Photography by Shortwave Collective

Shortwave Collective is a 10-member feminist art group founded in 2020. Collectively, we’ve been exploring the process of radio circuit assembly, considering the radio spectrum as an artistic material, and building self-powered radio receivers. Through an artist residency at Buinho Creative Hub in Portugal, we also spent a week of in-person and remote collaboration developing radio wave receivers and experimenting with designs with others in an open workshop.

Here are some of the lessons we’ve learned — and how to build your own radio wave receiver.

A FEMINIST APPROACH TO BUILDING RADIO

We support inclusive and participatory STEM education that transcends gendered stereotypes. We learn by collaboratively doing, with a goal of exploring creative possibilities. We believe in demystifying technologies and connecting with others by making and doing.

With our experimental radio projects we are interested in listening, in a broader sense. We measure success in ways other than by signal strength or tuning frequencies for the clearest sound. Instead, we are interested in all the sounds detected — data signals, talk radio, and sferics (radio bursts emitted by lightning) alike. We are fascinated by the idea that radio waves surround us, and being able to detect them and translate them into audio signals to listen to illuminates something about our environment.

What interests us about the radio wave receiver projects is their accessibility. It’s a great way to learn about the physics of radio through practical experimentation.

SIMPLE RADIO CIRCUITS AND OPEN WAVE-RECEIVERS

Probably the most famous example of simple radio design in action is the foxhole radio. These were made from materials that were accessible to soldiers in the trenches (foxholes) during World War II. Though designs varied, they typically used a razor blade, pencil, and safety pin for parts. The official military vacuum-tube radios used during the war could be traced to reveal broadcast or reception locations, but foxhole radios operate without a power supply, and could not be detected. Thus, soldiers used them as a way to safely keep up with the world from their posts.

Crystal sets are another form of early radio circuitry — a popular DIY project in the 1920s and even today — that relies on a mineral crystal (usually galena) as a radio wave detector.

WARNING: If you’re listening through headphones, be mindful that volume increases can be unpredictable. To avoid damaging your hearing, make sure you have a complete circuit with both diode elements touching before you put your headphones on, and take them off before these pieces are disconnected.

We began our experiments by examining popular designs for radio receivers, such as crystal sets and foxhole radios. There is a basic recipe to build simple radio circuits, and we found many how-to examples and diagrams on websites, YouTube, and in books. Soon we found ourselves more fascinated with the process and experimentation, rather than the end product of replicating others’ radio visions. Hence we refer to our project (and variations of it) as making an Open Wave-Receiver.

The fun of building an Open Wave-Receiver is in exploration and experimentation to find materials and environmental conditions with strong enough signal to receive radio waves. These radio constructions can be simple or souped-up, depending upon how the found materials vary the aesthetic or the elements of the circuit.

EXPERIMENTAL MATERIALS: FOUND, FENCES, AND TENT PEGS

Building Open Wave-Receivers enables DIY communications reception, and allows anyone to freely listen to the broad spectrum of radio waves around us. All you need are a few easy-to-procure supplies and, if you want to try it, a neighborhood fence or other receptive antenna proxy.

Why a fence? Antennas are necessary for radios to receive signals, and many things can be antennas. Fences can make great, and very long, antennas! Other materials can work well too; even a tent peg can become a useful part of a radio. Open Wave-Receivers allow us to explore the relationship between different combinations of materials, antennas, and radio waves, creating a new technology literacy, a new medium for artistic expression, and a new way to explore the airwaves in our communities.

We have found making Open Wave-Receivers to be a fun adventure. The ability to use simple scraps to create variety and personalization in each radio makes this a great maker project for anyone wanting to play with radio.

BUILD YOUR OPEN WAVE-RECEIVER

Let’s get building! Here’s how to make an Open Wave-Receiver from readily available materials. Building it will enable you to listen to airwaves and to reveal the invisible sounds that surround you — transmitted near and far — while becoming aware of how environmental and atmospheric conditions affect radio reception.

MATERIALS

  • Board cardboard, foam, wood, or found object
  • Alligator clip jumper wires (5) aka crocodile clips; or use basic insulated wire (e.g. hookup wire) and 10 bulldog clips
  • Cardboard tube such as an empty toilet paper roll; or try an alternative hollow cylinder or glass bottle
  • Magnet wire, enameled copper, 22–28 gauge (10 meters) for the coil
  • Pencil stub, 2″ or less
  • Safety pin, medium sized
  • Razor blade or galena crystal for the radio wave detector. Also try experimenting with a metal tent peg, iron pyrite (fool’s gold), silicon, a germanium diode, or other metal objects.
    LEAD WARNING: Galena is a mineral that contains lead, and its dust is toxic if inhaled or ingested. However, the mineral can be handled safely if there is no lead dust present. Always wash your hands after handling galena. You can wear gloves and/or a dust mask to be extra safe.
  • Metal tent peg for a ground rod
  • Wire, any type and length to connect to ground. Longer allows you more flexibility.
  • Speaker wire (30 meters) or as long as possible; for the antenna
  • Mini audio plug, 1/8″, with wire leads
  • Speakers, battery powered or audio recorder with strong preamp and headphones


TOOLS

  • Electrical tape
  • Wire strippers
  • Wire cutters
  • Pliers
  • Candle or gas stove
  • Disposable gloves and a dust mask if working with lead crystal
  • make.co
  1. MAKE THE COIL
Figure A

Start with your cardboard tube. Using a pin, poke a hole about 1cm from the rim at the top (Figure A ) and bottom of one side.

Figure B

Thread 5cm of enameled wire through one hole, from the outside in (Figure B ).

Figure C

Tape the wire to the inside of the tube to hold it in place (Figure C ). You’ll pull it out later to clip to the rest of your circuit.

Figure D

Wrap your magnet wire approximately 120 times around the cardboard tube (or until you’ve used your 10 meters of wire). Ideally, the coil should be wrapped tightly and no loops should overlap (Figure D ). Tuck the end of this wire into the second hole that you poked in the tube to keep it secure, with the end protruding from the tube.

Scrape the enamel coating off each end of the magnet wire using sandpaper or a blade to make bare ends for your connections. Make sure you scrape around all sides!

Figure E

Put a strip of tape along your coil to keep the wire secure (Figure E), then tape your coil to the board, on its side.

Figure F

Stick a crocodile clip onto one of the stripped ends of the coil (Figure F).

  1. BEGIN THE DIODE

If you’re using a razor blade, prep it by heating it until it turns blue. This creates a thin layer of magnetite, which is a semiconductor — an important part of your diode. Try steel blades such as vintage shaving types or X-Acto or Stanley knife blades. Hold the razor blade with insulated pliers and put it in the flame of a candle or gas stove until the topside turns blue.

Figure G

Fix your blued razor blade or galena crystal (also a semiconductor) on top of the board, opposite to your coil, using glue or a loop of tape underneath it (Figure G). We’ll come back to finish the diode later.

  1. WIRE THE ANTENNA

Take your speaker wire (30 meters, or as long as you have) and strip the coating off 5cm at one end of the wire. This wire will be your antenna.

Figure H

Connect the stripped end to the side of the board between the coil and the crystal or blade, using the other end of your crocodile clip. The clip should now be connected to the coil on one side, and the antenna on the other (Figure H ).

String your antenna as high as you can in a long line, parallel to the ground, perhaps on a washing line in your garden, but don’t let it touch any metal!

  1. ADD A GROUND

Take your ground wire and if coated, strip a section of the insulation off both ends. Wrap one end around a tent peg and push it into the ground outside, or if you’re indoors, wrap it around a water pipe or radiator pipe. Use a crocodile clip to connect the other end to the middle of the board, above your antenna, between coil and diode.

Figure I

Connect the other end of this crocodile clip to the loose wire at the top of your coil (Figure I ). You’ve now made half a radio circuit.

  1. CONNECT THE OUTPUT WIRE
Figure J

Take your mini audio plug and strip the end of both strands (Figure J ).

Figure K

Connect a crocodile clip to each end (Figure K).

Figure L

On the black strand, connect the crocodile clip to the board so that it also connects with the antenna wire, and touches the other crocodile clip positioned there (Figure L ).

Plug your mini jack into your speaker.

  1. FINISH THE DIODE

On the red strand of the audio plug, connect the crocodile clip to a safety pin. This is your cat’s whisker — the other part of your diode.

Figure M

Your circuit should now look something like Figure M . The white nest of wire is an unconnected ground and the red wiring is an antenna that has yet to be hung. In this model, the safety pin touching the galena crystal completes the circuit.

Figure N

If you’re using a galena crystal for your diode, touch your safety pin directly to your crystal to complete the circuit (Figure N). If you’re using a blued razor blade for your diode, stab the safety pin into the pencil lead at the blunt end of your pencil stub so it sticks.

Figure O

Touch your pencil point directly to your razor to complete the circuit (Figure O ). You’ve built a radio wave receiver!

TROUBLESHOOTING

This kind of radio is powered entirely by the energy of the radio waves, and so the signal is likely to be very weak. You might not hear anything at all when you first assemble your radio. Don’t worry though! Wait until sunset, take your radio outside, climb a hill, and string your antenna up as high as you can in a straight line parallel to the ground — these are the conditions that we’ve found give the strongest signal.

If you’re still not hearing anything, look again at the radio circuit diagram. Are your parts in the correct sequence? Have you stripped the ends of your wire enough that your connections are solid? Are all the necessary parts touching, without any extra unwanted contact points?

Some things to test:

• Turn the volume of your speakers up to the maximum. You should hear a hum that gets quieter when your cat’s whisker touches your razor or crystal.

• If there’s a loud hum, change your ground connection. If you’re inside, connect to the metal of a radiator or water pipe. If outdoors, really drive your tent peg far into the ground and test it again.

• If your antenna is suspended in the air, change its position. Don’t let your antenna wire touch your ground wire.

• Be patient with your diode. Try moving your cat’s whisker very gently over the razor blade edge or galena crystal.

LISTENING

Your radio is not just location specific, but time,
weather, and season specific! We’ve found signals to be strongest during “grey line” time — dawn and dusk. Dry conditions will also help.

We haven’t included a tuning arm in this build — it’s really part of our ethos to listen to the environment as we find it rather than look for a clean signal. (Foxhole designs with a tuning arm are well documented on the internet.) Though signal strength is important so you can test if your radio receiver is working, we feel it is just as exciting to listen to radio that is quiet, perhaps sounds out with strange beeps and hums, or has multiple stations competing rather than one clear signal. We are making audible the invisible radio waves around us and listening to them as they interact with our environment, rather than aiming to filter them to a predetermined mode.

EXPERIMENT!

• Try throwing your antenna up in the air, and hear how the volume increases as it flies.

• Is there a metal wire fence nearby that you could use as an extra long antenna (e.g., a fencetenna)? Clamp it with a crocodile clip.

• Try making a new coil by wrapping another length of enameled wire around a found object.

• See what metal objects you can swap your diode for to detect your signal.

Our experiments, and those by participants in our workshop at Buinho Creative Hub, Portugal, include:

Figure P

• A rock at the center of the coil, altering its air-core properties (Carlos Alcobia) (Figure P )

Figure Q

• Cork bark local to the area as a base-board (Anaïs Schendekehl) (Figure Q )

Figure R

• A wearable radio in the shape of a hat, made from scrap material (Brigitte Hart) (Figure R )

• Tent-peg diode radio — replacing the razor/crystal and “cat’s whisker” diode (Hart, Lisa Hall, and Hannah Kemp-Welch)

• Found-object diode radio (Hart, Hall, and Kemp-Welch)

Figure S

• Roof radio — coil wrapped around a roof tile (Hart, Hall, and Kemp-Welch) (Figure S )

Figure T

• Multiple diode design, with numerous rusty and blued razors built in (Georgia Muenster) (Figure T )

Figure U

• Basket-weave coil for a crystal radio, work in progress (Kate Donovan) (Figure U )

• The Fencetenna project was a selection of radio receivers including foxhole, crystal, and shortwave receivers that were connected to fences as antennas, implemented by Shortwave Collective members Alyssa Moxley, Brigitte Hart, Georgia Muenster, Hannah Kemp-Welch, Lisa Hall, and Sasha Engelmann. Behind-the-scenes support came from members Sally Applin and Franchesca Casauay, with thanks to Soundcamp 2021 for inviting us to their event program.

HOW DOES IT WORK?

• The antenna picks up radio waves from all directions. Radio waves flow through the metal, creating an electric field, which moves along the length of the aerial to produce an alternating current.

• The coil exchanges current with the antenna. It stores the current and smooths it as it runs through the circuit.

• Diodes have two parts: a crystal or razor blade and a “cat’s whisker.” When the two parts meet they act as a gate or semiconductor, only allowing current to flow in one direction. They strip the radio wave, leaving only an electrical signal.

• The phones convert the electrical signal into sound.

• The ground allows the current collected through the antenna to dissipate and leave the circuit.