Tone Modulated Transmitter
This is a second and improved MCW transmitter. The one in project Modulated continuous wave Transmitter MCW in radio section produces a strong but distorted audio signal in the receiver while this project provides the same results but with a much cleaner sounding signal.
Battery current drain with this transmitter is only 0.5mA without modulation and 5mA with modulation. This is about 1/4 of the current required by the circuit of project Modulated continuous wave Transmitter MCW.
Because of this low current requirement the power output is also lower, so you may want to use your an Antenna (green wire) for this transmitter. You may want to try different Battery voltages (from 3 to 12 volts) with this transmitter. You may also experiment with Resistor values, but don't decrease the 100K to below 22K, or the 220K below 47K.
Notice the effect on tone and frequency when making changes. If you have a VOM you will want to see what effect these changes have on Battery current drain.
The audio oscillator output may be heard by connecting the Earphone across one of the Input Transformer windings. Compare this with that from the AM receiver which is tuned to the transmitter frequency. Have fun!