The Wallace miner. [volume] (Wallace, Idaho) 1907-current, 1922-12-07
RADIO EXPERIMENTS TO
ASSIST MINE RESCUERS
TESTS SENDING WIRELESS I'M
PULSES FIFTY FEET UN-
DER GROUND.

Radio communication between res
cuers on the surface and miners en-
tombed in mines following fires and
explosions is a hope held out by the
United States bureau Of mines to les
sen the horrors and losses of mine dis
lasters. Preliminary tests conducted
by the bureau with the cooperation of
a great electrical manufacturing con-
Germ in an experimental mine at
Bruceton, Penn, 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,
says publication of the Mines bureau
they indicate clearly that elechomag-
netic waves may be made to travel
through solid strata. In the Bruceton
experiments signals were heard dis
tinctly through so feet of coal strata,
although the audibility fell off rapidly
as the distance was increased The
absorption of loss of intensity with
distance is very great for the short
wave lengths used in these tests
Longer wave lengths are known to
suffer less absorption and may posi-
bly, be found practically effective I'M
der certain conditions.
Interesting Tests.
In this connection it is interesting
to note tests conducted by the United
States bureau of standards in drop
ping wireless antennae down deep. un-
used oil wells to underlying rock strata
in order to send the wireless impulses
through the rock instead of through
the air. The results, it is believed,
may be the same as projecting anten-
nae upward into the air strata.
The desirability of substituting the
wireless system of communication for
the present telephone systems in use
in mines is evident in considering that
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 it is Civ
ing satisfaction in most mines where !
the wiring is we'll insulated, the bu-
reau of mines announcement cOntin-
ues. Very often the telephone can not |
be depended upon on account of falls |
of rock, grounding due to worn insult
alton or extreme dampness. In The |
event of a disaster it frequently hap
pens that the mine telephone system |
is put out of commission by the agen-
cy that causes the disaster at the very
time when it is most urgently needed.
On this account the mining industry
is interested in any kind of telephone
system that can be counted upon in an
Many requests have been
received by the bureau OF mines to de-
wise means of utilizing wireless meth
DDS for this purpose.
Experiments Described.
The preliminary experiments con
sisted first in receiving signals from
without the mine by means of a re-
ceiver located inside the mine, ana |
second, both sending and receiving |
underground through the |
strata. It was found that with a re-
ceiving instrument set at a point 100 /
ittl uAlhIi AOAAllnf oi-A HNAAt AioAA
station KDKA of the Westinghouse
Electric & Manufacturing company. at (
East Pittsburgh. IS miles away, could /
be heard distinctly. About so feet from /
he receiving station used in the mine
n this test was a 6-inch borse hole
extending from the surface, lined with
ron pipe and containing electric light /;
wires which extended therefrom
through the mine. The presence of 3
hese wires, according to the expert '
nenters, evidently assisted greatly in ]
he reception of the signals, for when
he receiving set was carried to an ]
,ther point in the mine removed from S
he wires and tracks the signals were
rarely audible through so feet of COW
r. The fact that signals were detect
ID at all, however, even though faint. s
Y, was declared sufficient evidence of f
through ground to en- I
further experimenting. J
Wave Length. {
In sending waves underground a t
was used in such a man {
Ter as to send out continuous waves ]
f 200 to 300 meters length. On ac- I
cunt of the limited time at disposal c
10 attempt was made to modify the j
pparatus in such manner as to pro- I
luce waves of greater lentgh. t
In all experiments the vertical an /
ennae were found to give better re- J
ults. The horizontal antennae gave {