I having an assignment that need to design AM Transmitter using Multisim with following specification:
• Audio input (200-14000Hz)
• Double Sideband Full Carrier
• RF carrier frequency of 50 MHz
• Carrier Power 1 mW
I have totally no idea how to design a AM modulator from scratch, so i found this video, and built this circuit and try to modify the carrier signal frequency from 11kHz to 50Mhz it fail and didn't show any signal at the oscillator.
I know some basic concept about how AM can be achieve using transistor,but have no idea how to design it.
Is there any detail guideline i can refer or follow to design a circuit from scratch?
How do all the value of resistor is being calculated, and why is capacitor and inductor being use at the collector of the transistor.
Update: I had revise about the DC biasing of the transistor and made a update about my prototype. Here I will explain what my understanding and how I design.
First, I hope my Q-point is in the middle, so i check the datasheet of BC107B and found that Vce(sat)=200mV while Ic=100mA (there are another value Vce=70mV when Ic=10mA). Then i go though some calculation. There are too many variable, therefore i assign some of it to simplify the calculation(Re and R1). For the tank circuit, I use frequency 50Mhz as my question RF carrier require and remain capacitor unchanged to find out the inductor value. The final circuit result is as follow. The circuit is not working. Please tell me if there any mistake or what i did wrong.