US2076710A - Radio direction finding system - Google Patents

Description

` April 1.3, 1937. H. M.' DoweiETT ET AL 076710 RADIO DIRECTION FINDING SYSTEM Original Filed May 18, 1933 ATTORNEY `55`aerial or, where a Bellini Patented Apr. 13, 1937 ATE.

oFFlca RADIO DIRECTION FINDING SYSTEM Harry Melville Dowsett,

and Roland John Kemp;

Winchmore Hill, London, Chelmsford, England,

assignors to Radio Corporation of America, a corporation of Delaware Application May 1s, Renewed June 14, 1 25, 1932.

'7 Claims.

This invention relates to radio direction .iinding systems and has for its object to provide an improved receiver arrangement wherein the direction of a radio beacon or other transmitting station is indicated by the clear reception of a television picture.

A further object of the invention is-to provide an improved system wherein the level of the synchronized impulses provided at the receiver for synchronizing the receiving television scanning apparatus with the transmitting television scanning apparatus shall be received at a substantially constant level.

, Arrangements wherein television transmission i and'reception are employed for direction finding purposes are described in the specifications accompanying co-pending application Serial No. 672,552,'filed May 24, 19331 It is very desirable for practical reasons that when a receiving station equipped with.A television apparatus and employed for bearing finding and directional purposes has its receiving aerial system correctly oriented to obtain a bearing on a particular beacon or transmitter, the received television picture obtained from that beacon or transmitter should appear` clearly and the principal object of the presentjnvention is to provide an improved receiver arrangement whereby this is achieved, the received picture being only received soclearly when the aerial system is correctly oriented or approximately correctly oriented and the character of the said received picture clearly visibly different for other orientations of the receiving directional aerialsystem.

According to this invention a receiving television station for use for bearing finding and similar purposes comprises a frame or equivalent directional receiving system, an open aerial or equivalent substantially non-directional receiving 40 system, a television scanning and picture synthesizing system, means for building up by means of said scanningand picture synthesizing system a picture derived from signals received uponv the substantially non-directional aerial system, and

means for superimposing upon said signals, signals of reverse phase derived from the directional aerial system.v`

The directional aerial system may take any convenient form: for example, it may be constituted i by a rotatableframe aerial or by a Bellini-Tosi aerialsystemY in co-operationwith a radiogoniometer and similarlyV the substantially non-directional aerial systemlmay take diierent forms, for example, it may be constitutedsimply by an open -Tosi directional system 1933, Serial No. 671,646. 935. In Great Britain May (Cl. Z50-11) is employed, the vertical effect of said system may be utilized in manner known, per se, for non-directional reception.

The phase reversal of the signals from the directional system with respect to those from the non-directional system may be obtained in any convenient way, for example, a low frequency arnplirler following the detector energized from the directional system may contain one more or one l less stage oi magnification than the corresponding low frequency amplier following the detector energized from the non-directional aerial system or, again, the type of detection employed for the signals received from the directional system may be different from that employed for the signals from the non-directional system, leak grid detection being employed for one set of signals and anode bend detection forrthe other.

It will be seen that with arrangements in ac-, cordance with the present invention the signals" received by the directional system will be substantially non-existent when that system is correctly oriented to the direction of the station being received, and in carrying out the present invention` the arrangement is preferably made such thatt Awithin a predetermined number of degrees of the correct bearing direction, e.,g. within 10 degrees of that direction, thestrength of signals received from the directional aerial system is approxi-V l lmately the same as that from the'non-direc-A tional system. Thus, since the effect of the su- ,perimposition in the picture synthesizing apparatus of the signals received from the directional system upon those received from the non-direck tional system is is, as it were, a negative of the picture from said non-directional system, it will be apparent that within the predetermined limit of 10 degrees or thereabouts there will be a sharp contrast in the total received picture as between the combined positive and negative pictures obtained when the signals from both `aerial systems are about the same strength and the clear positive picure obained at the correct bearing position when the signals from the directional system are'substan-'U tially non-existent. Y

The invention is illustrated in the accompanying diagrammatic drawing which shows a rreceiving station in accordance therewith.

Referring to the drawing a tuned rotating frame aerial A tuned by a condenser as shown is employed as the directional system and the signals obtained therefrom are applied, after r amplification at the carrier frequency by means of a Valve V1, between the grid and cathode of a Y to superimpose a picture whigh..H

lamp GL breaks down nizing pulses, which are of an amplitude substanthermionic valve Va to which the requisite potentials are applied to cause said valve to operate as an anode bend detector. This detector valve is resistance capacity coupled to a triode V3 in cascade therewith and acts as a common amplier both`- for `the directionally received signals and thenon-directionally received signals. The non-directionally received signals are picked up upon a vertical aerial B which is tuned in the usual Way by a condenser as shown,- the signals from this aerial being applied, after amplification at the carrier frequency, if desired, between the grid and cathode of a triode Vi in whoseA grid lead is inserted the usual grid condenser GC and grid leak GL so as to cause said triode to operate as a leaky grid detectormThis detector isresistance-capacity coupledt'o a further ltriode V5 whose output is resistance-capacity coupled to the aforementioned common triode amplier V3. The output from the common amplier is further amplified, if desired, e. g., by valves Ve, V7 and applied to a4 neon lamp NL 0r equivalent picture building device incorporatedin the television picture synthesizing apparatus. 'I'he output from the detector Vi energized from the open aerial system B is also applied to a vfurther amplifier containing any predetermined number of stages, this amplifier being adapted toselect and amplify the synchronizing signals for the television transmission and to apply these amplified synchronous signals to control the electric motor or like device, not shown, drivingand/ or synchronizing ythe television scanning apparatus. In the figure this further ampliiier consists of two valve stages Vs, V9 coupled together in cascade. vThe valve V8 has in, its plate circuit a neon lamp or otherglow kdischarge lamp 'GL' and the ignition voltage of this lampis such and the remaining constantsof the circuit are such that the said only when the synchrotially greater than rthe peak amplitude of the picture signals, appear in the anode circuit of the valve Vs. Thus the valve V9 is energized by synchronizing pulses onlyvand the output from this valve is employed. for energizing the synchronizing winding, not shown, of the motor driving the television scanning apparatus, not shown. It will be seenthat with the above described arrangement when the signals from the aerials A` Vandrlare equal or nearly equal, the result of their mixture in ranti-phase at the grid of the Valve V3 will besuch as nearly to eliminate any image, e., there will not be a clearpicture built up by the lamp NL. When, however, the frame aerial at A isrturned in such a direction that the signalsv picked up thereby approximate to zero, a clear positive picture will be built up vby the lamp NLvand the existence of this clear positive picture will indicate that the frame aerial has been turned in the direction of the station being received. r01 course, the rotatable frame aerial may be replaced by mutually perpendicular xed frames associated with a radiogoniometer. A receiving station in accordance withy the present invention may be employed to receive signals from transmitting stations as described in the specication of cti-pending application Serial No. 672,5 52 above referred to for example, the transmitt'er may be Such that the majorl intelligence comprising an image of a moving scale station, identification letters, and synchronizing impulses are transmitted by an'` o'nini-directional aerial 5 and a I'ninimunfi` indicating signal, such as a vertical bar appearing across the picture, is transmitted by a revolving frame.

Where a receiver in accordance with the present invention is utilized in conjunction with a transmitter as just described the minimum indicating signal, thevertical bar, will appear clearly onlyvwhren the receiving frame is correctly oriented towards the transmitting station.

i Having thus described our invention and the operation thereof, what we claim is:

1. A receiving television station for use for bearing finding and similar purposes comprising, a frame or equivalent directional receiving system, an open aerial or equivalent substantially non-directional receiving system, a television scanning and picture synthesizing system, circuits connecting the receiving systems and the television and synthesizing system, means for building up by means of said scanning and picture synthesizing system a picture derived from signals received upon V,the substantially nondirectional aerial system, and means for Asuperirnposing upon said signals, signals of reverse phase derived from the directional aerialgsy'stem.

2. A receiving station as claimed in claim 1 comprising in addition a detector connected with the directional system and a. low frequency ampliiier following the detector ,energized from the directionazl system for producing the phase reversal.

3.v Aj receiving., station as claimed in claim 1 comprising in addition means for obtaining the required phase reversal comprising `diiierent types of Idetection means for detecting the signals received yfrom the directional system and from the non-directionalsystem respectively. i

v4. A receivifg station as claimed in claim 1 comprising in addition means for independently and separately detecting the signals received upon the` non-directional aerial system and upon the directional aerial Vsystem means for combining the outputs from the two detectors, in Aantiphase relation, and a common amplier for amplifying the combined signals for controlling the picture reproducing device of the television receiver. i

5. A station f or receiving wave energy on which synchronized impulses have been impressedin addition tc the television signals comprising a directional aerial, a vertical aerial, a television scanning and picture synthesizing system, signal relaying circuits connecting lthe aerial systems to the ,television and synthesizing system, driving means for said television scanning and picture synthesizing system, means for building up by means of said scanning and picture synthesizing systerna picture derived from the relay connected with the vertical aerial, means for superimposing upon said signals, signals of reverse phase derived from the relay circuit connected with the directicnal aerial, means connected with the relay connectedto the vertical aerial for separating the synchronizing impulses from the signals picked up by the vertical aerial, and means for utilizing said impulses for synchronizing the driving means for thereceiving television scanning system..

6. The method of receiving the wave energy of asingle carrier frequency on which synchronizing impulses and electro-optical representations are impressed by modulation which includes the steps of setting up oscillatory energy characteristic of the electro-optically modulated carrier wave energy and of the direction of propagation of said wave energy, setting up oscillatory energy characteristic of the carrier wave energy modulated by synchronizing impulses and non-characteristic of the direction of propagation of said wave energy, and combining said energies to produce Visual representations characteristic of the direction of propagation of said energy, and controlling said combining in accordance with the impulses in said oscillations non-characteristic of the direction of propagation of said Wave.

7. A receiving television station for use for bearing finding and similar purposes comprising a frame aerial or equivalent directional receiv- 10 ing system, an open aerial or equivalent substan-

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