US2066928A - Network for tower lights - Google Patents

Description

Jan. 5, 1937. R. 1.. DAVIS NETWORK FOR TOWER LIGHTS Filed Dec. 12, 1934 W NESSES INVENTOR Faber! Aflaw's.

ATTORNEY Patented Jan. 5, 1937 UNITED STATES PATENTQ F IcE to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa", a corporation of Pennsylvania Application December 12, 1934, Serial No. 757,143

1 Claim. ((1250-3 f My invention relates to transmission by radio and more particularly to a circuit for permitting the mounting of a beacon light or other apparatusin the immediate; neighborhood of radio antennae, or on-radio towers which either support the antennae, .or which in themselves constitute the antennae;

Customary practice in the field of radio transtion of the field pattern and consequent losses I of radio frequency-energy due to the absorption of the tower, to insulate the tower from ground at radio frequencies and in some instances, it has been found advantageous to sectionalize the tower itself by inserting insulators between the various sections.

With the development of aviation and air traffic, these tower structures have become a source of danger to airplanes in flight and it, therefore, has become mandatory to provide beacon and aircraft warning lights or other means on these towers to indicate the presence and location of the same to the pilot of an airplane.

To operate such beacons or warning lights on the towers, it becomes necessary to feed power to them from power circuits, which circuits are either directly grounded, or may be considered as being effectively grounded at radio frequencies by reason of the large capacity existing 40 between the power circuits and ground. Thus, the circuit comprising the feed lines running up to the tower to the light, being effectively grounded at radio frequencies, will constitute a source of distortion and a source of loss for the radio frequency energy emitted from the antenna, in the same sense that a grounded supporting tower constituted a distorting medium and a source of loss for the radio frequency energy. However, one cannot dispose of this problem as easily as one would in the case of the tower structure itself, by reason of the fact that one cannot effectively insulate a power I circuit from ground at radio frequencies, since such circuits are, as stated above, either ground ed directly at various points in the system, or

have such large capacity to ground at radio frequencies due to its length and close proximity. to earthed objectsthat the system might be considered as, grounded at radio frequencies.

A similar: problem'is encountered where the towers themselves constitute the antennae. The power wires running up the towers to the beacon lights or other-warningdevices must not be permitted tov distort. the radiated hi h frequency field nor effectively ground the tower, in spite of the fact that the power system itself may be directly grounded or effectively grounded at radio frequencies.

It is an object of my invention, therefore, to provide a feed circuit for a transmission tower which will be efiectively opaque to radio frequencies.

.Anotherobject'of my invention is to provide means for feeding energy to indicating devices mounted in a high frequency field which feeding means shallbefsubstantially opaque to the flow of high frequency energy therein.

Further objects of my invention will be pointed out in the accompanying description of the same.

As an aid to a clearer understanding of my invention, reference will be made to the accoinpanying drawing wherein the figure discloses the preferred embodiment of my invention as applied to a warning light mounted on a radio antenna tower.

In this figure, I have illustrated a radio tower l fabricated of structural steel and supported above ground by heavy insulators 3 to effectively insulate the tower structure from ground at radio frequencies. At the top of this tower or at some other convenient location thereon is mounted a warning light 5 or other means for indicating the presence and location of the tower to the pilot of an airplane. Energy for use in the operation of this light or indicator is conveyed thereto over a pair of wires 5 which are strung up on the tower and preferably insulated therefrom. The energy may be derived from a source of power supply 9, which may be either a direct-current source or a low frequency alternating-current source, either of which I refer to broadly as a source of power of a frequency of a lower order than that of radio frequency. In the specific example illustrated in the drawing, I have shown the energy as being derived from a conventional lit! volt, 6U cycle supply source both leads to the light being coiled and preferably very tightly coupled. Between the terminals of one of the coils I3, I provide a variable condenser I5, the values of the effective inductance of the two coils l3 and I9 and this shunting condenser [5, plus whatever shunt capacity may exist due to the tower and ground, being such that the circuit is tunable to the radio frequency of transmission from the antenna I! supported by the tower. A large condenser 18 is connected between the coil I3. and the other coil l9, and by reason of the fact that these coils are closely coupled, a similar tuned circuit.

will also be effectively included in the power load containing the coil 19.

Thus, in each lead extending to the light, my system effectively provides a parallel resonant circuit tuned to the frequency of transmission.

and these tuned circuits will render the power' circuit substantially opaque to the flow of radio frequency energy, without impeding-the flow of the power energy to the light. Therefore, itwill be apparent that the circuit network disclosed by me will insulate the power circuit from, ground at the frequency of transmission as effectively as the tower supporting insulators insulate the tower from ground at radio frequency.

In the power supply circuit to the, light, it is desirable that the same be balanced with respect to ground. Should the power system happen to be grounded on one side; a balanced relationship to ground as regards that portion of the power system which is in the high frequency" field, can be obtained by inserting a" powertransformer I l in the line and grounding the midpoint of the secondary.

To relieve insulation in the system from effects produced by energy at radio frequency, the power wires 1 to the tower may be" bridged by a pair of condensers 20, the midpoint of this condenser bridge being' connected to the tower or to the metal conduit enclosing the wires if such is employed.

A circuit similar to that just described will be employed in connection with the other tower 2| shown in the drawing, although such circuit is not illustrated by reason of the fact that it will involve mere duplication of the circuit already illustrated and described.

It will be apparent from the above description that the circuit or system described fulfills the objects of my invention in that the distortion of the field pattern and the radio frequency loss which would otherwise occur due to the presence of the power circuit in the dense radio frequency field around the. antenna will be reduced to a minimum and power energy may be safely and conveniently conveyed to an indicating device mounted on the tower, or if desired, on a separate supporting structure located in the proximity of the tower.

While I' have described the preferred embodi- -ment of my invention in great detail, I do not desire to be limited to the details disclosed and described above, except as may be necessary in view of the prior art and the appended claim.

' I claim as my invention:

In combination, an antenna. tower, an electrical indicating device mounted on said tower, means comprising an electrical circuit for supplying energy of a lower order of frequency than radio frequency to said indicating device, said circuit including a transformer, a coil included in each of the wires of said circuit on the secondary side of said transformer, said coils being closely coupled and connected together at one end of each coil by a condenser of low impedance to radio frequencies, a condenser shunting one of said coils, said coil and shunting condenser being of such value as to constitute a tuned circuit resonant at a desired radio frequency, and means for symmetrically grounding said power circuit at radio frequencies.

ROBERT L. DAVIS.

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