The input stage is the same circuit as the mixer amplifier we've used in several past Labs. Its three inputs will be the carbon microphone, the dynamic microphone, and the function generator.
If your mixer amp is in good shape, you can use it as is. If it's looking tired and ragged, tidy it up or rebuild it.
Connect the mixer amplifier output ( ) to the A/D input for the transmitter VI (ach5, pin 47 on the interface strip). Set the function generator to produce a 1 V 400 Hz sine wave and connect its output to the input of the mixer amp.
Load the transmitter VI from the previous section. Press Run and verify that the AM signal appears at D/A output 0 (pin 51 on the interface connector).
If you haven't already done so, have Mr. Dye install an Antenna Interface module in your breadboard. Connect D/A output 0 (pin 51 on the interface connector) to the transmitter input (pin 39).
Use a BNC cable to connect the output of the Antenna Interface (J4-1) to the oscilloscope. Set the switch on the Antenna Interface to Transmit. Verify that the AM signal appears on the oscilloscope.