The Cordova daily times., 1922-12-01
HOPE HELDOl)T
 FOR MlNERSBY RADIO TESTS

TOTS ana losses or mine ulbASCcIe. Iio- lins3na.y tests conducted by the bur eau, with the cooperation of a great electrical manufacturing concern, in an experimental mine at Bruceton, Pennsylvania, already have resulted in degree of success.
 While these experiments have so far failed to develop any practical method of using wireless waves for under ground communication, nevertheless, eau, they indicate>clearly that electro says publication of the Mines Bur magnetic waves may be made to travd through solid strata. In the Bruceton experiments signals were heard dis tinctly through 50 feet of coal strata, although they audibility fell off rapidly as the distance is very great for the tests. Longer wave lengths are known to suffer less absorption and may pos sibly be found practically effective under certain conditions.
 Tn this connection it is interesting to note tests conducted by the United States Bureau of Standards in drop ming wireless antennae down deep, un- used oil wells to underlying rocK strata, in order to send the wireless impulses through the rock instead CT through the air. The results, 1t IS ne lieyed, may be the same as projecting the antennae upward into the air strata.
 The desirability of substituting tbe wireless system of communication TOT thn present telephone systems i'll use in mines is evident in considering tna' a rock fall or explosion, by breaking wire connections can put the entire system out of order
 The mine telephone has been per fected to such an extent that u IS giving satisfaction is most mines where the wiring is we'll insulated, the Bur eau of Mines announcement continues. Very often the telephone cannot be de- pended upon on account or faiis oi rock, grounding due to worn insuia- tion or extreme dampness. In the evant If a disaster it frequently hap pens that the mine telephone system ia nut out of commission by the agency that causes the disaster, at the very time when it is most urgently needed. On this account the mining industry ;s interested in any kind of telephone system that can be counted upon m an emergency. Many requests have been received by the Bureau of Mines in devise means of utilizing wireless methods for the purpose
 The preliminary experiments con sisted first in receiving signals from without the mine by means Of re ceiyer located inside the mine, ana second. both sending and receiving messages underground through the strata. It was found that with re- ceiving instrument set at point loo feet underground, signals sent from station KDKA, of the Westinghouse Electric and Manufacturing Company, at East Pittsburgh, IS miles away, could be heard distinctly. About o0 rect from the receiving station used in the mine in this test was 6-inch bore hole extending from the surface, lined with iron pipe and containing electric light wires which extended thereffom through the mine. The presence of these wires, according to the experi- mentors, evidently assisted greatly m the reception of the signals, for when the receiving set was carried to an other point in the mine removed rom wires and tracks the signals were bare ly audible through fifty feet of cover. The fact that signals were detected at all, however, even though faintly, was declared sufficient evidence of transmission through ground to en- courage further experimenting
 In sending waves underground transmitter was used in such man. ner as to send out continuous waves of 200 to 300 metres length. On ac- count of the limited time at disposal no attempt was made to modify the apparatus in such manner as to pro- duce waves of greater length
 In all experiments the vertical an tennae were found to give better re suits. The horizontal antennae gave practically no reception. A loop of single turn was used with fair results. All these experiments were tried with a wave length of 200 to 300 metres, except the reception from KDKA, which was 360 metres.
 The strata at the experimental mine lie; almost horizontal The direction &of atrafa if waa aatd may have some