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Re: Can a coil replace a gridstopper?

It also forms a resonant circuit with the capacitances, that could induce parasitic oscillations. A typical "plate stopper" in h.f. amateur power amps is a 2-watt carbon resistor with #18 magnet wire wound around it as a coil form, making a parallel R-L. The small inductance shorts out the resistor at the frequency of interest, and the R damps the resonances out-of-band (v.h.f.) where parasitic oscillations are expected. Perhaps this could work as a grid stopper, using more turns of finer wire, where the inductor would short out the resistor at audio, and the resistor could still damp parasitic oscillations in the r.f. range. This could eliminate the thermal (Johnson) noise from a relatively large series resistor at audio while the resistor acts as a stopper at higher frequencies.

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