PURPOSE

1. To build a radio frequency oscillator using 2N3904 transistors, and calculate proper capacitor values to produce the desired frequency.

2. To measure the output frequency range provided by the variable inductor, and then set the oscillator to a frequency of 750 kHz.

3. Calculate the effective inductances of the variable inductor at the two frequency extremes.

INTRODUCTION - Carrier Frequency Oscillator

Modulation is the process of placing information onto a carrier frequency. The carrier is nothing more than a radio-frequency (RF) sine wave whose characteristics are modulated (vibrated at the information frequency) by changing either the amplitude, frequency, or phase so as to attach the information to it. In this experiment, an RF oscillator will be constructed as the first stage of an AM broadcast transmitter.

PARTS

(2) 2N3904 NPN transistors

(1) 50-100uH variable inductor

(2) 15 kohm 1/4 W resistors.

(2) 10 kohm 1/4 W resistors.

(3) 220 ohm 1/4 W resistors

(1) 47 ohm 1/4 W resistor,

(1) 10 μ1F electrolytic capacitor"

(1) 0.1 uF mylar capacitor

(1) 0.01 uF mylar capacitor

Capacitors C1, and C2 are to be calculated by the student.

1. A theory section that describes the purpose and operation of the circuit. This section should include a description of the function of each component in the circuit. This section must also include all equations used to design the circuit, and to obtain the numeric results. Equations should be typed into the report using Microsoft Equation Editor 3.0 found under Insert/Object/Microsoft Equation 3.0. Include comments about special measurement techniques to be used.

2. A data section that includes the results of your design equations, and the measured results of the lab work. If applicable, calculate the percent of experimental error using the following equation:

Percent error = (|X_theory -X_measured|/X_theory) x 100%

3. The complete schematic of the circuit must be drawn with Orcad/PSpice, EagleCAD, LT Spice or Multisim and include the values of all the parts used. This should be pasted into the lab report.

4. A conclusion section that describes the results of the lab work in complete sentences. Comments like, "I really learned a lot from this lab", or "this lab was really fun" do not belong here. You should discuss whether or not the lab achieved the desired results. Quote actual numbers from your data section to support your conclusion. State possible sources of error, and even suggest ways that the circuit could be improved.