An inductor used in the output tank circuit of a shortwave radio transmitter. It is a plug-in unit, so it can be replaced to change the output frequency. The coil has a small adjustable coupling link which is used for "neutralization". A negative feedback signal is applied to it from the plate circuit of the output vacuum tube to cancel positive feedback though the tube's plate-grid interelectrode capacitance, to prevent parasitic oscillations. It shows typical high Q construction: the winding is a single layer with the turns spaced apart to reduce losses due to proximity effect and parasitic capacitance; to reduce dielectric losses it is supported by only a few thin plastic supports. Alterations to image: cropped image out of a larger image of an RF amplifier in a shortwave transmitter.