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Transmitter Prototype
We chose the analog FM transmitter shown below to implement
as our final design.
FM transmitter (88-108 MHz) #5
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1.4V supply voltage
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11 components: 2 transistors, no tunnel diode
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Substituted 2N3904 npn transistors for the 2
transistors in the schematic
Figure 1. Schematic of transmitter circuit
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No antenna
resulted in a clear transmission distance of about 10 feet with
the breadboard prototype shown below
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The circuit
is powered by a 1.4V size 10 hearing aid battery.
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Composed of basic resistors, capacitors,
transistors, and an inductor
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Components are inexpensive and readily available
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Relatively simple to implement
Figure 2. Prototype of the
analog FM transmitter.
Final Printed Circuit Board
(PCB)
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Utilizes surface mount components
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Height: 7.8
mm
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Width : 11.6
mm
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Small enough
to easily fit within the ear
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Calculations
show approximately 35 hours of battery life with a 1.4V hearing
aid battery
Figure 3. Final PCB.
Figure 4. Microphone and PCB in an ear mold.
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