US1962169A - Device for reducing the effects of static or fading - Google Patents

Description

June 12, 1934. H. H. BEVERAGE DEVICE FOR REDUCING THE EFFECTS OF' STATIC OR FADING Filed Nov. 11, i952 NNW.

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W 1 Ml I.. @ws $5@ INVENToR ,maw /f 5f/H455 BY ,w'l/(A/ TroRNEY Patented June 12, 1934 PATENT OFFICE DEVICE FOR REDUCING THE EFFECTS OF STATIC OR FADING Harold H. Beverage, Riverhead, N. Y., assigner to Radio Corporation of America, a corporation of Delaware Application November 11, 1932, Serial No. 642,172

Claims.

.1Q to repeat the signal characters at the transmitting station a plurality of times at predetermined intervals, and, at the receiver, to store up and compare the received characters before passing the signals on to the printing mechanism. In

l? this way, any false character, such as might be due to static, which was not received identically in all transmissions, would be prevented from operating the recording mechanism, and only those signals which were received in every repe- ?Q tition would set up the storage apparatus to operate the printer.

Such methodof repeating signal characters has greatly increased the accuracy of transmission, and itis one of the objects of the present ,Z invention tofretain the advantage 'of signal repetition without actually repeating the signals, and by using much simpler equipment.

Y This object is accomplished in the present invention by employing a plurality of diversity receiving systems at stations which are widely separated from one another in order to cont-rol, in common, a central oflice utilization circuit. At the central oice, relays are operated by the signals from each station. In one particular em- ,35 bodiment of the present invention the relay contacts are connected in parallel so that their combined output mitigates against fading, and in another embodiment the relay contacts are connected in series so that their combined output 19 is free from local static clicks. f

Observations have shown that both fading and some kinds of static, particularly on short waves, are random and local in their occurrence, and, hence, if signals are received at two separated points neither the fading nor certain types of static will be simultaneous at both locations.

`An essential feature of the present invention resides in the diversity receiving! arrangement located at each station for insuring reception,

, 6() whereina plurality of energy collectors are separated an appreciable fraction of the length of the communication wave, say of the order of a few wave lengths. The signal, it has been found, does not fade similarly at each of the spaced energy i. ,5,5 collectors, and the possibility, therefore, of the signal fading out equally at all of the energy collectors or antennae is consequently reduced with increase in the number of antenn.

In the accompanying drawing, Figures 1 and 2 show, diagrammatically, two diierent embodiments of radio receiving systems illustrating the principles of the present invention.

Figure 1 shows a system comprising two Widely separated diversity receiving stations A and B whose individual output currents are combined at a common central station to overcome local static clicks. At each station A and B is shown a diversity'receiver consisting of two receivers 3 and 4 which are associated with directive antenn l and 2. The output of each receiver 3 70 and 4 is rectified and the rectified currents are added together to operate a tone keying unit 5, the latter functioning to translate the rectified currents into currents chopped up at intervals corresponding to the interruptions of the received signal characters. One suitable arrangement for eiTecting such reception and translation, to which reference is made, is described in United States Patent 1,874,866, granted August 30, 1932 to Messrs. H. H. Beverage and H. O. Peterson.

The receivers at stations A and B are tuned to the same signals, and the outputs of the tone keyers 5 are sent to a central oilice over wire lines 31 and 33. The signals are there further amplified by amplifiers 35 and 37, and are then 35 rectified by rectiers 7 and 9 which, in turn, cause the operation of relays 11 and 27, respectively.

Relay tongues 13 and 19 of Figure 1 are connected in series so that both relays must close before utilization circuit 29 operates, a condition which must exist for anti-static. As an illustration, if a static crash is received at station A, but not at station B, relay 1l will close, but

cause relay 27 is open. The utilization circuit .29 may, of course, be a printer, recorder, or any other suitable device.

It has been suspected from observations, that some short wave static came from long distances by sky Wave, similar to the manner in which short wave signals are propagated. This was believed to be true, because the directional static distribution on short waves was found to be similar to the long distance static on long waves, although the intensity of the short wave static was much less than on long Waves. On the other hand, it has also been noticed that local thunder storms do not create severe disturbances except when the storm is within a few miles of the receiving station. Even then, the disturbances are usually sharp clicks associated directly with lightning flashes.

If it is assumed that short wave static is propagated like short wave signals, the observations mentioned above are quite logical. Local static produced by local lightning storms would produce electrical disturbances that travel along the ground as ground waves. The energy would be rapidly attenuated by losses in the grcund, and the ground wave would quickly disappear. Hence the static might exhibit skip effects the same as signals. The ground wave from a storm 50 miles away might be inaudible, although disturbances from the same storm might be audible thousands of miles away via the sky wave route.

Therefore, if we assume that station A is at Riverhead, Long Island, for example, and station B is at a point in New Jersey, more than 100 miles away, a local storm in New Jersey wouldv be inaudible at Riverhead, and vice Versa. Under these conditions, a click from a lightning iiash at station B would not occur at station A and its eiect would be eliminated at the central ofce, because only one of the relays 11 and 27 would close.

If local storms were in progress at both stations, the clicks would be entirely random, and both relays would close simultaneously only at rare intervals.

As an alternative, the distance transmitter might radiate energy for space and interrupt it for mark. Both relays would normally be closed for space and open for mark and the recorder would be adjusted accordingly. Now if static prevented the relay from opening at one station, but not at the other, the recorder would still be operated correctly by the relay that opened.

Much of the long distance static, it has been found, may be eliminated by directive reception and this is effected in the present invention by the proper positioning of antennae 1 and 2, thus enabling accurate reception free from effects of distant static or fading. A similar arrangement to that shown in Figure 1 may be used for anti-fading by connecting the tongues of relays 11 and 27 in parallel in the manner illustrated in Figure 2. If the signal fades out for a few seconds or even minutes at one station, but not at the second station, the recorder will operate correctly, as it will register when either relay closes. The parallel relay anti-fading arrangement should be useful in overcoming the condition which is termed Territorial Fading. This is the condition where the signal fades simultaneously over a large area, but may still be received well, say, fifty miles away. This condition has been observed on numerous occasions.

An advantage of the present invention is that the separation of the two receiving stations in entirely different locations guards against interruptions due to power or tone line failures, fires, sleet, or any other disaster that might interrupt the service at a single station for an extended period of time.

I claim:

1. A radio receiving system comprising a plurality of widely separated diversity receiving stations, each of said stations including at least two spaced antennae, circuit apparatus at each station for receiving and rectifying the currents received at each antenna and for additively combining the rectified currents, a tone keyer at each station for translating the combined rectied currents into alternating currents chopped up at intervals corresponding to the interruptions of the received signal characters, a cential oice, and lines extending from each tone keyer to said central oiiice, relay apparatus at said central oiilce under control of the signals sent out by said tone keyers, and a utilization circuit responsive to the operation of said relay apparatus.

2. A system as defined in claim 1 including amplifier and rectifier apparatus at said central oice for amplifying and rectifying the signals from said tone keyers, said relay apparatus being connected to said rectiers.

3. A radio receiving system comprising a plurality of widely separated diversity receiving stations, each of said stations including at least two spaced antennae, circuit apparatus at each station for receiving and rectifying the signals received in said antenna and for additively combining the rectified currents, a tone keyer at each station for translating the combined rectified currents into alternating currents chopped up at intervals corresponding to the interruptions of the received signal characters, a central oflice, and lines extending from each tone keyer to said central ofce, amplifier, rectifier and relay apparatus at said central ofiice in circuit with each tone keyer, contacts for said relay apparatus, and a utilization circuit serially connected with said contacts and operable only upon the operation of all said relay contacts.

4. A radio receiving system comprising a plurality of widely separated diversity receiving stations, each of said stations including at least two spaced antenna, circuit apparatus at each station for receiving and rectifying the signals received in said antennae and for additively combining the rectied currents, a tone keyer at each station for translating said combined rectified currents into alternating currents chopped up at intervals corresponding to the interruptions of the received signal characters, a central oice, and lines extending from leach tone keyer to said central oiiice, amplifier, rectifier and relay apparatus at said central office in circuit with each tone keyer, contacts for said relay apparatus, and a utilization circuit, said contacts being connected in parallel to said utilization circuit.

5. The method of operating a receiving system comprising a plurality of widely separated diversity receivers, each of said receivers including at least two spaced antennae, and a central office circuit connected in common to said receivers which includes receiving the signal at each of said widely separeted diversity receivers, rectifying the signals received from the individual antenn at each receiver and additively combining them at said receivers, and subsequently translating the rectiiied energies into alternating currents, transmitting said alternating currents to said central oiiice and rectifying said alternating currents to effect signal reception.

HAROLD H. BEVERAGE.

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