Making a Transmitter out of a crystal Radio.

Intro - 	Our goal is to show that a crystal radio "rings" with radio waves.
		We pick those up with an am radio.

Equipment - 
		1.  Crystal radio modified so the earphone/diode/resistor can be disconnected.
		2.  Small, battery-powered AM radio.
		3.  Square Wave generator
		4.  Oscilloscope
		5.  9V Battery
		6.  Small DC Motor

Steps - 
		1.  Feed a small square wave (200-2000 Hz) into the aerial of the crystal radio. 	
			a) With the earphone connected, you can hear the square wave
			b) Placing the scope across the capacitor, you can see the square wave.
			c) Students can vary the frequency of the square wave and see the change on the scope.
		
		2.  Get students to look closely at the "square" steps.  
			a) Zoom in on the fuzz and see the "step" is in fact the ring-down of the LC loop.
			B) Adjust the frequency and the ring-down stays the same.
			C)  Adjust the tuning capacitor and the ringdown does change.
			So, the ringing is made by the radio.

		3.  Disconnect the earphone and turn the square-wave up to full power.
		Turn on the AM radio and tune to a blank part of  the spectrum (eg 1000kHz).
		Place the radio close to the crystal radio.  You should just hear the square wave.
		Now tune the radio or the crystal set and the buzzing will get very loud.
		Move the radio a reasonable distance away.

	
		Let the student play to tune the two radios, adjust the square wave frequency, etc.

		4.  Replace the square wave with voltage pulses from the 9V battery.

		5.  Replace the square wave with electrical noise from the DC motor spinning over.