An amateur may receive messages from anywhere at any time without a license provided that his station is not also fitted with transmitting apparatus.
In other words if the amateur possesses a receiving outfit only which is in working order or if he has both transmitter and receptor and the former is not powerful enough to send signals out of the state in which he lives, or to interfere with the reception of messages by another when the messages come from beyond the state boundary a license is unnecessary.
This is of course somewhat unfair for those living near the center of large states for they may operate almost as they please with ordinary instruments with no fear of the signals going beyond the border, while those living within a few miles of another state must secure a license.
If an amateur has a license he may transmit messages beyond the state border, but he must not employ a wave length greater than 200 meters or a power input into the transmitter of more than 1 K.W. without special permission.
Fig. 148. Experimental Amateur Station of W. Haddon, Brooklyn, N. Y.
If the amateur is within five nautical miles of an army or navy station equipped with radio apparatus his power input must not be more than 1 K.W.
Complying with Law.—After a license is secured, or rather as a matter of fact in order to secure it, the wave length must not be greater than 200 meters. In order to secure such a wave length the effective portion of the aerial cannot usually be made greater than 115 feet in consideration of the amount which the lead-in, helix and ground wire add.
Fig. 149. Complete Receiving Outfit Consisting of Receiving Transformer, Detector, Fixed Condenser, Loading Coil, Two Variable Condensers, Potentiometer, Battery, Switches, etc.