L1 is 0.112uH (this tunes to the middle of the FM band, 98 MHz, with VC1 at its centre value of 33pF). L1 is 5 turns of 22 swg enamelled copper wire close-wound on a 5mm (3/16″) diameter former. Alternatively, you can have a fixed 33pF cap instead of VC1 and have L1 as an adjustable molded coil (eg UF64U from Maplin). VC1 will give you a tuning range of 85 – 125 MHz, and a possible choice is the Philips type polypropylene film trimmer (Maplin code WL72P). source

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

This is a very popular HIGH POWER FM Wireless Microphone with beginners and experienced constructors alike. It has been used inside guitars and as the basis of a remote control system.It can transmits over 1Km range (under ideal conditions) and is good on microphone sensitivity. This has been achieved by adding an RF amplifier buffer (with 10dB gain) and an AF preamplifier to boost the modulation a little.source