I am working on the 100 Mhz version and I do not use a module but a transistor oscillator with frequency command with varicap diode, I do not use a coil printed on the pcb, but a flat coil placed horizontally, while on the sensor stage an equal coil but placed vertically , with the aim of minimizing the transmission of the signal from the oscillator to the sensor stage. In this way, a good result is obtained by keeping the oscillator about 7 cm from the sensor stage. As soon as I have finished drawing the scheme I will post it.
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