US1875050A - Antenna - Google Patents

Description

Aug. 30, 1932. N. E. LINDENBLAD ANTENNA Filed Jan. 20, 1928 INVENTOR NILS E. LINDENBLAD BY ATTORNEY Patented Aug. 30, 1932 UNFTED STATES ,IPATENT OFFICE,

NILS E. LINDENBLAD, OF ROCKY POINT, NEW YORK, ASSIGNOR TO RADIO CORPORATION OF AMERICA, A CORPORATION OF DELAWARE ANTENNA Application filed January 20, 1928. Serial No. 248,057.

This invention relates to antennae and more to other installations, and inasmuch as the particularly to antenna systems which are adversely affected by a proximate building.

In large cities it is sometimes desirable to erect antennae on the top of a large building. Such antennae have often been below normal in radiating efficiency. This, I believe, is largely due to the electrical characteristic of the building on which the antenna is located, or other nearby high buildings, having a naturalperiod which is unfavorable in value, It is an object of my invention to improve the radiation from such antennae, and this I do by artificially providing a path of low reactance to energy of the transmission frequency from the top to the base of the building. The low reactance is preferably obtained by inserting condensers in series with the lead, and this, in effect, provides a series resonant path to ground. The invention is described in connection with the accompanying drawing, the single figure of which schematically represents an embodiment of the invention.

Referring to the drawing there is a building 2 on which there has been erected an antenna structure 4. Between the top and base of the building there is provided a conductor or system of conductors including series reactances. In simplest form there is a lead such as 6, with series condensers 8 distributed along its length. Theoretically a condenser at any point of the lead will'be satisfactory, so long as the lengthof the conductor does not exceed one quarter of the wave length, but it should be remembered that if the lead is long the potential developed along it becomes large, and therefore may cause considerable circulating currents in its vicinity. It is therefore preferable to break up the lead by condensers distributed at several points.

The lead 10 includes series condensers 12 which have been shown variable. This of course, is not essential for the operation of the system, when once adjusted, but inasmuch as each installation is experimental, relative tuning should difler for different frequencies of transmission, it is in some cases desirable to use variable reactances. The lead 10 is also shown provided with series inductances l4, and these, in most cases are not necessary inasmuch as the natural inductive reactance of the lead is usually sufficient. The conductors used for tuning the building may be suitably tied together to form a network by means of conductors such as 16 and 18.

This invention is equally applicable to antenna systems the towers of which are grounded to the building, and antenna systems employing insulated towers, with a counterpoise instead of a ground connection. It should also be noted that the low reactancc leads may be located outside the building, as well as within it, and, in fact, should preferably not be located within a closely enveloping electrically conductive structure, as an elevator shaft, for then the efiicacy of the low reactance lead may be reduced.

I claim:

1. In combination, a building, a transmitting antenna system located thereon, and a conductor separate and distinct from the antenna system, including a condenser connecting together the top and the base of the building, for providing a path of low reactance from the top to the base of the building for energy transmitted by the antenna system.

2. In combination, a building, a transmitting antenna system located thereon, and a conductor separate and distinct from the antenna system, including a plurality of tuning reactances connecting together the top and the base of the building, providing a path of low impedance between the top and base of the building for energy supplied to the antenna system.

3. In combination, a building, a transmitting antenna system located thereon, and a conductor separate and distinct from the antenna system, including a plurality of confor energy ofthe frequency supplied to the 1 transmitting system.

4. In combinatlon, a

metallic supports, a transmitting antenna 10- cated on the top of said building and electrically insulated therefrom, and a, 10W impedance lead separate and distinct from saidentenne conductively connecting the top of the 7 building to the base thereof.

, NILSE. LINDENBLAD;

building comprising

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