Radio Coils

Dave Schmarder's spider coil

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Welcome to my coils page. Coils are very important in radios. All radios have them. They, along with other components determine what station a radio is tuned to.

Coils or inductors are one of my favorite subject to write about because they are so easy to build. Try building a variable capacitor and you will see what I mean. My personal favorite type of coil is the spider form coil. They are easy to wind and adjust.

Besides the coil former, there is the coil type. For main tuning tank coils, especially in crystal radios, I like the contra coil. They just give a bigger bang for the buck. There are extra considerations to watch out for when designing and building them. I hope that these pages will assist you in building the best radio that you are able.

The coils that I show on these pages are made from litz wire. This is a special type of manufacturered wire that is designed to lower your coil losses. My designs can be ported to standard insulated magnet wire.

I have some practical examples of coils that are useful in radio building. I have cylinder, spider, variocoupler, and variometer examples. I have variation on coils called contracoils.

Spider Coils

Spider Coils English
Bobinas de tela de araña En español

Contra Coils (cylinder and spider)

Contra Coils English
Bobinas de contra devanado En español
Kontraspulen Deutsch
Kontra Gewikkelde Spoelens Nederlandse

Cylinder Coils

Cylinder Coils Coils wound on cylindrical forms. This is the most popular coil style.

Variable Coils

Variometer A two terminal coil used in very old radio receivers.
Variocoupler A main coil, with a variable tickler winding. Popular in early regenerative receivers.

Coil Related Links

Gollum's Spider Coil
Gollum's 2 coil dx receiver
Gollum's shortwave spider radio
Mike Tuggle's Spider Coil
Formula for calculating spider coils