A simple high quality FM remote wireless speaker system can be designed using the LM LM566 VCO and LM565 PLL Detector . This high quality, noise free, wireless speaker system is composed from two stages : radio transmitter and radio receiver .
The LM566 VCO is used to convert the program material into FM format, which is then transformer coupled to standard power lines. At the receiver end the material is detected from the power lines and demodulated by the LM565.
The complete wireless speaker system is suitable for high-quality transmission of speech or music, and will operate from any AC outlet anywhere on a one-acre home side. Frequency response is 20±20,000 Hz and THD is under 2% for voice and music program material.
The receiver module includes a 2.5W power amplifier to drive a speaker directly.
The input signal level is adjustable by R1 to prevent overmodulation of the carrier.
The receiver amplifies, limits, and demodulates the received FM signal in the presence of line transient interference sometimes as high as several hundred volts peak.
The PLL detector operates as a narrow band tracking filter which tracks the input signal and provides a low-distortion demodulated audio output with high S/N. A mute circuit is included to quiet the receiver in the absence of a carrier .
As you can see in the schematic circuit , this wireless transmitter and receiver system electronic project require few external electronic components . To work properly this wireless transmitter and receiver electronic project require few adjustments .
T1 for both transmitter and receiver are tuned for maximum coupling to and from the AC line. Plug in both receiver and transmitter; no carrier modulation is necessary. Observe or measure with an AC VTVM the waveform at T1 secondary in the receiver. Tune T1 of the transmitter for maximum observed signal amplitude and then tune T1 of the receiver for a further maximum.
The final adjustment is for modulation amplitude at the transmitter. Connect the audio signal to the transmitter input and adjust the input potentiometer R1 for a signal maximum of about 0.1V rms at the input to the LM566. Adjustment is now complete for both transmitter and receiver and need not be repeated .
This wireless transmitter and receiver system was designed by National Semiconductor and you can power this circuit from a 12V DC power source ( in that case you should remove the power supply part from both of circuits ).