Organize and Share your Electronics the way you want. Sign-Up for a free account now. It takes only 30 seconds!

VHF Center Frequency FM Transmitter

VHF Center Frequency FM Transmitter

The circuit was designed to function on the middle of the FM band, 98 MHz, since the FM frequency ranges from 88 MHz to 108 MHz.
The circuit works as the transmitted signal is a Frequency Modulatedwhich means that the carrier’s amplitude stays constant and its frequency varies according to the amplitude variations of the audio signal. When the input signal’s amplitude increases the frequency of the carrier increases too, and vice versa. For this circuit to be tuned at the center frequency (98 MHz) of the FM band, it utilizes an inductor rated at 0.112 uH with a variable capacitor VC1 in the center value of 33 pF. The inductor has a standard wire gauge of 22, made of enameled copper wire that created its winding 5 times around a 3/16” diameter and 5mm long bolt. Otherwise, an adjustable molded coil can be used to achieve a fixed capacitor value of 33 pF from the variable capacitor. Without setting the variable capacitor to a fixed value, the tuning can provide the range between 85 to 125 MHz.

To produce a repetitive electronic signal, to op-amp oscillators were used in the circuit. The electret microphone used was an omnidirectional type while the antenna is a single vertical wire above a ground plane known as whip, stub or monopole, around 76 cms of 22 swg copper wire. The combination of the transistor and LC oscillator (a variable capacitor in series with an inductor) produces a clapp oscillator on Q1 which prevents the circuit to have a variable feedback voltage and cause it to less likely achieve oscillation over a portion of the desired frequency range.

Visit Here for more.

 

More Articles to Read

Debugging ARM Cortex-M0+ HardFaults
Debugging ARM Cortex-M0+ HardFaults
EMP Jammer build
EMP Jammer build
A 3D-printed e-drum pad
A 3D-printed e-drum pad
Interactive geodesic LED dome = extreme geometric fun!
Interactive geodesic LED dome = extreme geometric fun!
Guide to build your 3.3v power supply
Guide to build your 3.3v power supply
SDR radio breathes life into a 75 year old Marconi CR100
SDR radio breathes life into a 75 year old Marconi CR100
A Time for Ranting!
A Time for Ranting!
Emulate a Commodore 64 keyboard with a modern PC and an Arduino
Emulate a Commodore 64 keyboard with a modern PC and an Arduino
USB2005 and USB97C202 Sharing ATA/ATAPI Drive w/ Another Controller
USB2005 and USB97C202 Sharing ATA/ATAPI Drive w/ Another Controller
Robotic Cat Laser
Robotic Cat Laser

Top




Shares