Fm Transmitter By Samuel Nyall Stearley!!! 12/6/2002

The Schematic!!

Going on…

So what do the specifications mean? Input impedance? Very obvious. It is the internal resistance of the microphone. This microphone has a 1.6k ohm resistance. Good microphones have a 400 ohm resistance.

So what do the specifications mean? Frequency Response? Obvious. The microphone will operate between 50 to 12k hz. Good microphones will operate between 30 to 20k hz.

So what do the specifications mean? Effective output Level? Not so obvious. The units are in decibels so what is being amplified?

Amplification The amplification relates air pressure caused by the voice to the output voltage. So how much air pressure should be expected? A loud air plane will cause 70 PASCALs of air pressure. This equates to 0.2 volts of output from the microphone.

Therefore my ac /sinusoidal sources are going to have a magnitude of 0.1 volts and a dc offset voltage of 0.1 volts to keep it positive. For a combined total of 0.2 volts maximum.

Simulation: Ac sweep

Monte Carlo, Worst Case

Actual Construction The circuit was constructed on a Bread board. It has only been operated at dc. I probed it at various points to measure voltages. Thos voltages where very similar to voltages given by pSpice. The microphone has not come in, when it does I will continue testing.

Further Improvements The Filter would be at least 1 2 nd order band pass with variable capacitors.

-The End- Time for questions.