Making The Spider's Web

Generally coils are cylindrical.  We have chosen a spiders web coil because these are simple to wind. You must however pay attention that you lay the windings nice and tight when winding the coil.

The material chosen is 3.4 mm MDF as is easy to work with.   If you make a former then you could also use an old CD perhaps.

On the former shown on the left 7 segments have been created. For the crystal radio in the article below,  the coil has been made with 9 segments at 40° intervals. The inner diameter is 2.5 cm and the outer diameter is 12 cm. The former is 4.75 mm thick and there are about 60-70 turns on the winding. The wire should be reasonably thick as very thin wire can very easily break when winding. For calculating the coil we used Professor Coyle's Spiderweb Coil Calculator

Below are a couple of photographs of the completed crystal radio that the Vught North Scouts constructed during the their "Jamboree On The Air".  The spiders web coil is a very interesting feature of the set and was chosen because it was thought to be easier to wind for the younger scouts.

The scouts were provided with a package that contained all the required components including the former for the coil, suitable wire to wind the coil and a base panel onto which they could build the spiders web crystal set on their Jamboree. They had to ensure, however, that great care was taken when putting up the wire for the large antenna for the wire which was a minimum of 10 meters long.  The crystal set also had to be connected to an earth point and a water pipe was used for this.