The Superheterodyne Radio: No really, that's its name
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- čas přidán 24. 12. 2018
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The superheterodyne receiver may seem like a radio with a silly name, but in fact it’s a completely logical name that describes the key action these radios take to become excellent radios. The superhet solved a tricky problem in a clever way, and using our friend Algebra (as well as wave phenomena) proved to be the most effective way of tuning in a radio signal.
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that internet pun was so painful, it hertz
Lowen You won the internet. Congrats.
*inhales* "BOI!"
Please, don't hurt me more, take my money.
I trust you will find the door on your own.
maybe it's a hert
I didn't know that Capacitors were called Condensers in the past. They're still called "Kondensator" in German.
Anton1699 same in polish :)
And in finnish
"Condenser (コンデンサー)" also stuck in Japanese. It's like "capacitor" is the odd one out.
There's still the condenser microphone.
And my axe!
7:09 I love how those old engineers put ball bearings in there, they wanted the radio to last forever. Not like now they don't even put bearings in the wheels of some kids' bikes.
I think it has more to do with alignment and smoothness of operation, than longevity.
@@EddSjo You are being a contrarian for no reason at all. Gabriel is right. Smooth operation leads to longevity.
@@vulekv93 you’re so cool and smart
The dial drive cords on some of these radios were a work of art in their own right. As a pre-teenager I was fixing broken cords for faintly and friends.
Why do I bother with comments replies?
It's always the same pattern.
It's amazing how complicated "simple" things like a radio really are.
Understatement of the century, especially when you actually work on them
The wonderful world without, or before, the silicon microchip. The most mundane things become incredibly complex.
@@buckrodgers1162 You're joking right? 4 active components in this radio.
@@hansjanssen3364,
Your trolling right? Or maybe you just didn't watch the vid at all.
@@buckrodgers1162 I replied your comment where you indicate things were more complex before the microchip. They weren't.
In 1980 when I was in high school, transistor radios were all the thing. One day at lunch when we were all outside, I was playing my transistor radio on an Atlanta rock station 96.1FM someone else standing near by was playing a country radio station at 106.7FM on their handheld FM radio. We wanted to compare radios to see which handheld FM Radio was better. We first wanted to see which radio would play the loudest. So my friend turned up the volume all the way playing a country song and I did the same with a rock song. We brought the two radios together to see if one could be heard over the other.
To our amazement, my friends radio quit playing the country station and started playing the rock station. Other kids standing around started laughing. I was wondering what was going on. He moved his transistor radio away from mine and it started playing the country station again. We were all dumbfounded...??? There was another kid playing a pop station at the time at 92.9FM and the country station and pop station played together. We put the rock station 96.1FM together with the pop station 92.9 and got the same results as each radio continued to play the perspective stations. We put the Rock station 96.1 together again with the country station 106.7 and the radio playing the country station started playing the rock station.
We never really did compare the radios, but we did know that Rock music would beat out country music every time. I later in life learned that the effect was known as Super heterodyning. I repeated the experiments years later with two totally different radios and got the same effect. I thought it the strangest thing.
Looks like one radio was leaking an awful lot of EMI on the intermediate frequency, and the second radio was picking it up.
I spent time listening to something similar, including listening to WKLS, but also spent a lot of time on 88.1 WRAS and once in a while that weird Tech station. And man, that Clark College WCLK 91.9 jazz, man oh man. I hated Atlanta for its snobs, but musically, it was one of the finest, I'm convinced. BTW I started with AM 79 WQXI "Quixie" on the handlebars of my bicycle, back in Beatles time. One of the DJs there inspired the creation of "WKRP in Cincinnati".
@@Bill_Woo I started in 1976 with WSB AM750 listening to {Something} theater on Saturday nights starting at 8pm and ran commercial free till 10 pm. I wish I could remember the name of the program. It was the only AM station that broadcast after dark. My mom also would say that I had to go to bed when the station signed off the airwaves at 10pm. When I made it to high school I changed to WKLS when all the cool kids in the school was listing to Z93.
@@nathanwoodruff9422 WSB and some other powerful stations were called "clear channel stations" (not just a current cute marketing name as it's used now) and they didn't power down after sunset, so you could have an adventure at night picking up stations like WWL in New Orleans or WLS in Chicago (who was top 40, which was fine since music was totally excellent back then). When Atlanta traded away my absolute hero Joe Torre to Saint Louis, I listened to their clear channel KMOX in the dark in my bedroom. Yes, I too remember other stations rather dropping out after sunset, and pretty much everybody switched to WSB every night as that happened.
@@Bill_Woo I would spend summers in Pensacola Florida at my grand parents house and would still listen to WSB in Atlanta after dark there in Pensacola. My grandfather was a radio operator for a NAVY ship and was big into HAM radio after he retired. He had this huge 5/8th wave antenna running the span of the roof and if I connected the AM radio antenna to it, some nights I could listen to an AM station in New York. I believe my grand father said that I could only pick it up if the moon was in the right position. I never knew if that was correct or not, but it was only one or two nights a month I could tune it in out of the two months that I was there during the summer.
You are seriously my favorite account on CZcams. Not afraid to dive into the real technology left behind by our shiny gadgets of today. And you are really true to yourself and what motivates you! Thank you so much for your videos, even on Christmas! Happy Holidays.
Technology Connections is one of the best channels on CZcams.
Gadgets of today are also real technology
Hey now, I never said today’s tech wasn’t real either. I just said this was left behind.
Actually the Super Hetrodyne design is still in extremely wide spread use for radio based technologies. There is a good chance that both your cell phone and PC (if it has WiFi) are probably using them right now whether you realize it or not.
Good point. Crusty old tube amplifiers make the best sound, don't advertise that too much. Then we will have a hard time finding these old (underrated) amps. Most people have no idea how much base an old low wattage tube amp can make.
BTW I love all technology and without the knowledge of the old stuff we would be lost.
Listening to the interference between waveforms is something I was trained to do as a musician. If you’re playing in a band or orchestra, it’s really important to be able to hear that “wobble” of interfering wave forms because it means that someone is playing out of tune. The explanation given in your video is MUCH better than the explanation I was given when I was first learning how to tune my instrument. Great video!
That's interesting! Is orchestral music written to eliminate interference between the frequencies of instruments?
@@rpbajb Yes! Basically any Western/commercial music you hear (outside of experimental/esoteric genres) is written this way. Math is essentially the foundation of music theory.
The notes in a scale are based on 'pleasant' sounding frequency ratios that basically repeat each time you hit the same note above/below what you start with. This is a bit reductive, but to our ears, good music sounds like a well-reduced fraction.
With composition, it's about managing these frequencies and multiples and understanding how any 'interference' might potentially color the harmony/overall song.
When you're composing you aren't actually thinking about frequencies or math though. That was all worked out back in a 16/1700s. Rather you rely on a language of abstraction and consider things like scales, keys, intervals, modes and all the techniques that have been developed over the centuries working with those tools. But there's well-defined math at the core of all of those.
@@barcodenosebleed5485 That's very interesting, thanks for your time in explaining it so well. I love music but I know nothing about it technically. I fooled around with guitar in my youth, but never got serious about it. I'm fairly good at math (up to derivatives and integrals) but musical notation remains a foreign language to me.
I was shocked once while attending "Music 101" at Heinz Concert Hall, when the guest violinist showed the audience that her instrument had no frets! The level of dedication and the amount of practice to play professionally must truly be astounding.
As a dude with no background in engineering, your videos are a really good insight on how tech evolved over time. This is seriously good content.
To be honest, it is also the same for engineers
1:51 "ok, how does that help?" My response to everything I've looked at while trying to learn the dark arts of RF wizardry.
Radios, how do they radio?
us -> wizardry and bullshit -> them
Indeed, anything RF is some voodoo magic shit, I have no idea how it works but it works.
@@GoldSrc_
Not really, all AM stuff (modulation, demodulation, etc) can be done through simple trigonometric identities
I am a superheterodyne.
@@matthewpalmer9820
As long as you are not a Heterodyne descendant, we will have no problems.
Heterodyne RF oscillators are also how a theremin works, too - one is at a fixed frequency and the other is varied by the position of the player's hand, and the resulting beat frequency is a tone in audio range.
I built a theremin from a kit in high school, and was floored when I realized half-way through that the darn thing was pretty much just a messed-up AM radio.
There are theremin kits?! Time to pay Google a visit!
@@mrb692 The one I made was the Paia Theremax - that was 20 years ago but it looks like it's still available!
Ironically, the machine was actually designed as a research into capacitive proximity sensors, not radio. And guess what our smart phone touch screens are today? Essentially they're tiny Theremins pointing along both of the screen's axes.
"Theremins that don't play music"
rjhelms Do keyboards work the same way?
I am a Polytechnic student and watched this video WAY before I got this topic on book. When I finally got it on book, I faintly remembered this video and rewatched it. This video is so much more comprehensive than the book! I have found more comprehensive explanation from yours two channal than I got from my books. Things like Heat pumps, Radio stuff, TV Things , CRT, Imaging technique, EV and so much more. Please keep making these videos. For your casual viewers (like me) and also for engineering students(also like me).
Thanks!
The outtakes at the end are a real education in how difficult it is to speak clearly and accurately into a microphone. Makes me feel better whenever I stumble over my words.
Safety precaution: This is an AA5 radio without a power transformer, therefore No isolation from the AC line. Also, originally it would have been fit with an unpolarized power cord meaning that depending on which way the plug is inserted into the wall outlet there is a 50/50 chance of having the chassis at or close to HOT power line potential. For safety power cord SB replaced with polarized line cord making sure to wire it correctly if not already done. Any capacitor from line cord to chassis SB replaced with XYZ safety cap of same value. Getting a knob for the on-off volume control is a must, even if it doesn't match, touching that bare shaft is an extreme shock hazzard. That is a nice radio and worth a good cleanup and restoration. Just my two cents hoping to keep you safe.
Wow, I'm amazed it's legal to plug into the grid at this point.
Hehe the bare aluminium shaft issue, of the ON-OFF/Volume pot... Some old knobs have metal and also the holding screw (in-)visible and keep shock-joking around ;)
50’s standards lol
Hopefully he plugs everything into a gfic outlet
Daniel, even with a polarized plug, you pay still get a hot chassis if lester put the wires on the wrong terminals in the outlet. White to silver ( big slot), black to gold ( small slot) , but black is ground in the radio go figure..
It's a result of designing receivers as inexpensively as possible. They eliminated the power transformer and used a half-wave rectifier tube with a sufficient filter capacitor (Or two usually in combined in one unit.) You get 160 volts DC that way, sufficient for vacuum tubes. Going to a permanent magnet speaker also eliminated some copper windings. The "Five tube American" became a standard design for nearly all small units. But the chassis was directly connected to one lead the 120 volt power cord!
The superhet today has been partly replaced by direct conversion, iroinically what we used to have before the superhet.
The advances in digital technology means modern radios used for mobile phones/wifi etc.. convert directly to baseband without any intermediate frequency and use DSP techniques to provide the selectivity.
Direct conversion has shortcomings but in the digital domain they can be tolerated as data can always be re-sent and forward error correction exists too.
Some manufacturers such as Ubiquiti in the states have overcome the problems with direct conversion radio chips by adding a superhet stage that acts as a tracking filter. This converts to an I.F. then filters there then converts it back to the original frequency albeit now with just the channel needed present. Easy enough to do as you only need the one injection oscillator to convert down and back up again. They call it AirPrism which is a nod to the early Intersil prism radio chipsets that used superhet techniques as standard.
Back in the AM radio days a 455khz I.F. was fine as the image was always out of band, however later they added double conversion. a common frequency for this was 10.7 MHz . this placed the image 21.4 MHz away and meant the entire shortwave band could be tuned from a single radio.
they used double conversion so they could do most of their gain and selectivity at 455khz and have less stringent filtering at 10.7MHz.
Even when broadcast FM radios came out the first I.F. was 10.7MHz , hence the band was usually 88 to 108 MHz, a 20MHz span , meaning the 21.4MHz image was again out of band at either end (depending if they mixed high or low).
Later of course as the spectrum got more crowded and higher frequencies were used they had to increase this I.F. further and 21.4 MHz became popular then 45 MHz and even 90MHz as the technology, mainly in Crystal/ceramic filters improved and so did the high frequency performance of active components.
Later still the early WiFi chipsets used SAW (surface acoustic wave) filters that were smaller and cheaper to make than crystal ones and operated in the hundreds of MHZ range.
Now we are back at square one, using direct conversion because the technology we have allows it .. Full circle :)
live one day as an even moderately attractive woman and I think you'll find superhets are alive and well
(I kid, I kid)
Just to add in a bit... some of the early superhets used other IF frequencies before 455kc became standard. I've seen sets with an IF as low as 155kc.
I do not get the joke. Someone explain to the slow kid?
@@nickwallette6201 if this is about my comment, superhet - extremely heterosexual (and not shy about it)
I'd say what we used before superhet was not direct conversion but DIRECT AMPLIFICATION. The only application for direct conversion was morse code receiving, where frequency difference between local oscillator and signal itself defined the pitch of 'beeps'. To receive sound using direct amplification, phased-locked loop is needed badly. Not a thing you'd meet in tube designs :)
6:38 fun fact, capacitors are called "kondensator" in Polish. I often mix those terms and get "condensator" in English and "kapacytor" in Polish
We use both "kondansatör" and "kapasitör" in Turkish too
In german it's called "Kondensator" as well.
The hair, the jacket, the voice, the wit... The more I watch this chsnnel, the more i love this guy. It doesn't hurt that his content is interesting, extremely well-researched and always clearly and rigorously explained.
So my grandfather, who was a NASA engineer in the 1960s during the Apollo program, sent me a book back in 1988, when I was about to graduate high school and go to college, where I planned to major in electrical engineering. This book had been written in the late 1940s, before the advent of transistors, and it explained many different radio and amplifier circuits, beginning with the simplest "crystal" radio sets and ending with the superheterodyne FM receiver -- all done with vacuum tubes, of course. And no stereo, of course - that hadn't been invented yet. It was a fantastic book that taught me a great deal -- but it was *so complicated.* It had clearly been written by an engineer, for engineering students (which I wasn't quite yet at the time.) I wish there'd been videos like this one back then to help with my understanding... Kids these days have it so easy. ;-)
Was it the Radio Designer's Handbook by F. Langford-Smith? I'm sure there are several books like that, but this one came to mind. It's absolutely filled to the brim with technical discussions and formulas. I bought it for the chapters on audio circuits, and even though it only covers vacuum tubes, most of the concepts also apply to solid state.
@@therm0tt0 Yes, I believe that is it! I could not remember the name or the author, and, although I still have the book, it's in an off-site storage unit, so I didn't have the ability to simply go to my bookshelves and look.
I'm ashamed to admit it took me about ten seconds for the penny to drop on the 404 joke... ;)
I only just got it from your comment.. :(
@@ChrisGozzardThatPhysicsGuy Me too... Seems like I'm not geek enough :)
As a youngster, I explored ( took apart ) many old radios obtained from various sources. I never had a clue how all that worked. Yours is the first real explanation I ever heard. Thanks for sharing.
I'm really blown away by what a brilliant idea the whole superheterodyne thing is. You did an excellent job presenting it, not to mention figuring it out and how to demonstrate it.
Also, your attention to details like mouth noises and such helps make yours an easy channel to watch.
I love your old "cringetastic" videos, though! They're what got me subscribed to you in the first place.
I came here to say the same thing!
Same same.
I love em too, but they also nicely demonstrate how much Alex's skills as a host have grown.
@@dcurry7287 Don't want to mess with you, but his name is "Alec", not "Alex". Yes, he is greater now than the early ones.
Great video as usual!
If you wanna get REALLY nestolgic there were promotional radios usually distributed by contest or lottery that lacked a superhet as they were tuned fixed to the station. They were usually powered with two batteries and considered fairly disposable.
The issue with filtering variable frequencies is that the bandwidth of an L-C filter (the simplest kind, and what old radio sets used) is proportional to its resonant frequency. The AM broadcast band traditionally ran from 540 to 1600 kHz - that's about a factor of three. So the selectivity of a pre-superhet set varied by a factor of three: at the low end of the band, audio quality suffered because the high frequencies (which in AM are further from the center of the signal) got cut out. At the high end, selectivity suffered and the set would tend to pick up multiple stations at once. That was the main problem the superhet solved: the selectivity of the set no longer depends on the frequency being tuned.
The fact that every superhet receiver is also a weak transmitter was (and probably still is) used by the British to detect unlicensed TV sets. (Yes,*receivers* are licensed in the UK; the license fees are how the BBC is funded.)
Yes, that's the word that was missing. It's not just about improving how sensitive a radio is, it's about improving how selective it is. TRF (Tuned Radio Frequency) radios had a wide passband so would pick up the intended transmission along with lots of noise and potentially other nearby transmissions too.
Actually, the BBC licence service probably never did. However the Nazi's did during WW2, giving rise to the use of "trench radios" which were basic crystal (and therefore not heterodyne) radio set.
As he stated he stated SDR does not need to use heterodyne techniques as we can do it all in digital using a FFT after sampling (for receive) allowing very broad bandwidth SDRs.
It should also be noted, that changing to the local oscillator to the right frequency to mix that would give the intermediate frequency is based on one of those old L-C filters itself. The tuning part didn't change much, we just started adjusting to other component out of those that work together to set the frequency.
@@EwanMarshall TV detection is a real thing: en.wikipedia.org/wiki/TV_detector_van
Yes, the IF is an L-C filter, but it's fixed frequency, so the bandwidth stays the same regardless of where in the band the set is tuned.
With a normal FM radio, I can detect the LO signal of another FM radio one or two meters away. With my $10 RTLSDR I can detect the signal 10-15m away through several walls. By recording signals for several minutes, it may be possible to detect LO signals from hundred meters away, buried well below the noise floor. Now the "problem" is that modern receivers are heavily shielded thus the LO leakage is insanely low (a few nanowatts)
Oi m8! U go' a loicense fer tha' TV set?
When I was young and had all ratty furniture, I had an amplifier/receiver missing the lid. For fun I wrapped part of the loop FM antenna around the antenna coil core. My friend who knows even more about electronics than I was visiting and scoffed, "What do you call that?" I replied, "That's Super-DUPER-heterodyne!"
5 minutes into one of my 4th year classes the prof said superheterodyne as if we knew what that meant. Thank you for teaching me lmao
Your puns could be considered a crime against humanity. I love you so much
I would like to add a correction, or rather an improvement to your explanation. Around 5:10, you said former filters were not very precise. Precision in filters is given by the Q factor (blablabla you can search for it). Now, Q = (Frequency / Bandwidth). As the frequency the filter is tuned to increases, so does que the bandwidth it lets pass through. The real problem with this tuning filter is that you cannot have the same bandwidth throughout the whole spectrum, so you would have higher frequency stations having their signals mixed up under the bigger bandwidth of the filter.
So yes, you are partially correct, they were not very precise, but it might would be better to say that their precision varied with the frequency.
I love your channel, you seem to be so passionate about older technology! People were really clever back in the analog days. None of that microcontroller gibberish!
It's a little more complicated than that. For perfect sound reproduction we'd like to have rectangular filter, that is, it passes without any loss at nominal frequency, plus-minus 20 kHz let's say, and rejects everything else. To achieve this kind of response with resistors, capacitors and inductors, several L-C filters are needed with slightly different resonant frequency. And yes, this thing is extremely difficult to tune to arbitrary frequency!
I think a bigger issue is that selective filters require a multi-pole topology with different parts that would all need to be tuned to the desired frequency. One could produce a brilliantly selective radio for the 0.5-1.6MHz band using a four-pole passive LC filter if one didn't mind having to set four separate tuning knobs, and not getting any good indications of what one was doing unless or until all of them were set near the right position. Using a superheterodyne receiver makes it possible to have a multi-pole filter which is calibrated at the factory and won't need to be changed after that.
Precision is not the correct word to use. The RF filter combined with the antenna is precise when you consider the center of the band that it is passing, you want that to be maximized since you haven't amplified it yet. Therefore you can't make it too narrow a bandpass, cause that would reduce the signal strength. The IF filter can be very narrow since it's already been amplified, so the bandpass is the important character, and not a maximized signal strength.
Is that why the tuning dial on radios like this tend to be nonlinear? If you look at this one, 500-600 is about the same dial distance as 1200-1600. I’ve seen linear tuners in things like hi-fi components, but having the higher frequencies crammed together seems more common.
@@flatfingertuning727 You didn't see William W. Campbell-Shepherd IX's message to you, maybe you can reply and he can miss your reply too :)
What a fantastic explanation. I restore Philco radios, nice to see one on display!
I only wish I had the resources to support you, the History Guy, Dr. Mark Felton, and Drachinfel! You all do outstanding work!
SAT TV is almost impossible without this method. There are basically three very high frequencies that can enter and pass through the atmosphere without being dampened. Those frequencies are far too high for copper wiring to be passed to your living room without serious losses. First generation dishes had to be 30ft in diameter or more to get enough signal to the receiver or the receiver had to be real close to the dish.
The LNB in the focal point of the dish mixes down the incoming frequency so a common coaxial cable can handle the signal.
Though one has to say that coaxial cable is still stressed quite a bit to push that signal. It can get warm and bundled even melt the insulation together. Not fun to deal with in large buildings with lots of those running through the ducts. Most modern installs now transmit the last hundred feet via ethernet which also adds the benefit of wifi tv and recording straight to disk on a nas. Those boxes are expensive though so you only really find them in hotels and multiunit buildings.
In those early days of satellite t.v. the frequency was ...in the KU band, and the broadcast power was limited by the FCC to 5 watts. This was to limit interference with Ma Bell telecomucations on the ground. Since the orbital satellite was limited to 5 watts, a large surface area receiving dish on the ground was a must! In later years the frecuency was changed on the satellites as we entered the digital age. They were allowed to broadcast more power, requiring a much smaller ground receiving dish.
No, it is impossible without down mixing. C-Band (2.4GHz) and Ku band (11.7GHz) can only be routed through "waveguides" which are not wires, they are hollow metal cavities that allow the raw GHz signal from the dish to reach the LNB, which is only inches away from the dish focal point. At that point, mix 1 occurs, leading to an IF frequency of 950MHz-1450MHz, at least in North America. That is routable over RG-6 cable from the dish LNB to the satellite receiver inside a home. That cable run can be 40 feet or longer. The satellite receiver does another down mix in frequency to an intermediate frequency that is manageable for IF filter selectivity, and amplification. Given the extremely weak satellite transponders, at least in the early days of C band, some were only 10W, it is amazing this works at all. Even with a 10 ft C/Ku dish, observing a 10W radio source 22000 miles away and getting a viewable signal is quite remarkable.
About dampening: Ku band frequencies are affected by rain, so called "rain fade". This is why image quality is lower/lost during heavy rain storms, even for Dish Network. C band is immune to this phenomena.
As you can imagine, I'm a serious Satellite TV hobbyist. I've got 2 C-Band 10ft , one 3ft Ku and one 18 inch Ku dishes, all in operating condition. I got into the hobby in 1994, which was well before the "digital transition". There was lots of very interesting things to watch then. There still are, but it is much harder to even find satellites, as nearly everything is digital. I think ARTS and C-SPAN are the only two remaining analog NTSC signals up on C band to this day.
You could get coax fancy enough for Ku band, but the price is quite unfunny;) Using 950-MHz-1450MHz IF allows to use typical dirt-cheap 75 ohm TV/cable grade coax and F connectors, also one could in some cases avoid getting any new cable in existing installation (using diplexer to combine signal from OTA antenna & dish LNB and then splitter at the other end).
@@shana_dmr Possibly so. However, the consumer satellite market is competing with cable, today. 80s-90s C-Band hobbyists were mostly considered Pirates, except for the 2-3 million satellite subscribers to premium channels. Remember Videocipher / Videocipher II / II+ RS? Back to your topic. As the existing consumer satellite market is exclusively Ku band today, competing with cable, Internet streaming services, anything they can do to keep costs down, they will. Using an IF signal over 5 cents, or less, per foot RG-6 cable is part of that calculation. It has been ever since the C band market was barely a C band market, and before LNAs were replaced with LNBs.
For those of you who had never heard of "beat" in that sense before, here's a fun fact: Deliberately causing beats similar to the first demonstration is what produces the "wub wub wub" sounds in dubstep.
Thats not what that is 🤦♂️
I just found your video. Very well done! I'm into collecting and restoring antique radios as a hobby, and I never understood what a "local oscillator" meant. It didn't make any sense to me why a radio needed its own oscillator. I just assumed that the tuning capacitor simply put the circuit into resonance with whatever frequency you wanted to tune to, and so it would selectively pick up only that particular frequency. I had no idea that it was kind of a 2 step process like this. Very interesting!
The type of radio you describe did actually exist before superhets came into existence. They're called tuned radio frequency (TRF) radios. They were highly sensitive and could really pull in weak, distant stations, but they were poor at rejecting adjacent stations close in frequency, which is where the superhet excels. Some superhets had an extra, radio frequency (RF) amplifier ahead of the converter to improve sensitivity, especially car radios and nice, expensive consoles.
I just love geeking out by watching you! So good and you are so unapologetic about how you enjoy your work. Bravo! Love your channel, man!
i can’t tell you how much i appreciate the care, attention and humour that goes into your subtitles. thank you!
You did a better job with this subject than most of the HAM Radio training books and videos I've ever seen. Well done! -W8SDF
I love your videos! So informative, you mix tech, history and humour and it’s just awesome!
That was a great video, thanks. I've tried reading about heterodyne receivers (via radar detectors on Wikipedia) before but it never quite clicked for me. Now it all (mostly) makes sense!
Love your videos. I've been into electronics since I was 10 (I'm 56 now), I have been into computers for over 25 years and have been an Amateur Radio Operator for almost 30 years. I'm not afraid to admit that your videos teach me things I didn't know or even thought about. I think the very first video of yours that I watched was the one of the original PlayStation copy protection. I have a feeling that if we were to have a face to face conversation, we could talk all day, or at least I could, but I'm sure I might do more listening than talking. LOL Merry Christmas.
Another ham!
Nice, another ham!
@@theencube5379 74 from CT9ABQ -M0IVC
73 de AE7EC
Terry C. What’s your call? W7ZAR 73’s from WA I’m good on QRZ
I first heard the term "superheterodyne" in radar detector design. They made it sound like the latest thing and not a holdover from the early days of radio!
This was one of my favorite of your videos. I found it really interesting.
I LOVE tubes and I love watching your videos on them even though I already know most of this stuff. Great presentation, I have used your videos to explain radio concepts several times now
Thanks for giving me the term "beat frequency". I tune my bass by that, listening for the "waver" in the harmonic tones (octave), and adjusting 'til it goes away, leaving a clean unwavering octave. Now i know what to call what I'm listening for.
You're really good at this. I'm so glad you've decided to keep it up.
So, honestly, I find all of your videos to be great and top-notch, but this one was absolutely amazing. I'd admittedly never really considered how a radio could receive a specific frequency through all the noise out there, but this was a jaw-dropping realization. Kudos, buddy!
Okay the amount of joy that I just experienced from hitting play on this video I've never seen before from CZcams because I've never been actively thinking and mulling over in my head a title and then finished the mulling just when I hit play and then you seamlessly pick up the conversation that was going on in my head and steered in a new direction. It was perfect. OMG
This is the best channel on CZcams! It's detailed, but with fun things as well. Thank you so much, Alec!
Absolutely love your videos! I'm really excited about teletext and the vinyl video discs in particular. Merry Christmas and happy holidays, keep it up!
Thanks for that explanation, I really enjoy the amount of detail you include in all of your videos.
Great, simple explanation for this concept. Anyone can give a difficult to understand explanation of a complex problem, to simplify it and making it more easily understood is a true talent.
That is probably the best explanation of a superhet radio that I have ever heard! I built a 10 tube superhet when I was a teen in the mid sixties. I used parts that I had, built it on a Philco tv rf chassis. It sounded great, but I never worked out the tracking so I kept it tuned mainly on one station. :)
You need mixing, NOT just interference. If you measure the beat frequency from two good speakers with a good microphone and then look at the spectrum, you will find no actual spectral line at the desired frequency, because the signals were added in a linear way. You need a nonlinear element to create mixing products.
Yup, it is the multiplication of LO and the RF (not addition) that is performed by the mixer to produce IF
Good points.
@@TechnologyConnections
Excellent video
@@TeslaLegend Actually, the mixer produces the sum and the difference of the desired signal and the local oscillator signal - not their product.
@@russbellew6378
The mixer multiplies LO and RF waveform, the product of the waveforms will result in difference and sum of the frequencies as in:
cos(a)*cos(b)=0.5(cos(a+b)+cos(a-b))
Another great video. You are one of the hallmarks of the internet age of content. Thank you for what your doing. We have a group of friends that meet up and watch your videos together and discuss/argue with each other as we watch. Your show is worth it’s weight in gold. Good on you.
WOW!! You're channel is so informative and entertaining. Thanks for posting!
It's obvious from what we see and the tone of your voice, you are on a very personal journey, thank you for allowing us to look over your shoulder and enjoy the experience!
7:15 the tuning knob rotates on a ball bearing. wow.
I was thought tube theory in Vocational school in the late 70's and we built a "5-tube AC/DC Superheterodyne Radio" in class. This approach was excellent to understanding the fundamentals of electronics.
Great explanation and presentation! I learned that in school in 1980 and currently work with air navigation aids which use the BFO principle. Nicely done!
By the way I love that you're covering radio topics. Please stick with that! I would love to see your explanation of single sideband or FM vs AM etc
Great videos, keep 'em coming. Merry Christmas! If you multiply 2 frequencies you get sum and difference of the 2 frequencies, i learned that when I tried to write a software modem... and used it again when I wrote a software RDS decoder. The Goldwave audio editor has an expression evaluator which makes testing and seeing these effects quite easy too.
This is a great channel. Truly. It's funny, informative, and insightful. Thank you for making these videos.
Really enjoyed this. Doing my intermediate amateur radio course at the moment and the practical examples here (e.g. beat frequency) were really helpful.
Great video, I'm a huge fan of your content!! Thanks for sharing your knowledge with us!
Now go take an advanced HAM exam and you'll be licensed this is basically as harsh as the material gets
You do have to study for it though. If your knowledge of electronics can fit inside a matchbox, there's some stuff you have to pick up on.
Thanks so much for the videos. You spend alot of time on them and we highly appreciate that. Keep up the good work
This is the very best explanation of how a receiver works that I have ever run across. Thanks for your hard work and research. I remember having problems with harmonic signals or signals that would ride in with the one that you are tuned to. Back in the days of yor, some people would use single side band modulation and most of us could not understand the garble but we learned that adding a AM carrier to the SSB carrier would make it readable without owning a special SSB reciever.
The hi frequency tones set off my tinnitus! ❤ your videos!
deserved
Thank you, you explained something about how radios work that has always mystified me. Also I lol'd at your 404 joke. When 4:04 rolls around I often think "time not found"
Scheduling ability not found (April 4th)
One interesting fact I think a lot of people don't know is that there is a whole system for these numbers; anything starting with 4 (404=not found, 403=forbidden, etc.) is a user-error, anything starting with 5 is a website error, anything starting with 3 is a redirect, anything starting with 2 is success, etc.
WOW. I have wanted to know about exactly this topic for many years.
A truly fascinating and informative video. Best I have ever seen on this channel .
I love seeing clever solutions like that. Seems so simple in hindsight but definitely took some clever thinking to come up with I'm sure.
This is how sound cancelling technology works, if I'm not mistaken.
Edit: I love the flubs at the end. Sometimes it hertz to talk.
We must credit the genius inventor of superheterodyne Edwin Armstrong who also invented FM radio.
The greatest genius of the 20th century!!!!!!!!!!
@@ralphburns6659 And RCA killed this man.
@@vaclavcepelak4276 They certainly did. And that is why there was no channel one on analog TV in the USA. It was supposed to be the FM band. The whole Dolby system is just a ripoff of Armstrong's FM noise reduction system of high frequency pre-emphasis and de-emphasis.
@@vinquinn Oh, a discriminator, are you?
@@vaclavcepelak4276 But his widow got revenge. She took them to court and won ALL of his patent infringement suits.
Such a clear discussing of radio tuning. I’ve never been able to get my head around it before. Thanks 👍
It constantly blows me away what engineers in the past were able to accomplish with their circuit designs. Like who just comes up with a way to do things like this? Truly geniuses.
I’d love a video of you discussing AM Stereo!
Mr Carlson's Lab (channel) has a ton of videos on these old radios, how they work and how to restore them. Worth checking out. :)
I just found this video because I found that radio at an estate sale and picked it up. I've been searching for videos/tutorials on how to convert it to a internet streamer with a raspberry pi. I was already subscribed to your channel previously and I loved being able to see how my radio would have worked ~80 years ago! Thanks for your work!
Seriously, the best explanation of the SuperHet I've seen. Got here from a link dropped on QRZ. Well done.
The capacitor in the (breaker points) ignition system of an internal combustion engine is still called a condenser, at least it is in the US.
Why is there a Nut Glued to the speaker paper? If I may ask
What a fine question! The speaker cone was torn in a transit accident, and while I was able to repair it with a special adhesive, it has buzzed really badly ever since. When the chassis is in the case, the front of the case presses against that nut which eliminates the buzz. It actually ended up improving the sound markedly!
@@TechnologyConnections My grandfather used that old trick! He had a cheap set of speakers with paper cones, and if they ruptured then he would just hot glue them back together. He used the same nut trick to reduce the buzzing, however the sound probably didn't come out as good since the hot glue created an unevenness in the cone.
@@boxman139 plus, the pressure will impact the drivers' ability to move freely, which, from my experience, makes it sound worse. But thats entirely subjective
I didn't originally notice this, and went back to look for a hazelnut
@@TechnologyConnections Sounds like the surround may have come unglued, it's not an uncommon sight even when the speaker has not been involved in any accidents. Something worth checking in any case.
I recently bought a 1930's philco radio like yours, and now I understand how it works . Thank you!
Your outtakes are priceless.
The internet needs these type of technology channels.
There are many in depth technical channels for we technicians, this channel helps the non techs to understand technology.
Hope that made sense.
Minor detail regarding the mathematics, but your explanation on 'mixing' isn't entirely correct. Mixing two HF signals together means the two signals are in fact mutiplied together, not added: The mixer tube has an amplification circuit that can amplify (multiply) one signal with the input of another, it is a VCA. By multiplying two signals which have a sine waveform, you will produce a pair of signals which are either the sum or the difference of the 'carrier' (local oscillator) and the modulator (the radio front-end). There's some math involved which is fairly easy to look up, but that's the principle on which both AM modulators ánd superhet receivers work -- which also meant making a *trans*ceiver out of a superhet radio was very straight-forward.
Heterodyning works best when the signals are perfectly in phase, which renders the highest signal strength, so the invention of the phase-locked loop catapulted the technology into the 21st century, paving the way for television and digital telecommunications, with the basic principle still being used on modern tech like WiFi and 5G today.
Yes, mixing means multiplication. In analog receivers such as the vacuum tube type shown, multiplication of the two signals is performed by adding the signals on a nonlinear transfer curve. That nonlinearity is the key feature of the mixing stage. Any nonlinear curve means that a portion of the input signals are multiplied.
Later and better analog receivers have a multiplier circuit as a mixing stage such as a sp-called Gilbert cell. Now multiplying is easy in software.
Hang on. The frequencies are added/subtracted, right? Not the signal levels. Are we confusing the two here?
@@MichaelWillems Correct, multiplying two signals in the time domain means adding or subtracting their frequencies.
Adding the signals together and passing it through a nonlinear fillter (like a diode or NPN transistor) has the same effect.
@@wernerfritsch6436 Of course. I should have remembered that. Thanks, now it's clear.
@@wernerfritsch6436 didn’t these circuits basically turn on and off the input at the oscillator frequency by having the local oscillator change the bias of the pass stage? So it’s performing mixing like the Gilbert Cell, but with no input balancing
beat frequency, thats how we tune our instruments e.g guitar, bass, piano, violin etc
great work! Its also music, not just math/science
Very informative. Elaborate technical explaination about complex concepts. Thank you for the time invested in mystical force of radio waves that still strong holds emergent forms of futures.
Great job making the complexity of radio reception more accessible.
Small nits. The mixer in a superhet requires an explicitly non-linear element. Adding signals in the time domain as was done in audacity does not produce beat frequencies. Multiplying them does. Also, you pointed out the front end filter required to eliminate imaging, but did not mention the act of mixing produces both the sum and difference. The 455 kHz IF strip filters out not only other stations, but also the image of the desired station. Consequently, supersets can either be high injection, or low injection, depending on whether their filter is designed for the sum or the difference from the mixer.
The property of imaging also allows single-sideband (SSB) transmission, which is essential for TV. After modulation, the signal will have two sidebands and for SSB transmission one of the sidebands is filtered out because it is redundant anyway.
TV is vestigial sideband. Single sideband, but incompletely performed.
@@erkinalp Which is on purpose, BTW, because there are some elements in the other sideband that actually help with recovering the video and audio more easily.
Yes, that 400+401 Hz demo doesn't actually produce a 1Hz sound - and if it did, you couldn't hear it anyway as your ear can't hear frequencies that low. Similarly, adding 5000 and 5400 Hz won't produce an audible 400 Hz tone (unless there's some nonlinearity, as you say). Presumably there is some nonliearity somewhere in his demo, but small - hence the very quiet 400 Hz.
I read somewhere that superheterodynes were the real reason why soldiers behind enemy lines during WW2 had to avoid using radio except under specifically defined conditions. The local oscillators in their portable units tended to be noisy, which allowed the enemy to triangulate their location whenever the units were powered on, even when they were only receiving.
Noisy oscillators also gave away the presence of speed radar detectors, at least the models that were around when I was younger. Many states outlawed radar detectors, so police could detect your radar detector and ticket you, even if they weren't actually using their radar at the moment.
First comment on one of your fantastic videos. I'm really amazed how well your contents are researched, how well are presented, and actually how long they are! I can't imagine what amount of time and effort is behind a production of every single piece. Thanks for being here and giving us these material to watch!
Regarding this particular piece: even if I'm interested in electronics from childhood, radio technology has been always some kind of mystery for me. I'm an audio enthusiast, you know, whatever oscillates beyond human hearing is an issue for me ;) So actually I knew the term from childhood, but I had to wait until your video to know, what it exactly means at how it works. And this explained to me something else as well.
Being born on the rusty side of that famous iron curtain, I knew there were really dark times when people got arrested only for listening certain (banned) radio stations. I heard stories about special equipped vehicles which were able to measure what stations the people were listening to. Now, your explanation of how the radio receivers are actually work, enlightened the way how it was possible: they had a sensitive receiver on-board and they actually captured the radiation of the local oscillators, and I can imagine, with some kind of directional antennas, they could locate the source as well. Then they could instruct the leather-jacket people in the black Volgas, which house to go to...
Thumbs up again, you gained an another subscriber :)
Ok I've been a ham operator for 15 years, and recently started learning to design receivers.. I was struggling to understand the superhet and found your video... WOW! THANK YOU! Suddenly the multiple IF's of my radios all make sense.
Damn!! I am again impressed at the level of detail you describe the way radio works! I should note this technique is in fact still used even in digital wireless communications. Look into QAM and DSB-SC demodulation. Other than that you pretty much covered 2 weeks of material I learned in a university graduate class in wireless comm this past fall semester!
Replying to 2yo comment... but demodulation isn't mixing or filtering
@@donaldviszneki8251 mixing down is often a part of demodulation. I guess if you want to be very precise then fine technically it is an intermediate step. whatever haha
@@power-max I guess as an amateur I feel like it's important to get this distinction right, or else I'll be forever confused
@@donaldviszneki8251 My knowledge in the field is only a single 4 credit hour elective from a few years ago haha. That and Wikipedia/google.
"Its Science, Its Math, Its Fantastic." ❤️
Great video, Most of the tech stuff went right over my head, but I still learned a lot. Thanks for posting....
You know, I’m an erstwhile electronics engineer AND a radio ham (VA3MVW), and yet you clarified a couple of small issues for me. Excellent!!
10:22 That was sometimes solved by stuffing that oscillator into a metal cage. Or coating the inside of the radio with a metal. I had seen such stuff pretty often.
That high pitch sound from the headphones hertz my ears
Watt did you say?
As one of our college students said "after a few KHz your ears start to drop off".
Alec, as I have learned is you name, thank you. I don't know what inspired you to this all of this. But I am glad you decided to make this fascinating videos!
I followed your dissertation as best I could but did not understand a dam thing while being fully engaged, focused, interested, mesmerized, fascinated, and filled with wonder about how people can think in ways to bring sound from frequencies into and out of a speaker ...
Thanks. 😃
Great vid...very interesting! I only wish you had mentioned Howard Armstrong, who not only invented the superhet, but also invented regeneration (which allowed the vacuum tube to not only detect, but also transmit radio signals) and frequency modulation. He was a true genius and is the man most responsible for making radio what it is. I consider him--not Marconi or DeForest--to be the true "father of radio."
I'm surprised you didn't get into the history and development of the Super-Het circuit. Edwin Armstrong was a brilliant inventor who not only invented AM but also FM. Unfortunately he ended up in a massive law suit with RCA over patent rights and came to a tragic end.
It's almost criminal to talk about the superhet and not mention Armstrong. :-)
Exactly! I'm surprised Armstrong wasn't mentioned. It also brings to mind the excellent book--and NPR video--"Empire of the Air". Armstrong is one of the three key players in this fascinating look at the development of radio (from a USA perspective). Ken Burns, of "The Civil War" documentary fame, directed Empire of the Air. There's a full version of it right here on CZcams.
@@4nradio782 I've seen that one. I think it was directed by Ken Burns.
I have the DVD of "Empire of the Air" at my house. I watched it at home one day when I was home from school sick. I even had a license plate, "W2XMN." Didn't Lee DeForrest take credit for the SuperHet?
@@rayceeya8659 I thoght that might've been before Burns' time, but that may have been one of the first uses of the, "Ken Burns Effect." 1992.
en.wikipedia.org/wiki/Empire_of_the_Air:_The_Men_Who_Made_Radio
Greetings,
I expect you know this, but you are very good at what you do. The subject matter is interesting and very easily explained. That second part is NOT so easy and requires someone who has that gift to make technical subjects relatively simple to understand. Few people have that gift. I am happy you found yours and exploit it with such apparent ease. I also like the casual format of your presentations. I loved your percolator installment. A humorous, yet informative topic. Your site looks to be huge, and the dedication to educate must be a driving force. Keep up the great work!
Been long infatuated with our analog era of gadgetry wizardry. Your videos have highlighted how much brilliance was involved in the various important milestones through the decades. Even analog computers are kind of cool for some classes of problems.