This is just a variable oscillator based on a bf245 or k 161 fet. By changing the coil it can generate frequency between 0.5 and 300 MHZ. this circuit is useful to test radio circuit such as filter, receiver, transmitter and so on.
http://digilander.libero.it/alfred73/eprojects.htm#Gate Deep Oscillator
Up to 140 MHz, 1 W into 50 ohms.
http://www.edn.com/archives/1996/101096/21di_02.htm
This circuit makes 1W output from a 2SK513 is power-Moss-FET
http://www.intio.or.jp/jf10zl/hpo.htm
It is a Drain Dip Oscillator based upon a Wheatstone bridge circuit; the oscillator being one resistor of the bridge.
http://web.telia.com/~u85920178/use/gdo.htm
FM Band
http://www.uoguelph.ca/~antoon/circ/rfosc-1.htm
Circuit for a VCO and buffer that operates across the entire FM broadcast band (88-108 MHz). It doesn't require a tapped coil, it tunes very broadly, it's stable, and it has a nice, hot output.
http://www.ee.washington.edu/circuit_archive/circuits/F_ASCII_Schem.html#ASCIISCHEM_010