This basic RF oscillator circuit is easy to build and the components are not critical. Most of them can be found in your junk parts box. The circuit operated with 9VDC power supply.

The L1 antenna col can be made by close winding 8 to 10 turns of 22 gauge insulted hookup wire around 1/4 inch form such as a pencil.

You can experiment with the size of the coul and the number of turns to see how it affects the frequency and signal output of the oscillator. You should be able to pick up its signal with standar FM radio receiver. The “Signal In” should be coupled by disc capacitor of about 0.1uF to the stage in front of it.