I'm trying to understand a component of an AM radio kit that I have. (There is a document available here: https://www.elenco.com/wp-content/uploads/2017/10/AM-780K_REV-K-2.pdf describing the build procedure and the circuit in more detail.) I was researching coil windings for a regenerative receiver, that had me come back to this circuit, and there are some things I don't understand. The radio works great, I just have some questions about it.
The part I'm confused about is the bottom left of the circuit diagram (L1, L2, and C2):
Is there any reason why L1 and L2 are in series like this? Is there any difference between a component with C2 and L3 = L1 + L2 and a component with C2, L1 and L2?
Also, I'm a little confused by the diagram showing 1,2,3, and 4 as antennas. Can I add an external wire to act as antenna somewhere in this component?
Other diagrams show taps in the coil to switch between different resonant frequencies (adjusting the length of the coil) along with the variable capacitor. I was wondering if these points are potentially taps, as well.