I have problems about building AM radio

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Jul 1, 2016
Hello, everyone in here. Very glad that i can post my questions here to get your help.
I have been following the tutorial below to build an AM radio, and when powered on I was picking up what id presume to be radio waves (what I'd describe as a mishmash of "whooshing" sporadic oscillations).
Simple OP Amp radio
Alright all I need for this project are the following:

x1 LM386 op amp IC chip (From LM386N-4/NOPB - Ti - IC Chips - Kynix Semiconductor Hong Kong Limited.)
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.)

This was great, but I wanted to single out a specific frequency and listen to a radio station. I did some research and figured out that I have to add a resonance circuit called an LC circuit to single out specific frequencies. I made one with a variable inductor I made with 47 coils in 10cm with square steel railroad spike of diameter 1.5 cm in the center and a capacitor like below. I experimented with 220 pF capacitors in parallel to make 220, 440, and 660 pF and tried using my variable inductor to tune into a station for each of them but it did not work.

(apologize for the poor drawing)
I chose that coil count using the following equation to tune into mid freq radio singles (535-1500 khz), I made sure it covered the lowest frequency and then I could shorten it to get the higher frequencies.:

At this point I was stumped, I heard that you had to put a diode in to single out high frequency singles so desperate, I inserted it between pin 3 and my LC circuit but it didn't help. I also made a home made variable capacitor but likewise I coundn't tune into a station. Most importantly I heard you had to ground the circuit so I attached a wire for the tuner circuit to my computer(which is ground) and it changed the tone slightly but still couldn't tune into a station.
I started to wonder whether there were any am stations in my area due to its falling popularity, but a quick test with my mother's car radio yielded handful of them.
I apologize if my troubleshooting may seem stupid but I'm a little new to this circuit building stuff. I Thank you for reading thus far, and I appreciate any assistance you guys may offer.



Premium Subscriber
Dec 1, 2005
Grand Junction
As with your previous project that you posted here, This is not going to be able to give you a cheap ATC receiver. If you want to listen to the Air Traffic AM radios you will need to purchase a receiver designed to do it or build a VHF AM receiver designed for the band and bandwidth of the transmissions.
Looking at the instructable page you have copied the schematic from,
Simple OP Amp radio
this is posted as an oddity that the author discovered while playing with an op-amp and not as a method of building an operating radio.
If you lived right next to the transmission towers this might get you a mashup of any transmissions emanating from it. It will never be selective enough to pick up specific frequencies.

Might I suggest
Air Band Receiver | eBay
or if you are intent on building
PG1N's HAM Radio Site - VHF Airband - Receivers

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