The Vacuum Tube and the Invention of Radio 

When I was a boy (early 1970s), my uncle (who worked for the British telephone service, the GPO, which later became British Telecom) gave me one of the best presents I've ever had. It was a kit for making my own crystal set. I put it all together and it worked just fine! I remember sitting in my room listening to radio from around the world on my headphones... and it never needed batteries, of course. Such an educational gift, and he must have put quite a bit of work into it. I'm eternally grateful for his thoughtfulness.

Y'know, there's a certain charm to this old intro... I'd like to see this make a comeback in 2020

I'm visiting from 2023 and I feel like I'm in the archive section of the museum! What a treat! So glad you've never lost this passion, TC ❤

In under 11 minutes you explained stuff I had no clue about for decades and now its all laid out there! Superb content!

This is the best and most succinct description of "tubes" I have seen, and I have been working with this stuff since 1967. Great job.

We need more people like this guy in the classrooms.

"Thermionic Valve" sounds so much cooler than "Vacuum tube"

I've been studying radio since the late 80's and have been an FCC licensed amateur (ham) radio operator for 25 years. You did a fantastic job explaining the "magic" of radio and vacuum tubes. Your video on the "superhet" was also fantastic!

Thank you for remembering one of our heroes from the Brazilian homeland, Father Roberto Landell de Moura

Listening to the local AM radio station with nothing but a metallic-diaphragm headphone speaker with a germanium diode connected across, one side going to a really long wire as the antenna and the other side grounded to the pipework used to be pretty much on par with magic. No power source needed...

No, radio isn't magic. *moments later* This thing makes sound with CRYSTALS.

Vacuum tubes are one of those phrases i have heard for years but never understood. Thanks for the work you do on these channels. They are consistently fascinating.

Vacuum tubes have always confused me. I was not REALLY sure how they worked. You provided the best, most simplistic explanation I have yet seen. AWESOME WORK and THANKS!

Thanks for this video, I have never understood the basics of how AM radio works until now, despite having a degree in physics!

Haha, he still has the same jacket. Cool lol.

I'm a ham radio operator and this is the best explanation of how vacuum tubes operate that I've ever seen. 73

Your videos are just awesome. Tehcnical enough for the layperson to gain new understanding without wading too deep into engineer speak.

If you were a teacher, or professor, the students would have a great edge in learning. YOU ARE GIFTED.

This channel deserves to be way more popular, and should probably be part of PBS digital by now! Keep up the great work!

The best explanation of radio valves I've ever heard. Just brilliant!

Thanks for recognizing Landel de Moura. That's why I follow your channel. You're great , man.

How great are these old videos in their straightforward and no-nonsense (one might even say "rushed and nervous") delivery? Loving it.

I’m just now discovering your channel and I think it’s amazing. You teach things in a very clear, humble, and humorous manner!

This is the first time i have heard anyone explaining why the diode is necessary.....without it, the average voltage will be zero. Youe explanation is excellent.

one of the best explanations of the working of a vacuum tube that have come across

Great video, I've watched a number of videos about amplifier tubes, but this one really helped me understand how they work! I still use them in my guitar amplifier (1966 Fender Deluxe) so it's nice to know how they work!

Uau, you are the fist person outside Brazil that I saw talking about Landell. You really now your facts.

your explanatory skills ROCK!

I just wanted to say, I love your channel. Keep up the great work! So interesting and your explanations are awesome!

This is the best channel on RU-vid. And, it's not even close.

You're a legend dude! As soon as I leave class and get home, I search your channel for whatever we were taught. Always super helpful!

That is the clearest explanation of how amplification works that I've ever heard. It makes perfect sense. Thanks!

This the best explanation of triode amplifier I've heard.

Perfect description. I’ve always wondered about the radio and tube relationships

Thanks for making this video! I have a couple of non-working tube radios from the 1930's and 1940's. My daughter is 4, but when she's about 7 we'll work on them together and get them working, that way she'll be able to learn how they work.

I am watching this in February 2023 and it's just as good as more modern Alex productions. It'd be great to do re-makes of these old videos, as they would be exposed to a brand new audience.

Congratulations! You're the first on YT that has made me understand the amplification bit in a tube. Even beating Mr. Carlson's Lab.

I like this new character Bill Hammack (The Engineer Guy) has created

I would love to see this video re-done. You have come a long way and today's video's are much better. Great content either way!

Nicely done. I was aware of all of the individual bits, but you've put them together into a coherent story and without getting too bogged down with implementation.

watching your old school videos about old school radio is so awesome. Glad you are still doing great content.

Great explanation as always - you make difficult concepts/science really easy to understand; keep up the good work!

I made my first crystal radio in shop class when I was 15 and when I showed it to my son in 1980 he was amazed! Yes it works and doesn't need a battery! The following year I made a transistor radio, and put it in a 3inx4inx1in plastic storage box. The biggest components were the the speaker, 9 volt battery and the channel dial, the actual radio components were tiny! My teacher told us eventually every thing would be so miniaturized that wrist radios-TVs, and miniature telephones would be possible. I wish he were alive today he would be amazed at the new tech!

Okay, that's it. You are now officially my hero because I understood your explanation of how triodes amplify signal. It was like a light bulb coming on. THANK YOU! I have subscribed and gave you thumbs up. All good wishes! P.S. Good explanation of how speakers work, too. I was pretty good on that already, but it was still helpful. -AN

Kudos for mentioning Landell de Moura. Not everyone remembers the Brazilian guy.

I keep getting these older videos reccomended. I can't complain still good content

Just discovered this channel and am diving deep into all this cool stuff. Keep up the great work! Love it

How have I watched you for years now and just now seeing this?

That example early triode is brilliant it looks like it's made out of two old broken light bulbs glued together... and if it's from De Forrest's lab, it probably IS just two old light bulbs glued together.

I've been collecting & tinkering on old radios since the 80's. I've tried but just couldn't quite understand how exactly a detector & an amplifier work...until now! Great work!

Discovered your channel recently and randomly watching your videos. Yours videos are great educational tool. Keep up the good work. 👍👍👍👍👍 Subscribed!

i think you just got 500 subs in 1 day? thats awesome. Im glad i know how Vacuum tubes works. Thanks man, keep up the good work.

I can usually follow your videos. But this one went right over my head.

there haven't been really many videos made - which is shame, i really enjoyed the way he simply explained everyday tech.

I love your expllenations man! This is so easily similated and well explained

I learned a lot from this video. Thank you for all the great work you do on these videos.

Best explanation of the vacuum tube I heard so far! Thanks.

Very nice explanation of how vaccum tubes work

0:10 When that mains hum kicked in it really got me

I wish you'd been around in the 70s when I was studying radio electronics to be a ship's Radio Officer. Brilliant explanation.

Great job dude, love your channel!

I can't believe you mentioned Landel de Moura... Pretty nice.

Thank you for your brilliant bud guests! Outstanding!

Those vacuum tubes used to work TVs also when I was a boy. You had to wait 5 minutes for the set to "warm up" before you get a proper picture.

Really good video Alec, you do a great job on your stuff! I liked the one about the Sony Playstation duplicating.

Extremely clear and helpful!

Great video..... I'm a degreed engineer, use "radio" at work as a pilot, and my hobby from the time I was a boy was radio, now an armature radio operator (ham). I restore old tube equipment, radios, test equipment.... Even though I know all of this, I found you stripped down but accurate explanation and graphics fascinating. Of course radio typically has IF ( intermediate frequency ) internally, where all signals received through the tune front end are up or down converted to a single IF frequency. This allows all the circuits to be tuned to that one frequency. There may be several IF stages (at the IF Freq 455Khz for AM radio and 10,7 Mhz for FM aradi) to boost the signal to the point an audio amplifier can reproduce audio. Consumer AM RADIO (Amplitude Modulation on the MW - Medium Wave band, or BCB - Broadcast Band) and FM RADIO (Freq Modulation on VHF - Very High Frequency) use IF stages to boost the RF (Radio Freq) signal before the Audio amplification. The history of IF or Intermediate Freq radios known as superheterodyne radios is interesting; "An intermediate frequency concept and application used in the superheterodyne radio receivers, was invented by American scientist Major Edwin Armstrong in 1918, during World War I. A member of the Signal Corps, Armstrong was building radio direction finding equipment to track German military signals..... After the war, in 1920, Armstrong sold the patent for the superheterodyne to Westinghouse, who subsequently sold it to RCA. The increased complexity of the superheterodyne circuit compared to earlier regenerative or tuned radio frequency receiver designs slowed its use, but the advantages of the intermediate frequency for selectivity and static rejection eventually won out; by 1930, most radios sold were 'superhets'." (Wiki). The short (long) answer of why this is amazing (changing or converting one Freq to another using heterodyne) is the early radios of the day (regenerative and tune radio) had to tune many stages to the desired incoming frequency. This was difficult, complicated and expensive. With a "Superhet" radio you still had a tuned circuit for the desired frequency at the "front end" of the radio, the frequency you wished to receive, but that was converted through heterodyning, By converting the desired incoming signal to one Freq regardless of the incoming signal Frequency the radio was design to amplify only one Freq the IF.... Then all stages of the radio could be the same and tuned accurately. Having more than one stage or stages by the way is a way to boost a very weak RF signal, with each stage boosting the signal more. There is only so much gain one stage can get. So by putting them in series you can boost very weak signals. Typically a cheap radio had one stage. Better radio's with more sensitivity had at least 2 or 3 stages. Some radios also had a wide RF amplifier at the front end before the tuning circuit, to boost all frequencies on that band before entering the radios tuned circuit. *This use of hetrodyne where the desired incoming signal was converted to the IF for the radio to amplify. greatly simplifying made the radio have far better in sensitivity and selectivity than any other design. This was Armstrong's invention or discivery.* The most simple tube AM radios from 1930's to early mid 1960's are called "All American Five", for the 5 tubes it had inside. The first stage is the converter which coverts the incoming signal Freq to the IF Freq. The second stage is the single IF stage which boosts the RF signal. The third stage is the detector as this video shows cuts half of the AM or amplitude modulation to get a usable Audio signal. The 4 the stage is the Audio amp to drive a loud speaker. The fifth tube was a rectifier or diode to turn AC to DC. as the radio ran on DC. The rectifier was the "pwr supply" to drive all the vacuum tubes heaters that emitted the electrons. Some high end radios had 2 or 3 IF stages and even a Pre RF amplification stage, adding 3 or 4 more tube's. Some deluxe radios by the end of the 50's and early 60's had 9 to 12 tubes. This is also when FM radio was just starting to enter the market, so it was two radios in one, an AM radio and FM radio, with the radio sharing some of the same circuits for both the AM side and FM side (amplification, power supply). However AM radio is in the 600 to 1700Khz range and FM 80-108Mhz range required their own IF tuned sections. Also the method of "detection" of AM audio is different than FM, often called demodulation or demodulator. AM and FM differences are interesting but simply put the audio sent with AM is accomplished by changing amplitude at one set frequency, and audio using FM is sent by changing frequency (at one amplitude). This is why static in the atmosphere say due to a storm affects AM radio as the static is picked up as amplitude, where FM radio ignores changes in amplitude. So FM is less (not immune) to static. However if there is RFI (radio Freq interference) at the desired frequency it can make FM radio noise. With anything operating in the FM radio band from ab 76Mhz to 108Mhz. FM radio although introduced in the 50's did not catch on. In part because there were not many FM stations and AM radio was so imbedded in the market and culture. Also an AM/FM radio was more expensive. However by the 1970's with the advent of rock stations playing full albums, FM radio took off and out stripped new AM stations, with the better audio frequency range and resistance to static over AM radio. By the 1970's transistors were now most of the consumer radio market with smaller lighter less power hungry devices. However audiophiles still use Tubes but mostly for the Audio amplification. (My be Tech Connect can do a video on difference in sound between transistors and tubes?). Ed Armstrong is one of my favorite people in Radio who also invented FM radio which as you know is static resistant. His life ended tragically partly because RCA stole is FM radio and used politics to change the FM radio band making his early radio stations and radios obsolete. He ended his own life after years of legal battles and spending huge sums to fight the massive corporation run by a true prick (David Sarnoff), but never the less Armstrong's contributions to radio with superheterodyne and FM radio's were ground breaking and long lasting with implications all through the electronics of today. However now with solid state and digital signal processing it is a different story. There are many ways to encode and decode information on an RF signal, but for the most part it has been been the superhetrodyne radios of Armsrrong that has been used since the 1930's to present day. If you have not already done it, consider doing a superhetrodyne video....

Ok, you are great, what an awesome channel! Just wanted to say that. Binge watching your videos now...

Thank you for pointing out the amazing work that professor Landell de Moura did!

Your tech kung-fu is strong! I really enjoy your videos. I used to live in Rockford IL, it's too bad I didn't find your channel before I moved north of Madison WI. I have some stuff I would have happily given you to use in your videos. I have an amazing working auto flip laser disc player with the "xenomorph" CD tray included. It is a beautiful work of end of the laserdisc era art. I also had some very classic speakers and other such stuff that I had to get rid of before moving. Anyway, thanks for the awesome vids. Keep up the amazing work my friend!!!

Thank you for such a great video. I learn so much from you!

This takes me back to university - I studied Electronics and Communications Engineering (Marine) and it’s covered Radio and Radar systems. It’s funny now but we touched on ‘mobile communications’ with cellphones and how systems were established across a city.

Thx so much for the enlightenment ! Triggered so many wonderful thoughts in my brain.

I just discovered this channel and I love it so much. I cant believe (from your other vids)I know how speakers and shit works I always assumed it was magic. You are a good person doing good things.

Great explanation and presentation.

1:50 oh my heart. It's adorable how you used to once care about silly things like "time constraints". Saying this as someone who's watched the CED videos like 4 times now.

Your explanations are great. Thanks

Hey! Love all of your videos. At least, the ones I've seen so far. Are you into ham radio at all? It'd be fun to have the radio topic revisited in one of your videos. Fun stuff!

Hey Alec nice to see some of your early work.

Is this the most underrated youtube channel?

Awesome video. This might be your best yet technical video and you got it almost exactly right. One very minor point is only relatively modern speakers have rubber surrounds. Foam surrounds, which tend to rot and fail, were popular before rubber and before that it was mostly paper pleated surrounds. You're forgiven for being too young to know such things.

I learned more about radio technology than in school here.

Wonderful explanation!

I love the old theme song! Great video

great explanation of the vacuum tube.. going to watch the vacuum tube vid now..

Thank you for sharing. Amazing video.

my man's been churning out bangers since i was a literal child lol

This video is superb. 3:47 is the eureka moment for me. I knew that diodes detect the signal but never really understood how. It stops the RF signal averaging to zero. Of course!

I miss the little intro jingle! So lovely

thanks dude! i learn a lot from you! i think its the way you present things!

As much as I love your new content, I do miss the aesthetic and dry humor of your old ones!

Nicely done!

Great explanation

I like the explanation. Thank you!!

Watching this from Ocean Bluff, Brant Rock, Marshfield, MA!!!

Very interesting channel, did you ever get to make the video on superheterodyne receivers you mention at the end of this one?

02:58 A.M is used beyond those frequencies. AM is also used on pretty much all amateur bands, and also on air traffic control on VHF. Early TV also used AM on both VHF and UHF.

Look at how young you were! So young. So carefree.

wow this was recomended to me today July 2022, never ventured into old TC videos

Hi, I enjoy many of your videos. Where did you get that Koi lamp? It looks really cool.