilloscopes and radar) might be very different.

[@rennethjarrett4580]

Thanks for this info. My dad would have appreciated your history. I think he knew this about the FM radio, and maybe did try to teach some of us about it. Ironically Armstrong looks a lot like my dad,

[@pneumatic00]

Armstrong was truly a visionary genius.

[@proudsnowtiger]

And Armstrong gave the US military all the FM patents in WWII which, together with the adoption from the ham fraternity of quartz crystal controlled tuning, gave the US (and the Allies) a hugely more effective signals system. But wireless at war is such a huge topic...

[@Kathy_Loves_Physics]

proudsnowtiger yeah I had to cut out so much material to fit it under 15 min.

[@keithstudly6071]

ALL patents were taken by the military during WW2. Their was no "giving" about it. If you were making something for the War Dept. you were not subject to patent laws, either payments or royalties.

[@hewitc]

@@keithstudly6071 He was making it for the War Department. He was a boy hobbiest who continued to pursue his interst while in the military.

[@davidatrakchi2707]

What can I say, Most of my professional life was around electricity but never knew it’s sources. Interesting!

[@scharkalvin]

What's amazing is that today generating an FM signal is as simple as putting a vara-cap diode across the turned circuit of the transmitter oscillator, and feed the audio signal into that diode. (It can also be generated via DSP, something not available back then).

[@lawrencemiller3829]

Depending on what is to be made simple, creating the heart of a Software Defined Radio (SDR) FM transceiver with one chip should be possible too.

[@murraymadness4674]

Thank you so much for the video. I had not heard this story before. So typical of how nasty and criminal such businessmen operated, all for their profits.

[@petermainwaringsx]

Fifty years ago, I had to learn about all this in books and night school. I never knew the back story though. Thanks for the video.

[@paulr.3220]

As an Amateur Radio operator and lifelong radio geek, I am hooked on this channel. Kudo's Kathy.

[@RadioJonophone]

In the 1960s I messed about with silicon diodes and PNP transistor colpitts oscillators to make a simple low power FM transmitter, based around 100Mc/s. Thank you Howard Armstrong for showing the way.

[@KutWrite]

Kathy, was that Rush Limbaugh you were dumping all that static onto? I knew some of this from my studies for ham and commercial radio licenses, but you filled in some gaps. I never knew the personal side of it. Seems to parallel other stuff Sarnoff pulled.

[@jhonwask]

I enjoy watching reruns of your shows.

[@ronmercado3322]

Wonderful videos Kathy. I'm hooked!

[@jeffharrison1090]

Gee, I love this guy Armstrong! So unfortunate that we humans get so narrow minded with our ego, when there's plenty of room for all. Sarnoff's ego is a reminder to us all! As ALWAYS, your 12-15 minutes just fly by! Hadn't even finish my coffee at Starbucks b4 the podcast ended. So, I'm watching another one...lol!!!! Great job as always!

[@paulsenjohannes]

I enjoyed this particular presentation. Very informative and stimulating. Very sad as well.

[@BroadcastBlueprint]

I don’t know how I haven’t seen this video before now, but it’s fantastic!

[@saltnutzzzz]

After watching Oppenheimer, I really got back into science, especially physics. I unsubscribed from most channels and make an effort to watch some of your content every week. Thanks so much for you videos.