Oscillator

The purpose of this lab was to build and test a Hartley Oscillator for use in our AM heterodyne radio.

First, we constructed the circuit shown in figure 1. We were to observe the output of the oscillator as the trimming capacitor was adjusted. When the trimming capacitor was adjusted, we did not see a change in the peak. We checked the circuit and realized that R1, Re1, and C3 were not grounded. This helped but it was still not producing a sine wave. We decided to change the circuit to the circuit shown in figure 2. This fixed the problem and we got flow = 720 kHz and fhi = 1.26 MHz. This was the expected results.

Figure 1: Hartley Oscillator

Figure 2: Altered Hardware Implementation of the Oscillator Circuit

We decided to use the rest of the time in lab to work on our radio so we did not connect the bandpass filter, mixer, and oscillator to the circuit to test.