April, 1919
THE WIRELESS AGE
19
increases its capacity
to earth increases and at some point becomes sufficient to close the loop.
"As this capacity increases,
however, the currents originating in this increased length have various
paths in |
length to the height is unusually
large. It follows that the aerial which is pointed in a direction
away from the transmitting station is a much better receiver of the signal
energy than the aerial which runs in a direction toward |
which to flow, one of which includes
the receiving apparatus but others are through the capacity to earth between
the conductor and the receiving apparatus, and the larger this gets the
greater is the proportion of the currents originating in the ends of this
aerial, which are diverted and do not flow through the receiving apparatus.
This method of considering such an aerial 'is further supported by the
fact that the greater the capacity per unit of length which exists between
the conductor and the true underlying earth, the shorter is the maximum
length which can be used to advantage. This capacity is a maximum,
of course, when the aerial is actually buried in the ground or under water,
becoming less when the wire is run on the surface of the earth and till
less when the wire is suspended at some height above the earth, tests having
shown that wires suspended some 10 feet above ground can be used up to
some six miles in length, the signal increasing with length ; that a length
about one-half of this is effective when the wire is laid on the ground
and of approximately 2,500 feet when the wire is placed under, brackish
water.
"I have also found that as the
distance of such an aerial above ground is increased, its action becomes
more nearly that of an ordinary antenna, and that therefore on account
of its position relative to the incoming signal, it becomes less effective
in collecting this signal energy." |
the transmitting station.
Both aerials, however, pick up the same amount of static. The two
aerials, therefore, may have a very marked difference in their signal to
static ratio, and this effect will add to the effect resulting from their
phase separation when this separation is small. At times, this constitutes
a factor in the results obtained. While figures 11 and 12 show direct
coupling at the coil L, any of the well known methods such as electrostatic,
inductive or resistance couplings may be employed.
Mr. Weagant finds that this
principle operates in all of the arrangements shown in figures 12, 13,
14 and 15. Figure 12 shows the connections used in an experiment
in which the loop leads were connected together and each loop converted
into an ordinary aerial tuned to earth. I n figure 13, the leads were disconnected
from the loops and their ends joined, thus making them horizontal aerials
tuned to earth. In figure 14, one loop is used in the normal way
and balanced against leads of the other loop tuned to earth. In figure
15, one loop is connected in its normal way while the other one is arranged
as an earthed aerial. In all methods where an aerial tuned to earth
is employed, it was found that the counterpoise aerials gave the best all-around
results, although fair results were obtained with all the foregoing arrangements.
In addition to the foregoing
connections, other varia-tions in the circuits were also tried. |
| At an early
date, at the Marconi station at Belmar, N. J., additional experiments were
made by Weagant with the antenna shown in figure 11 and other combinations.
It will be noted that the arrangement shown in figure 11 consists of two
Marconi aerials of which the ratio of the |
ELIMINATION OF INTERFERENCE
BY THE
WEAGANT SYSTEM
A discovery of vital importance
in connection with the looped antenna of the Weagant system was the fact
that |
|
Previous
Page
Next
Page
