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

Step 1: 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)
<p>Have you tested this thing for harmonics?</p><p>How would I get rid of harmonics to make the signal cleaner?</p><p>Thanks in advance!</p>
<p>Oh it's GOT harmonics, i don't have to build it for that, it's a square wave, odd harmonics everywhere. You fix it by using a lowpass filter, or better use a band pass filter. Basically since this is a crystal and you're not using any tuning mechanism, so it's a single frequency, you just want to pass that single frequency plus any intended deviation (up to maybe 6 kHz) and that's it. If you can't get that specific you want to at least block the harmonics, and subharmonics if there are any. </p>
<p>i looked everywhere and had to quit because even when i found one it was 24$ for one lousy crystal. i'm glad it worked for you.</p>
<p>mouser.com or amazon should get you a whole bag of the suckers for 5 bucks</p>
<p>pleease answer: how do you know how much power a ocilator can take?</p>
<p>Ebay $0.99</p>
<p>What is the maxim Amperage I can pump into this puppy. I want this little guy to broadcast my morse code message across campus! Possibly a mile radius? </p>
<p>I'm not sure, but get the lowest possible frquency.</p>
<p>could i replace the jack with a mic?</p>
<p>Yes, but you will need to build (or buy) a small amplifier.</p>
<p>omygosh ware in the world do you get that cristal? i've looked evorywhare.</p>
<p>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!</p>
<p>You have a nice all explained how to make the radio transmitter on the site: https://www.youtube.com/watch?v=_4-Sx-T6VBc</p>
<p>I build this and using an audio output transformer and it works great. Found a 1mhz crystal and audio output transformer on ebay.</p>
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 &quot;set off&quot; a little easier. You need to kick it in the pants to get it vibrating. <br> <br>The &quot;modulation&quot; (the signal) is being generated at the source (the mp3 player) and passed to the circuit so a carrier wave can be added. <br> <br>If you don't use an mp3 player, but just just a voltage source, you have made a &quot;CW&quot; transmitter (for morse code).
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.
I have a crystal of 1.8432 Mhz , is it okay?<br><br>thanks!
1.8432 mhz is in the &quot;shortwave&quot; range. <br>AM radios are in the &quot;mediumwave&quot; range. <br>To receive the rf made by this crystal, you need an AM radio that receives in the shortwave range.
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 &amp; 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/ <br> <br>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&amp;feature=share&amp;list=PLtv36f0AWivbNwZWXflk1OATeJlMk3B-P <br> <br>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!
Hate the new layout for instructables. BRING BACK THUMBNAILS. So Stupid!
I made a transmitter using an oscillator and an audio transformer, run off EITHER a 9v cell or usb<br>
Greattt............stuff in here!!!!
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?
I have a 1.00 MHz crystal like bmlbytes, how high of a voltage can this crystal withstand?
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.<br><br>If you were to boost the power, you would then be subject to FCC rules.
do you need an audio transformer for this? i have a 600: 600 ohm 1 to 1<br><br>Thanks!
what kind of antenna do you use ?<br><br>thanks!
Just some wire shold do it.
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
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?<br>
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....

About This Instructable




Bio: A current student at the University of Advancing Technology. Currently studying Robotics and Embedded Systems.
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