AM Radio Transmitter on ESP32

This video shows how to make a super simple AM radio transmitter using the ESP32 microcontroller.
The parts, code, audio converter, and details can be found on the project page: bitluni.net/am-radio-transmitter/
plz share :-)
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Twitter: @bitluni

[@AhmetAkifKaya]

Is that the recording in the end an ascription to the Hawaii wrong nuclear alarm

[@bitluni]

Funfact.. the video was scripted just before Hawaii happened. I almost removed that gag since I was kind of tasteless. But since the release was postponed by a week I kept it :-D The text is influenced by the ridiculous propaganda videos from the cold war in USA "duck and cover" where children were conveyed they could hide under the table from a nuclear impact ( kzbin.info/www/bejne/f3zUiahjas-qbJI ). The text is spoken by my girlfriend. We also were trying to use a similar inflection like flight attendants are using as if this was something trivial

[@AhmetAkifKaya]

bitluni's lab , Yes the cold war era was something interesting and It's so cool that how humourous this video is about that. Also I really appreciate your projects and experiments.

[@kc8omg]

Really enjoyed the video, awesomely simple solution. I like sharing the following because I found it interesting when I discovered it: Having done some research for a paper I wrote, hiding under a desk from an atomic bomb is not as ridiculous as it sounds. Just like regular bombs the damage is worst at the center and gets weaker as you get away from the center. Essentially if you're at a distance from the detonation that you could see a flash and react to it ("duck and cover"), you're at a distance where the initial blast/heat isn't going to kill you, but the heat flash could still burn you and the flying debris from the incoming pressure wave could hurt you, so putting something between you and that debris/heat can actually prevent a lot of injuries. Also, while you would receive some dose of radiation, if you're at a distance from the epicenter where "duck and cover" would make a difference, it would not be a life threatening amount of radiation. With the nuclear weapons currently in service around the world, if you're close enough to receive lethal radiation, you'll be killed in the initial blast anyway. Interestingly, at these "duck and cover" distances the heat wave can still be strong enough to cause 2nd and even 3rd degree burns, but it's so brief that clothing and even something as thin as a sheet, tablecloth, or even newspaper can stop it from hurting you. So no, if you're near the center of the detonation it won't do you any good, that much is obvious. But we're talking about a bomb that can have an effect on many square kilometers of area, and there is a significant portion of that area where "duck and cover" could quite possibly save your life and/or prevent injury.

[@bitluni]

That indeed is quite interesting. What kind of radiation is involved? I guess alpha and beta are probably blocked by the air at the distance you survive the blast....

[@DewaldPierreNel]

You can try making a magnetic loop similar to the loop on your receiver. The magnetic loop can be adjusted using a variable capacitor to allow it to resonate to your carrier. There are many online calculators available. I would also suggest adding an amplifier circuit to drive the loop while keeping the output pin on the transmitter safe. Thus a high impedance input seen from the pin and the gain of the amplifier will help boost the signal to make it propagate further to your granny next door.

[@onlyrgu]

I remember AM transistor radio kits i use to play with in the late 90s..It took me 100 times the effort to build one...Thanks for the video

[@bluegizmo1983]

I know this video is old and I'm sure someone already commented this, but antenna length (without going into crazy details) should generally be 1/4 wave in length for optimal range.

[@TommyHelgevold]

Simply super clever. This is what I've been looking for to give my old radio's some extra life. I have tube radios like yours, big console radios, one of them is from 1949, and this would be nice. I can imagine streaming audio to it, and using that as the transmitter.

[@CiprianBindiu]

This one was really awesome!!! I really like your style and sense of humor!

[@BEdmonson85]

The antenna length for a radio transmitter is generally some multiple of 1/4 wave length. But that's only part of the story, the transmitter's output impedance should match the load impedance of the antenna. This load impedance differs depending on the type of antenna you use. I suspect that if you were to cut a wire the same length as the antenna and attach it to ground, you may get better range. This wire is called a counterpoise and gives the antenna a "ground plane" to radiate from. Or if held inline with the antenna wire, you'd have a dipole, though for a much higher frequency than intended. Also you could add a coil to the bottom of the antenna to add some inductance to it, which makes the antenna appear electrically longer to the transmitter. Good Luck!

[@tunahankaratay1523]

1/4 wavelength dipole with an impedance matching balun is definitely the way to for high power applications. But for such a low power transmitter, it's not worth having a massive 180m dipole antenna.

[@abathurwaifu3302]

what

[@MaxC_1]

@@tunahankaratay1523 or use coils instead of a massive 180cm antenna I'd say. Still obviously it'd be pretty overkill anyway

[@tunahankaratay1523]

@@MaxC_1 Yes, coils are the only sensible antennas for medium wave in small applications. Because it is not 180cm. It is 180 METERS. That's why the actual stations use such large antennas. 180cm would actually be reasonable, even low power FM stations use a proper dipole antenna because they are easy to make, place and maintain.

[@macgyver5108]

4:49 not sure if you've discovered it by now but an "ideal" antenna length for transmitting/receiving is either a 1/4 wavelength vertical using a ground plane (like on a car hood, the car body is ground) or a dipole antenna with two 1/4 wave elements that alternate +/- fields, like on old TV's that used "rabbit ears".

[@Aemilindore]

Love the simplicity of this design and that you used a simple esp32 dac. Your videos are good food. Going to sign up for patrion for you

[@tomaims]

I think antennas can be 1/2 or even 1/4 of the recommended length. Also, coiling the wire if it is long can help manage these potentially long antenna wires. Various modern antenna designs can do amazing things with short wires. The problem is they are not free. Nice project I just subscribed as you appear to have some unique projects/ideas I'd like to explore.

[@RoSi4You]

*It is a joy to watch your videos!*

[@Really2950]

You’re quite an amazing genius. No one else covering audio like this. Original content...because genius :)

[@sagarshubham8660]

You Rickrolled us! :') I am so glad you made this awesome video! Thanks.

[@GeekMustHave]

I am in awe. The level of technology here is amazing, you explained some things about AM transmissions is such an easy way to understand. The vintage radio looks like a Grundig? On top of all this, you are a musician. I bet you know how to cook too. ;-) I think all you need now is a 1kw linear amplifier and you can become Radio Bitluni. Keep broadcasting!!

[@martinj9268]

This is a really cool weekend project, man! Keep it up

[@manuelminutello3027]

the antenna type that you want is a monopole antena, that type require a length of 1\4 wavelength, but that requires a counterpoise to work properly. also an antenna do not works just by length, tha shape and position takes a good part of the data to characterize an antenna, also your transmitter do not have a constant output impedance so a precisely shaped antenna will be worthless. in this case coil up as much wire as you can and you will be fine :) manuel, 18 years old ham radio operator from italy

[@donjoergo]

Haha your humour is fantastic :D Also very nice use of the 8bit DUCK

[@zolatanaffa87]

Hello Ah! old amateur radio memories come back to life! (I hope not to say nonsense: I go to memory 20 years ago) for good signal transmission there are at least three very important variables: the power of the transmitter (I think ESP32 does not have much to put out) The length of the antenna (based on frequency and wire propagation factor) The relative position between the two antennas, (RX and TX) the higher the frequency the higher the influence of relative positioning of the antennas is. In your case, given the frequency and the distance between TX and RX, I believe that the main responsible for signal attenuation is the microscopic output power of the ESP32. The antenna of the modern tuner is then of the ring type, so as it is done it should not be affected by the position of the transmitting antenna and is calculated to pick up microvolt so even the small power of ESP32 is captured, a short distance away, but as soon as you move away. .. The power drops with the square of the distance, so ... You could use the output signal to excite a linear amplifier (for these frequencies: a simple amplifier with a normal transistor and a band-pass filter, you can find amateur schemes on the internet) adjusted for the AM frequency and drastically improve the range of your ESP32 . for some proof it can be done, but I do not know the German laws and I would not give you problems of transmission nonn authorized, of these times I would not want someone to accuse you of acts of terrorism :-) P.S. in case you could think of making yourself a long antenna do not do it in full wave, but at most 5/8 wave. if I remember well, You do not get a good signal transfer.

[@mobluse]

High Five! I've got this project running, on the same 5" B/W video monitor that I run your first composite projects on, because it also have an AM receiver and FM receiver.

[@piero957]

Amazing trick and nice video editing. Your videos spark my interests.

[@JerryEricsson]

It was back in 1977, I was just completing my 2nd enlistment in the US Army, since I was going to get out, the recruiting station where I was located put me on terminal leave, so with nothing to do, I enrolled in college studying to be an auto mechanic. I was a bit of a older student at the time, and it happened that one of my fellow students had rolled his muscle car by driving a bit over the speed limit, (read about twice the limit) so he was without a ride to college. I drove right through his town to go to the Tech every day, so stopped and picked him up to give him a ride. I was driving a little Opel Manta, neat little car, and my experience as a police officer gave me a bit more skill to drive those wandering back roads of rural Minnesota. The little bastard used to brag all the way to college and back about his driving skills, so I began getting even with him. First, I would drive, a bit over the speed limit when I came to where I knew he had wrecked his car, then I began getting closer and closer to the guard rails that protected us from the narrow bridge crossings on the back roads, and last but not least, I found an 8 track tape (after in 77 what else could you play in a car?) with police sirens, So when I neared that bridge, I floored the little German car, she jumped forward like a spurred stallion, up across that old wooden bridge, the door handles nearly scraping the guard rails, I pushed in the tape and told him to hang on, the Sheriff is behind us. He ducked down and began to weep, so being the kind hearted man that I am, I only kept up the fake chase for another mile or so before announcing that I lost the cop. Result? The dude never again asked me for a ride to college.

[@avijitdas6872]

This is a kiss from love of technology 😘Mmmmmmmmmaaaahhh, well done my dear luni, your work have won my heart

[@manickn6819]

Damn I have a lot to learn on this but videos like this are quite an inspiration.

[@pch4287]

Amazing work.Congratulations

[@AHamAtHrt]

I just tried this and it works great. It's brilliant in it's simple implementation. Congratulations. The only issue I had was the I2S_NUM_0 is the DAC1 pin not GPIO_0, missed that point in the video. Once that was figured out, I received my wav file on 835Khz.

[@abathurwaifu3302]

what

[@ettorediblasio7241]

Good job!!! Thanks for sharing, Bruno!

[@reneweise]

Congratulations for the video! Your videos teach and make me laugh a lot too!

[@DanielStinebaugh]

Awesome job! It reminds me of the numbers station project for the pi

[@avijitdas6872]

Best antennas for MW band are ferrite based, those are lossy too. In order to improve the range a band pass amplifier is mandatory along with such antennas

[@TheLenstaa]

That's pretty awesome, you should buy a cheap wideband RF amplifier (you can get miniaturised ones from eBay and such, also they run on 5V), then link it up and see what the range is like afterwards.

[@bitluni]

it's most probably much higher... I was just curious what we can do with no components :-)

[@danielpare9129]

Great project, I love the Hawaiian touch at the end.

[@GutsyGibbon]

another great little project.

[@phizicks]

ROFL enrick!!!! that got me on the floor. Usually antennas are 1/4 wave length. been 30 years since I had worked on it at a technical college.

[@dl8cy]

Awesome work - thank you!

[@jontech_Lab]

Always Genius,i admire your creativity

[@ThiwankaWimalasuriya]

great project. i will be doing this today

[@olivercrain5768]

Funny way to learn something. Thx for this.

[@texasyojimbo]

In the US, the FCC has rules about the size of AM broadcast band antennas used with unlicensed transmitters. I think it's like 1 meter long or something. As far as practical small antennas for medium wave, I'd suggest multiturn loop antennas.

[@JohnoScott]

Fantastic yet again.

[@davidgmos]

Great work!

[@manwithafork]

This video is a classic. Makes me spit my coffee out laughing every time.

[@samykamkar]

Nice!

[@tony91200211]

Samy Kamkar bro where have you been no new videos?

[@emmanuelvidales505]

Funny and Simple.. good video!

[@RPhulNewsTrue]

You videos are great...

[@dasworkshop4967]

The Rick-Roll was simply outstanding! Subscribed!

[@MadLabZ]

Your electronics room tho, so clean, SUBBED!!!...my "project" room looks like someone shot off a cannon filled with components -_-

[@skane01]

Hi, great video, fantastically simple yet so powerful. Have you set up a transmitter / receiver pair?

[@pedrojacob7156]

I too do not have much knowledge about antenas, but in my university(UFCG), people use this book as a reference of the class that studies it: from Constantine A. Balanis, Antenna Theory: Analysis and Design. I think you can start with that... Great video! If you want some help to find the book, comment below... :)

[@MNfishing]

Hey mein bester, hammer videos und ein mega geiler Kanal!!!! Bin ein riesen Fan!!!!! Mach bitte immer weiter so. Viele Grüße Michi

[@MNfishing]

Ah und grüß Eunice von mir :)

[@abedamraie7879]

Nice one! thank you

[@mohawkmike5271]

DUDE YOU ARE AWESOME!

[@mafhper]

THIS IS SOO COOL!

[@EVERY.CIRCUIT]

Nice idea

[@deejeymx]

You're a genius !

[@2ftg]

Put a coil in series with the antenna (at the ESP32 end) to match it better to the pin's output impedance and to lengthen the antenna electrically.

[@tommymairo8964]

You can add a push pull amplifier to increase the output power.

[@joinedupjon]

IIRC the theory... you always want the best aerial on the transmitter and then it matters less what aerial you have on the receiver. This is to do with getting your desired signal further above the 'noise floor'. So maybe borrow the AM loop seen at 2.53 for the TX and use the wire (or a ferrite out of a junk AM boombox) for the receiver. Might also be possible to tune the loop (which is inductive ofc) using a variable cap across the twisted pair feeder.

[@zolatanaffa87]

joinedupjon youre right but we are making a broadcast radio like Deutsche Welle with a poor crystal microtransmitter

[@raymondtwm]

Awsome!

[@richardgrier4721]

1/4 wavelength wave is best. Load with an inductor (coil) in series for a shorter physical antenna.

[@bitluni]

thanks

[@Jefferson-ly5qe]

Good luck getting anything close to a quarter wave on the AM BC bands

[@richardgrier4721]

That's why a loading coil is used. It matches (as closely as is practical) the impedance that the transmitter sees to that of a 1/4 wavelength antenna -- allowing a much shorter physical antenna to be used.

[@Moonblade042194]

It also depends on the shape of the antenna that you are trying to send the signal to.

[@Jefferson-ly5qe]

Richard Grier yeah, fair enough. The inductive ballast will help. It's just a long way from a quarter wave. May as well call it a whip antenna

[@TheDIYGuy999]

Ingenious

[@sincerelyyours7538]

Very nice! Been looking for a home Hi-Fi AM transmitter to broadcast oldies music to my tube radios (one of which is a Grundig Type 2030 W/3D radio from 1955 that looks strikingly like the nameless one you have in your video). I'm especially interested in getting bandwidth as close to 15 kHz as possible to reproduce the best Hi-Fi AM sound, which is what those old radios used to receive before FM became popular in the 1960s. Today 10 kHz BW is the legal limit for AM but as long as no commercial stations are nearby, exceeding that by a few kHz in a very localized area should theoretically be possible. By localized I mean keeping your signal under 1/4 watt so your range will barely make it out your front door.

[@stewartrv]

Or instead install a wireless USB bluetooth adapter and insert the signal into the valve amp. Then you can send stuff from your phone or laptop to play on the old radio as if it was a bluetooth dock.

[@avijitdas6872]

Or you can attach a 225 meter vertical wire 😵 which is a 5/8 wavelength antenna at 833 kHz.

[@planker]

Excellent

[@ajnstajn100]

my dude its all good your radio is beast. But I will suggest a trick I discovered that works most times. Take a antenna from a car and just stick a jack to it works wonders xD

[@gazzacroy]

brilliant video.. your a cleaver fella :)

[@chriskall6276]

The younger generation will never know the joy of rick rolling someone *one tear runs down my face*

[@lintangwisesa]

Masterpiece (y)

[@hollensted]

This is sooo funny and impressive. :)

[@MrNoorino]

You are the best

[@albygnigni]

Well done! I think you can get better transmission adding a unity gain op amp, since the DAC is really low power

[@Harvid.]

DAC won't be really interesting, if possible :-D

[@bitluni]

that's true.. it's just few components more

[@martinj9268]

Isak Thjellesen am I misinterpreting this, or are you saying digital to analog conversion wouldn't be interesting if it were even possible? Or does DAC stand for something else in this case?

[@delusiongaming2506]

Im your fan!!!!

[@aonoymousandy7467]

Would this work on an arduino uno r3?

[@Valentiy]

Пять балоффф... Поучительно и с юмором.... :)

[@mihalym.6876]

Thank you for this project, it is very interesting. To check the operation of a crystal foxhole radio I decided to build a simple transmitter. This solution seems OK for me therefore I started to study and understand your project. The HW side is presented well, no question about that. The SW side left open a couple of questions. Unfortunately the video and the comments on the source code does not show much about this. First the carrier frequency: I do not know how could it be 835khz. If clock is 240Mhz than PLL_D2_CLK is 240Mhz. The divider is (1/3)(1/2) in master mode gives 40Mhz clock frequency. Where the 6.5 Mhz come from?. The most interesting part is the modulation of the carrier frequency. The code is simple and dense but I was not able to figure out how it works. Unfortunately I do not find useful information about the decoded audio data format. Not knowing this is a barrier to understand the decoder code. Any help is appreciated in advance!

[@Dixitkushagra175]

You need a ferrite loop antenna. That's your best bet. Remember that it is "noise cancelling" so you need to place it in the correct orientation.

[@youssefaly97]

This antenna is known as a monopole antenna, it's linearly polarized, so it must be aligned to be parallel with the receiver antenna as much as possible specially with such low transmission power. It should also have a ground plane connected to the ESP32 ground and the antenna should be normal to it. Ground plane dimensions are not very critical, at least not for this, it's best if it's circular though. The antenna length commonly used is 1/4 of the wavelength or a multiple or fraction of that. The feed line, the yellow in this case, is best if it's shielded and the shield connected to the ESP32 ground as well as the ground plane.

[@bitluni]

Awesome! Thanks... this should be helpful!

[@youssefaly97]

bitluni's lab also try to amplify that signal with an opamp or even a 2N3904 amplifier and tell me how much range you can get out of that, would be awesome if you can get 5 meters or more!

[@AdityaMehendale]

A monopole should be 1/4th the wavelength (longer is never better; shorter is acceptable but worse) - but this assumes you have a large ground plane. If you don't have a large ground, then a dipole (i.e. a double monopole, L/4 to one side and L/4 to the other, so L/2 total wire-length) would be best, shorter is okay, but longer is never better. Think of it as if you have a sinusoidally varying electric field. You want to sample the highest and the lowest point (with say a superfast multimeter). Where would you put the leads of the multimeter? The red wire at the peak and the black wire at the valley - this is essentially the dipole --> L/2 distance between the peak and valley. If you go shorter with your leads (dipole antenna) you'll get a smaller measured voltage (signal strength). Having longer wires will never be better, as then you would go "downhill" again.

[@AdityaMehendale]

Did you see SpriteTM's video BTW, where he uses the internal clock-calibration-register of an 8-pin AVR to make FM?

[@youssefaly97]

Aditya Mehendale sorry I couldn't get to reply earlier. In theory, multiples of 1/4 wavelength is better in some aspects, including better gain and directivity, in practice not, specially frequencies less than 1 Ghz which tend to have quite long wavelengths. Earth or soil, can be used as a ground plane but be sure to isolate the feedline center/positive/antenna from the soil/ground.

[@juliusfucik4011]

Use an analogue amplifier for the radio signal. The controller generates the signal, but it simply needs more power.

[@tarablecode6115]

Can the frequency be changed? This is cool as heck but I don't understand the math behind it :/

[@ProtoG42]

Awesome! Any luck with FM transmissions?

[@TomBruner1]

Have you tried hooking up a standard AM loop antenna like you have on your receiver?

[@odissey2]

I must've missed the trick, but how AM modulation was done? Do you calculate whole Ampl(t) * Sine(wt) and send it to the DAC in real-time?

[@enaudeni]

I was just wondering the audio you used for the esp32 “This is an emergency broad cast. Nuclear missile inbound detected…” Where did you get that from? Thanks.

[@DaveJunior]

how to make a 20hz / 20khz audio transmitter and receiver to use as a wireless ear and also a guitar transmitter?

[@fixmix4954]

Super! I go to make it.

[@justinmallaiz4549]

Lol, your awesome. Please consider some fun projects using the JeVois smart camera.. I would love to see and build them. ( light strips that follow your movement / or lights on with guesture/ Or make a giant virtual key board to re-Inact Tom Hanks in “big”? Interested?) I could put to practical use these projects :) -Requires creating some test patterns and train neural net by doing.. Someone of your skill and knowledge could really rock in this area, and get others like me out of the gate 🙂Thanks for all your vids!

[@justinmallaiz4549]

- I’d offer to send you the camera if your interested ( I’m interested in smarter home uses)

[@adamkrasuski4743]

Love the quick jokes!

[@kristiangronberg3150]

That's awesome, now you culd tweak the code so that you might have one input channel as Audi input? So you can use an mp3 player for audio sources. You might want to bias the input channel, si you get negative portion of the voltage in the ad converter. What it comes to the antenna, there is a lot of info online about the antenna design This is how I wuld go oon with it. If the pin output voltage is 5v and the max amps ia example 1A you have ability off 5w into a 1 ohm load. End feed 1/2 and full wave antennas have a really high feed iimpedance, closer to 3000 or 5000 ohm. So not going to work without advantage tuning system. An 1/4 wave antenna has about 50 ohm but it needs a lot off ground. An half wave middle feed or as called dipole has abaut 50 ohm. So you need a ground in your system, not only the radiator of the pin. @50 ohm you should have about 0.5w. Of course that's the peak number, so as am modulation head room you carrier is abaut 0.25w If you built a balun, it's a fancy name for transformer. Let's say 1 to 4 your 50 ohm loud looks like 12.5 ohm to the board, so you get around 2w peak power and 1w carrier. I probably wouldn't go much higher than that without knowing how the antenna really works, there is a lot of impact from whats around the antenna that impacts both impedance and resonance. You probably won't go that far away, but at least having a big coil might help the range a bit

[@avijitdas6872]

This is the second sdr project by you on esp32

[@RelianceIndustriesLtd]

i just found yur channel.yur awesome..is it also possible to build an FM transmitter with esp32? can we boost the signal strength with an opamp? does the the esp12e have any DACs?

[@zolatanaffa87]

for boostin signal it's better a simple transistor amplificator than an opamp: usually opamp are for signal not for power

[@hasa4979]

Nice tube. The sound track on 3:30 is cool, will you upload the complete file of it?

[@jaredgray7872]

I should've seen that coming

[@shafik80]

Hi can you make video on how to make anlog cctv camera wireless with node MCU, can u make analog to digital video transmitter with wifi

[@tekvax01]

make the antenna a 1/4 wavelength of the carrier frequency

[@tunahankaratay1523]

It would be 90 meters for monopole and 180 meters for dipole, which is not only quite impossible, but also such a low power transmitter wouldn't be effective on such a long antenna.

[@alexsmith2632]

sounds very cool, could it be use to be a realtime broadcaster?

[@Brausepaul123]

Is it possible to use an Analog input pin for audio in? I'm not confirm to audio signals on an 3,5 mm jack but may the voltage drop on a resistor could be used as input signal

[@bitluni]

I will try to build a basic audio filter in future, so we can try that then

[@mihigyver]

why not bluetooth?

[@Puch1981]

Very interesting work. But unfortunately I don't have the right libary's in my arduino IDE. Can you tell me wich libaries I need?

[@MrEoxs]

do you think that a esp32 would be capable to decode a component or s-video signal and convert to vga? like a video adapter?

[@Zhaymoor]

How do you create the file ? what happens to the audio when you convert it

[@biker2k3]

Exelente!

[@avijitdas6872]

Antenna lengths become practical at frequencies above 20 Mhz