How to Make AM Radio Transmitter

[@goldeneyeMCMLXXXI]

that's awesome dude seriously, one day people are gonna wish they had knowledge on how to communicate with one another

[@RimstarOrg]

The annotations are already there. Maybe you have annotations turned off? But I appreciate your pointing that out anyway. When I tested that a long time ago, for some reason I got it wrong. I'm glad you liked it.

[@RimstarOrg]

I'm happy I could help! Make sure you don't make your transmitter too powerful (don't use too powerful a sound source or too long an antenna.) You don't want to interfere with anyone's radio or communications.

[@RimstarOrg]

I'm glad you liked the video. I do have it on my todo list to do a different circuit with reduced noise but I don't know when I'll get to it.

[@InnovationBlast]

I really like how your videos have easy to follow instructions, and how you make a follow up videos explaining how it works. I want to be an electrical engineer when I grow up, and I can't wait to make this project!

[@RimstarOrg]

I'm delighted to hear that it works, and so well too! Thanks for letting me know. I don't know how to make an antenna that can transmit 7 miles and I wouldn't recommend it. Certainly not with this transmitter since it broadcasts on so many frequencies, as I point out in this video. You shouldn't transmit more than a few feet to be sure you're not interfering with anyone else's radio. In many countries there are laws about radio transmission. You should check for where you are.

[@RimstarOrg]

Thanks Brit! Glad you enjoyed it. Thanks for watching.

[@RimstarOrg]

Glad you like it. I glued the breadboard because I didn't want to put too many holes in the wooden board but I screwed the transformer anyway since it weighs more - didn't want it falling off. As for the side rails, I could have sworn one side went all the way and when the other side didn't, I just figured that side was busted. Just rechecked and they go 1/2 way like yours. Looks like annotations are in order. :( Thanks for watching!

[@Moronvideos1940]

I interfered with my neighbor's radio .... he heard it on his radio...I got my little radio and turned it on and said, "gee, you're right.....must be an alien invasion or something." He does not know I dabble in building little transmitters, for the joy and fun of it, so in my pretended ignorance I suggested, "Maybe we should call the cops or something." He mulled, "Well, I don't know, nah.....the hell with it." Then he offered me a beer. Now you know why I will keep my secret forever, to cover my black lies, his good friendship and the free beers!

[@RimstarOrg]

If the microphone has and amplifier or you connect it to an amplifier first, then it might work. So your sound card would be the amplifier. I wouldn't guarantee it would work since I don't know the power output of your sound card. It's something I wanted to try but I didn't have anything to plug the microphone into. And thanks! I'm glad you liked my video!

[@Dark_Matter2]

For better performance, buy a 1 to 1.5 Mhz oscillator. Connect the computer speaker amplifier to the transformer and make a parallel LC circuit connected in series with the output of oscillator and antenna. With LC circuit the square wave will turn into a sine wave, I saw it on the oscilloscope it works. Use an antenna about 20 meters long. I was able to pick up my signal at a distance of 100 meters. Be careful there may be laws that do not allow broadcasting without a license.

[@RimstarOrg]

Yes, that's it exactly. I did look at the voltages on my oscilloscope and it didn't seem high, only 10 or 20 volts, but I didn't really make a mental note. It was pretty cool to see though. I first got the oscillator working and saw the 1.8kHz waveform on the scope. Then I added the sound and transformer and saw the modulated version. It was clear as day, very cool to see! Now that I have a transmitter I can do a video following the waveform from source to earpiece.

[@RimstarOrg]

Thanks. It's transmitting on a bunch of frequencies, but as long as you don't transmit far then it's a simple, fun one to make.

[@RimstarOrg]

I have no experience with them. However, I've heard other people say they've bought from them, including this oscillator chip, and I haven't heard any complaints.

[@RimstarOrg]

You're very welcome! I had a few people ask for one but I didn't make a note of whom. At least everyone gets the result.

[@RimstarOrg]

Thanks! It was super fun to do, especially seeing it on the oscilloscope (which of course I didn't put in this video :(). Was that your LM339N? I don't recall a video about a radio transmitter.

[@RimstarOrg]

The side with the most turns is connected to the chip and the side with the least turns is connected to the sound source, the CD player in this case. Other than that, which wires go where doesn't matter.

[@RimstarOrg]

My CD player was a random choice. I'd suggest trying it, though if you have oscilloscope then you could look at the voltage range of the wave coming from the speakers first.

[@RimstarOrg]

You're welcome. I'm glad to hear it helped.

[@RimstarOrg]

That's a programmable oscillator which means that the frequency it outputs is controlled by the voltage you give it. The voltage we give is varies all the time since it's amplitude modulated (AM). The frequency would be constantly changing. So no, I'm pretty sure you can't use it.

[@RimstarOrg]

Thanks! I would like to make my own oscillator, and might just do that. One of the people who asked for a transmitter video specifically said they wanted one using a chip oscillator so I went this way first. Of course, a variable oscillator would be even cooler.

[@RimstarOrg]

Thanks, my friend. That's good to hear coming from the man with the golden voice!

[@Kevin_Carlson]

I just built this AM transmitter according to your diagram, and it works! It transmits a very strong clean signal. I used my iphone as an audio source and there was no problem with the volume level.

[@RimstarOrg]

Cool! Glad to hear you got it working! Just be careful to not transmit too far and interfere with other people's radio. This circuit is especially dangerous in that case since it transmits on multiple frequencies. You don't want to interfere with emergency response systems.

[@Kevin_Carlson]

@@RimstarOrg Thank you for the words of caution. So far the signal is contained to the interior of my house.

[@fantasi4037]

RimstarOrg Please tell me how you managed to do that! I’m doing a science project and I really need a way to transmit sound by a phone. Thanks!

[@RimstarOrg]

That's in the shortwave High Frequency radio range. I think that's for marine radio, though I'm not 100% certain. I don't know if a normal AM radio will be able to pick it up on a subharmonic frequency. It'd probably be best to keep searching for something in the right range so you don't interfere with anyone else's signals.

[@RimstarOrg]

Thanks! Glad you enjoyed this one! You said you made one using a cell and some foil - what kind of cell do you mean? And yeah, those pesky sparks throw out many frequency electromagnetic waves. Cool that you used the Kelvin thunderstorm to test with.

[@lutzweb]

Good demo: 1 thing, AM radio receivers do not use the long stick antenna for AM, they all use an internal ferrite antenna , the stick is only for FM (or SW), so just tune the receiver and rotate it to align it with the magnetic field.

[@RimstarOrg]

Interesting. Thanks. I'm used to making crystal radios where we use long wire antennas -- though having some AM radio stations nearby, I'm able to use relatively short wires (5 meters).

[@RimstarOrg]

You're welcome, Jona. Steve from Canada.

[@Frogmancdw]

If you want to look more into am radios, pop open that one in the video, or any one really. Chances are, you'll find what's called a ferrite rod loop antenna. Pretty interesting type as it interacts with the magnetic portion of the radio wave, not the electric as the common whip or wire antennas.

[@RimstarOrg]

It's still fairly strong around 6 feet, around 2 meters. I don't want it to transmit any farther since that would interfere with radio stations.

[@RimstarOrg]

Cool. Yeah, I have trouble showing things without trying to explain the why or how of them. :) If you make this, make sure you don't make it able to transmit too far. You don't want to interfere with other people's radios.

[@RimstarOrg]

I can add it to the todo list to keep in mind but I went with an AM transmitter so I could receive it on my crystal radio and possibly make another video about AM waves.

[@RimstarOrg]

The transformer for stepping up the voltage of the audio signal coming from the CD player. Without it the output of the CD player is only around 1.2 volts peak-to-peak. That's too low given the the oscillator powered by the battery is putting out around 6.3 volts. With the transformer the CD's output it raised to around 10 volts peak-to-peak, which is more suitable for being chopped up by the oscillator. See my "Amplitude Modulation with Simple AM Radio Transmitter" video for diagrams.

[@RimstarOrg]

Welcome! You'll definitely find lots of tech here. I hope you continue to like what you see.

[@RimstarOrg]

Thanks. I guess I was making the assumption that some viewers wouldn't know which side is which, so I just told them to try both.

[@RimstarOrg]

+Greg Mitchell Use a more powerful sound source. PS There's no Reply button under your comment because of your Google+ settings. - go to your Google+ page, - in the top, right corner click on your thumbnail icon, - in the popup that appears, click on "Settings". - for the 2nd question down "Who can comment on your public posts?" set it to "Anyone".

[@GregsAStar]

RimstarOrg Ok I fixed the reply settings, thanks for telling me there was a problem. Would the audio output on my computer be any more powerful? Is there a way to amplify the input?

[@RimstarOrg]

Greg Mitchell I really don't have a feel for the the strength of the audio output of a computer. I suspect it's about the same as the CD player in this video though, since both are used with headphones. There must be an amplifier in PC speakers that makes it louder. You can buy small amplifiers like this one comingsoon.radioshack.com/radioshack-mini-audio-amplifier/2771008.html#.VYM7d0bSnbg or you can make your own like mine here kzbin.info/www/bejne/gKWzqKuYhMx1ftk

[@RimstarOrg]

+Electronic Experiments I haven't worked with 2 pin oscillators but from what I read of them a while back you'd have to add more circuitry to get it to work, basically circuitry to make up for what's in the 4 pin oscillator that's missing in the 2 pin oscillator.

[@RimstarOrg]

You're welcome. I agree, they are pretty interesting.

[@RimstarOrg]

Thanks, Samimy. Radio controlled car, able to survive in the sea? Where'd you get that idea from? I like it though. I might leave that one to you, fits better with your awesome channel. :)

[@RimstarOrg]

Glad to hear it! And you're welcome from Canada!

[@dylandopsovic7045]

Instructions unclear, got raided by the FCC

[@fidelcatsro6948]

congratulations

[@wastefulengineering]

this is actually a very probable event

[@RimstarOrg]

+Raul Rifaie Ronney Yes, it should work with the portable crystal radio. (Please fix your reply button. It's takes extra time to reply in this way.)

[@RimstarOrg]

Thank you for the suggestion, but I feel the general interest would be too low for that for my channel.

[@RimstarOrg]

I don't have the one from sci toys, but from the photo on their website it looks like 3 prongs and 2 prongs. In that case use only the outer two of the 3 prong side to go to your sound source. If yours really does have 3 and 3 then I'd suggest trying using just the outer prongs on each side and testing both directions to see what works. Is there anything written on the transformer or did it come with any documentation?

[@RimstarOrg]

Yeah, I had a few requests so that's why I made it. Just make sure you don't make one that's too powerful and interferes with other people's communication and radio.

[@Slider2732]

Very clear ! Tried this a few months back and it worked well. Got a few osc's from an ancient (early 1990's) PC peripheral card. Range is short but it's fun and easy to wire up :)

[@RimstarOrg]

It's a 1 megahertz oscillator which is 1000 kilohertz. That makes it 1000 on the AM radio dial.

[@photonik-luminescence]

One question though, is the coil only amplifying the source signal ? If so does that mean if you have a higher power source like 12V and is hooked to a transistor (to act as a amplifier).

[@primodernious]

i actually realized you can make one out of a boiler and steam going trough a flute that goes trough a big piezo electric crystal that is connected to a antenna spark gap circuit by using wood as energy source. you can also use a water wheel system that use a bowel to create frequency mechanically by resonant frequency of material and connect that to a piezo crystal. for the voice part we need a piece of graphite in between the arc gap connected to a speaker funnel like a old hearing aid. by speaking into the funnel the graphite will vibrate the current and the bowel or flute will act as carrier wave and the crystal will create the electricity to provide electical power to the contraption. the receiver is just as simple. you use same type aparatus for receiver but as sound will come out the other way but this time the graphite will play the sound instead of sending it. if you can't hear the sound the other end, you need a way to tune the signal by adding some metal to the funnel or crystal electrode and it chould works as a tuner by regulating quantity or pressure to the contact point.

[@mw10259]

dumbcreaknuller YOU FORGOT THE BALLOON THROUGH THE HAIR STATIC ELECTRICITY FLUX CAPACITOR

[@kennymolina1555]

If im not mistaken most whip antennas in am/fm radios are only connected to the fm circuitry. Thus putting the whip antenna near the am transmitter make little to no improvement to signal. Most am/fm radios use a ferrite rod antenna for the am circuitry that is housed inside the radio case. As ferrite rod antennas are directional one must turn the back of the radio to face the desired and get as near as possible to the source to improve reception.

[@RimstarOrg]

I've no experience with powered AM radios, ones with ferrite rod antennas, but with crystal radios, which get their power from the incoming radio waves themselves, the longer the straight antenna the better, and preferably pointing at the radio station, though that's rarely practical.

[@kennymolina1555]

I was just saying because around 6:37 it looked like you were trying to improve reception by getting the whip antenna closer to the transmitter's antenna.Either way this is a good informative video. Do you happen to be an amateur radio (Ham)? you seem to know quite a few things that might also correlate with amateur radio.

[@RimstarOrg]

No, I'm not a Ham operator. My experience in radio is only with crystal radios.

[@finthegeek]

You got it close. FM and AM antenna are the same, the difference is the frequency. AM being 1khz ideally wants a 150m antenna!! FM@90mhz is happy with 1.58m ish The reason AM is set up like that is to compensate for the lack of an 150m antenna The AM antenna you described is a compromise antenna. Either way the losses in the output of that radio will be mental. But the extend length probably helped. At the power levels being talked about it's all irrelevant anyway as you wouldn't even dare to try and optimise that thing without significant filtering. That said well observed re antenna differences And very cool little project, questionable legality but genuinely know harm in doing the experiment for experiment sake

[@RimstarOrg]

I'm happy I could help. And thanks!

[@RimstarOrg]

I'm no expert on making a full radio. There's a lot that goes into making on properly, not to forget getting a license in some countries. But I do know more power and a longer antenna wire are two things.

[@RimstarOrg]

Added to the todo list. Thanks!

[@RimstarOrg]

It depends on the country. As I say in the video, keep it low power and with a short antenna and make sure you can transmit well only a few feet at the most.

[@SouparnoBardhan]

this was a great video,but could you please show how to reduce noise that is being transmitted as well as received (by the receiver you made),and how to make an effective antenna (like the circular loop or the delta loop)?

[@quesocat42069]

You may want to adjust your annotations to say that in this case the long bus rows didn't connect to eachother, but do in some cases. Great explination of the breadboard by the way, those things baffled me when i was younger.

[@RimstarOrg]

Oh I have no idea. The todo list is long. It won't be for a few months at least.

[@ozgtzt7281]

you used a 1.8 megahertz oscillator in the video.wavelength=(3x10^8)/(1,8x10^6)=166,66 meter. so you need 166,66/4=41,66m antenna. is this true? Did you use a 41,66 meter antenna?

[@RimstarOrg]

You can use a shorter antenna, mine it very short as you see in this video. It's just not as efficient. However, this is not a circuit you want to use for transmitting more than a few meters since it broadcasts on a bunch of frequencies (harmonics).

[@ozgtzt7281]

@@RimstarOrg I want to send the signal with module 2 meters away. How long should the antenna be on both the transmitter and the receiver?

[@RimstarOrg]

I don't have an precise figures for you but what that's about what I did in the video. Just keep in mind that with all the harmonics (the different frequencies) it'll be transmitting on, you may even interfere with other electronics of your own. Also, make sure to keep it very low power, i.e., so you don't transmit any farther, since you'll interfere with other people's electronics. In most countries, transmitting like that is illegal and requires a license. If it's possible you'd transmit farther then look for a better circuit. This one's intended only as a simple, fun, educational thing.

[@RimstarOrg]

You're welcome. And thanks for letting me know.

[@ArtOfTheProblem]

cool project! thanks for sharing

[@genetomblin2883]

Thanks for showing me a simple variable capacitor. I need something to tune a receive loop antenna. I think I can get a value in the range I need with your design.

[@cri8tor]

What kind of electronics can a 1 MHz crystal oscillator, or any crystal that would work for AM, be salvaged from? Thank you for the great tutorial. Cheers

[@RimstarOrg]

Maybe look for an old transistor radio.

[@rocky61469]

Thanx you made this sir, i was waiting for this for a long time now.......

[@AndrewR-y9h]

You are a scholar and a gentleman and a superlative instructor. Also I made thing and it works. Wow.

[@RimstarOrg]

Thanks! I'm glad you enjoyed it and found it useful!

[@FeaRcarlcool]

Thats so awesome and useful, thanks from Australia!

[@helraiser666painkil]

That AM transmitter is absolutely amazing I'm going to buy all of the stuff from Amazon and I'll give it a go and see if I can make up one of these AM transmitters and they look quite easy to put together and I will give it a go when I get the spare time OK and I'm really into electronics anyhow because I'm a Amateur Radio Operator and I like to make up projects like this all the time plus many other things as well. Great video and a really good demonstration cheers. Stephen M3SNV 73's.

[@RimstarOrg]

Oh I doubt it would be mid-June. It takes longer than that just to get the parts through the mail. I guess you'll have to look elsewhere.

[@coroamanicolai4527]

This was explained very well. Many thanks for the video!

[@TeodorMusic]

What if I want to broadcast myself speaking? Will simply plugging a 3.5 mm computer microphone in instead of the cd player output work? Or will I need some sort of sound card? Nice video!

[@aerofart]

Great video(s). In this video It appears you are modulating the voltage to the oscillator using a high voltage signal from the transformer. Is this correct?

[@RimstarOrg]

You can use a stronger sound source to begin with, like a PC speaker amplifier or a stereo amplifier, instead of a CD player. And also use a longer antenna. But it's not a good idea. If you broadcast over a larger area then you may interfere with other people's radio. This transmitter is especially bad since if transmits over many frequencies at once. In some countries it's even illegal to broadcast more than a few feet without a license. So no tutorial :).

[@tenlittleindians]

I read somewhere that a typical audio transformer has a 12:1 ratio. I'm thinking a 9 volt transformer is closer to this ratio than your 6 volt transformer and may perform better. That's something that might be interesting to compare against your 6 volt transformer. An old 9 volt wall wart style power supply may contain a transformer about the right ratio.

[@RimstarOrg]

Thanks! Glad to hear it.

[@johncsunil4049]

Thank you for making a radio transmitter video !!!!!

[@AJ_FILMS]

ok thanks your awesome every one else dose not reply to our questions but you do and you answer them really fast thanks

[@RimstarOrg]

That would be a whole other circuit. I haven't done any others yet.

[@RimstarOrg]

There's a link in the description below this video to scitoys' website where you can order it.

[@Oinikis]

cool! you should make your own ocilator, whitch is basicly a fast blinker. then you could make it variable frequency, becouse there are alot of schematic on variable blinkers. i think putting smaller capacitor will make it blink faster.

[@K5DVT]

RimstarOrg, I has one of these transmitters and they worked very well.But,now being a ham radio operator i have multiple frequency bands and spectrum. Operating on 1.8 Mc will also cause transmission at the end of our 160 meter band which spans to 1.8-2 Mc. Using it in this case is illegal with out a ham radio license and because am covers 3 Kc ether side off the central frequency(1.8 Mc) you are transmitting even out of our band and in to the narrow band am frequency.To solve your harmonics and sub harmonics you can use a circuit called a pi filter. It uses coils and capacitors to let only the frequency you are transmitting on to be passed.

[@K5DVT]

Also, the resown why the harmonics and sub harmonics are there, is because during oscillation, the oscillator probably has a "virtual tank circuit" ( witch is a coil and capacitor in parallel) and the circuit works by rejecting all frequency expect the one it is tuned to . All of the rejected frequency either go through (harmonics) or so far off tuned frequency, they just dissipated and become week.

[@RimstarOrg]

K5DVT I'm aware of the issues re transmitting. that's why in the video I advise people to keep transmission distance short, no more than a meter or two distance. I advise people that in my replies to comments too when it sounds like someone is trying to transmit further. And thanks for all the tips. I hope to do a filtered one someday. Also, thanks for the explanation re the probable causes of the harmonics and subharmonics.

[@FuZhixiang]

Hi there. Also this question is a little off topic but I still would like to consult you. Recently I assembled an quite simple AM tube transmitter with tube, coil winded ferrite antenna and variable capacitor and such. It now works but the sound is strange. Normally the sound becomes clear when a radio tunes into the exact frequency and becomes fading out when it tunes away from the exact frequency. But mine is weird. When I tune it toward the frequency say 1000kHz, the sound becomes more and more obscure but when I tune it away a little, say 1002 kHz, the sound goes up and clearer. So what's the matter with this setup? Thanks in advance.

[@pricemac]

Now, I'm no expert, but in playing with crystal radios, I find that super strong stations can overload a speaker if you have an amplifier hooked up. Also if the transmitter is right near to the induction coil (coil winded ferrite rod) you might have an issue with the magnetic field from the transformer affecting the induction coil, while also getting signals from the antenna. If they are opposite directions on the coil, they will cancel each other out when you tune the station, but being slightly off will allow one to be more powerful than the other. Just my guess from messing around with home-made crystal radios.

[@ivanrodionov9724]

+pricemac I dont think the transformer would play a big role in the frequency if it is on a continuos ferrite, however if it is an air core or a tapped transformer, it would be a whole different story. Probably what is at play here is harmonic and subharmonic frequencies. Since the frequency is really low, and i am asuming your antenna is not 60 meters (because of the period of the wave)(rod antenna), you would have a lot of harmonic and subharmonic frequencies. And it probaly just so happens that one of them is 1002khz.

[@pricemac]

ivan R Very possible, I haven't got the most ideal setup for testing, but that sounds like a probable cause for the interference I experience... I will have to play around some more.

[@ivanrodionov9724]

pricemac yeah probably, my advice to you is you either use a directional antenna or use a higher frequency. Let me know if you get it to work better :)

[@Dazzwidd]

This sounds like you're getting more FM than anything else

[@Slider2732]

Oh nah, didn't video it. Built another couple of years ago that used a 1.5V AA, it had a transmit range of about 30ft..lot of fun bending the 4 or 5 turn small copper coil to change the frequency, really hands on that one in an intuitive way ! Found it on one of those 100's of circuits type websites.

[@RimstarOrg]

Thanks! Glad you liked it! And I'm trying! :)

[@justcama]

Interesting music choice for something like this . It makes it seem like a battle or level in a video game lol

[@SAMIMYS]

awesome tutorial very educational. good video too. next time make a radio controlled car to be able to survive in the sea as well :)

[@RimstarOrg]

I don't have any way of knowing. I suspect if the information's on the web, it's probably in German. Just keep it low power and with a very short antenna that can transmit less than a metre and you won't bother anyone.

[@tehcno007]

nice one!! i had made one of the simplest one using a cell and some foil..connecting the two leads together makes a faint "dot" enough to trasmit morse code using a transformer you can get pretty high voltages from the battery which is also fun...did you try and see that when you touch the cans or there is a spark in kelvin thunderstor there is a dot in the radio (AM) your videeos are very educational...,

[@RimstarOrg]

It worked for me, but I can see not having the right transformer being a problem for some.

[@muzhikforchaplin1203]

With this setup, increased voltage and a much larger antenna how far could the signal travel?

[@RimstarOrg]

I don't know but it's illegal without a license in most countries anyway. That's why I kept the signal weak in the video. It's just fun to experient with.

[@zundfolge1432]

@@RimstarOrg u.s.a. limit is 100milliwatts and an antenna less than 10feet long. This transmitter is not illegal. I doubt its more than 100millivolts

[@RimstarOrg]

Thanks. That's good to know. I hadn't known there was a lower bound.

[@masonnero9038]

@@zundfolge1432 99 milliwatts and an 11 foot 9 antenna it is then.

[@finnthewitch]

wonderful tutorial! let’s say i wanted to add an on/off switch to my transmitter, as well as an LED light to indicate that the transmitter is on. how would i do so? looking forward to doing this as my first transmitter project

[@RimstarOrg]

You can cut either of the wires coming from the batteries and put a switch there. For an LED, I guess you can put one leg at the side of the switch farthest from the battery and the other at the battery (i.e. in parallel with the whole circuit). Be sure to include an appropriately sized resistor so that you don't burn out the LED. Keep in mind that you shouldn't transmit more than a few feet. Transmitting is illegal in many countries without a license (look for HAM radio license) and this circuit also transmits on multiple frequencies, which is not good. It's only good as a fun project.

[@aerofart]

Good info, Rimstar. I look forward to seeing the waveforms!

[@InnovationBlast]

Don't worry, I want to build it for the concept rather than actual functionality. But in theory, if you want to be able to broadcast farther away, what variable(s) would you need to increase (like using more power, a longer antenna wire, a lower frequency, a combination of those, or etc.)?

[@RimstarOrg]

It would transmit on harmonic or subharmonic frequencies. For the harmonics, multiple 1 megahertz by 2, 3, 4, ... so 2MHz, 3MHz, 4MHz, ... For the subharmonics, divide by 2, 3, 4, ... so .5MHz, .333MHz, .25MHz. And it's pretty sloppy around those frequencies, i.e. a lot of frequencies around them. That's the same as for chip I used, except it's harmonics and subharmonics of 1.8MHz.

[@brfisher1123]

While it's absolutely true that it is very illegal for us to transmit radio signals without a license and we could get in a lot of trouble if caught, people with those personal FM transmitters tend to pick unused frequencies to get around that problem, but as you said we should NEVER risk it by making the signal too powerful. AM (unlike FM) can be tricky however as it can be difficult to tell if a particular frequency is unused or not due to AM's susceptibility to interference.

[@sergiofrinchezki9089]

Ah crap this is EXACTLY what I wanted to do

[@freakytesla1733]

Hey, Great project as always! I am getting a two pin crystal oscillator locally. The 4 pin one is not available... Can I use this one instead? If yes what would be the new schematics?

[@RimstarOrg]

Thanks! The answer is, yes you can use the 2 pin one instead. I have seen some schematics online in the past but I didn't save any links. Some were KZbin videos. You'll have to search for them.

[@FabiP1997]

I've got a question: Do you think, it's possible to make this transmitter with a transmitting power of about 10 to max. 100mW in order to power up a crystal radio with a very small antenna about 1/1.5metres away? Because I'm planning to build a very small crystal with a as small as possible antenna. Could you answer my question whether it's possible or not? If your interested in my project, we can also discuss a little bit more about it - it would be a quite great thing if it works. Thank you in advance!

[@ivanrodionov9724]

+FabiP1997 yes it could work, but you already would need a much much higher frequency for a meter antenna(assuming it is a rod antenna), would need a frequency of at least 0.2 meters or more in order to get any gain from it. And if you use a 300 meter frequency (1mhz), you would only have 1/60 or 1.6% of the power converted to that frequency. You would also have a lot of harmonics and subharmonics. So if you would want to hear it, you would need more power(much more power) or use a different type of antenna or easiest of all, use a 400mhz crystal. That is well under a meter and you would have 75% gain from it.

[@brobrio]

Thanks Bud! It's amazing you can do that! Thanks for sharing!

[@GregsAStar]

RimstarOrg How could I improve the range of the transmitter (other than using a longer wire)? I understand I shouldn't broadcast very far, this is just for the sake of learning. Could coiling the antenna wire help?

[@SudiptoGhosh]

I am making a radio and a transmitter for my school science project. I have all things except crystal oscillator. I searched all stores but can't find a 0.9 to 1.2 MHz oscillator. I found a good 0.8MHz oscillator. Will that work? The 1MHz oscillator has only 2 pins while the 0.8MHz has usual 4.

[@RimstarOrg]

Sudipto Ghosh 0.8MHz will work. The normal AM radio range is 0.54MHz to 1.6MHz, so 0.8MHz is right in the middle.

[@spib65]

Just made this,..works a treat, many thanks

[@edwardbatista7920]

for those of us that don't know much about antenna and are trying to learn it be good to explain what each component is doing. Like why do you need the transformer and the AA batteries?

[@RimstarOrg]

Good questions. I answer them in this follow-up video kzbin.info/www/bejne/lWWQhKtjiZuJeMU

[@brandonlaragirl]

​@@RimstarOrg the link doesn't work 😭😭😭

[@RimstarOrg]

That's off. I just tried it and it worked for me. Try this short version of the link kzbin.info/www/bejne/lWWQhKtjiZuJeMU

[@basimpson2161]

Hello from TN. The link takes me to this same video! I have almost everything for this project. I’m just waiting on the wire to come in.

[@user-hm7fy4go9w]

Sir can you make a on video on how polarized antenna work?

[@luigi2999]

Correct me if i'm wrong, but I think one could theoretically replace the crystal oscillator with a crystal rated for 12 mhz, and transmit in the SW band, or one for .225 mhz, and transmit in the LW band.

[@RimstarOrg]

I would think you could. Just be careful not to interfere with other people's radio.