Short Wave Reception and Transmission on Ground Wires (Subterranean and Submarine)

After an historical review of the work of the United States Navy with underground and underwater receiving systems, the author gives data demonstrating the possibility of effective reception on such systems, particularly when using amplifiers. These systems are found to be directional toward waves travelling parallel to the length of the wire pair. This directional selectivity, which is marked, is applied in control stations for duplex working. For such underground systems, an optimum wire length for best reception is found to be roughly proportional to the wave length (for short waves) and independent of the direction of approach of the signal. The existence of this optimum length gives further utilisable selectivity. This length is independent of the nature of the surrounding medium and varies inversely as the capacity per unit length of the wire. The wire in question must be well insulated. Reception thru violent storms, and suppression of summer strays (particularly at short wave lengths) are found. It is found that lowering such wire systems from above ground into wet soil or into water greatly increases the signal strength and diminishes strays. Transmission at short wave lengths, over considerable distances, using such systems has been found possible with low power sustained wave transmitters.