Simple OP Amp Radio


Introduction: Simple OP Amp Radio

This is just what you think it is, a radio made with an op amp. This is just as accidental and simplistic as my other radio instructable (the 555 radio) and actually made me ask myself if I was just an RF magnet or something. There is only about a handful of parts you need and while somewhat pricey they are all obtainable at Radioshack. So if you feel like making your own simple radio for field reception. This is a good choice (if you've seen my 555 radio instructable you'll bee happy to know I was able to get two decent signals from two stations this time). For those who want to see the 555 radio follow this link here:        - otherwise let's get to building!

Step 1: Parts You Will Need

Alright all you'll need for this project are the following:

x1 LM386 op amp IC chip
x2 1000 microfarad capacitors (any capacitor works but it's louder with these)
x1 100 microfarad capacitor
x1 8 ohm speaker
x1 9 volt battery
x1 project board
some wire (I used about a foot and a half)

optional - a wire parabola (such as a mini fan cage, a colander, etc.)

And that's it. Of course this isn't a crystal clear signal, but I think you'll be surprised how easily you can understand the voices and the music is pretty clear too, there is some minor static but after listening for a while it's barely noticeable.

Step 2: Building in 1 Step!

Simply put this circuit doesn't take much to make. It surprised and annoyed me because it gave me a radio signal when I was trying to make a backpack boombox circuit, so I fiddled with this and I present it to you here. And here are the 4 steps to creating this circuit.
(Please realize that when I talk about the pins I refer to the pins in counter-clockwise order from the clocking mark (probably an indent or circular mark at one end of the chip near pin 1. Pin 1 is the most counter-clockwise going down the left side to pin 4 and continuing at the bottom of the other side at pin 5 going up the right side to pin 8.)

1. Plug in your op amp and add a jumper wire from pin 6 to power and a jumper from pin 4 to ground.

2. Plug another jumper wire from pin 2 to ground and plug your antenna into pin 3.

3. Plug your 100 microfarad capacitor's positive side into ping 7 and the negative side into ground. Plug one your 1000 microfarad capacitor's positive side into pin 1 and the negative side into pin 8. The other 1000 microfarad capacitor's positive side into pin 5 and the negative side into a blank space on your board. Plug your speaker's positive side to the last capacitor's negative side and the negative side of your speaker to ground.

4. Plug in your battery's terminals to their respective rails (red to power, black to ground)
 and then (if you have a switch added) turn it on and simply move your antenna wire around to get your signals. If you want a good signal using a metal fan cage works very well.



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    21 Discussions

    It is not working, im not getting the signals and the speaker is not giving any sound

    I did an experiment with this and I got FM and AM radio stations on my lm386. Pretty easy setup so I won't make an instructable unless it is requested:
    1 breadboard
    1 lm386
    1 stripped USB wire (for power...instead of 9 volt)
    1 8 ohm speaker
    some hookup wire unstranded

    Connect pin 2 to ground. Connect pin 4 to ground. Connect Pin 5 to positive side of speaker and connect negative side of speaker to ground. Connect Pin 6 to positive power. Connect antenna to pin 8 (I've used a combo of things for antennas, but an alligator clip hooked to a small piece of wire will do). Plug your USB power supply directly from computer to the breadboard. Presto! You now have a radio.

    I have no idea how this happened, and it only works for me if I use my computer's USB cable as the power source. Pin 3 also works for the antenna but it sound very fuzzy.

    4 replies

    The reason this poster thinks that only the computer USB power source was working was because he was hearing the noise produced by the various components in the computer come through the power wires.

    A battery is a much cleaner source of power than a switched power source like a computer USB port for a project like this.

    I think an Instructable on this would be nice. Your project seems simple enough to follow and is rather straight forward. An Instructable on your design would not go unappreciated, I'm sure of that. =]

    Hello MacDynamo - I thought you and your readers might like to look at a thread at The Radio Board. I built a few of the versions posted there this last week, and found that the LM386 properly wired can give first class results...



    Does anybody know what frequency this picks up or if there is a way to get it to pick up NOAA or one of those things you hook up to an ipod to get it to play over car sterio?

    Lemme just say that as a ham radio operator i can assure you that there is no way it could detect an fm signal. 1. Its way out of the frequency range ofvthe chip. 2. It requires a much more complicated detector for fm. Im 99% sure u are hearing am broadcasts from 0.5 to 1.6 mhz. Although there is a small chance u are hearing shortwave (<6 mhz) the other 1%.

    i just made this using two 3300 uf capacitors and one 470 uf capacitor and it works great i can pick up what sounds like the people talking in the control towers to other planes and it comes in really clear and loud its like a phone on the speaker phone setting. The antenna i used was just an alligator clip that i put at the top of three tall soda cans stacked on each other.

    I know this is a very old comment, but I thought anyone in the future might like to know how to tune stations and such. To my understanding, and through experience, a "variable capacitor" or otherwise known as an air capacitor or air variable capacitor. They are expensive to by, yet are very simple in concept. Plates are used to adjust surface contact with the plates, adjusting the overlap between the plates adjusts the capacitance. Changing the capacitance helps change the frequency or amplitude or any said combination of the two. This is what allows you to "tune" in to other stations. 98.5FM or whatever, you just change stations by changing the capacitance so you can receive and demodulate the RF into AF for any given station. If I am mistaken please feel free to add corrections. So in summary: variable capacitors use plates, ones that don't move, and ones that you rotate on some shaft, the overlap between the plates determines capacitance, which helps tune in to the station that you desire.

    Also, it's worth being said that adding a variable capacitor between the antenna and the input should do the trick. Hope this helps.

    instead of lm386 can a iuse the lm358

    Why at pin 1 & 7 capacitors c1 & c2 are connected? while 7 should be -Vcc (

    what kind of antenna wire is used here? it doesn't seem to be included on the parts list.

    A joule thief adds power for an LED, is there any way possible it could be used to amplify a speaker?

    i think your speaker is messed up

    if u want i choose a station u should use a tuner circuit which consist of a capacitor and inductor (in parallelwith each other) and place it before the antenna. Preferibly a variable capacitor or inductor or both.

    if u want i choose a station u should use a tuner circuit which consist of a capacitor and inductor (in parallelwith each other) and place it before the antenna. Preferibly a variable capacitor or inductor or both.

    u said, it is a radio.. Is it FM or AM? which frequency? plz..