In this instructable, I'll show you how to modify a normal, analog AM/FM (or FM) radio so that it can pick up the broadcasts from airplanes and airplane control towers.
First, a little background on how this works. Airplanes broadcast using AM. AM means Amplitude Modulation, for the uninitiated. They transmit from around 115 MHz to about 140 MHz; for comparison, the AM broadcasts that are normally picked up by a radio are from 530 KHz to 1705 KHz.
We will be converting the part of our radio that normally picks up FM to pick up AM in the airplane frequency band.
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Step 1: Supplies
All you need for this (other than yourself and batteries) is:
1) A REALLY cheap analog FM or AM/FM radio. I picked up mine for $5.
2) A way of opening your radio without breaking it (usually a Phillip's head screwdriver)
3) A flathead screwdriver
Step 2: Crack It Open!
Open up your radio, most likely with the screwdriver (unless it just pops open from its cheapness).
Observe its parts.
Step 3: Convert It to AM
Notice a little silver box with a circle cut out on top and a colored circle recessed inside with a line just perfect to fit a flathead screwdriver in? Well, we need to loosen it to allow us to pick up AM, and not filter out everything but FM. To do this, insert the flathead, and rotate counterclockwise about 5-10 times. Your radio may have a few more of these. Repeat the aforementioned step for all of them.
Step 4: Change the Fequency
You will notice a few coils in there. If your radio also picked up AM before it was modified, it will have a large ferrite coil. Ignore it. All we are focusing on is the few small coils. Spread them apart as much as possible, keeping them in a generally coily shape. It is easy to do this with your flathead screwdriver.
Step 5: Close It Up and Enjoy
Close up your radio--you are finished! Set it to receive FM (even though we know it will actually be receiving AM). You will be able to hear broadcasts from aircraft from where the dial says about 700 MHz and up. Below that, you will hear some normal broadcasts. Go outside for somewhat better quality, and when you are close to an airport, you will be able to hear the ATIS.