Loop Antenna Crystal Radio

A loop antenna crystal radio is of interest on account of its selectivity and portability. But, with respect to signal strength, it is no match for a crystal radio using an external vertical wire antenna and earth.

If signal strength could be considerably improved with increased loop size, then its portability would be compromised.

As usual, 2 configurations are possible - parallel-tuned-series-fed and series-tuned-shunt-fed.

1. Parallel-tuned-series-fed version 

Parallel-tuned-series-fed Loop Antenna Crystal Radio
2. Series-tuned-shunt-fed version

Series-tuned-shunt-fed Loop Antenna Crystal Radio
The loop antenna was rigged up using a 4-legged stool as a makeshift frame. The stool was laid on its side on the table, making it convenient to wind the loop on its legs.

4-legged stool as Loop Antenna frame
Both the versions were tested with the plane of the loop oriented towards the local 612 kHz, 200 kW AM broadcast station.

Signal strength was the same with both, though a far cry from another crystal radio using a vertical wire antenna and earth.