US2135234A - Dual band antenna transformer - Google Patents

Description

NOV. 1, 1938. J V 2,135,234

DUAL BAND ANTENNA TRANSFORMER Filed Oct. 10, 1955 1500 2000 2500 Jose 5500 I FREQUENCY K/LOCYCLES 33 43 fia a 9'- 4 I Patented Nov. 1, 1938 2,135,234

UNITED STATES PATENT OFFICE DUAL BAND ANTENNA TRANSFORIVIER John V. Fill, Chicago, Ill., assignor to Ferrocart Corporation of America, New York, N. Y., a corporation of Delaware Application October 10, 1935, Serial No. 44,444

8 Claims. (01. 250-20) This invention relates to radio receivers and uum tube T is illustrated as a simple triode ammore particularly to antenna transformers formplifier whose control grid and cathode serve as ing part of radio receivers designed for operathe input terminals of the receiver. Other types tion on a plurality of frequency bands. of vacuum tubes may be used in this input stage The commercial development of iron-cored which works into other amplifier and detector radio inductances has resulted in reductions in stages which may be of any appropriate design the size and improvements in the performance of and are indicated schematically by the block AD radio receivers. Inductances and transformers which precedes the reproducer R. of high efficiency have been produced for use in The described receiver circuits will be recogthe broadcast and higher frequency ranges, but nized as those customarily employed in dual range 10 the same high efficiency was not obtained in receivers operating on the broadcast and police the case of iron-cored antenna transformers of bands. As usually constructed, the secondary the type having a tapped grid coil, one section of windings L1 and L2 have been a continuous solethe coil being shorted out during the reception noidal winding and, in adapting the iron-cored of signals in the higher frequency band. inductances to this dual range receiver, it was 15 An object of this invention is to provide a pr pose to u a sin pp niv l W ndradio receiver for operation over a plurality of s 011 a Core Consisting 0f fi e y d v d a frequency ranges, the receiver including an ironinsulated iron part c This arrangement had cored antenna transformer of such design that a go efiieiehcy Over the lower qu y range the shorting out of a section of the grid coil or in which the entire coil was used, but had a low 20 transformer secondary is not accompanied by efficiency Wh n one i n w s shorted r a loss in efficiency. A further object is to proception in the higher ranges. vide an antenna transformer for a double range In accordance with this invention, the sections radio receiver, the transformer including an air L1 and L2 are arranged, as shown in at core primary and a pair of spaced secondary pp e of 81 COmmOh Cy r a e M 25 sections on a common magnetic core, the secof fi ly divided magnetic material, and the p ondary section which is to be shorted out being y W ding L3 is coaxial with the secondaries more remote from the primary than is the secand spaced therefrom at the side adjacent the ondary section that is tuned over the higher higher frequency range 2- All Of the Coils frequency range. are of the universal winding type, and the an- 30 These and other objects and advantages f the tennacoil L3 does not have a magnetic core. The invention will be apparent from th follgwing relative arrangement of the coil terminals in the specifications when taken with the accompanyradio circuit is indicated by the reference numering drawing, in which: als of Figs. 1 and 2. The inner terminal I of the Fig. 1 is a fragmentary circuit diagram of antenna coil L3 is grounded, while the outer ter- 35 double range radio receiver; minal 2 is connected to the antenna. The outer Fig. 2 is a side elevation, partly in section, of terminal 3 f t high frequency du t L2 an antenna transformer embodying the present is Connected to the Control grid of tube t invention; and junction 4 of the inner terminal of coil L2 and Fig. 3 is a curve sheet illustrating th l ti the outer terminal of coil L1 is connected to the 40 merits of the novel antenna transformer and one Contact of Switch 3, and the inner terminal 5 of having a s ngle tapped secondary coil. coil L1 is connected to the AVG lead.

In the drawing, the reference character Aiden- In the particular physical s y Shown in tifies an, antenna which is coupled to the vacuum 2, the Core M is fitted Within the Outer d 475 tube T in the input stage of the double range Of an insulating tubes Which y he of p p radio receiver through a transformer having secand the Coil L1 is p t y a ined with the ondary sections L1, L2 and a primary winding L3. Outer end of the Core- Coil L2 is eppleXimetely The secondary is tuned by a condenser C and a alihed With the pp end of the Core, and the switch S is provided for shorting out the sec- Primary 0011 L3 is Spaced below the 0011 2 t0 ondary section L1 when the receiver is to be op- P v the desired cellplihgerated over the higher frequency range. The In one particular embodiment of the invengrid will usually be returned, for direct current, tion, the coils L1 and L2 had a combined inductto an automatic gain control system, as indicated ance of 220 microhenries, the inductance of coil by the lead AVC, and for radio frequencies is L2 was 40 microhenries, and the inductance of grounded through the condenser C1. The vaccoil Ls was 2 millihenries. The core and the 5 several coils may be individually adjusted along the tube 6 to bring the self and mutual inductance of the secondaries to any desired values, and the parts may then be fixed in place by wax 7. A dowel 8 is fixed in the lower end of tube 6 and carries a bolt 9 for attaching the transformer assembly to a chassis.

The advantages of the invention will be apparent from a comparison of the curves of Fig. 3. Curve l0 illustrates the relationship between the factor Q, equal to and frequency over a range of from about 1500 to 3500 kilccycles, for an iron-cord antenna transformer having a tapped secondary in the form of a single universal winding. The entire coil had a good Q value When used at the lower frequency range but the Q value fell to values of from about 50 to when one section was shorted out by the switch S, Fig. 1. A transformer such as shown in Fig. 2 had a Q value as indicated by curve H. The Q value is a fair measure of the merit of a radio frequency element and it will be noted that this invention provides a means for materially increasing the eiiiciency of operation in the higher frequency range of a dual range receiver.

It is to be understood that the invention is not limited to the particular frequency ranges or to the values herein given by way of example. Various changes which may be made by those familiar with this art in adapting the principles of this invention to the same or other design requirements fall within the spirit of my invention as set forth in the following claims.

I claim:

1. In a radio receiver adapted to be operated over a pair of frequency ranges, an antenna transformer comprising an air core antenna coil, 2. pair of serially connected secondary coils spaced at different distances from said antenna coil, 2. core of magnetic material in substantially fixed position axially spaced from said antenna coil and in the field of said secondary coils, and switch means for short circuiting the secondary coil more remote from said antenna coil.

2. A dual range radio receiver of the type including an antenna transformer having a secondary winding in two sections, means connecting said secondary winding across the input terminals of the first vacuum tube stage, and switch means for shorting one section of said secondary winding for operation at the higher frequency range, characterized by the fact that said secondary winding comprises two space wound multilayer coils spaced apart along and in substantially fixed position with respect to a single magnetic core.

3. In a dual range radio receiver, the combination with an antenna and an input stage including a multiple electrode vacuum tube, of an antenna transformer comprising three spaced coils in axial alinement, a stationary core of magnetic material within two of said coils, said third coil being a single continuous winding, means for connecting said third coil between antenna and ground, means serially connecting the first two coils between two electrodes of said vacuum tube, and switch means for short circuiting one of said first two coils.

4. The invention as claimed in claim 3, wherein said switch means short circuits that one of the first two coils which is the further removed from the third coil.

5. In a double range radio receiver, an antenna transformer comprising an insulating tube, means at one end of said tube for securing the same to a support, a stationary core of magnetic material fixed at the opposite end of said tube, a pair of space wound secondary coils on said tube adjacent said core, and an air core primary coil on said tube and spaced from said core and secondary coils.

6. The invention as set forth in claim 5, Wherein the inner terminal of the secondary oil adjacent said primary coil is connected to the outer terminal of the other secondary coil.

'7. In a radio receiver, an antenna transformer comprising a paper insulating tube, means at one end of said tube for securing the same to a support, a core of magnetic material fixed within said tube and spaced from the supported end thereof, a pair of space wound coils mounted on said tube about said core and spaced from each other, said coils being serially connected, 4;

a tuning condenser connected across said coils, and means coupling an antenna to said coils.

8. A radio receiver as claimed in claim 7, wherein said antenna coupling means comprises an air core universally wound coil mounted on said tube.

JOHN V. FILL.

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