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Build Your Own Crystal Radio

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Have you ever wondered how a radio can grab signals that are transmitted through the air and convert them into sound? In this science project, you will build your own AM radio receiver from scratch and use it to listen to AM radio broadcasts. With your crystal radio you will be able to experiment with the circuit and the antenna to get the best reception.


Areas of Science
Time Required
Short (2-5 days)
To do this science project, you must live in an area where you can receive at least one strong AM radio station. You can check for this with a car or portable radio.
Material Availability
Specific circuit items are required. A kit is available from our partner Home Science Tools. See the Materials section for details.
Average ($40 - $80)
Never operate your crystal radio during a thunderstorm. When not in use, always disconnect your antenna from the radio circuit, and connect it directly to the ground rod. Be sure to wear safety goggles when installing the ground rod, especially if you are using a metal hammer. An adult's help might be necessary for some steps in the Procedure.
Ben Finio, Ph.D., Science Buddies
The Crystal Radio Project Idea is dedicated to the memory of Richard Morton Hess, a lifelong builder and creator. In 2001, Hess was named a member of the Packard Electric Excellence Hall of Fame. He inspired many young people in his local community of Warren, Ohio through his passion for engineering.

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Build a simple crystal radio receiver and experiment to improve your reception.


Before the 1950s and the dawn of television, people would gather in their homes with family and friends around the radio—just as we do with our TVs today—to listen to sports, music, news, and entertainment programs. Then, as now, the radio acted as a gateway to the world. But what exactly is a radio and how does it work?

A radio is an electrical device that receives an invisible signal, or radio wave, from a radio station and converts the signal into sound that we hear and understand. A radio wave is a type of electromagnetic radiation that can be used to convey audio information. Radio waves have energy associated with them. Using a transmitter and an antenna, radio stations transmit waves like the ones in Figure 1, which shows both a 1-cycle wave and a 3-cycle wave, each occurring in the span of 1 second (s). The number of cycles per second is called frequency. The unit for frequency is the hertz (Hz). A 1-cycle wave per second is a 1 Hz wave, and a 3-cycle wave per second is a 3 Hz wave. Every AM radio station transmits its signal at a given frequency, and the frequency band for AM radio stations in the United States is from 530,000 Hz to 1,710,000 Hz. So a radio station transmitting at 1,590,000 Hz (expressed in kilohertz as 1,590 kHz) is sending out a signal that is 1,590,000 cycles per second.

Drawing of a graph with a single period wave over a graph with a wave that has three periods

Figure 1. (Top) A 1-cycle wave, and (bottom) a 3-cycle wave.

Radio stations send out waves, and the radios in our homes receive those waves. But how do our radios turn these waves into sounds and how do stations transmit different sounds? Waves have both a frequency and an amplitude, which is the height of the wave. If someone yells at you from across a room, the amplitude of the sound wave is high. But if someone whispers to you from across the room, the amplitude of that sound wave is very low. It is important to note that a sound wave is different from an electromagnetic wave; radio stations send electromagnetic waves, which are then converted into sound waves by your radio. When radio stations transmit electromagnetic waves, they can vary or modulate the amplitude of the wave and that is one way we hear the different levels and frequencies of sound. Stations that transmit signals via amplitude modulation are called AM radio stations (as opposed to FM stations, which use frequency modulation, but these will not be discussed in this science project).

Drawing of a crystal radio made of a slide tuning coil, antenna, detector, ground and headphones.

Figure 2. A diagram of the various parts of an early crystal radio. In the early days of radio, the detector was literally a "crystal." Modern radios use a diode instead of a crystal.

A crystal radio is a very simple radio that was popular in the early history of radios. It is an electrical circuit that can pick up and play sound from AM radio stations. Rather than rely on outside electrical sources, like a batteries or plugs, crystal radios get their power directly from the radio waves. The diagram in Figure 2, shows the parts of a crystal radio: antenna, tuning coil, diode (labeled as "detector"), earphones, and a connection to an electrical "ground." You can learn more about some of the concepts listed below at the Science Buddies Electricity, Magnetism, & Electromagnetism Tutorial.

Graph of amplitude-modulated waves over frequency-modulated waves

Figure 3. AM radio stations transmit signals via amplitude-modulated (AM) waves. The antenna of the crystal radio converts these waves to alternating current (shown in A). In order for the current to be converted into sound, the current is rectified by the diode so that only the positive halves of the waves get through. This rectified current (shown in B) is known as direct current.

In this science project, you will build your own crystal radio from scratch, and make adjustments to tune in to as many stations as possible.

Technical Note

The circuit you will build in this science project also includes a capacitor. A capacitor is a circuit component that can store electrical charge. The old-fashioned crystal radio in Figure 2 just relied on the capacitance of the antenna itself, but adding a separate capacitor allows for better tuning. The tuner coil in the circuit is also called an inductor. When a capacitor and an inductor are combined in a circuit, it is called an LC circuit for short. This is because L is the mathematical symbol for inductance, which has units of henries (H), and C is the mathematical symbol for capacitance, which has units of farads (F). An LC circuit has a resonant frequency, f, defined by the following equation:

Equation 1:

  • f is the resonant frequency in hertz (Hz).
  • L is the coil inductance in henries (H).
  • C is the capacitance in farads (F).

In the circuit you will build, the capacitor has a fixed value, but when you move the tuner along the receiver coil, you change the inductance of the coil, and thus the resonant frequency of the circuit. This is what allows you to tune into a certain station. Figure 4 shows the circuit diagram for the radio. The capacitor and adjustable coil act as a tuner, and the diode acts as a rectifier.

Circuit diagram for a crystal radio

Figure 4. The circuit diagram for the radio you will build in this science project.

Terms and Concepts



Here are some sources to get you started:

If you want to learn more about radios, visit The Amateur Radio Relay League website:

This FCC website can be used to locate AM radio stations in your area:

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Experimental Procedure

Building Your Crystal Radio

  1. The first step in building your crystal radio is to wind the receiver coil using the 22 AWG (American Wire Gauge) enamel-coated magnet wire and the cardboard tube.
    1. The cardboard tube has a total of six holes punched in it, three at each end. The larger holes are to attach the cardboard tube to the wooden base with screws. The smaller pairs of holes are to thread the magnet wire through.
    2. Put two pieces of double-sided tape lengthwise in the middle of your cardboard tube, one on each side (opposite each other), as shown in Figure 5. This will help keep your coil in place as you wrap it.
    3. Thread one end of the magnet wire through a pair of holes, as shown in Figure 5. Pull about 12 inches of wire through the holes.
    4. Now, begin to carefully and tightly wrap the magnet wire around the cardboard tube, starting just above the holes you just threaded. Each new wrap should be pushed up against, but not overlapping, the previous wrap, as shown in Figure 5.
    5. Continue tightly wrapping the coil until you reach the set of holes on the other end of the cardboard tube. Keep approximate count as you go; you should be able to fit approximately 75 complete turns of wire.
    6. Cut the wire, leaving about 12 inches extra dangling off the tube. Thread this end of the wire through the open set of holes at the opposite end of your coil from where you started.
Three photos show a short section of cardboard tubing being wrapped in double sided tape and wire

Figure 5. Steps for making the receiver coil for your AM radio receiver. Be sure to leave at least 12 inches of wire sticking out on both ends of the coil, after threading it through the holes.

  1. Optional: before you continue with the rest of the project, you can decorate your wooden base board using paint, markers, or other materials. Customize your radio! See Figure 20 for an example.
  2. Attach the cardboard tube to the wooden base board using two #6 x ½ inch screws (these are the smaller screws that came with your kit; notice how the other types of screws are larger) and your Phillips head screwdriver. The wooden mounting board has multiple pre-drilled holes; be sure to use the correct ones for the cardboard tube, as shown in Figure 6.
Three photos of a small cardboard tube wrapped in wire being glued to a wooden board

Figure 6. A diagram of Attach the cardboard tube to the wooden baseboard. Be sure to use the correct holes, as labeled in the figure.

  1. Attach the Fahnestock clips to the base.
    1. Loosely mount the four Fahnestock clips to the wooden base using four #6 x ½ inch screws, as shown in Figure 7. Do not tighten the screws all the way yet.
    2. Use scissors to cut apart the "ANTENNA," "GROUND," and two "HEADPHONE" labels. Peel off the adhesive backing and place them on the board, as shown in Figure 7.
Fahnestock clips are attached to a wooden board that has a wire-wrapped cardboard tube glued to it

Figure 7. Attach the Fahnestock clips and the labels to the wooden mounting board.

  1. Install the detector tie point.
    1. Attach the final #6 x ½ inch screw and the #6 washer to the wooden mounting board in the open hole closest to the edge, as shown in Figure 8. Note this is the smaller washer that came with your kit. Do not tighten the screw all the way.
A washer and screw are inserted into a wooden block that has Fahnestock clips and a wire-wrapped cardboard tube glued to it

Figure 8. Attach a screw and a washer to the detector tie point.

  1. Mount the tuning rod to the wooden board.
    1. Slide the loop at the end of the brass rod and two #8 washers onto the #8 x ¾ inch screw (these are the bigger screws and washers that came with your kit), as shown in Figure 9.
    2. Insert the screw into the remaining open hole in the wooden mounting board, as shown in Figure 9. Do not tighten the screw all the way yet.
    3. Important: Carefully and gently press the black plastic knob onto the end of the brass rod. You may need to gently wiggle the knob or twist it back and forth to get it to slide onto the rod. Using a file to round down the end of the rod, or water to lubricate it slightly, might be helpful. The end of the rod might be sharp, so be very careful and get an adult to help if necessary.
Photos of a tuning rod installed on a homemade crystal radio

Figure 9. Sandwich the loop of the brass rod in between two #8 washers on the #8 x ¾ inch screw. Then insert the screw into the wooden board, but do not tighten it all the way yet.

  1. Connect the tuning coil to the "HEADPHONE" and "GROUND" clips.
    1. As a general rule of thumb, in the following steps, whenever you wrap a wire or a component's lead around a screw, wrap it in the clockwise direction. That way, when you tighten the screw, the wire will be pulled tighter instead of being pushed loose and coming unwound.
    2. With the wooden mounting board in front of you and the tuning coil farthest from you, loop the extra wire on the right-hand side of your tuning coil around the screws under the top "HEADPHONE" and "GROUND" clips, as shown in Figure 10. Make a mental note or use your finger to mark approximately where the wire is under the "HEADPHONE" screw. This will give you an idea of where you need to remove insulation from the wire, so it can be electrically connected to the clips.
    3. Unwrap the wire and use the sandpaper supplied with the kit to rub insulation off a short (about 1 inch) section of the wire where it loops under the "HEADPHONE" clip. Be sure to remove the insulation around the entire perimeter of the wire.
    4. Loop the wire back under the headphone clip (wrap it completely around the screw at least once so it stays in place), ensure the stripped piece of wire is wrapped around the screw, and stretch the end out to opposite side of the wooden mounting board to the "GROUND" clip. Again, make a mental note or use your finger to mark approximately where the wire is under the screw.
    5. Unwrap the wire from the "GROUND" screw (you can leave it under the "HEADPHONE" screw) and use the sandpaper to remove insulation from a short (about 1 inch) section of the wire where it will loop under the "GROUND" clip.
    6. Once you have removed the insulation, loop the wire back under the "GROUND" clip. Wrap the wire completely around the "GROUND" screw at least once so it stays in place. Do not tighten the screws yet.
Wire from a homemade crystal radio tuning coil connects to ground and headphone clips

Figure 10. Loop the stripped portions of the tuning coil wire under the top "HEADPHONE" and "GROUND" clips. Remember to loop the wires around the screws in a clockwise direction.

  1. Connect the antenna clip to the tuning rod and detector tie point.
    1. Cut a segment of the enamel-coated magnet wire about 6 inches long.
    2. Loop the wire under the "ANTENNA" screw, the tuning rod screw, and the detector tie point screw, as shown in Figure 11. This will give you an idea of where you need to sand off insulation.
    3. Remove the wire from under the screws, and sand off roughly a 1  inch strip of insulation from where the wire will connect to each of the three screws. It is OK to sand off some extra insulation, so you have a little room for error when lining up the wire.
    4. Loop the wire back under the three screws again, as shown in Figure 11, ensuring the stripped sections are under the screws. Be sure to wrap the wire around each screw at least once so it stays in place. Do not tighten the screws yet.
Metal wire connects the tuning rod screw to the antenna and detector tie point in a homemade crystal radio

Figure 11. Connect the "ANTENNA" screw, the tuning rod screw, and the detector tie point screw with an extra piece of 6 inch wire. Be sure to sand off insulation in the appropriate spots first. Note that the kit does not come with labels for the "TUNER" and "DETECTOR TIE POINT" screws. You can print and cut your own labels if you want.

  1. Attach the capacitor, resistor, and diode to the circuit. Note: No insulation stripping is needed in this step.
    1. Slightly bend the ends of the leads of the capacitor, and loop these around the screws for the "GROUND" and "ANTENNA" clips, as shown in Figure 12. The direction of the capacitor does not matter. Tighten the screws to hold the capacitor in place.
    2. Slightly bend the ends of the leads of the resistor, and loop these around the screws for the two "HEADPHONE" clips, as shown in Figure 12. The direction of the resistor does not matter. Tighten only the top "HEADPHONE" screw to hold the resistor in place for now.
    3. Slightly bend the ends of the leads of the diode, and loop these around the screw for the "HEADPHONE" clip and the detector tie point screw, as shown in Figure 12. Important: Make sure the black stripe on the diode is facing toward the "HEADPHONE" clip.
    4. Double check and tighten all of the screws except the tuning rod screw.
Photo of a complete homemade crystal radio circuit

Figure 12. Wrap the capacitor, resistor, and diode leads around the screws under the appropriate clips, as pictured.

  1. Sand insulation off the tuning coil where the brass tuning rod contacts it.
    1. Move the tuning rod all the way to one side of the coil.
    2. Test the tuning rod's contact with the tuning coil by sliding the tuning rod back and forth across the coil, making sure it always touches the coil and applies even pressure. If it presses too hard, or loses contact with the coil, you may need to bend the tuning rod slightly using pliers (do this near the base, where it is already bent).
    3. Place your sandpaper between the brass rod and the coil wire, and pinch it around the tuning rod, as shown in Figure 13. Move the tuning rod back and forth in order to remove the enamel insulation where it contacts the coil.
    4. When you are done, you should see exposed, shiny copper, which is a different color than the enamel insulation, as shown in Figure 13.
    5. For now, you are done working on the wooden mounting board, and your circuit is complete. Double check that your crystal radio circuit looks like the one shown in Figure 12, and that you have sanded off insulation like in Figure 13. You can use scissors to trim any excess lengths of magnet wire that are dangling off your wooden board, then move on to step 10 to go outside and set up your ground rod and antenna.
Insulation on a copper tuning rod, in a homemade crystal radio, is removed with sandpaper

Figure 13. The tuning coil, showing exposed copper, after sanding off insulation where the tuning rod contacts it.

  1. Set up your antenna. Warning: Never work outside during a thunderstorm. Do not install your antenna near power lines.
    1. Use plastic zip ties to string up a length of the enamel-coated magnet wire from the Science Buddies kit that is as long and as high off the ground as possible. Try to make the antenna as long as possible, but do not use all of your remaining wire. You will need a few feet to connect the ground rod (see step 12). If possible, have an adult use a ladder to attach the ends of the antenna to high places like rain gutters. Important: Leave enough wire at one end of your antenna to reach the ground and connect to your radio.
    2. The plastic zip ties will ensure that the antenna does not "ground out," or become electrically connected to the ground, if some of the insulation wears off (for example, if you have the antenna connected to a sharp corner on a metal fence).
    3. Figure 14 shows an example antenna strung up in a back yard, connected to a rain gutter and a wooden fence using plastic zip ties.
    4. Safety note: Thin wires hanging in midair can be hard to see. If your antenna is close enough to the ground that someone might walk into it, you should hang "flags" on it to make it more visible. The flags do not need to be anything fancy; you can just fold pieces of paper in half and tape them to the antenna.
A white zip tie secures a thin wire to a black metal fence Photo of a long wire highlighted in red that is strung between two trees

Figure 14. An antenna strung up between a tree and a fence in a back yard (the antenna is highlighted with a red line in the bottom photo, since the wire is too thin to see easily).

  1. Install the ground rod.
    1. If you have a metal fence or exposed metal water pipe in your yard, it will work as a ground rod only if it is not rusted or painted.
    2. If you purchased a ground rod, have an adult use a mallet to pound it at least 2–3 ft. into the ground, preferably near the end of the antenna that has extra wire to attach to your radio.
    3. Cut a segment of enamel-coated magnet wire that will be long enough to reach from your ground rod to your radio, with an extra 2 ft. to wrap around the ground rod. Use the sandpaper to sand the insulation off of 2 ft. at the end of the wire.
    4. Tightly wrap the un-insulated end of the magnet wire around the ground rod, and tie a tight knot so it doesn't fall off. You can also wrap the wire in masking tape to make sure it stays in good contact with the ground rod. Figure 15 shows a ground rod with the wire wrapped and secured around it.
Wire is taped to a copper pipe that is inserted into the ground

Figure 15. A copper pipe used as a ground rod with a ground wire attached (which will be used to connect the radio circuit to ground).

  1. Take your crystal radio outside and hook it up to your antenna and ground rod. Remember not to operate your crystal radio during a thunderstorm.
    1. Use sandpaper to sand insulation off 1 inch of wire at the end of the extra wire dangling off your antenna, and from the free end of the wire connected to your ground rod.
    2. Attach the antenna and ground wires to the "ANTENNA" and "GROUND" Fahnestock clips on the wooden mounting board, respectively. Figure 16 shows a close-up of how to use a Fahnestock clip, and Figure 17 shows both wires attached to the circuit.
Three photos show a wire being connected to a Fahnestock clip

Figure 16. To connect a wire to a Fahnestock clip, first press down on the tab of the clip with your finger. Use your other hand to thread the end of the wire through the clip, as pictured, then release the tab.

Photo of a complete homemade crystal radio circuit

Figure 17. Connect the antenna and ground wires to the appropriate Fahnestock clips on the wooden mounting board. The two wires leaving the left side of the picture connect to the ground rod and antenna respectively.

  1. Attach the audio amplifier to your crystal radio.
    1. Slide the battery cover off the back of the amplifier (in the direction of the arrow), and install a 9 V battery. Replace the back cover.
    2. Insert the 1/4 inch plug end of your audio cable into the port labeled "Input" on the audio amplifier, as shown in Figure 18.
    3. Connect the ends of the audio cable to the two "HEADPHONE" Fahnestock clips, as shown in Figure 18. It does not matter which of the two wires you plug into which clip.
Photo of a handheld amplifier next to a photo of two leads connected to both headphone clips of a homemade crystal radio

Figure 18. Attach the split ends of your audio cable to the two "HEADPHONE" Fahnestock clips, and plug the other end into the audio amplifier's "Input" jack.

  1. As a last step, install the felt footpads on the bottom of your crystal radio. Congratulations! You have finished building your crystal radio. It should look like the completed radio shown in Figure 19. You are now ready to move on to the next section, Testing Your Crystal Radio.
    1. Optional: if you haven't already, you can decorate the wooden base of your radio, as shown in Figure 20.

Photo of a complete homemade crystal radio circuit connected to a handheld audio amplifier

Figure 19. A picture of a completed crystal radio. The two wires leaving the left side of the picture connect to the ground rod and antenna respectively.

The wooden base of a homemade crystal radio decorated with paint
Figure 20. A decorated crystal radio.

Testing Your Crystal Radio

Note: The experiments you can do with your radio may vary greatly depending on where you live and how many AM radio stations there are in your area. This procedure is a suggestion, but you may need to modify it based on your location.

  1. Turn on your audio amplifier using the switch on the side. Adjust the volume to a comfortable level.
  2. Now, adjust your tuning rod to see if you can get clear reception of different stations. Take your time adjusting the rod to different positions on the tuning coil, and make sure that the tuning rod always makes physical contact with the coil. Check the full range of the coil, from one end to the other.
  3. If you check the full range of your coil but cannot receive any clear stations, try re-orienting your antenna (for example, rotating it by 90 degrees). The orientation of your antenna relative to the AM broadcast towers can have a big impact on reception.
  4. Once you have identified stations that you can receive, put a strip of masking tape lengthwise on your coil. Use a permanent marker to mark the location where you heard the station, and write down the station's call sign (for example, you may hear the DJ say "You're listening to WHCU", which is the call sign). You may also hear a number associated with the station, such as "WHCU 870." The number is the frequency at which the station broadcasts in kilohertz (kHz). You can also write this number down, as shown in Figure 21. This will help you find stations again easily. Note: Depending on the strength of a station, there may be a wide range (a couple centimeters) on which you can receive it using your tuning coil. If this happens, make a mark in the middle of the range.
Tape across the tuning coil of a homemade crystal radio is marked with the positions of certain radio broadcast stations

Figure 21. Use a strip of masking tape and a permanent marker to help you identify stations more easily on your coil.

  1. Once you have identified some stations using your tuner, you can also use the Federal Communication Commission (FCC)'s AM Query Broadcast Station Search to search for AM radio stations in your area.
    1. Search for AM radio stations by city and/or state using the FCC's AM Query link. If you search by city, remember to search neighboring cities as well, not just the one you live in.
    2. This will bring up a list of results that list each station's call sign, frequency, and some other information, as shown in Figure 22. You can click on a station's call sign to bring up more detailed information, including the coordinates (latitude and longitude) of their broadcast tower, as shown in Figure 23.
    3. Use an online mapping program like Google MapsTM to look up the location of the towers relative to your house. Note that you will have to check for the specific format to search for latitude and longitude in the mapping program you are using. For example, as of May 2013, in Google Maps the latitude and longitude 42° 27' 54.00" N, 76° 22' 23.00" W (from Figure 23), must be entered as a single line of text with spaces between the numbers and no symbols: 42 27 54 N 76 22 23 W.
    4. Print out a paper map of your area, or use an online mapping tool like Google Maps or Google EarthTM, and mark the locations of your house and all the radio stations in your area. Figure 24 shows an example map.
Screenshot of four different AM radio stations located in Ithaca New York

Figure 22. The search results for Ithaca, NY show two stations. The stations' call signs are hyperlinks that bring up more information about each individual station.

Screenshot of information for the WHCU station in Ithaca New York from the fcc.gov website

A screenshot from the fcc.gov website shows station information for the station WHCU in Ithaca, New York. The page provides information on the frequency the station broadcasts on, the owners of the license, tower information and much more. Near the top of the page, circled in red, is information on the latitude and longitude of the broadcast tower for the station.

Figure 23. Detailed station information, including the latitude and longitude of the broadcast tower.

Screenshot of Ithaca New York with four radio towers marked in Google Maps

A screenshot from Google Maps shows a top-down view of the city of Ithaca in New York state that has 4 radio towers marked with pins. Each radio tower is located on different edges of the city: one in the north, south, east and west.

Figure 24. This custom map shows the location of three radio towers relative to a house (this map was made using Google Maps Engine Lite in May 2013).

  1. Now, compare the stations listed on your map to the stations you marked on your strip of masking tape. Ask yourself a couple questions:
    1. Is there any correlation between location on the map and how loud/clear the stations sound on your radio? For example, does your radio do a better job picking up stations that are closer to your house? Or does distance not seem to matter?
    2. Are there any stations listed on the map that you could not pick up with your radio? If so, do you see any potential reasons, such as a mountain between your house and the broadcast tower (it may help to view a terrain or elevation map to determine this)?
  2. Now, try to adjust the position, orientation, and/or shape of your antenna to get better reception. Warning: Remember not to put your antenna near power lines.
    1. For ideal reception, your antenna should be perpendicular to a line drawn on the map between your house and the radio tower. So, if your antenna is pointed straight toward a radio tower, you may get poor reception for that station. What happens if you rotate your antenna, and then try adjusting the tuner again? Can you pick up new stations that you couldn't hear before, or do you lose stations that used to be clear?
    2. What happens if you change the location of your antenna; for example, move it from your back yard to your front yard? Does this affect the reception of different stations?
    3. What happens if you change the shape of the antenna? For example, instead of stringing it out in a straight line, you could tie it to different fence posts (remember to use zip ties) to form a square. You could even coil it around something like a barrel or a roll of paper towels.
    4. Can you find an "optimal" antenna configuration that gets you the best reception on the most stations?
  3. AM radio reception can be very different at night. Try using your radio at night — can you pick up any stations that you could not detect during the day, or vice versa? Do stations you can detect during the day sound clearer or fainter at night? Do some background research to find out why this happens.
  4. Important: When you are done using your radio, disconnect the antenna and ground wire from the Fahnestock clips, and bring your radio inside (it is not waterproof, so should not be left outside). Then, connect the antenna directly to your ground rod. This will protect the antenna from lightning and static charge buildup.


For troubleshooting tips, please read our FAQ: Build Your Own Crystal Radio.

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Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.


  • Test your radio with different-sized ceramic capacitors. How does this affect the resonant frequency range of your radio, and your ability to tune in to different stations?
  • What about changing the size of your radio's coil (the diameter, length, or number of turns)? Does this affect the radio's reception?
  • What happens if you use a different gauge of wire for the antenna?
  • How does changing the shape and orientation of your antenna affect your radio's reception?
  • Check out the Science Buddies project Make Your Own Low-Power AM Radio Transmitter. Can you build your own transmitter and use it in conjunction with your AM radio?
  • Can you build a radio from scratch using scrap materials instead of a kit? Historically, some prisoners of war had to be resourceful and do just that. For more information, see the Bizarre Labs website. Try building one of these radios and comparing its performance to the radio from your kit.
  • Can you use a multimeter to measure the current and voltage delivered to your audio amplifier from the radio circuit, and use them to calculate the electrical power of each radio station you receive? Do stations that sound clearer also have a higher power?
    • Hint: this might be more difficult than it sounds at first. You will need to hook the multimeter up in series with the amplifier to measure the current, and in parallel with the amplifier to measure the voltage. If you need help using a multimeter, refer to the Science Buddies reference How to Use a Multimeter.
    • Note that this method is not completely accurate. Remember that the signal from your radio circuit is AC (alternating current). Many consumer multimeters can only make DC (direct current) measurements. However, you may still be able to get an "average" reading for both current and voltage, which will allow you to calculate an average power, and compare the relative power levels of two or more different stations. It may be easier to do this using an analog multimeter (the kind with a needle gauge instead of a digital display). Just remember that what you are doing is an approximation, and not a true measurement of the amplitude (or average value) of the AC signal.
  • If you have access to an oscilloscope, use it to visualize the signals at different points in your crystal radio circuit. Depending on the type of oscilloscope, you may also be able to use it to measure more accurate average AC values than you can with a multimeter.

Frequently Asked Questions (FAQ)

If you are having trouble with this project, please read the FAQ below. You may find the answer to your question.
Q: I can't pick up any AM radio stations! What can I do?
A: First, make sure that you live in an area where you can receive AM radio stations with a regular radio. You can test this with a car radio or portable radio. You can also check the FCC's AM Query Broadcast Station Search to make sure there are AM broadcast towers in your area. If you live in an area with poor or no AM radio station reception to begin with, it will be very difficult to get a signal with your crystal radio.

Second, you may need to experiment with the size, location, and orientation of your antenna. In general, it is best to make your antenna as high off the ground and as long as possible, and orient it perpendicular to the direction of the AM broadcast tower. If possible, get an adult to help use a ladder to attach your antenna to a high place (like a tree or rain gutter) on both ends. It is also very important to make sure your antenna does not "ground out", or become electrically connected to ground. Make sure your antenna is insulated (e.g. using plastic zip ties) and does not come into direct contact with trees, fence posts, or other objects that touch the ground.

You can also try using a different ceramic capacitor (see question below for details).

Finally, you can try tuning your crystal radio at night, when you may get better reception for some stations. Why does this happen? Read this article from HowStuffWorks or this reference from the FCC to learn more.

Q: I checked, and there are AM stations in my area, but I still can't hear anything with my radio. What else can I do?
A: Double-check your radio to make sure there are no short circuits, or places where exposed, uninsulated metal parts are bumping into each other and shouldn't be. A short circuit can prevent your radio from working properly.

Also check to make sure that all the connections on your radio (screws, clips etc.) are sturdy and in good contact, and that you used sandpaper to remove insulation from the wire in the correct locations, as described in the procedure. If you have a loose connection, or didn't remove enough insulation from the wire where required, this can prevent your radio's circuit from working properly.

If you are completely certain that you built your radio properly, the next best things you can do are adjusting the antenna or tuning the radio at night (see previous question).

Q: How exactly do I use a different capacitor?
A: The capacitor helps determine the resonant frequency of your crystal radio circuit (see the technical note in the Background tab). A larger capacitor will decrease the resonant frequency, and a smaller capacitor will increase the resonant frequency. The Science Buddies kit comes with a 120 picofarad (pF) capacitor. To try tuning to stations at either the very low or very high ends of the AM broadcast range, you could try using larger or smaller capacitors. For example, try a 100 pF capacitor to tune to higher frequencies, or a 150 pF capacitor to tune to lower frequencies. Refer to step 8 in the Procedure tab to remember where to put the capacitor (remove the 120 pF capacitor before you swap in a new one).
Q: Do I need a ground wire?
A: Yes, the ground wire is very important. Follow the directions in step 11 of the procedure to install a ground rod and wire.
Q: Some of the insulation rubbed off of my antenna wire. Could this be a problem?
A: Yes, if some insulation rubs off your antenna (for example, because it rubbed against rough tree bark or a sharp metal edge on a fence), this could cause your antenna to "ground out," or be electrically connected to ground. It is important to make sure that your antenna remains insulated from ground. You can help ensure this by using plastic zip ties or twist ties to secure your antenna in place, and make sure it does not touch any sharp or rough edges.
Q: Can I use my radio to listen to FM stations?
A: Your crystal radio will only work to listen to AM radio stations. You may hear a buzzing noise from other nearby sources of radio waves, like TV stations or airport radar, but FM stations will not be heard at all. FM stands for frequency modulation, which requires a different type of receiver.


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If you have purchased a kit for this project from Science Buddies, we are pleased to answer any question not addressed by the FAQ above.

In your email, please follow these instructions:
  1. What is your Science Buddies kit order number?
  2. Please describe how you need help as thoroughly as possible:


    Good Question I'm trying to do Experimental Procedure step #5, "Scrape the insulation from the wire. . ." How do I know when I've scraped enough?
    Good Question I'm at Experimental Procedure step #7, "Move the magnet back and forth . . ." and the LED is not lighting up.
    Bad Question I don't understand the instructions. Help!
    Good Question I am purchasing my materials. Can I substitute a 1N34 diode for the 1N25 diode called for in the material list?
    Bad Question Can I use a different part?

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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Science Buddies Staff. "Build Your Own Crystal Radio." Science Buddies, 8 Sep. 2023, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Elec_p014/electricity-electronics/crystal-radio?from=Blog. Accessed 4 Mar. 2024.

APA Style

Science Buddies Staff. (2023, September 8). Build Your Own Crystal Radio. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Elec_p014/electricity-electronics/crystal-radio?from=Blog

Last edit date: 2023-09-08
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