Transistor Radio Hack!




Posted in HomeLife-hacks

Introduction: Transistor Radio Hack!

About: Tinkerer, hackster and prankster. Hit me up on Facebook: Thanks for checking out my Instructables!
Take an old AM/FM transistor radio and make a quick modification so it picks up Air Traffic Control, Air Shows and other Civil Aviation Band transmissions. Amazing! Thanks to Cy Tymony for the Make Magazine article. See the Test Results in the video.

Step 1: Get Started

The only thing you need for this project is an AM/FM transistor radio, an older model that has a physical adjustment for tuning rather than digital. This will be a wheel or slider that changes stations. The only tool you should need is a small screwdriver.

Open the radio by removing all the screws. Watch for the hidden screws located in the battery compartment.

TIP: Stick them to a magnet so you don't lose them.

Step 2: Locate the Components

Now we need to locate the components we will be modifying. First, look for the main tuning capacitor. It will be a square, usually clear, compartment that houses the tuning controls. It will be right next to the tuning wheel. Near the main tuning capacitor you will see two coils of copper wire. These are what control and limit the frequency range of the radio.

Step 3: Tuning Transformers

The tuning transformers are square transformers with tuning slots in the top. Mine had five.

TIP: The best way to locate the one we will be adjusting, is to look for a couple of diodes closest to one.

Step 4: Get to Work

Now, turn on the radio and tune it to the clearest station on the high end of the FM band, near 108.

TIP: Confirm you have found the correct copper coil (one controls AM, the other FM) by touching it with a screwdriver. You should hear a change in the station.

Using your screwdriver, slightly spread out the copper coils. The station will fade away and you have just increased the range on the upper end of the FM band beyond 108MHz!

Step 5: Final Step

Tune the radio in between two stations where you can hear hiss. Adjust the tuning transformer until the hiss is the loudest. Turn it slowly to hear the change and make note of where you started so you can return it to the original location if you want to reverse the modification.

Step 6: Test It Out

Put the radio back together and bring it outside.

Tip:the closer you can get to an airport the easier it will be to find a transmission

Tune above the 108MHz range and should hear transmissions from the Civil Aviation Band (108-138MHz). It may take some patience and you may even have to adjust the tuning transformer a bit. Have fun!



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    how do u know which transformer is the right one to tune I trying to get better stations in a building


    I think i did something wrong cause it didnt work. But the good thing is that suddenly it got increased antenna power so i could hear normal radio stations better! Thanks anyhow.

    4 replies

    Because u shrinked the coil. Frequency Range decresed . quality incresaed.because dampong factor decreased

    what do you mean by that
    i try to make spark gap telegraph
    how should i wire up the coil
    do you have any idea???

    Beacuse inductance increased also .lol

    I sound like school teacher lol

    need one for move one step forward

    It can catch far radio stations or not

    I am using both a hacked DVB-t receiver working as a SDR and this radio, the SDR gives much more precision but this build works fine!

    I think intercepting radio signals from a government establishment is jsut saying "harass me please"

    7 replies

     listening to airplane traffic control =/= intercepting radio signals from a government agency

    Not really. I am a pilot and I know we have handheld two-way radios. We are allowed to use them around the airport or for training purposes. Anyway, if you are using them to monitor air traffic at home for hours each day, you might be deemed suspicious. You can check the Code of Federal Regulations if in doubt. As always, if you think it might be against the law, better not do it until you are sure it is legal.

    Those are not "secret frequencies" anyone can BUY an air traffic receiver or even listen for free online. Also, the "government" does not know (nor CARE) what you listen to on over the air radio. They have no way of telling what you hear unless they are creeping around your windows.

    Sorry you are wrong there, we could determine what stations you were listening to back in the 50s if not before, In England they go around or use to in vans to monitor what tv station you were listening to so they could charge you. But I don't think you have to worry about that, unless you are already on one of their lists, then it is anyones guess. Would depend on the number of assets they have in the area.

    "Detector vans" did not detect what station you were watching, they picked up the faint radio emissions of the old CRT tubes themselves. Since nobody used CRTs, and EM emissions of electronics in general have decreased dramatically since the invention of the microchip, detector vans have fallen out of use.

    The BBC now just assume that everybody has a TV, and send enforcement notices to any address that doesn't have a TV licence. If you do not own a TV, you have to fill in a bunch of paperwork to register the absence of a TV, rather than the presence of one.

    You are wrong, they detected the hetrodyne signal, which changed depending on which channel you were watching.

    I wonder how you know that, since the BBC has never released the details of how their vans worked (even after an FOI order), and there has never been a single prosecution using detector van evidence.

    Can i remove coil and put one with either more turns or more spacing or both to tune into higher frequencies? i dont understand much of the internal circuitry of the radio receiver but is the coil the only thing responsible to be able to catch hold of the various frequencies? Also Kipkay, okay we do not live in an ideal world so after my questioned mod if i simply knock my receiver into AM mode will it work better?

    Thank you Kipkay this was just the information I was looking for, and I fixed my radio.
    I actually didn't use the instructions as you meant them to be used here...not exactly.

    A friend had this little cheap Chinese AM/FM radio and they had broken the antenna. I do not know if they had opened it up and disturbed the copper coils or not.

    The radio reception absolutely sucked at her camp so I gave her a multi-band radio and she can now listen to her favourite station.

    Not that this little radio is worth my time, but I was curious to see if I could make something out of it. I replaced the broken antenna, but I then noticed that the radio would not pick up anything above 103.xx

    Using your instructions to increase the range I was able to put the station 104.3 right back on the dial where it is supposed to be. Yeah!

    The radio reception still sucked though, so I went a bit further and "messed" with the main tuning capacitor. This radio does not have the small square tuning transformers.

    One of the adjustments on the main tuning capacitor made a hugh improvement to the reception. Seemed like a gain control. This little radio must have been put together on a Monday. My Thursday adjustments made it into a nice working radio.