There is an option with the Induction coil to run it direct with an antenna connection, or to wrap the Induction Coil with about 10 wraps of 22 gauge wire that runs from the antenna to ground. The first method gives a better chance of a station signal being loud enough with a short antenna. The second wrapped inductor method is best for using a long (20 foot plus) antenna. See schematic for clarification.
I like the inductive method even with a short antenna, because it gives a clearer signal with less 60 cycle hum. The amplitude of sound will be less in AM tuning unless a long antenna is used however. The amplitude can be partially made up by using the human body as an antenna by touching the jam jar ring, which has a connecting wire that goes to the antenna + wire when the lid is twisted on.
The other advantage of wrapping the inductor is that it gets supported inside the jar by the heavier wires.