Picture of Make a simple AM transmitter
Make a simple AM transmitter that will cost you less than $5.

Step 1: Stuff you need

Picture of Stuff you need
A crystal whos frequency is between .9000 and 1.2000 MHz.
Some wire
A male headphone jack
A breadboard or experimental circuit board (optional)
stoobers5 months ago

Have you tested this thing for harmonics?

How would I get rid of harmonics to make the signal cleaner?

Thanks in advance!

fartnuckles7 months ago

One thing to note though, Many crystal oscillators have a maximum power supply voltage of 5V +/- 0.5V. Indeed some are only rated to 3.3V max. You will need to check the data sheets for your selected oscillator for it's maximum power supply voltage BEFORE applying 9V as shown. Otherwise they will stop oscillating permanently very quickly if their maximum rated voltge is exceeded!

You have a nice all explained how to make the radio transmitter on the site: https://www.youtube.com/watch?v=_4-Sx-T6VBc

I build this and using an audio output transformer and it works great. Found a 1mhz crystal and audio output transformer on ebay.

Is the Modulator in the Drawing below that looks like a Transformer? How can we purchase one, and what do we look for?
The transformer is changing the voltage coming in from the mp3 player so the crystal can be "set off" a little easier. You need to kick it in the pants to get it vibrating.

The "modulation" (the signal) is being generated at the source (the mp3 player) and passed to the circuit so a carrier wave can be added.

If you don't use an mp3 player, but just just a voltage source, you have made a "CW" transmitter (for morse code).
bilsat1 year ago
Where i can find the crystal? I live in europe, and greece specifically. Please i want it to find it offline because i got no money for credit cards and i dont use paypal or anything that pays online.
Find a place that takes bitcoin.
nodoubtman3 years ago
I have a crystal of 1.8432 Mhz , is it okay?

1.8432 mhz is in the "shortwave" range.
AM radios are in the "mediumwave" range.
To receive the rf made by this crystal, you need an AM radio that receives in the shortwave range.
fenwaydog3 years ago
I'm using an old crystal will this still work? The problem is it doesn't have a MHz Rating anyware on it.
As long as you tune into the frequency that the crystal is transmitting, yes. Substitute any crystal value with the one listed and the results will work. Tuning the receiver to the same frequency as the transmitter is the only difference.
Can a receiver be made in a similar way?
Yes & No. A receiver to pick up the signal can be done, but sometimes it's a bit weak. It is much easier to make a receiver to tune into local radio stations. The Instructable that I used by MacDynamo is at... http://www.instructables.com/id/Simple-OP-Amp-radio/

I know you asked for a similar way, but the purpose of the crystal in this Instructable is to transmit at that frequency, the Instructable I linked is how to receive signals, so similar in function, not really. But simple in design and easy to build, absolutely. I hope this helps you. Additionally, there is a ton of videos on YouTube, most notably... http://www.youtube.com/watch?v=4E6uwEiOGsQ&feature=share&list=PLtv36f0AWivbNwZWXflk1OATeJlMk3B-P

There is also a follow up video with a schematic and partslist. (Although I noticed he hooked things up differently and sometimes the parts were different but nonetheless it works.) The simplest radio to use in my opinion would be the old school Crystal Radio or Foxhole Radio. Personally MacDynamo's Instructable is the easiest to follow and has the best results of the ones I tried. Enjoy!
eric m2 years ago
Hate the new layout for instructables. BRING BACK THUMBNAILS. So Stupid!
jcox242 years ago
I made a transmitter using an oscillator and an audio transformer, run off EITHER a 9v cell or usb
Evo72 years ago
Greattt............stuff in here!!!!
TuxedoRonny3 years ago
Hm... I did everything exactly as you stated (without using a modulator) and this didn't work- at all. I have all the exact components, tried several different radios, etc. and still nothing. Are you sure this works on its own? Has anyone else tried this?
electronicz3 years ago
I have a 1.00 MHz crystal like bmlbytes, how high of a voltage can this crystal withstand?
account3r23 years ago
if i make my own transmitters and receivers using a 50 MHz crystal, since the crystal isnt in the FM or AM range, would the FCC rules apply to it?
That is in the Amateur Radio range, and this circuit does not have enough power to really go far. Low power projects like this aren't enforced by the FCC, it's much like one of those mp3 audio devices that broadcast your mp3 player on a radio station in your car.

If you were to boost the power, you would then be subject to FCC rules.
nodoubtman3 years ago
do you need an audio transformer for this? i have a 600: 600 ohm 1 to 1

nodoubtman3 years ago
what kind of antenna do you use ?

Just some wire shold do it.
Wesley6666 years ago
Also what if I want FM not AM?
get a 100MHz oscillator ...and tune your radio to 100MHz FM
so I would tune a radio to 33.3 FM if I had a 33.33 MHz oscillator. (The only oscillator I have is 33.33 MHz) Also how would you build a receiver for a specific Frequency? (Preferably 33.33 MHz!)
well first fm is from 87MHz to 108MHz what you have there is close to the range of remote controlled airplanes,49 i suppose you might be able to modify a radio to recive 33MHz (try by turning the little "screws" on the radio's circuit board?) also,since it is not in the am or FM range,you could broadcast it for MILES,ive hear of someone sending morse code from one side of the country to the other at 20something MHz
M0HIZ ReCreate3 years ago
Firstly, FM and AM and not bands of frequencies, they are types of modulation. Secondly, do not try to modified a radio to receive on a different frequency as you will almost certainly change the tuned circuits to something totally different to what you want. Finally, it is very common for people to talk to poele or send Morse code to people on different continents or the other side of the world. This is one of the many aspects of ham radio.
very cool. I found it in a computer motherboard or whatever and I tested it and it worked and I have never touched it since. I was hoping to build a receiver specifically for 33.33 MHz and I was wondering how I would go about that, and if it helps I have a crystal (two pins) with the same 33.33 MHz range if that helps. Thanks
if you find a crystal(2-legged) in a computer,it is used for timing,thats why replacing the crystal in a gameboy color speeds up the game. it speeds up the timing,making time trials unfair,crystals are used to keep track of time in computers,but oscillators...i have no clue why that would be inside a computer
crystals are a very important part of an oscillator, normally they are used in a oscillator circuit to set the frequency, and yea, the crystals on mobo are for timings, the 33.33 mhz crystal on the motherboard is to control the timings on pci slots, may pci cards also have 33mhz crystals on them,
this isn't a crystal its a oscillator, so it gives off a signal at that frequency, crystals don't give off signals, plus I have never seen a computer with another one in it ever and the computer it came out of had no 33.33 MHz crystals in it any how, they were all 14.6 MHz.
i assumed it was a crystal because he said 2 pin, never heard of a 2 pin ocillator. most new motherboards have digital oscillators so you can set the pci bus clock in the bios, so you might not see many crystals (if any) on new boards, im not sure what 14.6 mhz would time
well the computer it came out of was older then the dinosaurs but the frequency is 33.33 MHz and all the other crystals were 14.6 MHz so I have no idea what it was doing.
i still have my windows 3.1 computer up in my garage somewhere... it used to run DOS so im sure my computer has plenty of crystals
I have seen many crystals (two legged) in a computer but I have only ever had this one with an oscillator in it. Very unusual.........
like i said below, fm is modulated different compared to am, the transmission frequency of fm is based of off amplitude or as the amplitude of the audible sound wave increases the frequency of the transmission increases, but with am, as the amplitude of the audible sound wave increases so does the amplitude of the transmitter though the transmission and audible sound dont have matching waveforms... i think i explained that right (hope so)
Can we use an NE555 based oscillator instead of a crystal oscillator for this`AM transmitter circuit?
You would not be able to replace the crystal with a 555 timer for this specific circuit, but... you can make a much better transmitter if you base the oscillator off of a 555 circuit, although it would be a lot more complicated than this. I would try to get a basic understanding of amplifier circuits (not just opamps) and learn what signals look like before and after it had been modulated for am transmission, before I would dive into a 555 based transmitter. It would be a lot of fun and a good learning experience tho. ....Maybe I should maybe make a how to sometime....
OK thanks
Dr.Bill3 years ago
I've never seen a transmitter this simple !
kceeno6 years ago
This isn't illegal, is it? Because I wanted to start my own mini radio station. :) What kind of wire would give the best signal? How long should the wire be to get a signal from, like, 2 miles away? Haha. And you can plug a normal microphone into the audio input jack and send a aignal, right? :D Just wanna check. :P
kceeno kceeno6 years ago
I meant signal. xD And if you have a crystal with a higher MHz what'll happen?
bmlbytes (author)  kceeno6 years ago
Legality is based on the country your in. In the US, there are laws about how powerful a station may be and how big an antenna can be before you need a license. To be honest with you, this was one of my first instructables, and it has been several years since I posted it. I dont do much with radio anymore. I dont know what would be best for transmitting a AM signal. Im pretty sure you can buy antennas that are "tuned" to give the best performance. Also, if you go with a higher MHz, the listener will just choose a higher frequency station to listen to you. Say you use a 1.2 MHz instead of a 1.0 MHz. With the 1.0MHz they would tune to 1000, but with a 1.2MHz they would tune to 1200.
bmlbytes (author)  bmlbytes6 years ago
As far as legality in the US would be, I wouldn't be too concerned. The most they will do for a first time offender is knock on the door and say to turn it off.
They know my address? O_o I guess the government does know everything :D
kceeno bmlbytes6 years ago
Alrighty. Thanks for all of your help!
Hi there, You mentioned something about speaker wire for the antenna. Would any type do?

Much thanks~ OldAviator
What freq would I need for 660? (AM station 66 AM)
Gubban bmlbytes5 years ago
Gubban kceeno5 years ago
RE: kceeno
I dont know if it is illegal, but you wil need approx 30-35 feet long antenna. you can use the cheep type of bad isolated speaker-wire. And, NO you cant just plug in a microphone, becuse the transmitter need power, BUT if you use a small microphone amp. -maybe it works! (PS! I got the same idea as you! i wanna to start a radio station!)
account3r23 years ago
between .9 and 1.2? :P all i have are 9 crystals that are 50MHz and a mysterious 2 legged one labeled 33.8688
atonix3 years ago
I think that we can increase its power by using an audio transformer .
jgabrielian4 years ago
how can i increase power?
Really neat idea! But do you have to worry about the FCC Because you are transmitting radio signal?
bmlbytes (author)  computergeek7 years ago
Not if its not too powerful
fgul bmlbytes4 years ago
Can't we use NE555 IC based oscillator?
Thanks! Also I found a copy of the FCC Rules and regulations available here. See section 15.23 home built devices.
If your intent is to act as a low power broadcaster, I believe FCC regulations other than Part 15 may apply. In the event there isn't the following would be the applicable portion of part 15;

Section 15.219 Operation in the band 510 - 1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heater
power) shall not exceed 100 milliwatts.

(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3

(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the
level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification
may be based on measurements at the intentional radiator's antenna output terminal unless the intentional
radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by
measuring the radiated emissions.

The above "jives" with what I have read on the topic since 1968. Fairly restrictive, doesn't allow for a very effective antenna in the AM broadcast band

______4 years ago
Do youy have a pic of yours fully assembled, can you post it?
I'm assuming a 46000.00 KHz crystal would be way too high a frequency to use with a standard radio, correct? That would be something like AM 4600 right?
bmlbytes (author)  the.texas.trucker4 years ago
First of all, that is 46MHz and yes, that is out of a standard radio range.
You would probably need to amplify it. Microphones don't output much power, so your transmitter signal would be extremely weak.
ummm... Don't you need a battery or something?
A microphone generates a current with it's structure, however, this signal is very small. That's why it says "To audio source (an amp will help)" The amp would be powered by a battery, increasing the signal of the microphone.
 could I use a female jack in instead to plug in a microphone? 
Kinda you cannot directly plug in a microphone w/o an amplifier
TheFawns4 years ago
check this out http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.html
arihant5 years ago
what is the range??
it matters on the type of antenna and how it is fed
id say a few meters with like a 3 ft piece of wire but maybe a mile or more with a nice dipole and matching feed line or direct fed dipole
twitsl5 years ago
What kind of device could i salvage one of these crystals from?
i think if you have an old computer it should have 1 or 2 of the crystals somewhere on the motherboard but alot of slightly newer computers only have the little crystals not the oscillator. I got a few of mine out of a old 486 box laying around
id say the best free place to get the crystal oscillator is a dump or transfer station they should have a big container for old electronics...thats my best bet
hope i can help -73
arihant5 years ago
can we reverse same schematic to get a am receiver
fd185 years ago
Can I reverse the process to make a very small AM Receiver?????? Just on the one frequency I need instead of all of the variable inductors ad capacitors.
jules155 years ago
so.. if i wanted to just add a mic, how would you connect it, and of course the power?
bmlbytes (author)  jules155 years ago
You would just need to connect a mic to an amplifier before running it through this.
karanraj5 years ago
The founder of scitoys wrote gonzos gizmos

conrad24685 years ago
movieman975 years ago
Is there a way to make the circuit tunable? would you be able to lower the frequency by putting a potentiometer between the battery and the oscillator?
where can i find this crystal none of the store around here have one.
u don't need to buy, take apart a radio, u'll for sure find it there
i only have crystal with 2 leads, not 4 lead.
can i use it (crystal with 2 leads) ?
No.  The package with two leads is a just plain crystal, not the whole crystal oscillator enchilada, which is what comes in the 4-pin package.

The rest of the circuit typically looks something like this:

Usually it is easier to just buy the 4-pin oscillator package, if you can find it:
I dont think so... But u can try!
szechuan536 years ago
can you use an adjustable oscillator?
bradster6 years ago
where do u get said crystal?
nrepak bradster6 years ago
I got some from from electric goldmine but radioshack might have it
Gubban nrepak5 years ago
No, i checked, radioshack dont have an crystal ossciliator
wat u actually mean by crystal
digikey under oscillators, electronic goldmine under crystals then click on oscillators. i like elec. goldmine because their stuff is cheaper(1 MHz oscillator)
Gubban5 years ago
so all you need is a jack, an antenna and an oscillator?
In australia, radio and television is like nowhere past certin power and frequencies
Will it work with IPOD
I built the version of this project that used a modulator and a 9v battery and at first I thought it didn't work. But when I removed the modulator, leaving the battery, I got the transmitter to work.

I connected it to a normal radio antenna, then laid the antenna vertically on top of a camera tripod.
At first I thought it could only transmit within my house, but when I called my friend who lives around 30 miles away and told them to turn their radio to the frequency, it turned out that they could just barely hear my transmitter. 
Lightning25 years ago
what is the difference in the circuit between the one with the modulator and the one without?
Lightning25 years ago
do i have to use a nine volt battery, or could i use a smaller battery?
rengawtm5 years ago
can you put a volume control on this

yes, just add a pot between the crystal andheadphone jack
gohsthb5 years ago
If you have an oscillator of a higher frequency that you can easily divide by multiples of 2, you can use D-type flip flops to divide down the frequency.  For instance: you have a 4.00 MHz oscillator.  Each D flip flop will divide its input by 2.  So 2 D flip flops and you get a 1MHz signal out of your circuit.  Google "frequency divider flip flop" for more information.
riverreaper5 years ago
would 500 watts be too much ? im jokein by the way i know id get in trouble if caught lol
bluescope935 years ago

Question, Iam a Radio Amateur Operator (Ham Radio) Out of interest what Antenna are you using weather its a 80 Meter fullwave Dipole or a Helix quarter wave Vertical?

Win7Maniac6 years ago
I have a 4.0mHz crystal oscillator from a cordless phone. How can I use this (and lower the frequency because there is no "4000AM")?
can you get a oscillator (1mhz) from a radio?
the judge5 years ago
can u use a 3 pin ceramic resonator to do this? if so how?
kroq-gar786 years ago
male to male 3.5mm jack, right?
can er this ceystal in a card less phone
hai, iam a starter.if u dont mind can u pleas tell me how a wave of a particular frequency is sent through a distance through air. i mean how waves are coupled with other frequencies and sent through the air
bmlbytes (author)  kroq-gar786 years ago
No more like no end to a male 3.5 mm jack. Cut a wire off of a pair of broken/cheap headphones.
also, is a 1/8" jack same as 3.5mm jack? (i calculated it (sorta) and it was pretty close) i used a 1/8" cable from radio shack and it fit snugly into my computer, and my headphones also fit well into my computer, so are my headphones also 3.5mm?
Yea, they will do, but it would be best just to cut some off of some old or cheap headphones.
so will this effectively play on your radio my car doesn't have a mp3 line and if i can broadcast it like some of those i pod things will it work effectively nice instructsble by daa way
amagoul5 years ago
couple questions: 1) how long do you have to make the antenna is you only want to pick it up no more than 15 feet away? My car only has AM radio and i want to use this so i can listen to my ipod while im driving instead of talk radio. 2) this thing is powered by your device right?
you stole the idea from scitoys.com!
petrixx6 years ago
please can u tell me where can i find this Crystal whos can i take it form a old radio
outlaws6 years ago
can you hook it up with a microphone instead of a ipod jack
bmlbytes (author)  outlaws6 years ago
if it is an amplified microphone
outlaws6 years ago
mine is at the top of my house in my attic on a medium sized house will I get in trouble for that
outlaws6 years ago
is this illegal cause i dont want the FBI showing up in my house?
bmlbytes (author)  outlaws6 years ago
Its not illegal if done the way on the instructable. It becomes illegal if you transmit the signal too far. Also you don't have to worry about the FBI. It's the FCC you would get in trouble with :)
outlaws6 years ago
is the jack the ipod earphones without the speakers
outlaws outlaws6 years ago
thanks, your really healpfull (said in a non sarcastic way)
bmlbytes (author)  outlaws6 years ago
outlaws6 years ago
in the antenna dose the height count or could you lay a 25 foot wire along the ground. Dose coiling it around a rebar help
szechuan536 years ago
what if you use a crystal with higher MHz?
nrepak6 years ago
would it be possible to hook a microphone up to this and broadcast your voice?
yeah, any audio input will work. you could even hook up a guitar amp.
kroq-gar786 years ago
my isn't working well. i connected a speaker that i took out of a radio up to the leads from the computer, and i could hear it loud and clear. when i hooked up the transmitter to the speaker area of the computer and tuned my radio to 1000 AM (1 MHz oscillator), i got static and a monotonous buzzing sound. could anyone please tell me what i'm doing wrong????????
update on last post: after 2 hours pof frustration, it works but with terrible signal strength. i tuned my radio to the frequency of my oscillator ( 1Mhz , 1000 AM ), and there is no reception. i think there is a radio station already broadcasting there, which may be the cause of the problem. i tune my radio to its highest possible frequency, and i can hear it a lot better. i can only receive the signal from less than 1ft away. can someone help me?
bmlbytes (author)  kroq-gar786 years ago
How big is your antenna? Can you use/do you have a different frequency modulator (like a 1.2MHz modulator would be 1200 on the AM frequency).
i don't have a different oscillator, and don't really want to use a different one. i have modified my transmitter with 3 antennae, with the smallest being ~1ft, and the largest being ~2-3ft. i also used a joule thief circuit to amplify the signal and it is working better. i hooked up the cable to the computer, looked on youtube for music, and can only play some mario paint songs. all the others i can't get the words to come out very well. i can get the reception to be clear ~1.5 feet now.
im probably going to get a longer wire, tie multiple wires together, or use a very long telephone wire as the antenna soon.
bmlbytes (author)  kroq-gar786 years ago
Use the modulator if you still cant get it to work. It will really boost the signal.
How do I male/where can I get a modulator? What does it do? Update: I can now receive my signal up to 7 ft using my old metal music stand. It served as an antenna. I still would like it to broadcast more than 20 feet
bmlbytes (author)  kroq-gar786 years ago
A modulator would allow you to hook up a battery to amplify the signal. I usually rip out my electronic parts from old electronics.
Where can I buy a new one?
bmlbytes (author)  kroq-gar786 years ago
i thought you meant modulator, not audio output transformer (sorry if they are the same thing, i don't know much about them...). and could you please tell me which wire to connect where since there are 5 wires?
bmlbytes (author)  kroq-gar786 years ago
The side with 2 pins goes to the audio jack, the side with 3 pins goes to the battery and oscillator. The middle pin on the 3 pin side should not be used.
bmlbytes (author)  bmlbytes6 years ago
No wait I lied. Its the other way around. In fact look at the diagram posted, you can see 1 side has 3 pins and the other has 2. Hook it up that way.
My bad. I meant make not male in the beginning of the previoud message
bmlbytes (author)  bmlbytes6 years ago
Im sorry I meant oscillator not modulator
nrepak6 years ago
also is this legal
wan8 years ago
i hav a 27.145 MHz transmitter from a remote control for a little car... what can i do with that? ne way of making it work?
You might be able to pick it up with a cb radio on channel 15 or 16.
dinsterzz wan8 years ago
i got the same, or you need a radio that goes that high, or it doesnt work, are there any others things you van get an ascilator out of that would work??
Biotele6 years ago
What is the range of this device?
bmlbytes (author)  Biotele6 years ago
It depends on your antenna
let say I am using the standard telescoping antenna, what is the transmission range?
I think YMMV (your mileage may vary) comes into play here... :) Could be 100 feet, could be 10,000 feet, it depends on topography, power, antenna length, weather conditions, etc... :)
IdrisB7 years ago
Is there a way to do this with a 2 pin 4Mhz oscillator?
those aren't crystal oscilators. oscillators are 4 pins. 2 pins are crystals. you need oscillators to keep it simple
techdeck6 years ago
actually the guy who made scitoys wrote that book but the website is free and has a bit more projects.
revhead6 years ago
cound this be connect to some kind of mic or sound receiver so that you could place it in a room and listen into other people conversations by tunning your radio to the set chanle. this sounds a little creepy but it would be so cool to make. anyone out there that can help would be great
is it ok if i bought a 1.2280 one? will it work?
abadfart6 years ago
you could make a am loop
cryptopsii6 years ago
yes but in this case you'll need 2x ~22pf cap. and a resistor (because your 2 pin oscillator must be a plain crystal in fact not an crystal oscillator).
What kind/model of crystal is this? Where can I get it?
sadiag6 years ago
I was doing this project for my son, and I wanted to ask you how it works, since I connected all the parts on the breadboard, but I am not sure is every thing connected right, It's not working till now, I am sure I am doing something wrong and I need help
SG1Oniell6 years ago
can you do an instructable for a very small vhf transmitter?
codyraskin7 years ago
i think you have the transformer backwards in your diagram. should be 8 ohms on the input, 1000 on the out.
But yes, it is backwards.
This isn't his diagram. It's from scitoys.com
kvswim6 years ago
Unfortunately, mine won't work no matter what I do. But I might try to redo the thing without the transformer...
Rishnai7 years ago
This is a trick I'm going to have to use next time I'm wrenching on my car in the driveway and want to listen to something like a record or a CD. Or maybe my computer's audio library set on random. In fact, I have a project that needed just this ingredient. As for the crystal, where did you get that?
kvswim Rishnai6 years ago
You can get it at Jameco Parts, or scitoys.com has an entire kit (breadboard, oscillator, transformer) and all you need is hookup wire and soldering materials. (Both online)
alfonso Rishnai7 years ago
You can get the oscillator at Jameco.com, just search for 1Mhz crystal.
trumpkin7 years ago
hmm, isn't that schematic from the book "gonzo gizmoz"?
kvswim trumpkin6 years ago
uhh...no its from scitoys.com
I have looked high and heaven for the proper oscillator but I cannot find a thing in my huge treasure of junk. Would someone please give me an idea where to find it, please!
this is the web site i beleave this first came from on this site it goes more
indepth, and has some other cool and simple projects for radio, lasers and others. it also has a catalog with basicly evrey thing they show that u cant get at radio shack.
make shure u got some hook up wire for an intena.
have fun
most online electronic stores will have them
Only electronic store I know of is Radio shack and you can't buy them at the store or online. If anyone has a current link where to purchase please post. Thank you.
electronic goldmine
BG micro
these are all good but there are hundreds, even thousands out there just google for "electronic component store" :-)
912345678906 years ago
this does not work at all what do u hook up the ground to
yoseferani6 years ago
what if i have a 400.000 mhz oscillator how do i do it
amando966 years ago
where can i get the crystal? and will RC car's crystals work? or is the frequency too small?
no the frequency is way to high for AM and too low for FM(if your rc car is 49MHz) but if it is 128MHz or so it just out of range of your radio without modifying it there is a instructable here that shows you how to extend the range to 130MHz
you dont wana forget that am and fm are modulated different ways; amplitude modulation and frequency modulation
well...it works
hmm i will try that, what if i wire a bunch of RC cars' crystals in paralel? lol would it work...?
hey...i really don't know, try it! wire two of them is series and figure out what it should be in total(frequency)
it only comes to 90 Mhz... i need more RC cars xD
oh then try 3...yeah 3 it should be in the ra...wait a minute radios can tune between 87MHz to 108MHz(mine is messed up and tunes to about 110MHz)! I was right!
oh so it should work?
by theory but it could just produce a signal 2 times stronger
oh... then i'll TRY to find o proper crystal, like the one you use in this instructable, they shouldnt be too expensive right? :S
i don't know,its 2 bucks online so they will probably be like 5 at radioshack
:S radio shack no way i can to one in a near future... those have four pins right? could i find one in a n old radio or something? coz the RC car ones have two pins...
Dms124446 years ago
Just for reference to everybody. THESE ARE ILLEGAL TO USE IN THE US WITHOUT A LICENSE.
if the power output is under a amount, i dont think its illegal
party pooper :P
i dont live in the U.S. :)
sc4rzz6 years ago
So.. I could just attach my mp3 or computer to this? I'm trying to build one of these.
amando96 sc4rzz6 years ago
hey if you go to my profile i have a diferent version of this, nothing compared to this though lol it has a range of two meters and u can plug your E-guitar to it and have a portable amplifier ;)
bas_antony6 years ago
I will try this i make one before my one transistor and it was great and i wanna try this one too . good work...
Wesley6666 years ago
How do crystals work? I know that they vibrate or oscillate but if you put DC power through a crystal (the ones with two leads only) if you looked at the output on a oscilloscope, would the DC current be staggered or make a slight up and down motion or would it do nothing? Would it be just a straight line or would it change?
Following your logic, would it be possible to use like an oscilattor for Fm trnasmissions? I was thinking on uilding a cicuit with both Am - Fm transmitter, so if Im at the city, I would go to am, since its less used than fm... and if im on the orad, i would just send it to fm.. somethign like that... what kind of oscilator would i use for that?
No, you can not use an oscillator for Fm transmission. That would require an entirely different circuit, and it would not involve an oscillator.
really,what if i used a 100HMz oscillator for it instead?
ReCreate6 years ago
hey will the 2-legged crystals work for this? and if it does then how?
so how is this powered? did anyone try? did it work?
1:you have to harvest the electricity from a lightning bolt...yeah millions of volts and all 2:no ,look at the next answer 3:no it exploded for someone taking them in the blast,so they where unable to report it :P whop-de-do
lol it only needs 5 watts no where near a lightning bolt and if i did where would i input it and really illegal? if the police search my house this would be the last of my worries lol. None of you better be police.....
*whistle goes here* if i find a ...i mean if THEY(cops) find a mysterious AM signal and search your house they will expect to find an illegal radio station...set ...thingy ...not some square shaped thingy connected to an antenna
lol like I said it's the least of my worries...too bad you cant track me even if you had some special technology I'm too good a hacker..........ok now that i said that i shouldent post this comment but i will anyways.
fire bat8 years ago
what is the range on these things can it brodcast across 5 km plzz hurry ps this took 4 ever to find but i did it yay me lol if any one wants to chat email me or messenger me at beambot_5@hotmail.com
bmlbytes (author)  fire bat8 years ago
That depends. The bigger the antenna and the more power you put into it will all add up to how far it goes (try a 10 ft store bought antenna).
The "bigger the antenna" should have no effect. You must tune the antenna.

If your crystal is 1 MHz, then it is 1 000 000 Hz.
The speed of light is 299 792 458 m/s which is how fast radio waves travel.

If you substitute these two values into the universal wave equation, you can determine the wavelength.

velocity = frequency * wavelength
wavelength = velocity / frequency
wavelength = 299 792 458 m/s / 1 000 000 Hz
wavelength = 299.8 m

Now obviously, this is HUGE for an antenna and clearly goes over the FCC limitations, so you create an antenna that is 1/4 or 1/8 or 1/50 the wavelength.

Now, this is probably completely overkill for such a rudimentary transmitter, but if you can cut a piece of wire that matches the wavelength or at least a fraction of the wavelength, then you may gain some range.
hi im new here does a transmitter mean jammer
bmlbytes (author)  wcobretti8 years ago
No, but if you got close enough to a radio you could overpower it. This will primarally allow you to play your music that is on your MP3 player over any radio.
ReCreate6 years ago
Im gonna make this and possible hook it up to a huge antenna in my attic for better signal
ReCreate6 years ago
i have one,its 49MHZ so at what frequency will the radio receive in?
CanisLupus6 years ago
Don't you need to supply constant power to the oscillator in order for it to maintain its oscillation at 1MHz? Your input may drop below the threshold value for the oscillator the function. (I guess it depends on whether you have an amplified input signal). The second schematic with the modulator should work since it employs a dedicated voltage higher than the threshold value (which depends on the specs for the oscillator). Did you get this to work as you have it? Did you connect ground to a water pipe? I've tried your first way and it doesn't seem to work as is.
milo156187 years ago
Hey, I dont know much about this type of stuff but is it possible to use this, powered by a 9V batter, send the signal to a small reciever on the other side of a house and have the reciever somehow activate a small electric motor? If so or if you have any ideas on how to do this please e-mail me at milo15618@yahoo.com
bmlbytes (author)  milo156187 years ago
Several people have asked me a similar question. The answer in short is, no. There are ways to do this, but it would be more complicated and not worth your time. A better idea would be to modify an RC car and it's remote to get better range, and use the motor for something else.
I disagree. All you would need to do is have an AM radio (set to the correct frequency) going into a transistor. The transistor would act as a switch, turning on when the signal is strong, and off when the signal is weak.
yeah I thought of that but would have liked it to be smaller... oh well I'll make it work. Thank you though
bmlbytes (author)  milo156187 years ago
Check out my computer controlled radio, you may be able to get the computer to send a signal and recieve one. But then again, a computer is much larger than an RC car.
hi i live in england and ive benn trying to find a crystal oscillator but all the ones i have found seem to only have two "legs" can anybody direct me to a site or tell me where i might be able to find one? thanks.
jameco.com has the right oscillator. the link gets you straight to the oscillator.
hamradio7 years ago
this operation is leagel with the fcc if you transmit to high, then it might be a problem trust me im a ham i have an fcc ham ticket
AceFace7 years ago
What would it take to get a good enough distance for this to work in the Mob Mov Project? I don't know exactly what but I would love to know, this could save me some big money in the long run. I just don't have enough to purchase a built one.
bmlbytes (author)  AceFace7 years ago
More power and a bigger antenna. You'll have to play around with voltages and wire lengths though.
IdrisB7 years ago
Where did you get the oscillator?
bmlbytes (author)  IdrisB7 years ago
Random junk
arstart7 years ago
I would like to do a project with my 5th grade class to make transmitters to go with their crystal set receivers. Would it be fairly easy to take one of the 1.2 mhz oscillators and hook it up to a morse code key to send CW instead of hooking it to a microphone?
bmlbytes (author)  arstart7 years ago
Check out the computer transmitted one I did in another instructable. Just hook the wires up to that instead of to the computer jack.
bmlbytes (author)  bmlbytes7 years ago
steven.exe7 years ago
Where can I get one of these crystals of this frequency?
maguye0077 years ago
Dude, how exactly does the Crystal oscillator work?
dudemonkeys7 years ago
How close do you have to be to pick up the signal on a radio?
5Volt8 years ago
I like it ! The crystal oscillator works best when power supplied. A 5V (3 or 4 AAA batteries) supply with a (small) resistor would help. The resistor is necessary otherwise the radio sees a short to ground (through the battery). The capacitor de-couples the DC component (the battery) and prevents DC from getting into the radio and damaging it. Only the AC component (the sound) gets through the capacitor and adds/subtracts from the power supply yielding AM modulation. I haven't tried this but it should work. Ciao 5V.
sry i dont really understand these stuffs...but why is there a range for the resistors? what do they do? and the capacitor is electrolytic right (the black is positive and white is negative)? thanks
bmlbytes (author)  J50Nunlimited7 years ago
Resistors are used to keep the curcuit from getting too much power. The range is so you don't use a too week or too powerful of one. And you have it right with the cap.
thanks =]
J50Nunlimited, sorry I missed your question. Thanks Bmlbytes. 5Volt
5Volt 5Volt8 years ago
Of course when I say "radio" I mean the audio source you want to send into air (not the receiver...) ! Cheers 5V
VIRON 5Volt8 years ago
If anyone can't get the instructable to work, I recommend your circuit, because it is well designed; the instructable is powered by crystal magic.
So are you saying 5volt's circut won't work. BTW does 5volt's circut need to be grounded anywere?
The 5Volt circuit works very well. It is also legal in the Western Hemisphere with the negative grounded to a cold-water pipe and 10 feet antenna (wire) straight up. There is a limit to the volume that causes distortion and static, which is marked 0 dB on a VU meter on professional equipment, but on the 5Volt circuit you have to listen for best sound. The other circuits will always produce distortion and static if they work at all. That would violate clause (c) below in the relevant rules: FCC Part 15.218 Operation in the band 510-1705 kHz. (a) The total input power ... shall not exceed 100 milliwatts. (b) The total length of the ... antenna and ground lead shall not exceed 3 meters (10 feet). (c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.
bmlbytes (author)  dogsrcool2me8 years ago
To your first question, no. To your second question, it is. The bottom of the battery that says 5v is a negative (ground).
bmlbytes (author)  VIRON8 years ago
Use the modulater version (last picture on last step)
rob64337 years ago
Will a 29.498mhz crystal oscillator work?
wcobretti7 years ago
can any one make me a am radio jammer please
jason2898 years ago
do u know this is ilegal?
not for this low of power its not. if it was a 500 watt one then you would probably get in trouble but this one is fine.
DIY Dave8 years ago
Where do you get one of those crystal things?
bmlbytes (author)  DIY Dave8 years ago
Look in old electronics. Specifically ones that transmit data (modems, serial port cards, etc).

Otherwise you could always do a Froogle search on it.

Hope this helps.

Thanks, now I will have a reason to take apart old electronics.
bmlbytes (author)  DIY Dave8 years ago
Also watch out for surface mounted ones (SMD). They lack the pins on the bottom making it harder to do.
locofocos8 years ago
What's so lame about K'nex guns, Sharpie_Samurai? Seriously, look at some of the videos of the automatic ones!
This is cool. This is what I come to instructables for, not some lame K'nex gun. What is the maximum safe voltage for the transmitter? I'm looking for something in the 20-40 volt range.
bmlbytes (author)  Sharpie_Samurai8 years ago
An oscillator this size generally uses 5 volts or 3 volts. If you used the oscillator and a VERY low amperage then you could maybe get it down to 5 volts with the modulator. Good luck though.
bmlbytes (author)  bmlbytes8 years ago
I ment modulator not oscillator

 If you used the oscillator and a VERY... 
aiden1200008 years ago
is this legal in uk, beacause itips arent
bmlbytes (author)  aiden1200008 years ago
I heard that FM transmitters just became legal. Not so sure about AM transmitters.
bmlbytes (author) 8 years ago
Sorry about my mistake. Yes it is a crystal OSCILLATOR, not just a crystal. Hope this didn't mess anyone up. To westfw 1MHz is in the AM range. If you went into the 2MHz range it would be outside of most radios. I personally use a 20MHz crystal oscillator, but I have a radio that goes from .3MHz to 40MHz.
VIRON bmlbytes8 years ago
20Mhz is an atomic clock station, not legal frequency. "If I were you" I'd look up the frequencies in your area, what your gov permits radio remote toys and walky talkies and other common radio products to transmit on. It is also easier to get a radio license, many countries have obsoleted morse code, knowing how to build a radio may not be essential but certainly half the fun, knowing how to use and work it legally is very important. If your country has a 1000khz broadcast band and a 100Mhz FM band, there is a serious reason why the FM is more restricted than AM, not because AM is "old" but bad FM interferes with frequencies that are ALWAYS a matter of life and death.
pyro228 years ago
scitoys.com2scitoys.comisnt this and your other instructable stright from there
bmlbytes (author)  pyro228 years ago
Ya. That's where I found them. I built them and then shared them with all of you.
robot8 years ago
can you do that for FM?
rgbphil robot8 years ago
FM requires that the frequency of the oscillator change with the input voltage (hence Frequency Modulation). In this case it seems that the amplitude of the oscillator output is proportional to the input....hence AM. FM transmission is actually quite easy to do with discrete components, google about for things like 'FM Bugs' and the like. Usually a tuned circuit (capacitor/inductor/amp) that is slightly untuned by the input signal creating the varying frequency output. A couple of transitors, inductor and caps will do it. FM receivers are rather complex however. AM has traditionally been a bit harder to create a transmitter for (though receiver is very simple), if you look at the texts they usually go on about things like envelope mixers, intermediate frequencies etc. The complexity of traditional AM transmitters is usually to provide a clean undistorted signal, I've my doubts on the linearity reponse of the crystal oscillator to the power supply+audio signal input......but it is nice to see a different approach. Phil
Ohm8 years ago
Cool I am going to have to give this a try, I did sort of a similar thing with a function generator that had an input in an ECE lab last year.
jeffreyf8 years ago
You forgot to add step 5, "rent Pump Up The Volume" :)
bmlbytes (author)  jeffreyf8 years ago
WHAT? I forgot that? Oh no what will I do now? RUN FOR YOUR LIVES!!!
"Rise up in the cafeteria and stab them with your plastic forks."
awoodcarver8 years ago
The hardest part was tuning the old 9 V transistors i have , and finding the crystal , you can find them here
bmlbytes (author)  awoodcarver8 years ago
Good job! You found the orignal source of the "modulated" schematic.
rgbphil8 years ago
Just being pedantic here.....but this device is based on a crystal oscillator.....not a plain old crystal. The can has some extra circuitry in it to make it oscillator....a plain crystal is just a bit of quartz with some electrodes. Nice to see AM modulation done so simply though...usually it is more complex. Phil
westfw8 years ago
To nit-pick, this is a "crystal oscillator"; inside that box are some electronic components in addition to the quartz crystal. 1MHz is a bit on the low side for the available frequencies, but not unobtainable. I'm a bit surprised that it does anything without a power supply (1st example) or with a 9V supply (2nd example: the oscillators are usually designed for 5V), but I guess I won't go against assorted people who have made it work !