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Oscillator

Objectives:
  • The objective of the Oscillator lab is to:​
    • ​Analyze a Hartley Oscillator
    • Build and test the oscillator for use in the AM heterodyne radio.

Oscillator

  • The Hartley Oscillator designed in this lab was to be used as the local oscillator source for the radio. The oscillator was to produce a sinusoidal output that was to be delivered to the emiiter of the mixer circuit. The frequency of the sinusoid was to be adjustable over a range of sufficient enough to pick up the desired AM radio stations. 

  • Theory behind this oscillator states that the loop gain must be at least 1, and the fed back signal must constructively add to the original signal. There are multiple feedback paths for the transistor in this circuitry. 

  • The trimming capacitor allows for variation in the oscillation frequency. The trimming capacitor used ranges from 8 pF to 120 pF. The constructed Hartley Oscillator can be seen below.

Figure 1: Hartley Oscillator

Once the Hartley Oscillator was constructed it failed to produce any output signal that would have been seen on the oscilloscope. In an attempt to create a sine wave, the altered hardware implementation of the oscillator circuit (which reduces loop gain) was breadboarded. The results yielded the same, as no output was realized. The trimming capacitor was adjusted in hopes of achieving an output signal but this also failed. As a result, we were unable to determine the range over which the oscillator operated, as it failed to operate completely. The circuit was tinkered with, but this was to no avail. Overall, this circuit was unable to be tested with the radio.  

The oscillator lab helped gain experience if nothing else. There are many reasons why this circuit may have failed to produce a desired output. As engineering goes, things will not always go as expected. The idea of being able to produce a sine wave without the use of the function generation as an input source is quite amazing however. This lab provides an example of how real world scenerios may go in such a case that an experiment does not work out as planned. The lab did include valuable information about how oscillation works and the requirements needed. In some ways, this lab is as a portion of Analog Electronics when speaking of gain and generating a desired output signal or signal range. It also relates to Control Systems in ways such as adjusting circuit parameters in hopes of achieving a desired output. 

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