Back in the early days, radio engineers speculated as to why it is that a crystal set can often receive much more distant stations when located in the vicinity of a tube set. Various more or less absurd theories were advanced, such as induction, a field of negative resistance, and so forth. Yet the true explanation is very simple. It was one of the first points about radio communication which Cabot explained to me after his return from Poros.
As for induction being the cause, one has only to consider the electrical law whereby the induction field diminishes as the square of the distance, whereas the field due to actual radiation diminishes only as the distance.
“A field of negative resistance”—I defy any one to explain what he means by that in such a connection.
One further theory remains, namely, electrostatic coupling. I do not know that this explanation has ever been seriously advanced. If advanced, it would be very plausible. But I should like to see a proponent of such an explanation draw a diagram of the electrostatic coupling between a crystal set with a coil antenna, and a vacuum set with capacity antennas, or vice versa. Maybe it is possible, but I don’t see how; and Myles Cabot, the greatest radio expert of two worlds, is my authority for saying that it can’t be done.
No, Cabot’s explanation which follows sounds a lot more sensible than any of the foregoing. And the fact that he has demonstrated his theory, and has put it to practical use on Poros, proves it to be so. The man who has done that, will some day find a practical use even for static. Enough said!
This is his explanation: Compare the situation in a sending set and a receiving set. In the former, with the tube oscillating, we have in the antenna-circuit an oscillating current with impressed sound waves. A regenerative receiving-set picks up this current, very weak, and builds it up to the limit of the capabilities of our tube; so that we have in the antenna-circuit of a receiving-set the same situation as though we were sending, only, of course, weaker because of the small size of our tube. And we actually are sending at such a time, although faintly, thus augmenting the impulse from the distant broadcasting station, and thus undoubtedly accounting for the hitherto unexplained phenomenon of long-distance crystal reception.
Cabot, while still on earth, demonstrated this theory to his own satisfaction by experimenting with a tube-set and a crystal-set half a mile apart, and by actually catching in his crystal-set the not-quite-damped-out sixty-cycle hum of the power-line which he was using to run his tube-set. Then, by substituting a large transmitting-tube for his small receiving-tube, although still leaving the set hooked up as a receiving set, he was able to relay even distant stations to friends with crystal sets scattered all over Back Bay, Boston. The removal of the phone circuit was the final step to convert his set into a pure radio relay-station, nothing more.
These early earthly experiments of his recurred to his mind when establishing the radio routes on the planet Poros. Hence the myriad relay-stations which dotted the planet, in one of which he now found himself a prisoner.
But as the ant man advanced to secure his captive, the long-impending tropical thunderstorm broke in all its fury.
Gusts of rain swirled in at the door. Crash after crash of almost continuous thunder shook the ground. The lightning fell in one continuous sheet of flame, so that all was as bright as daylight. But still the ant man kept his rifle pointed at Cabot. Quite evidently the creature wished to capture the earthman alive.