I have operated many times an AM crystal radio with the antenna/ground connection direct to the tank circuit (i.e. without an antenna-stage RF transformer and no connection to the center tap of the coil) and it works fine. But I've been led to believe that this configuration is a parallel-LC circuit and basically a wave trap; indeed, I've seen schematics with the same circuit used as a wave trap when used with the primary winding of an antenna-stage RF transformer. I know that it acts as a series-LC circuit when used in the secondary winding of an RF transformer but in this instance it's not used in that fashion. How and why is it working?
Many thanks! CJD
Many thanks! CJD