US1644906A - Frame aerial and the like - Google Patents

Description

' I 1, 44, 0 1927' v P. w. WILLANS I 6 9 FRAME AERIAL AND THE LIKE Filed April 5. .1926

Patented Get. 11, 1927.

UNITED STATES PETER WILLIAM WILLANS, F PATTISHALL, TOWCESTER, ENGLAND.

FRAME AERIAL AND THE LIKE.

Application filed April 5, 1926, Serial No.

This invention relates to frame and other closed aerials and the like and has for its object the provision of a closed aerial which will be adapted to minimize interference from any station operating on a higher Wave length than that being received. The invention is thus particularly useful in connection with receiving sets operating on the wellknown superheterodyne principle, since. it

will minimize interference from stations, op-

erating on a wave length corresponding to the intermediate frequency of such a receiving set. I have found that the electromotive force picked up by the turns of a frame aerial from a transmitting station operating on a wave length to which the intermediate frequency amplifier of a superheterodyne receiver is tuned is suflicient to cause interference when the frame aerial is connected across the grid filament circuit of the amplifier, no matter how well the latter is itself screened.

In accordance with the present invention the aerial has a part only of its winding shunted by a tuning condenser, the remaining part or parts being connected, in series with the tuned part, in the external circuit (say the grid filament circuit). The tuned and untuned parts of the frame aerial are so connected and proportioned that the sum of the electromotive forces induced in them by transmitting stations is zero.

As aresult of this construction the voltage produced across the terminals of the frame aerial will be equal to the voltage drop due to the current flowing in the tuned part. The latter will be negligibly small for wave lengths greatly in excess of the natural wave length of the tuned part and in this case the interference will be cancelled out.

Three embodiments of the invention are illustrated diagrammatically in Figures 1, 2 and 3 respectively of the accompanying drawings and the same will now be described, it being understood that the particular arrangements illustrated are susceptible of various modifications without 7 departing from the scope of the appended claims.

In Figure 1 is shown a frame aerial 1 having a solenoidal winding of say twelve turns, six of which 1 are wound in a right handed helix and shunted by a tuning condenser 2, and the remaining six 1 in a left handed helix but not tuned. The two sets of six turns are connected together in series 99,943, and in Great Britain April 7, 1925.

across the valve 3. V r

The electromotive force inducedrin the turns 1 by any signal is equal and opposite to that induced in the turns 1 by the same signal. The voltage across the turns l degrid' and filament of thermionic pends upon the value of the shunting con denser 2. If the value of this condenser 2 is such that'the turns 1 are tuned to a wave length Well below that of a certain transmitting station the voltage across these turns as a result of signals from such station is approximately the same as the electromotive force induced in them by such signals, and is therefore approximately equal and opposite to the voltage from the same cause across the turns 1*. The total voltage across the aerial as a result of the said transmitting station is therefore approximately zero. At the same time the voltage across the turns l as a result of signals on a wave length equal to that to which said turns are tuned is so large that the voltage across the turns 1* set up by negligible. It is thus clear that the aerial transmits impulses to the valve 3 as a result of signals on a wave length to which the turns 1 are tuned but does not. substantially transmit impulses as a result of signals on a Wave length considerably higher than that to which said turns 1 are tuned.

Owing to the fact that the voltage across the turns 1 as a -result of a signal on a higher wave length than that to which said turns are tuned is only approximately equal to the electromotive force induced in said turns by the same signal, it will be clear that in the case above described the total Voltage across the aerial will never be exactly zero though it is sufli'cient nearly so for all ordinary purposes. It is quite clear however that the turns 1 and 1 may if desired be so proportioned that a perfect zero voltage will be obtained for one given wave length higher than that to which the turns 1 are tuned.

The arrangement of Figure 2 differs from that of Figure 1 in that the turns 1 are of greater number than the turns 1*. In this case therefore the second terminal of the aerial is connected to some point intermediate the extremities of these turns l It will be clear to those skilled in the art that by suitable desi n this arrangement may be made to function in like manner to the arrangement of Figure 1.

the same s1gnal is The arrangement of Figure 3 differs from that of Figure 1 only in as much as the turns 1 are divided 'into two halves and the turns 1 are connected in series between them. It will be clear that this difference is without effect upon the function of the device.

What I claim and desire to secure by Letters Patent is 1. A frame or other closed aerial having its winding so arran ed that the electromotive force induced y anysignal in one part thereof opposes that induced by the same signal in another part thereof, and having "only a part thereof shunted by means of a tuning condenser, the arrangement bemg such that signals on a wave length equal to that to which saidfshunted part is tuned "will set up substantial voltages across the terminals of the aerial and that signals on a wave length greater than that to which said shunted part is tuned will set up nosuh- 'sta'ntial voltage across said terminals.

2. A frame or other closed aerial having its winding so arranged that the electromo tive force induced by any signal in one part thereof opposes that induced by the same signal in another part thereof, and having one of said parts only shunted by meansof a tuning condenser, the arrangement being such that signals on a wave length equal to that to which said shunted part is tuned will set up very much greater voltages across said shunted part than across said nonshuntedpart and that signals on a wave length greater than that to which said shunted part is tuned will set up suhstan t-ially equal and opposite voltages across said 7 shunted an dnonshunted parts.

3. A frame or other closed aerial according to claim 2 wherein the nonshiiinted part consists of two portions arranged one at each extremity of the shunted part.

In witness whereof I afiix my signature. PETER WILLIAM VVILLANS

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