The circuit shown depicts a wide band FM wireless microphone. Its power and range are similar to the commonly known circuits, which use bipolar transistors. One gate circuit of the MOSFET is a self excited RF oscillator, and the other gate circuit acts to bias the device and also as a microphone pre-amp and modulator.Tuning can be effected by making Ct a trimmer/padder capacitor, or alternatively if this is a fixed value, then expanding compressing the coil should give some variation in frequency. source

Here is a simple transmitter that when connected to a phone line, will transmit anything on that line (execpt the dial tone) to any FM radio. The frequency can be tuned from 88 to about 94Mhz and the range is about 200 feet. It is extremely easy to build and is therefore a good, useful beginner project.source

Here is a Bug detector with beep.The circuit designed by Tony van Roon.The circuit use two resistors,five capacitors and two TTL IC (74LS13).The circuit operate with 4.5V battery.This circuit very simple and no inductor is required.source