US 2036456 A
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VARIABLE ANTENNA ARRANGEMENT Filed June 2, 1.933
Patented Apr. 7, 1936 vUNITED VARIABILE ANTENNA ARRANGEMUENTE' tion oit Germany Application .lune 2, 1933, Serial No. @74,0% In Germany .lune 6, 1932 5 illaims.
It is well known toI use in short wave transmitters of greater wave range an antenna the length of which can be varied by means of a winding drum, in order to enable operation with a constant antenna resistance. In using a M4 antenna with coupling in the current amplitude, the antenna resistance is for instance 30 ohms. It is furthermore known to use as input supply line a line having a wave resistance equal to the antenna resistance, in'order to always obtain automatically, by avoiding special adapting transformers, the correct termination oi the energy line. In this case the input resistance of the line is aways equal to the wave resistance of the line, so that the transmitter, independent of the Wave and supply line length, is required to only supply a constant coupling voltage. I-Iowever, a practical difficulty is encountered by the construction of the antenna winding drum upon which the excess antenna wire is wound. In case of greater wave resistances and energies the drum requires very considerable dimensions, so that its distributed capacity against ground can no longer be neglected. Thus the capacity must be compensated for every wave by means of special tuning measures.
In accordance with the invention this drawback is overcome in that the drum is arranged in the interior of the supply line whereby the latter is widened so as to obtain the required space, while its wave resistance is retained.
An embodiment of the invention is shown in the accompanying drawing by way of example.
'Ihe transmitter not shown in the drawing which is arranged in the transmitting room S is coupled to the energy line at points k1, k2. The line consists of two coaxially disposed pipes b and c whereby the outer pipe is ground. A vertical antenna is electrically connected to the inner pipe c, the eective length of the antenna between tension roller r1 and insulator i can be adjusted to the respective wave length k/Ll. The tensioning of the antenna a may be accomplished for instance by means of a rope m passed over a roller r2 and loaded by a weight g.
In order to render the effective length of the antenna at the transition to another frequency equal to the altered value M4 and to thus continuously retain the antenna resistance, the antenna wire is wound upon or unwound from a winding drum h rotatable by means of a crank 7c.
In accordance with the invention the drum h is disposed within a chamber formed by the widening c1 of the inner energy line. Corresponding with the widening of the inner pipe, a
(Cl. Z50-33) widening b1 of the outer energy line is carried out and in such manner that for each cross section the ratio of the diameters is so maintained that the wave resistance remains constant. The Shaft a. supporting the drum h is composed of insulating material.
It is not a necessary requirement that the inner inactive part ca of the antenna wire consists of the same material as used for the active part a. The latter consists ordinarily of material resistible against chemical influences in particular against corrosion, such as bronze and the like, the specific conductivity of which is relatively small, so that the cross section oi' this antenna part becomes relatively large for reducing the impedance. If the portion of the energy line between drum and antenna is longer than the largest change oi' the effective length oi the antenna, i. e. than the length of the wire to be wound upon or to be unwound from the winding drum, the parts of the wire which may eventually form portions of the eective length of the antenna a will in no case reach over the drum. In this case the wire portion passing through the interior space of the inner pipe c, through which current never flows and which only serves as a pulling wire, may be composed of steel or any other material, iniective for high frequency purposes, but instead of greater mechanical strength. Thus it is made possible to substantially reduce the dimensions of the drum and those of the entire equipment necessary for the mounting of the drum.
1. An antenna system comprising a vertical antenna one-quarter of the length of the operating wave, high frequency apparatus, a pair of concentric inner and outer metal tubes, and a connection from said high frequency apparatus to said inner tube, a wire disposed within said inner tube and connected to said vertical antenna, a drum arrangement located at the end of said wire farthest removed from said antenna for winding said Wire therearound for varying its effective length and simultaneously varying the length of the vertical antenna, said wire being in electrical contact with said inner tube.
2. A system as dei-ined in claim l, characterized in this that said outer metal tube is grounded.
3. An antenna system comprising a vertical antenna one-quarter of the length of the operating wave, high frequency apparatus, a Wire extending from said vertical antenna and in circuit with said high frequency apparatus, a pair of concentric inner and outer metal tubes surrounding said Wire, said inner tube being in contact with said wire, a reel located at the end of said wire farthest removed from said antenna for Winding said Wire therearound for varying its effective length and simultaneously varying the length of the antenna, and a metal housing for said reel, said housing connecting with said outer tube and enclosing substantially completely said reel, said housing being connected to ground.
4. An antenna comprising a vertical antenna one-quarter of the length of the operative Wave, high frequency apparatus, a pair of concentric inner and outer metal tubes, a wire disposed within and in contact with said inner tube and connected with said antenna, and a drum arrangement located at the end of said Wire farthest removed from said antenna for winding said Wire therearound for varying its effective length and simultaneously varying the length of the antenna, said pair of metal tubes being appreciably Wider at the end of said Wire remote from said antenna than at said antenna, said drum being located Within said inner tube at its widened portion, and a connection from said high frequency apparatus to inner tube.
5.A system in accordance with claim 4, characterized in this that the ratio of the diameters of the widened portion of said pair of metal ftubes is so maintained that the Wave resistance remains constant.