SHOWALL FUN PRANKS HIGH VOLTAGE LAZARUS-64 PHOTOGRAPHY SPY GADGETS VIDEO GAME
Figure 4 - Wrap the bolt five times and you now have your RF coil
Figure 4 - Wrap the bolt five times and you now have your RF coil

The making of the RF coil is as easy as wrapping the enameled wire around the bolt five times and then cutting off the ends. Leave about half an inch of wire at each end so you can scrape the enamel off of the wire and solder the coil to your circuit board. That's all there is to making the necessary coil. Practically any wire close to 1mm in diameter will work as long as it has the protective enamel coating. You could actually get away with bare wire, but the coils would have to be extremely close together but not touching each other or the coil would fail. Enabled copper wire is much easier to use.

At one point I even tried making the coil with four and also six turns, and was still able to make the transmitter send the RF signal to an FM radio. Five turns seems best for reaching the center of the FM radio band, though. Try to get the coil loops as close to each other as possible by keep the wire tight as you wrap it around the bolt. Once the five turns are made, just unscrew the bolt from the coil.



Figure 5 - The completed RF coil after removing the forming bolt
Figure 5 - The completed RF coil after removing the forming bolt

Once you unscrew the forming bolt from the coil, cut of each end of the wire to about a quarter inch in length and then gently press the coil together to take up any gaps left between each loop of wire. The completed coil will perform just as good as any manufactured open air coil of similar size, and it only took 5 minutes to make. Some radio coils are much more complex, containing a ferrite bead or even some internal circuitry, but for these simple, low power, low frequency open air coils, you can almost always "roll your own" if you know how many turns are going to be needed.

Back Home Last Next
You are Viewing... Page 3 of 16
Lucid Science Electronics from the Fringe AtomicZombie Hack-a-day SparkFun