A Tuned Passive Radiator

The problem with my Portable AM Crystal Radio was that it worked well only at a sweet spot on the shack roof.

The presence of the sweet spot was traced to overhead CATV cables acting as passive radiators.

Hence it was decided to create a tuned passive radiator to further improve performance.

One half of my 40 m inverted 'V' dipole antenna was chosen as the passive radiator. The series-tuned circuit was connected to the core of the coax at the shack end and earthed as shown.

Tuned Passive Radiator - Schematic
This setup enabled faint reception of the local 612 kHz 200 kW AM station on the portable crystal radio inside the shack.

After tuning the passive radiator to resonance, performance of the portable crystal radio was found to be quite good across the shack roof.