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Aircraft Band Receiver
Weekend Project
This project is part of RadioShack's The Great Create.
Modify an ordinary analog AM/FM radio to eavesdrop on air traffic control communications. All you need is a screwdriver -- can't be easier than that!
- Author: Steve Hobley
- Time required: 30 minutes
- Difficulty: Easy
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The FM radio band (88-108 MHz) lies just below the Civil Aviation Band (108-138 MHz), which is used for air traffic control, air shows, and other ground-to-air communications. This means that it's easy to modify an ordinary analog AM/FM radio to receive these transmissions.
Check out more Weekend Projects.
Sections
- Get Yourself an Analog Portable Radio
- Remove the Back Panel
- Locate the Coils
- Adjust the coils
- Test it Out
Tools
Relevant parts
- Analog AM/FM receiver from RadioShack. Make sure to get yourself a receiver with an analog dial, not an LCD tuning display.
- View:
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Edit Step 2
— Remove the Back Panel
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Remove the screws from the back of your radio and gently pry open the casing.
Case screws to consumer electronics can frequently be found inside of the battery compartment, so make sure to look there if your case isn't coming apart when you think you've removed all of the screws.
Edit Step 3
— Locate the Coils
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Identify the three copper-colored coils (circled here in red) and the two tuning transformers (shown in the blue boxes).
FYI: That clear plastic box to the left of the coils is the radio's tuning capacitor. Move the dial around on the front of the radio and you'll see its parts move inside the clear case.
Edit Step 4
— Adjust the coils
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Switch the radio on and set it to FM reception. Tune to a station high on the dial, as close as you can to 108 MHz.
Using a flat screwdriver, slowly expand the coil windings on all three coils.
You should notice the tuned radio station is moving slowly down the dial. This is good, as we are expanding the reception range of the radio in the band above 108 MHz.
Edit Step 5
— Test it Out
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Retune the radio and check that the original station is still available, but lower down on the dial.
In the picture you can see that the station around 108 MHz has now moved down to the location marked 101 MHz on the dial.
The final step is to turn the radio dial in-between stations, so that all you hear is hiss. Now adjust the tuning transformers so that this hiss is at the loudest possible level.
Congratulations! The modifications are complete. Put the case back on and let's pay a visit to the local airport to try it out.
Get as close to the tower as you can, and tune the dial in the new extended region you just created. When planes are in the area, you should be able to pick up their communications!
This guide has been completed 9 times.
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Comments Comments are onturn off
Guide
Bill Cahill, · Reply
Really?!?! I think not, Have you really done this, or is this just radio shack finding a way to push themselves on to us, to have us open their product and void the warranty.
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I am an air traffic controller, we transmit using AM, yes it is an AM/FM receiver, but the on this receiver AM is between 530 kHz and 1.7MHz, tuning those coils up to 108 - 138MHz would require new coils.
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Highly skeptical
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Matt
right but the idea in this article is to re-tune the FM band on the radio, not the AM band, the remaining compromise is that AM detection on an FM receiver will not be ideal
This is a really good point.
I didn't understand how it was possible to decode AM broadcasts using FM tuning circuits. However AM is *very* simple to decode - you really only need to rectify the signal, and then let the amp speaker filter out the carrier.
I can say that when I took the radio along to the local airport it was possible to hear legible speech in the upper band (beyond 108Mhz).
My buddy has a plane - I'll set up a time when we can do some real testing with his radio.
Steve
From Canada - We no longer get Radio Shack it was replaced by "The Source" a few years ago. I purchased a similar radio (NexXTech) believing the hack would work on that brand. The inside of the radio was a big disappointment as the components were facing the back of the radio. The soldering and components seemed hacked together by a chimp. Attempted the hack with my son eager to intercept pilots conversations. Expanding the coils did not change the position of the 105.7 station we were listening to in the dial. Also, manipulating the transformers to increase the hissing sound didn't work either. We put the radio back together and I now regret having purchased a 22.84$ - Crappy radio. Anyway - Thanks for the hack. If it could be confirmed that it worked I would probably try again with a better radio.
AM can be received on an FM receiver using what is called "slope detection". Basically any FM receiver can demodulate AM if it is tuned slightly off frequency. The audio quality is terrible and sensitivity is low but speech should be intelligible.
actually slope detection refers to receiving FM on an AM receiver
This works :D my house is like 10-15km away from the atc tower and still i can make out what they are saying!!!!! this is so exciting :D
Jashan Jeet, · Reply
This is a nice hack but I have a question - I thought the aviation VHF band used AM transmitters and receivers. Although the FM portion of this radio has been re-aligned to receive at a higher frequency, it's still in FM receiving mode which would probably make the audio unintelligible at best. Am I missing something here?