Instructables
Picture of Easy AM Transmitter!
You are going to build an AM radio transmitter AND you will be shown how it works. When you finish your radio, it will look something like mine in the picture above.

I have attached the PDF file in the last step to this Inst'able for those without a pro membership.
 
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Step 1: Parts and Prep (Small Stuff)

Picture of Parts and Prep (Small Stuff)

==These are the small components you will need==

--Small Stuff--
- 555 timer chip
- NPN transistor
- two #103 capacitors (0.01 microfarads or 10,000 picofarads)
- #102 capacitor (0.001 microfarads or 1,000 picofarads)
- some short wires
- two 1 Kilohm resistors
- 10 Kilohm resistor
- 1/8 inch (3.5 millimeter) female audio jack (yours may have more or less than three
    wires, but it must have at least two)
- 5 Kilohm potentiometer 

==see next step for bigger components==

Step 2: Parts and Prep (Bigger Stuff)


==These are the bigger components you will need==

--Bigger Stuff--

- 1/8 inch (3.5 millimeter) male audio cable
- AM radio receiver
- Antenna. Yours doesn't have to be made out of a pop can, but the pop can works
- Breadboard

(see previous step for the small components)

Step 3: Schematic!!

Picture of Schematic!!

                  ==Now that we have all of our components ready, lets put this together!==

                                    I suggest constructing this on a breadboard first.
                          If you don't have a breadboard, you are definitely missing out!
                                                If you have any questions... ASK!


                                                P.S. Don't forget to SUBSCRIBE!       : )
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NirmalaN27 days ago

hai good day to you sir..just want ask if i want to set 550khz carrier frequency how should i set..and how to identify what capacitor value we should use to set that carrier frequency..tq

jensenr30 (author)  NirmalaN26 days ago
First of all, you would need to make sure your model of the 555 can operate up to 550 kHz. Check your datasheet for that.

Secondly, the easy way to calculate the values is to use this calculator: http://www.csgnetwork.com/ne555timer2calc.html

If possible, you should always verify that your circuit is working the way you intended it to. In your case, it would be nice to use an oscilloscope to look at the output of the 555 to make sure it is working at 550 Khz.
SmithM1 month ago

sir i am impress with your work. i have a challenge here. how should my transmitter circuit look like if i want to use and op am, a signal generator that will generate as low frequency as 32768Hz, a battery and a resonant anternna. waiting... thanks

jensenr30 (author)  SmithM1 month ago
well, 32.768 kHz isn't a very high frequency. I would imagine you would need something to boost the frequency of that signal, such as a phase-locked loop.

i am going to use a battery. Do you have any suggestion s in literature, i found Low power clock Oscillator 32768Hz which i think i can boost it with a 3 volts battery. i wish i know how i am going to amplify the signal and also a way to construct a fitting antenna. as for me i am trying to use a tank circuit but i don't know how to match the values of capacitor and the resistor. thanks

SmithM1 month ago

in another sense, i will like to do a smilar transmitter with an op amp and a resonant antenna. can you give me any suggestion on how the circuit will look like? thanks

aljapairai1 month ago

hello there

if i want to use carrier frequency about 750KHZ .. do i have any thing to change ??

ur work really appropriated ,, thanks

jensenr30 (author)  aljapairai1 month ago

To change the frequency of the oscillator, you need to change the frequency-determining components. The simplest thing to change would be to replace C1 with a 4.7 nF capacitor instead of a 10 nF. This would increase the frequency by roughly a factor of two.

Also, keep in mind the frequency limitations of your 555. Different types of 555's will have different maximum operating frequencies.

I found a 555 from Texas Instruments that worked up to 2 MHz. That would probably suit your needs. I did a search on digikey: http://goo.gl/DWtjrb
There are a number of 555 timers than can achieve frequencies up to 2 MHz and higher.

Another suggestion would be to prototype it by soldering components onto a protoboard or a cobber board like so:

copper boards:

perf board:

SparkySolar2 months ago

Lol Aliens lol

SparkySolar2 months ago

Lol Aliens lol

- mine melted
- aliens asked me to turn it off
- im in trouble with the fcc

no seriously, thanks for that I was just looking to confirm that you can actually use a 555 in this manner :)

royanirudh993 months ago

Sir could u pls tell me the circuit if i dont want to transmit sound? Also could u pls tell me how do u choose the value of these components? if i want the frequency of the transmitter to be fixed at some value how do i calculate the value of the components.

If u could provide me with some links of website regarding the same it would be highly appreciable.

Thank u

Anirudh Roy

EmptyH4 months ago

i built this circuit, and its not working.. help pls..

jensenr30 (author)  EmptyH4 months ago
I can't help if you don't tell me what is not working! xD

Also, make sure you have the transmitter very close to the radio receiver.
ChromeBit6 months ago

Do you have a breadboard (or a photograph from above) of your layout?

(Also, thanks for making this, explaining the physics aspect of it AND attaching a PDF for the none pro people.)

jensenr30 (author)  ChromeBit5 months ago

(also, you're very welcome for the explanations and the PDF :) )

jensenr30 (author)  ChromeBit5 months ago

I don't have any other pictures than the ones I've posted. I built this three years ago and have long since taken it apart in order to build other circuits.

Martin Smith6 months ago

As you mentioned, this IS NOT, an AM signal, an AM signal is around 1 MHZ, and a 555 is NOT EVEN CLOSE to that. It sounds like crap because it is 100% harmonics and sub harmonics that the AM radio can pick up

jensenr30 (author)  Martin Smith5 months ago

actually, depending on the model of 555 you purchase, the frequency operation can go as high as 2 MHz (well above the AM band).

I'm fairly sure Texas Instruments sells a 555 that can operate as this high of a frequency.

Of course, this doesn't solve the issue of harmonics you brought up.

To filter those it might be handy to use an LC tank circuit with a very high Q (resonance) factor.

Just spit-balling.

ChromeBit6 months ago

Do we need to have a section for 0v, and if so where?

Martin Smith6 months ago

Does the POT adjust RF Oscillation or Input/Output Audio Volume?

jensenr30 (author)  Martin Smith6 months ago
it adjusts the 555 timer's frequency (effectively changing the carrier frequency of the low-quality AM signal)

Ok thank you I am a newbie to the 555

jpawlowski6 months ago

The way the transistor is wired, it cannot function. So the only RF you're getting is from pin 3 of the chip. Indeed the circuit would work better if you just eliminated the non-functioning transistor, & attached the antenna to pin 3... the source of the RF signal (because the transistor is not functioning). You might also need to run a drain resistor of 10k from pin 3 to +5V, but I'm not sure on that. The transistor's collector is connected to +5 but there's not way to return the DC current through the transistors emitter. There should be about a 5k-10k resistor or an RF inductor from the emitter to the ground to complete the circuit & get the transistor to run (DC current must flow through the collector & emitter to function). The base of the transistor is not DC isolated for pin 3. There probably should be a .01uf capacitor between the base & pin 3. It should not be directly connected to pin 3. The transistor isn't biased either. You need about a 200k-500k biasing resistor from the collector to the base. If an inductor is used at the emitter the biasing resistor may be up to 1meg. You may also need a small drain resistor of about 10k from pin 3 to +5V but I'm not certain about that. The chip may oscillate fine without the drain resistor. With the transistor actually functioning there will be a significant boost in the RF signal & range by the signal being amplified by the transistor. Then the antenna could be connected to the emitter.

Thank you so much for the helpful advice, what is the point of a transistor radio, if the transistor doesn't work!? But could you tell me, (or anyone for that matter), the Increased range over about 10-12 Centimeters of the radio, after biasing the transistor and tying the emitter to ground with a 10K transistor? Thank you.

jensenr30 (author)  jpawlowski6 months ago

Thanks for all of the suggestions. I know this circuit isn't designed well. It is something I dreamed up three years ago when I knew a lot less about transistors and electromagnetic waves.

I can see what you mean about the transistor not doing anything. If I were to redesign this circuit I would play around a lot more with the biasing of the transistor and possibly try toying with the possibility of a ground plane to aid in the propagation of the radio waves.

However, I have far too many little projects that captivate my and steal my interest away from previous projects. I find this to be a blessing and a curse. While the newer projects that I work on tend to be very interesting to me, the nature of my creativity tends to lead me in the direction of newer projects all the time, only occasionally finishing older projects. This is the way I function.

Thanks for the comments.

karlitoboi8 months ago

sir...good day! i would like to ask a question...

a simple question...

what is the typical range of the radio receiver from the transmitter?

im talking about its radius... just to clarify...tnx sir.

jensenr30 (author)  karlitoboi6 months ago

because this is a really poorly designed radio transmitter, it can only broadcast at a range of 10 cm. It really isn't that great.
But it is quick and dirty. It needs to be right next to your receiver.

alainAlien6 months ago

olle friend have problems if the potentiometer is not going to land the leg up or if you're just using 2 legs, and if between leg 1 and 5 also stuck with earth. please Greetings

alainAlien6 months ago

olle friend have problems if the potentiometer is not going to land the leg up or if you're just using 2 legs, and if between leg 1 and 5 also stuck with earth. please Greetings

JigMcFigg10 months ago

I was wandering what formula you used to calculate the frequency range, or did you just plug parts in and see what range was there?

jensenr30 (author)  JigMcFigg10 months ago

good question! I used this online utility to calculate the frequency using different component values. http://www.csgnetwork.com/ne555timer2calc.html

david s_batton11 months ago
great
raven_squire11 months ago

How would you get a range between 27 Mhz and 49 Mhz ?

jensenr30 (author)  raven_squire11 months ago

Well, if you wanted a frequency somewhere in that range, chances are you would not want a 555 timer. I don't think they work that fast. You might want to look into transistor RCL oscillators like the colpitts oscillator and other similar ones.

Hope that helps!

sir when i tuch my hand with potentio meter then i heard audio
with out tuching transmiter does not work clearly................ why
and when i eject NPN and antenna from circut transmiter waking still
pleas helf me
Rajyedke1 year ago
what is voltage of power supply used here ? ?? where to connect it???
Rajyedke1 year ago
what is the voltage of power supply here..??? where to connect it ..??? sry i couldn't understand??
imaduddin1 year ago
thx guys, it's work but the sound is little loud, any suggestion?
jensenr30 (author)  imaduddin1 year ago
use a resistor in series with your speaker or turn down the volume on your radio.
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