receiving apparatus through long
low horizontal leads, and another loop with short leads erected at the
receiving station, as in figure 9. This arrangement was found for
the time being to give somewhat better results than that in figure 6, and
the improvement was found to result from the more perfect balance thus
secured, in spite of the loss of signal.
However, as mentioned above,
it was discovered later that the horizontal leads of the two loops as in
figure 6, picked up some of the static and signal energy and, as a result,
the static currents in a set of leads and in the loop tended to flow in
the same or opposite direction. Adjustments that were made in the
circuit shown in figure 6, to balance out static currents in the loop,
before this fact was recognized, caused the static currents in the leads
under some circumstances to add; but the simple expedient of placing reversing
switches in the circuits solved the problem.
The results thereafter obtained
with the Weagant system were found to be better with the use of greater
rather than less effective separation, by an amount proportional to the
separation.
It was observed that, in all
arrangements employing two closed circuit loops connected to a central
receiving station by long horizontal leads, local tuning of each loop was
necessary. This was not a very convenient procedure with aerials
.3 miles apart, for it became necessary to station an operator at each
loop and to inform him, by telephone, what adjustments were to be made.
UNDERGROUND AND SURFACE-GROUND HORIZONTAL
AERIALS
The low horizontal aerial for
radio reception was first used by Marconi. An antenna of the same
type employed by Weagant in the spring of 1914, at New Orleans, gave a
distinctly better signal to static ratio, than the large earthed aerial.
Later comparisons with a loop aerial showed the two to be substantially
identical in that respect.
One important deduction
resulting from these tests was the fact that the long horizontal aerials
laid under ground, on the surface of the ground, or suspended above the
ground, may act as a loop aerial. Because of the capacity to earth
(as shown diagrammatically in figure 10) a return path for the currents
exists between the ends, which effectively completes the circuit.
It has, been noted particularly
that, as the distance be- |
maximum of energy, the signals
are less in strength than would be secured with less spacing.
Quoting Mr. Weagant
"The usually accepted explanation
of the working of the horizontal aerial is that the wave front of the signal
wave is tilted forward and that consequently there is a component of electric
force in the direction of its length. It is to be noted, however,
that under some circumstances such an aerial may be acting equally well
as a loop. An aerial of this type is shown, in figure 10, lying on
the
surface of the ground and it is evident that by virtue
of its capacity to the true conducting earth, a return path between its
ends exists and, therefore, it is a form of loop; which method of consideration
will account for many of the observed facts, such as its directivity, in
a satisfactory way. It will also account for one observed fact which
the usual methods of explanation do not account for, namely, that when
an aerial of this type is laid on the ground, or buried underneath it,
its effectiveness as an aerial does not increase indefinitely with length,
but rapidly reaches an optimum value dependent on the cir-cumstances obtaining.
This can readily be accounted for under the present hypothesis by the fact
that as, the length |
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