I\`m trying to build a frequency modulated LC oscillator but all circuits I\`ve tried have terrible mains hum after demodultaion. The oscillator is tuned by capacitive sensor but I\`m using a fixed capacitor instead until I solve this problem. I\`ve tried different topologies: Franklin, Clapp, Vackář, Hartley at different frequencies from 60 to 500 MHz but there\`s no difference between them in terms of mains hum. I\`m using an SDR receiver for demodulation, it works fine and cannot be the source of hum. Using battery instead of AC supply didn\`t help. I`m using 10 µF and 10 nF capacitors for decoupling. Using physically smaller inductors helped a little, but the noise is still unacceptable. Here are some PCB drawings, maybe there are mistakes in routing?  Fig. 1: Vackář topology, the transistor is BF545C  Fig. 2: Franklin topology, both transistors are ATF-38143 [UPD:] Uploading my setup and schematics as requested. The setup is just an SDR receiver and the oscillator with a piece of wire at the output as a makeshift antenna. The capacitive sensor C<sub>var</sub> is absent, as I\`m using a fixed capacitor C<sub>4</sub> instead. >!  >!  >! 