US1736614A - Radio wave trap - Google Patents

Description

Nov. 19, 1929. 1J. MGDONALD 1,736,614

RADIO WAVE TRAP n Filed June 9, 1.927

tofm up Patented Nov. 19, 1929 UNITED STATES PATENT OFFICE JAMES J. MCDONALI), OF SANk JOSE, CALIFORNIA RADIO WAVE TRAP applicativa filed June 9, 1927. serial ivo.' 197,734.

capable of being connected with said first and second inductances in inductive relation therewith, whereby undesirable signals or waves emitted from any transmitting station may be successfully trapped, and desired signals received without overlapping interference from other signals.

An object of the invention is to provide an improved type of wave trap in which a plurality of inductances are inductively related and controlled by a single variable condenser for more efficiently trapping or cutting out radio signals from overlapping waves emitted from a transmitting station, or for trapping the waves from a nearby station, when it is desired to receive the Waves from a more distant station, which are rendered inaudible or indistinct, due to the high power of the nearby station.

A further object of the invention is to provide a wave trap of the type mentioned, to-

gether with means for selectively connecting the trap in the antenna circuit of a radio receiving set, or for disconnecting the same therefrom.

Other objects will appear as the description proceeds. In the accompanying drawings which form a part of my application The single gure is a diagrammatic showing of my improved wave trap showing the same connected in the antenna circuit of a radio receiving circuit.

Like characters of reference are used throughout the following specification and the accompanying drawings to designate corresponding parts.

A primary inductance l is formed by winding the desired number of turns about a form in spaced relation, the said windings being electrically connected through the wire 2 and grouped at the oppositeends of the form. A second inductance 3 is Awound upon a suitable form adjacent the first mentioned form and consists of two electrically connected and short circuited spaced groups of windings, inductively7 connected with the windings or inductance l. l third winding 4 is woundl upona suitable form, preferably at right angles to the winding 3 and within the inductivev field of the same, and also consists lof two electrically connected spaced groups of windings which are short circuited, andvis adapted to vbe selectively connected with the 'inductance winding l, vthrough themedium ofthe switch 5 and conductor 6.

An antenna 7, variable condenser 8 preferably of twenty-three plate type, and single pole, singlefthrow switch 9, are connected with the inductances 1, 3 and 4, and comprise the'essential parts ofthe wave trap. j

v4The wiring diagram or hook-up illustrated in the singleffigure is as follows The antenna? is connected to one end of the induc-y tance winding yl, while the other end ofthe said vwinding is connected to the radio receiving set. The variable condenser l3 is shunted across'the vinductance winding l. Theends ofthe inductance winding 3 are short circuited-and are connected to the wire connecting the variable condenser and the receiving set. The winding 3 is also electrically connected with ythe inductance winding 1'. Hence, it will be'seen that the short circuited inductance Winding 3 is inductively positioned with respect to the inductance winding l. Likewise the third inductance winding 4 is short circuited and may be electrically and inductively connected with the windings 1 and 3 when desired, by merely closing the switch 5. 4 are placed in the magnetic eld of coil 1, a decided inductive effect will be set up in coil 4. The coil 4 being connected to the rotor side of the condenser gives the coil 4 a variable inductance.

The method of operating the wave trap is similar to the method of operating a wave trap utilizing a single inductance winding and variable condenser shunted across it, in the antenna circuit. However, it will be Since the coils 3 and found that when the trap is in the antenna circuit, a very small change in dial setting will be required. The inductive efect between the inductance windings l, 3 and 4, 5 due to the closed or short circuited winding of the inductances 3 and 4: will cause a consequent increase in the efficiency of the trap. The desired waves will pass through the fcoi or inductance winding 1, while the windings 3 and 4 connected with one ,side .of the variable condenser acts to trap the undesired or interfering waves or signals.

It is pointed out that the importance and efficiency of this type of wave tmp depends on the manner in which the windings 3 and 4 are connected. The action fof the windings 3 .and 4 is entirely inductive :1a-s negar-ds the winding i. The third winding-may Jole-scounected with the windings l land 3, when it is zo desired to trap interfering 'waives from extremely high power .stations in -c'lose pmximity to the receiving set.

From the iEor-egoing description, it will 'he understood that I do `not intend to limit my self to the :specificccnstmtctionrdeecribed, but

rather .by the terms of the appended I.c1aim:-

1. A wave trap rer rad-io circuits including an antenna connection, a primary Wind 3g ing in series therewith, a Variable condenser shunted across saidprimary winding, a short circuited winding inductwely .connected with said primary winzding@` and 1a, second short circuited Win-ding selectively connected in nductive relation vwith said irst vrrientirmedshort circuited winding. Y Y

2. A wave trap for radio circuits .including ian antenna commotion, a primary winding in series therewith, a vari-ablecondenser o shunted across said primary winding, a vshort circuited s lit winding inductively .connected with said primary winding, .and a 'second short circuited .split Winding selectivel connected in inductive relation with `first mentioned short .circuited split winding,

In testimony whereof I have hereunto affixed `my signature, Y

JAMES J. MCDONALD.

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