In article ,
J999w wrote:
Simplest one you can make is by taking the main tuning capacitor and ferrite
rod antenna out of an old AM radio, wiring them in parallel, then putting that
circuit in series with your antenna. That will allow you to peak the frequency
you're tuned to, reducing all others. If you wire that circuit (an LC circuit)
from your antenna to ground, it will notch the frequency it's tuned to ...
kinda handy if you've got a local pest that splatters across the bands.

You've got that reversed. A parallel tuned circuit has its highest
impedance at resonance, so if you put it in series with the antenna,
it will act as a notch filter. In parallel with the antenna circuit,
it will as a selector, causing off resonance signals to be reduced.
Better performance may be obtained by tapping down on the winding, or
by using a small link winding, as the receiver's antenna input may be
loading down the tuned circuit.

One confusion is that if you use an unshielded loopstick, it's acting
as an antenna, too.

Mark Zenier Washington State resident