[34]

The Wireless of Nathan B. Stubblefield

by Aldrich Daimler

Nathan B. Stubblefield (1860-1928)

MANY would argue that Nathan B. Stubblefield's invention in 1885 of wireless telephony was the real advent of radio, and rightfully so. Academicians of the radio elite would offer that there is a significant difference between that of "underground telephony" and "underground radio". The signals used in underground telephony are said to travel thru the earth, while in underground radio, a portion of the signal reaches the surface of the earth and is propagated in a more Hertzian fashion. While this may be partly true, the method of propagation is essentially the same — the difference lies with the frequency used. Underground telephony utilizes audio signals — frequencies which are considered to be in the VLF (Very Low Frequency) range. Radio telephony utilizes RF (Radio Frequency) frequencies which are categorized as considerably higher than that of acoustic signals. So, Nathan Stubblefield did invent radio — VLF radio.

Stubblefield's underground telephony VLF system was very simple. Two metal rods were used for each "telephone set", and were inserted into the ground several feet apart. Each set was outfitted with a large horn to act as a loudspeaker. A small carbon button microphone transmitted the voice messages thru the earth to the other receiving set. The most interesting thing about the device is that it was powered only by the natural currents of the earth, derived solely from his patented "earth battery."

There is considerable evidence that Nathan Stubblefield demonstrated his VLF radio system several times, and there are many accounts of public demonstrations. The first documented public demonstration was held in his hometown of Murray, Kentucky in January of 1902. Later that year (March 1902) Stubblefield sent wireless messages from a steamship to stations on the shores of Georgetown. Stubblefield was then to demonstrate the apparatus in Manhattan's Central Park. Unfortunately, Stubblefield could not find suitable ground conducive to the experiment, and quickly abandoned the demonstration. In all of these demonstrations, Stubblefield never achieved any greater sending distance than one mile. While this may be considered a poor performance for a wireless communications system, one must remember that Stubblefield utilized only the natural power of the earth for these transmissions — his earth battery being the operative power source. Stubblefield later suggested that he was developing a more powerful apparatus using automatic relays in which "distance would be unlimited." For reasons unknown, Stubblefield would later abandon "earth telephony" in favor of experiments with wireless radio thru the air. Either Stubblefield became disenchanted with the performance of his ground VLF system, or he simply left the idea to the many patent infringers to figure out. It is probable that the latter reason combined with the Central Park failure caused Stubblefield to abandon any further explorations with his underground telephony system.

While we may pick up these experiments where Stubblefield left off, several considerations must be addressed. Most important, of course, being the fact that we do not have all of the information concerning his mysterious earth battery source. Many have tried to recreate Stubblefield's earth battery from the patent specifications only to be completely disappointed with the output. While it is well known that only proper placement of the earth battery will procure desirable results, no one to date has achieved the power suggested by Stubblefield. But, if we are to conduct our experiments chiefly to observe the characteristics of VLF propagation thru the earth, we may continue.

An obvious choice for power source/transceiver is a pair of matching public address systems. Here, one possesses the ability to greatly vary the input/output of the system. The volume control on most any amplifier suffices. Simply connect the output leads for the speaker connection to the ground rods of one unit, and connect the grounds of the second unit to the microphone input. The units must be DC or battery powered though, as a typical alternating current supply will sufficiently destroy the signal by its introduction of 60 cycle noise and ground feedback loops. Small portable amplifying units such as the PA system can be easily obtained or built for the purpose. One must take care not to perform the experiment with any proximity to conventional power sources as these will interfere with the signals. Special filtering circuits can be designed to rid the units of most noise.

Now, specific attention may be focused on the placement [35] of the ground rods for the experiment. While geomantic considerations (such as a dowser might use) should be implemented, one must not forget conventional rules of propagation thru a restrictive medium such as the earth. The range of transmission will be determined by many variables, including the homogeneity of the land in terms of direction, moisture content, time of year, terrain, etc. Since the earth becomes a giant sheet resistance, one must adjust the distance between the ground rods accordingly. Generally, the farther apart the rods are, the more distance the signal will travel (conventionally, about 30 to 50 times the rod spacing), so that a distance between the rods of 10 feet will yield a range of 500 feet, and a distance between the rods of 50 feet will yield a range of 2500 feet. Unconventional manifestations of range have been achieved on the order of several miles with proper placement of the rods, and sufficient power outputs.

One of the main drawbacks of this system which Stubblefield encountered was that there could be no privacy in such transmissions, as anyone with a similar receiver could easily eavesdrop on the conversation. Specific encoded modulations could be introduced into the signal to be demodulated and decoded at the receiving end, but this would warrant extensive modification to the present experiment. The significance of the experiment then lies solely on the investigation of the propagation of these VLF currents thru the earth, and to determine whether or not great distances can be achieved at fairly low output levels with the proper placement of the earth terminals.

For more on Nathan Stubblefield, his ground radio and related research efforts, read on with Gerry Vassilatos's "Nathan Stubblefield: Earth Energy and Vocal Radio".