But one of the most interesting things about radio is that if we can do something one way, we often can do it another way.
Let's see if we can improve our foxhole radio. We can very easily. We can change it into a crystal radio set. To do this we must go to a radio store and buy a crystal detector. It will cost about $1.00.
There are two main parts to a crystal detector. One part is a piece of crystal. This is a mineral called galena. The crystal is placed in a little holder which is hooked up to a post. This post is used to make a connection. The crystal takes the place of the razor blade.
The other part of the crystal detector is called a cat whisker and takes the place of the safety pin. The cat whisker is mounted on a little arm that we can move just as we moved the safety pin. The cat whisker is also hooked to a post where we can make a connection.
This is the way the crystal and the cat whisker look:
This is how our radio set looks after we have taken out the razor blade and safety pin and put in the crystal:
A wire goes from Nail A to Post X on the crystal detector. This is Connection No. 1.
A second wire goes from one of the tips of the earphones to Post Y on the crystal detector. This is Connection No. 2.
To make the crystal work, you must also hook it up to an aerial and a ground connection just as we did with the foxhole radio. Then you grasp the arm of the cat whisker and move it gently so that the end of the fine wire touches the face of the crystal. Listen carefully, and you will find a spot on the crystal which brings in a station best.
It is the crystal which acts like an electrical gate that lets electricity go through in only one direction.
Remember how we said that the combination of a coil and a condenser enabled us to get the station we wanted to hear and keep out those we did not want to hear.
We can add a variable condenser to our crystal set, and it will help to separate stations. The condenser also must be bought in a radio store. It costs about $1.50. The size you want has twenty-one plates, some of which turn and some of which are fixed. However, a condenser of either seventeen or nineteen plates will work all right.
This is how the condenser looks when it is put in the set:
One post on the condenser is connected to the plates that are fixed. From this post a wire is run to Nail A. This is Connection No. 1.
Another post on the condenser is connected to the plates that turn. From this post a wire is run to Nail B. This is Connection No. 2.
With the condenser in the set, we must first move the end of the cat whisker over the top of the crystal until we hear a program. Then we turn the condenser either to the right or left until the sound is heard the loudest.
There is no thrill quite like hearing a program on a set that you have made yourself. But you can see that there are many disadvantages to the foxhole radio and a crystal set. They cannot pick up all the stations you want to hear. They will not work if you are a long distance from a station. And they bring in a station only just loud enough to hear on earphones.
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