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A Slinky® antenna is an antenna made with the children's toy known as a slinky. Slinkies® are helical metal coils that, when used as toys, exhibit interesting properties like being able to “walk” down stairs and across flat surfaces. They can also be very useful for homemade antenna projects, depending on how the antenna is being used. Many toy stores carry Slinkies® and similar products made by other companies, often at very low cost, making them cheaper than some more conventional antenna-making supplies.
Slinkies® work as antennas not simply because they are long strips of metal that can pick up signals, but because of their resonance properties. A helical antenna can be adjusted to change the way it resonates by changing the number of curves or their amount of extension. It is important to be aware that with a Slinky® antenna, the metal has not been protected with anti-corrosive materials, so it may not be suitable for outdoor use.
The classic use of the Slinky® antenna is in a dipole antenna, with two Slinkies® extended in opposite directions and connected to an element in the center. The length of the Slinkies® can be adjusted so that they will resonate at different frequencies, providing multiple feeds to the tuner in the middle. This expands the range of frequencies that can be picked up, providing people with many different options to tune to.
The advantage to using a Slinky® as an antenna, beyond the low cost making it accessible to amateur radio operators, is the portability. Slinkies® can be compressed when they are not in use to create a compact coil that can easily be carried in a radio kit. The Slinky® antenna can also be stored when not in use, for people working in settings like homes where an antenna array might not be a desirable thing to look at when the radio is not in use.
When extended, the Slinkies® should be supported with a length of cable or wire. The coils are not strong enough to support the extended weight and the antenna will drop and deform otherwise. It is also important to avoid pulling the Slinky® antenna out too far, or the helix may lose its naturally springy properties. Slinkies® can also become prone to tangling when they are frequently extended and allowed to spring back. When the devices do become tangled, they should be gently unsnarled from one end to the other and not forced or they may distort.