Neutrodyne

The Neutrodyne was a particular type of tuned radio frequency (TRF) radio receiver, in which the instability-causing inter-electrode capacitance of the triode RF tubes is cancelled out or "neutralized". In most designs, a small extra winding on each of the RF amplifiers' tuned anode coils was used to generate a small antiphase signal, which could be adjusted by special variable trim capacitors to cancel out the stray signal coupled to the grid via plate-to-grid capacitance.