Crystal Radio Coil Terminals

If your crystal radio does not work then this page might help. One of the main reasons why a crystal radio fails to operate is due to the coil terminals making a poor connection. A radio coil usually has an insulating layer, which requires scraping off at all the terminating ends and preferably tinned with solder. Beginners generally fail to recognise this and therefore the coil makes a poor connection or no connection at all.

If there is an adult present, and if they are capable of using a soldering iron, then one solution is to tin the coil. This will not only strengthen the coil but also ensure a proper electrical contact.

You should also avoid the temptation of winding the coil around the screw terminals, because the coil is likely to break when the screw tightens.

Once the coil terminals are secure under the brass cups, use a continuity meter with the buzzer setting to make sure that the coil terminals are making a proper electrical connection. Check across the coil terminals, and if the continuity meter makes a sound like "Sha la la - la la - la la - la la - la dee dah" - Just like that :-) then it means that the connections are good. However, if the meter makes no sound, then the connections need to be improved.

Soldering to the Cups by an Adult

With my whippersnappers, I noticed that they were undoing the coil terminals and forgetting to make sure that the coil made a proper connection. In addition, the coil is thinner than a component terminal, and therefore sometimes the component terminal will catch first under the screw cup and the coil will remain loose.

To solve this problem I decided to solder the coil wires under the brass screw cups, which are hollow underneath. Brass solders very easily, and a grown-up with some soldering skills ought to be able to do this part. As you can see, the soldered coil connection is robust and much better.

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