M. 24, 1946. g. M. SHOOK ETAL 2,413,116 SYSTEM FOR GEOPHYSICAL EXPLORATION Filed Feb. 14, 1944 4 Sheets-Sheet 2 aduzlm mzOvEuw INVENTORS. Ear/2y M. Shoal: 0m! Ruben‘ M. Olson. 5V J ' 5 W #orney. %¢.21,1916. EMSHOOK “AL V 2,413,111 . SYSTEM FOR GEOPHYSICAL EXPLORATION Filed Feb. 14, 1944 ) 4 Sheets-Sheet 3 mm4- INVENTORS. Ear/cg M. Shock and Rob/arr‘ W Q/son. BY Dec. 24, 1946. E_ M_ SHQOK EI-AL 2,413,136 SYSTEM FOR GEOPHYSICAL EXPLORATION Filed Feb. 14, 1944 v 20 FIGURE'S 4 Sheets-Sheet 4 0 ‘20A FIGURE-7 INVENTORS. Ear/cg M. Shock and Eoéer/ W Olson. Afforney. 2,413,116 Patented Dec. 24, 1946 UNITED sures PATENT OFFlCE 2,413,116 SYSTEM FOR GEOPHYSICAL EXPLORATION Earley M. Shook and Robert W. Olson, Washing ton, D. 0., assignors, by mesne assignments, to Socony-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York Application February 1d, 1944, Serial No. 522,358 5 Claims. (Cl. 177-352) 1 2 This invention relates to geophysical explora tion, more particularly to re?ection methods of seismic surveying in which the time break, the uphole geophone, and communication signals are wires for the transmission of the time break, the uphole geophone, and communication signals from the shotpoint to the recording truck. The to be transmitted from the shotpoint to a record transmission by radio of these signals has been proposed, but spurious signals superimposed upon ing truck. the carrier have made difficult the transmission . The seismograph method of exploration en and recordation of the desired signals with su?i ables geologists and geophysicists to determine‘ cient clarity so as to be easily recognized on the the location and depths of geological structures seismogram. Systems such as shown in Shook favorable to the accumulation of petroleum and 10 et al. Patent No. 2,290,773 have been utilized, but other subsurface deposits. In brief, at a suit leave much to be desired in the faithful trans able location in the area to ‘be explored or sur mission and recordation of all or a selected por veyed, a shothole of a few inches in diameter is tion of the signals from the uphole geophone. drilled into the ground to a suitable depth, of the In carrying out the present invention in one order of from 50 to 100 feet. In the shothole is. 15 form thereof, a frequency modulated carrier wave inserted a suitable charge of a high-explosive is utilized for the transmission of signals repre such as dynamite. This hole is generally ?lled sentative of the time break and the uphole break with water in amount adequate for tamping. The and the same carrier is amplitude modulated for dynamite is exploded by a detonating cap con the transmission of communication or voice sig nected to an electrical blaster, preferably of the 20 nals. The combined AM-FM system which forms type shown in Minton Patent No. 2,189,741. The the subject matter of the present invention func explosion creates. seismic waves which travel tions faithfully to transmit an electrical impulse through the earth in all directions from the shot representative of the instant of creation of the point. By means of a geophone placed at the top seismic waves; it functions with extremely high of the shothole, the time required for the vertical 25 ?delity. to transmit the exact character of the travelling waves to reach the earth’s surface may ?rst seismic wave received and detected by the be ascertained. uphole geophone; and it functions to permit the At a suitable distance from the shothole, from simultaneous transmission of voice signals. A one to ?ve thousand feet for reflection shooting, minimum of equipment and power is utilized. and up to 5 or 10 miles for refraction shooting, The system further includes means automatically geophones or detectors are distributed along a operable after transmission of the desired uphole line Or over a selected area. These geophones geophone signal to disable the transmitting sys known as the spread geophones may be from 5 tem as a whole in order that the same galvanome to 50 in numberr They are connected through ter at the recording truck may be used for one of ampli?ers to a multi-element recording galva 35 the spread geophones. In this manner a single nometer to produce a photographic record of the galvanometer records on a single trace of a‘seis arrival of the seismic waves. They not only re-' mogram the time break impulse, the uphole break, cord the waves which travel directly from the and the signals received by one of the. geophones of the spread. shothole to the spread geophones but they also re cord re?ections of the seismic waves, which re 40 This invention further resides in features of flections occur between each interface of strata construction, combination and arrangement de having materially different physical characteris tics. scribed hereinafter. ' For a more detailed understanding of the in ' From the foregoing, it will be seen that not vention, reference shouldnow be had to the ac» only must the photographic record, the seismo 45 companying drawings, in which: gram, faithfully record the detected signals, but Fig. 1 is a block diagram of the transmitting also that the time of arrival of the differing waves at the respective geophones is of paramount im portance. - system; . ' Fig. 2 is a block diagram of a preferred receiv .- ing system; In areas to be surveyed, ?eld operations may 50 Fig. 3 illustrates the desired data as recorded be exceedingly difficult. Between the shotpoint' and the recording truck, there may be heavy un on a single trace of a seismogram; dergrowth, swampland or ?ooded areas. These mitting system embodying the invention; ’ Fig. 5 is a sectional elevation of a frequency greatly increase the cost of, if not preventing, ‘ Fig. 4 is a schematic wiring diagram of a trans entirely, the stringing of the necessary telephone 55 modulating device; and 2,413,118 3 through the doubler 18, the quadrupler 20, the Figs. 6 and 7 are views looking toward the crys tal and actuating unit, respectively. ?nal ampli?er I3, is radiated from the antenna l4. Referring to the form of the invention illus trated in Fig. 1, a blaster l0 includes a detonat As before, the FM carrier is demodulated at the receiver and the uphole geophone signals ing system preferably of the type shown in Min ton patent No. 2,189,741. During. preparation or installation of the explosive charge in the shot hole, and during the location of the spread of. geophones, the crew at the shotpoint maintains communication with the crew at the recorder by 10 means of a. microphone _II which through an ampli?er [2 produces amplitude modulation at the ?nal ampli?er [3 of the transmitting system. are recorded, as shown at 23, Fig. 3, on the single trace 2i of the seismogram. The instant of ?rst arrival of the uphole signals is accurately deter mined and the true character of the uphole break is faithfully recorded. The ?rst of the uphole signals, derived from the ampli?er IT by way of line 25, initiates op eration of a blocking means 28 for the applica tion of a negative bias, by way of lines 21 and 28, to the ampli?ers l2 and II, which bias renders each ampli?er inoperative or blocks the further The amplitude modulated carrier is radiated from an antenna l4. A radio transmitter of any suitable type for transmitting voices at the re cording truck and a radio receiver at the shot point (neither shown) may be utilized to com transmission of signals therethrough. This blocking means 26 eliminates all further signals from the recording galvanometer and makes it possible for the trace 2| to be utilized for the plete two-way communication between the ?eld parties. When. all is in readiness at both loca 20 recordation of signals 28 from a selected geo phone of the spread. Alternatively the blocking tions, with the uphole geophone l5 located on the means may be operated a time interval after pro earth's surface adjacent the shothole, word is re duction of the time break impulse. . ceived from the recording truck to detonate the The preferred form of the receiving system is charge of dynamite located in the shothole. This is done by operation of the blaster Ill. Co 25 diagrammatically illustrated by the block dia gram of Fig. 2. The carrier, frequency and amplitude modulated, is received by an antenna 30 and is applied to a conventional mixer 32 which also receives a locally generated signal incidentally with the explosion of dynamite, a single time break impulse is produced by gen erator I6, This single electrical impulse is ampli ?ed by ampli?er l1 and by means of the crystal oscillator and frequency modulator as indicated 30 from a local oscillator 33.‘ In accordance with at IS, a frequency modulated impulse is produced. The frequency modulated impulse passes through a frequency doubler l9, and frequency quad rupler 20, the ?nal ampli?er l3, and to the antenna I4. The frequency modulated carrier 35 is demodulated by a suitable receiver at the re cording truck and the single time break impulse is faithfully recorded on the seismogram by a suitable galvanometer appropriately connected to the receiver. , This time break impulse is in conventional superheterodyne principles, the re sult is an amplitude and frequency modulated signal at an intermediate frequency, which is then ampli?ed in two intermediate frequency stages 34 and 35. The ampli?ed output from the second IF stage 35 is applied by line 36 to a demodulator or detector 31 of amplitude modu lated signals and the audio output therefrom passes through an ampli?er 38 and to a loud 40 speaker 39. The ampli?edoutput from the sec trace of the seismogram coincidentally with the instant of generation of the seismic waves, which ond IF stage 35 is also applied to limiter 40. The two limiters 40 and 4| function to provide an output signal for a discriminator 42 of uniform amplitude and in avoidance of interference by are produced by the explosion of the dynamite. the amplitude modulated carrier. The frequency dicated at 22, Fig. 3. As above explained, it is known as the time break and it is recorded on a modulated signals are detected or demodulated It will be understood by those skilled in the by the discriminator 42 and pass by way of an art that a seismogram is produced by suitable attenuator 43 to one of several recording gal~ means such as a multiple-element recording vanometers 44 which produces the seismogram galvanometer. Each” galvanometer produces a single trace which may correspond with the seis 50 illustrated in Fig. 3. The output signal from the discriminator 42 may also be utilized to initiate mic waves received by a detector or geophone. operation ,of a master controller 45 which, in co The trace of Fig. 3 also records the time break operation with one or more ampli?ers 46, con 22 as already described. Across each trace are trols the gain in the signals from a plurality of vertical timing lines. The horizontal distance between adjacent lines is generally predetermined 55 geophones 41 comprising the geophones of the and selected to equal one-hundredth of a second. Since the uphole geophone may be but from . 50 to 100 feet from the seismic wave generating means, the time required for the waves to reach spread. The master controller 45 may be of a type like or similar to those described in United States Letters Patent No. 2,301,739,v 2,306,991, or‘ 2,312,934. With the foregoing understanding of the-broad the uphole geophone is exceedingly short. It 00 principles underlying our invention, reference usually is of the order of from ?ve thousandths may now be had to the wiring diagram of Fig. 4 wherein the blaster III, as above described, in cludes a. circuit effective upon detonation of the only operate to produce the single time break impulse but Within that exceedingly short time 65 charge of the dynamite to apply a voltage im pulse to the primary winding 48 of a transformer it must be rendered inoperative for the produc to two hundredths of a second. This means, of course, that the impulse generator [6 must not tion of other or additional impulses; otherwise, ' 49. - The secondary winding 50 is connected through coupling condensers 5i and 52 to the control grids 53 and 54 of a pair of gas tubes 55 obscured and indeterminable on the seismogram. The instant of ?rst arrival of the vertical travel 70 ‘and 58, each of which has the characteristic of continued ?ow of anode or plate current once the ling seismic waves at the uphole geophone I5 is grid loses control. Tubes-of this type are also detected and the resultant electrical signal ap known by the trade name of “'I‘hyratron." Each plied to the ampli?er I1, the output from which of the control grids 53 and 54 has a negative is utilized to produce at l8 frequency modulation of a radio carrier wave which, after passing 75 bias derived from the negative end of a voltage the signals from the uphole geophone would be ‘2,418,116 5 . ' divider 58 which bias is applied by way 01' the contact 58 of a double pole switch 88, conductor BI and by resistor 62 to control grid 53 and by way of resistor 53 to control grid 34. The cathodes and suppressor grids of each of the gas tetrodes 55 and 58 are connected together and to con ductor 84, which forms a common return circuit to a tap 65 located at a position marked at zero on the voltage divider 58. While gas tetrodes are triode tube 88 includes the coupling condenser 88 and a tank circuit 88 which functions as a fre quency doubling stage. The output from the ire quency doubler is applied through grid leak con denser 8| to the control grid of a tetrode tube 82, the output circuit of which includes a coupling condenser 83 and a tank circuit 84 which func tions to quadruple the frequency. The output from tube 82 is applied through the grid leak illustrated, it will be understood gas triodes may 10 condenser 85 to the control grid of a thermionic be used if desired. tube 88, the anode or output circuit of which By reason of the circuit connections including includes a coupling condenser 81 and a tank cir resistors 82 and 83, the negative ‘bias on one or cuit 88. The inductor 88 forming a part of the the other of control grids 53 or 54 is materially tank circuit 88 is inductively associated with the reduced in value by the'voltage impulse applied coils I88 and MI. The coil I88 has one end con by the blaster ‘I8, while the negative bias on the nected to the exterior of a concentric transmis other grid is materially increased. The exact op sion line and its other end is connected to the eration depends upon the polarity of the impulse inner conductor or wire thereof, which leads to as applied to the primary winding 48. Regard the radiating antenna I83. The outside of the less of polarity, however, any impulse from the 20 transmission line is also connected by conductor blaster I8 makes one Or the other of grids 53 or 54 su?iciently less negative to cause a gas tube to ?re or/to render it conductive. Plate current immediately ?ows through a circuit which may ' be traced from a tap 85 on‘ the voltage divider 58 25 by conductor 66a, resistor 81, meter 68, conductor 59,‘ resistor 18, switch 1I, condenser 12, conductor I82 to ground G. ' The coil I8I comprises a single turn and forms a part of a link circuit between the ?nal tank cir cuit 98 and the tank coil of the frequency quad rupler. This is accomplished by a second coil I84 comprising a single turn located in inductive re lation with the' coil or inductor of the tank cir 13, (and assuming gas‘ tetrode 55 is ?red) re cuit 95. Sumcient coupling of correct polarity is sistor 14, the anode of tube 55 and from the oath obtained to provide neutralization of the ?nal ode by way of conductor 64 to tap 65 on the volt 30 stage. , age divider 58. Current continues to ?ow until By means of a microphone I05 voice currents the condenser 12 is charged. This occurs very may be produced in the primary winding I86 of rapidly and when condenser 12 is charged, the a transformer I81 when a normally open switch e?ect is to remove the voltage from the anodes of I 88 is moved to closed position. This circuit may the tubes 55 and 56 and neither tube may ?re 35 also include battery I89, if desired. From the upon reversal of or production of subsequent im secondary H8 of transformer I81, voice signals pulses from the blaster I8. This fact is important‘ are applied directly to the control grids of a inasmuch as the blaster ordinarily-includes wires double triode tube III, the respective electrodes which are ruptured by the explosion of the dyna of which are connected in parallel with each mite. In many cases the wiresare not only blown 40 other. The grid circuits may be traced through apart but are also blown upwardly and possibly winding H8, the conductor 69, meter 68, resistor out 'of the shothole. During their travel-they may 61, conductors 86a and II 2, and the resistor'l I4, repeatedly engage and disengage. In many cases which is connected to the two cathodes of tube there are a number of impulses following the one III. The grid biasing resistor H8 is provided indicative of the instant of creation of the seismic 45 with the usual bypass condenser I I5. The out waves. By providing the foregoing circuit ar put from tube I I I is applied through transformer -angements for the two gas tubes, but a single III; to the control grids of a double triode tube impulse is generated-the one that coincides with II1. In this case, the respective cathodes are Ihe instant of creation of the seismic wave. connected by conductor H8 to a midtap of the It will be observed one side of the series com 50 secondary winding of transformer H6. The re .)ination of meter 68 and resistor 81 is connected spective trlodes of the tube II1 are connected in by conductor 15, resistor 16 and by conductor 11 to the control grid of a thermionic pentode ampli 9 push-pull relation, the output circuit including the primary winding of a transformer I28, having t‘ying tube 18, while the other side of the resistor a conductor I 2| leading from a midtap thereof 51 and meter 68 is connected by conductor 19 55 through a. resistor I 22 to the source of anode and resistance 88 to the cathode of tube 18. In potential, including voltage divider 58. The sec consequence, the current impulse through the re ondary winding of the transformer I28 is in series sistor 61 and meter 68 produces a potential dif ' with the source of anode potential for tube 96. ference or IR drop which is applied to the control Thus, one end of the secondary is connected grid of pentode 18. The result is the production 60 through an RF choke coil I24 to the anode‘ of the in the output circuit including the primary wind_ tube_96, while its other end is connected by con ing 8| of transformer‘ 82 of a voltage impulse of ductor I88 to B plus on voltage divider 58, the ampli?ed magnitude. This is applied by sec return being by way of ground connection G and ondary winding 83 to an operating coil 88 of a conductor I82 to the cathode of tube 86. 'frequency modulating device 85, the details of 65 As previously pointed out, the transmitting sys which will be later set forth. The application of the ampli?ed impulse to the device 85 produces a change in the frequency of the crystal oscil lator which includes the ?rst stage of a, double tem may frequently be operated in a region quite remote from good roads and usual power facili ties. Hence the design requirements are some triode thermionic tube 86, whose output circuit sumption. Ordinarily, storage batteries are uti lized, with a vibrator, and suitable transformers, includes the coupling condenser 81 and the tank circuit 88. The output of the crystal oscillator stage is applied through grid leak condenser 81a to the control grid of the second section of the what severe as regards weight and power con and ?lter circuits to provide the required poten tial for the supply of anode current. The tube H1 is preferably operated as a class B ampli?er double triode 86. The second stage of the double 75 and a relatively large condenser I28 is connected 2,413,110 so as to supply the peak demands of class B. modulation. - ‘ Members of the crew at .the shotpoint may utilize the microphone I05 to communicate with ' bered the resistor 61' was also utilized in conjunc ‘ tion with the capacitor ‘I2 to produce the single impulse representative of the time break. This impulse. resulted from the momentary ?ow of current through the resistor 61, a ?ow'which per sisted only long enough for the capacitor’ ‘I2 to seismogram is to be made, the blaster I0 is oper be charged. ~ ated and a single impulse produced by ?owof As shown in 'Fig. -3, this time break impulse, current through one of the gas triodes 54’or 55 which begins at 22, is of extremely short duration. is applied to the ampli?er ‘I8 and to device“ and a frequency modulated signal is radiated‘ 10 For that‘ reason, though this‘ impulse is also ap plied to the grids of tube III, it does not inter from the antenna I03. Almost immediately, the fere with operation of the microphone I05 even uphole geophone I5 applies an" electrical signal though-the impulse may be heard at the receiving by way of transformer I25 to a pentode amplify— station. ing tube I30, the output of which is’ coupled in It will further be observed that the tap 66 of conventional manner to the amplifying tube ‘I8, 15 the voltage divider 58 is utilized as the source of and in like manner frequency modulation in ac anode ‘supply. for the gas tubes 56, 55 and I33, cordance with the uphole signal is produced by while this same tap 66 is connected by conductor device 85 which is also, radiated from antenna H2 and resistor II4 to the cathode of the tube I03. It may here be observed the polarity of the geophone I5 is determined and the connections 20 III. The tap 66 is connected by conductors 6611, ‘I9, and resistor 80 to the cathode of the tube ‘I8. to ampli?er tube I30 are such that the ?rstv The‘anode supply for tubes ‘I0 and I II is derived seismic wave arriving at geophone I5 produces in from a higher-voltage tap, the one nearer B+. the output circuit of tube I 30 an electrical impulse In consequence, the tubes ‘I8 and I II operate with of negative polarity. The ?rst impulse of ‘nega tive polarity from the geophone I5, as it'appears 25 their cathodes well above ground potential, in fact, at a voltage substantially equal to that _of in the output circuit of the amplifying tube I30, tap 66. By arranging the circuits-in this man- _ is also7 applied by way of conductor I3I through ner, and asfurther pointed out herein, the single a condenser I32 to the control‘ grid of a gas source of potential indicated by B— and 3+ ade tube I33. ‘, . This gas tube I33 is negatively biased to a non 30 quately serves to supply the’ various tubes and thus avoids the need for thepresence of separate conducting condition through a circuit which in sources of supply. ' ‘ cludes the resistor I 34, contact I35 of switch 60, and by conductor I36 to the negative end (minus It. will therefore be seen that the tube I33 ?ve volts) of the voltage divider 58.. The return provides a’ means ,for blocking translation of the men at the recording truck. ‘ At the time a » circuit is by way of tap 65, conductor-s 64 and I38, 85 .further signals through both of tubes ‘I8 and and to the cathode of gas tube I33. Because the > III, the net result of which isthe elimination ?rst impulse or half cycle of the uphole geophone of radiation from the antenna I03 of modulated signal is of negative polarity as it appears in the signals of any character. All subsequent dis output circuit of tube I30, the application of that turbances of the uphole geophone and micro half cycle to the control grid of gas tube I30 ren 40 phone cannot produce modulation of the carrier. ders it more negative. Hence it does not ?re and In consequence, at the receiving'station, there is accurately recorded by one of the galvanom ‘ does not interfere with the transmission of said half cycle to the recorder where the true char eters M, Fig. 2, on the trace of the seismogram acter thereof is recorded on the seismogram. a time break impulse 2.2, Fig. '3, indicative of the instant of creation of the seismic waves. On However, upon the appearance of the subse quent half cycle of opposite or positive polarity, the same'trace of the seismogram there are re corded the ‘uphole geophone signals 23 repre the application thereof through the circuit in cluding condenser I32 reduces the negative bias sentative of the uphole break. By operation of on the control grid of gas tube I33. Hence this‘ the tube I33, all further signals ‘from the shot tube immediately ?res or becomes conductive and pointare blocked, but a geophone 41 of the spread current ?ows through a circuit which may bev such as shown in Fig. 2 is connected to the same traced from its cathode by way of conductors I38‘ galvanometer and on the same trace there may and 64, taps 65 and 66 of voltage divider 58, con be recorded seismic signals 28 detected by the geophone 41. As further shown in Fig. 3, after ductor 66a, resistor 61, meter 68, conductor 69, ‘ the uphole'break 23 has been recorded, the sig resistor ‘I0, switch ‘II, and to the anode of tube nals generated by the geophone 41 as indicated I33. Because of the characteristic of gas tube I33 at :28, are recorded. The accuracy and the high current continues to ?ow in this, circuit and the ?delity with which the time break and uphole voltage drop across the resistor 61 and meter 68, signals are recorded is accomplished in the pres which is included in the grid circuit of tube ‘I8, is immediately effective to bias the tube ‘I8 to‘an 60 ence of spurious‘ noise or signals such as are produced by static, commutator ripple, or other 4 inoperative condition through a circuit which in ' cludes conductor ‘I5, resistor ‘I6, conductor 11, re sistor 80, and conductor ‘I9. At the same time the voltage drop across resistor 61 and meter 68 extraneous sources of electrical energy which have heretofore played havoc with radio trans-~ mitting systems utilizing amplitude modulation ' negatively biases the amplifying tube III to an 65 of a- carrier 'for the transmission of seismic inoperative or non-conductive condition, through It will be recalled that the time break or‘ shot a circuit including conductor 69, and through the instant was determined or represented by a single secondary winding IIO to the grids, the return electrical impulse produced by the ?ow of a surge circuit being from the cathodes, ‘resistor H4, and by way of conductors II2 and'66a to the othe 70 of current through one of the gas tubes 55 and 56 while charging the condenser ‘I2. .Further im side of resistor 61. 1 pulses from the blaster I0 were blocked or pre Since the resistor 61 and the meter 68 are both vented from affecting the tubes 55 and 56 by included in the grid circuits of tubes ‘I8.and III, operation of the condenser ‘I2 to remove the the foregoing current ?ow is effective to block both tubes. In this connection, it will be remem 75 voltage ,from the anodes thereof. Further im signals. . . v > 9 pulses from the uphole geophone and‘ micro 10 crystal 200 mounted on a metal back plate 20I which is itself carried on a support 202 of in- ‘ phone are blocked by a constant bias resulting sulating material such as “Bakelite.” An elec from the IR drop across resistor 61 and meter trical connection 203 leads to the metal plate 83 when tube I33 is conducting. 20I. The crystal 200 is rectangular in shape and It is seen that during the process of making is preferably cut so as to be stable in operation a seismogram, the transmission of time break, even with temperature variations. As shown in ‘uphole and voice signals was interrupted. The Fig. 6 both the crystal 200 and back plate 20I circuit arrangement as shown provides complete have the same rectangular shape. restoration of the circuit to its original condi A cooperating metallic plate 204 is carried by tion by the operator at the shotpoint when he is 10 a metallic diaphragm 205 operatively connected compelled to reset the circuit to reestablish byv linkage 206 to an electromagnetic operating communication. unit 201. This unit is provided with operating To restore the circuit to its original condition coils 84, cooperating magnetic structure 208 and and in readiness for the next ?eld operations, the switch ‘II, normally spring biased to its il 15 an armature 200. The’ diaphragm 205 is pref lustrated position, is momentarily depressed.‘ erably provided with several corrugations to This opens the anode circuit of tube I33 and completes a discharge circuit for the condenser minimize resistance to movement by the arma vide proper tuning for the selected resting tube 92, Fig. 4, also multiply frequency changes produced by device 85. ture 209 and linkage 206. The corrugations also insure return of the diaphragm to its original ‘I2. Upon return of the switch ‘II to its original position the negative bias on the grid of gas 20 position after movement therefrom in either‘ direction. > tube I33 prevents further current ?ow until the To provide easy adjustment and rigid secure application to its grid of the next positive im ment of all parts in desired ?nal positions, the pulse; and the condenser ‘I2 having lost its charge outer frame, annular in shape, consists of inter is in readiness to assist in producing one im pulse representative of the shot instant or time 25 iorly threaded members 2I0 and '2“ locked to gether by a series of screws, two of which, the break and for blocking all subsequent impulses screws 2I2 and M3 are shown. The housing which may appear in the blaster I0 and which 2I-4 threadedly engages frame member 2I0 and may be applied to the control grids of tubes 55 is locked in position by threaded ring 2I-5. The and 56. For testing purposes, the spring biased switch 30 insulated support 202 threadedly engaging frame member 2“ is held in position by a locking ring 60 may be momentarily operated from its illus_ 2I6. The frame 2I0--2II is mounted from a trated position. The contacts 59 and‘ I35 serve part of a chassis or stationary member 2I‘I by not only to remove the negative bias on tubes means of an upright support 2I8 and a base 55, 56 and I33 but also to apply a positive bias plate 2 I 9 which by means of screws 1220 is secured thereto. to member 2 I1. ' Circuit elements not described in detail repre The diaphragm 205 is clamped by a'locking. sent conventional practice. For example, the ring 22I against the inner’ edge of the housing plate or anode circuits of tubes 86, 92 and 96 are 2M. shunt fed with RF choke coils included in each As shown in Fig. 4, the device 05 which in circuit. The anode voltage for tube I30 is ob 40 cludes crystal 200 and plate 20I is connected in tained from B plus by way of conductor I00 the grid circuit of the tube 86;. In manner under and conventional resistors. The cathode of tube stood by those skilled in the art, the crystal 200 I30 is connected‘ directly to B minus and to is ‘connected to the ?rst section of tube 86 which ground. The tube ‘I8 has its anode connected through primary winding 8I to conductor- I60 - makes up a conventional crystal controlled oscil lator. and to B plus while its cathode is connected Upon application of signals to the operating through resistor 80 and conductors ‘I9 and 66a coil 80 the armature 209 through linkage 208 to tap 68. Similarly tubes III and II? have moves the diaphragmecarried metallic plate 200 their cathodes connected to tap 56 with their anodes connected to B plus. In this manner the v .toward and away from the face of crystal 200. The resultant changes in the air gap between single voltage divider 58 and the one source of ~p1ate 204 and. crystal 200 produce a change in potential indicated by B minus and B plus serve ' the frequency proportional to the change in the . the various tubes in manner already described air gap and in amount adequate for transmis in detail. The antenna I03 may be of the “whip" type; In Ll sion and reproduction with high ?delity of the time break and uphole geophone signals. The that is, it may comprise telescopic tubes which frequency multipliers, second section tube 86 and may-be elevated to the desired height to pro frequency. _ When the uphole geophone is not to be used, the normally open switch I12 in shunt with the capacitor 12 is closed. Hence, the current ?ow ing to the gas tube 55 or 56- which ?res continues to ?ow through resistor 01 and the meter. The tubes ‘I8 and III are blocked in manner already described to prevent further transmission of voice signals or any further signals from an It will now be realized that a signal electrical impulse representing the time break or the in stant of creation of the seismic waves produces frequency modulation and at the recorder pro duces a photographic record coincidentally with --the instant of their generation. Almost instan taneously thereafter, within as little as about one hundredth of a second an electrical signal is pro duced in response to arrival at the earth's surface of seismic waves from the shotpoint. This signal ing the frequency modulation of the carrier 70 likewise produces frequency modulation of the carrier and the true character of the uphole radiated from antenna I03. It also serves ‘to gcophone signal is faithfully recorded on the ‘determine the resting frequency, or the frequency same trace of the seismogram as the uphole of the carrier in the absence of frequency modu break. Thereafter seismic waves and their re lation. It may take various forms, but the one preferred, the device 85, comprises, Fig. 5, a 75 ?ections are detected by a geophone of the spread tenna I03. ' ' The device 85 has been described as produc 2,418,116 11 12 which is wire-connected to the recorder and these location for recording on‘ a. single trace said im pulse and said seismic waves after travel through the earth. demodulating means responsive to the frequency modulated carrier for actuating said recorder to record said impulse and said signal, said demodulating means including signal-limit-q too are recorded on said trace of said seismo gram. Before and during the frequency modulation of ' said carrier, the voice modulating means is oper able to produce amplitude modulation of the car rier but as soon as the uphole geophone signal ing means for preventing operation of said re cording means by amplitude modulation of said has been transmitted, both the amplitude and frequency modulating means are rendered inop carrier, means operable immediately after said erative until the manually operable switch ‘H has 10 impulse produces said frequency modulation for been operated. ‘ so biasing said ampli?ers as to prevent further frequency and amplitude modulation of said car rier during the period of recording of said seismic signal produce frequency modulation of said car waves at said receiving location, and means for rier without interference between them. And the 15 rendering said biasing means ineffective thereby to render effective said frequency and amplitude invention further embraces the features of con modulating means for subsequent modulation of current amplitude modulation of the carrier said carrier. without interference with the frequency modu 3. In a system for geophysical exploration in lated signals and the other features already de scribed in detail. 20 which seismic waves are created below the earth's surface and their travel time through the earth While we have illustrated a preferred embodi measured, the combination of a single radio ment of our invention, it is to be understood We transmitter for radiating a carrier from a sending intend by the claims to cover all modi?cations which fall within the true spirit and scope of our location, means for producing a single electrical invention. 25, impulse coincidentally with the instant of crea What is claimed is: tion of said seismic waves, means including an 1. In a system for geophysical exploration in ampli?er operable by said single impulse for fre which seismic waves are created and their travel quency modulating said carrier substantially dur time through the earth measured, .the combina ing the period of said impulse, means including tion of a single radio transmitter for radiating 30 an uphole geophone for producing an electrical a single carrier from a sending location; means signal indicative of the arrival at the earth's sur for producing a single electrical impulse coinci face of seismic waves which have travelled dentally with the instant of creation of said through at least a part of the weathered layer seismic waves, means including an ampli?er and of the earth's surface, means inicluding said operable by said single impulse for frequency ampli?er for applying said signal to said fre In its broader aspect the invention embraces the system by which the time break and uphole modulating said carrier substantially during the period of said impulse, means including an uphole geophone for producing an electrical signal indi cative of the arrival at the earth’s surface of seismic waves which have travelled through at least a part of the weathered layer of the earth's surface, means including said ampli?er for ap plying said signal'to said frequency modulating means to produce frequency modulation of said carrier during the period of said signal, .a second ampli?er, sound responsive means including said second ampli?er and concurrently operable for producing amplitude modulation of said carrier, means including a seismic recorder at a receiving location for recording on a single trace said im pulse said signal and seismic waves after travel through the earth, and means operable imme diately after said geophone signal produces said quency modulating means to produce frequency modulation of said carrier substantially during 40 the period of said signal, a second ampli?er, sound responsive means including said second ampli?er and concurrently operable for produc ing amplitude modulation of said carrier, means including a seismic recorder at a receiving loca tion for recording said impulse and said seismic waves after travel through the earth, demodulat ing means responsive to the frequency modulated carrier for actuating said recorder to record said impulse and said signal, said demodulating means, including signal-limiting means for preventing operation of said recording means by amplitude modulation'of said carrier, means operable im mediately after said geophone signal produces said frequency modulation for so biasing said ampli?ers as to prevent further frequency and. frequency modulation for rendering said ampli amplitude modulation of said carrier during the ?ers inoperative thereby to prevent further fre period of recording of said seismic waves, and quency and amplitude modulation of said carrier manually operable means for rendering said bias thereby to prevent application to said recorder of ing means ineffective thereby. to render effective further signals and impulses during the period of said frequency and amplitude modulating means recording of the seismic waves which have trav~ for subsequent modulation of said carrier. elled through the earth to said recorder. 00 4. In a system for geophysical exploration in 2. In a system for geophysical exploration in which seismic waves are created below the earth's which seismic waves are created below the earth's surface and their travel time through the earth surface and their travel time through the earth measured, the combination of a single radio measured, the combination of a single radio transmitter for radiating a carrier from a send transmitter for radiating a carrier from 2. send ing location, means for producing a single elec ing location, means for producing a single elec trlcal impulse co-incidentally with the instant trical impulse'coincidentally with the instant of of creation of said seismic waves, means includ creation of said seismic waves, means including ing an ampli?er operable by said single impulse an ampli?er operable by said single impulse for for frequency modulating said carrier substan frequency modulating said carrier substantially tially during the period of said impulse, a second during the period of said impulse, a second am ampli?er, sound responsive means including said pli?er, sound responsive means including said second ampli?er and ‘concurrently operable with second ampli?er and concurrently operable for said frequency modulating means for producing producing amplitude modulation of said carrier, amplitude modulation of said carrier, means in means including a seismic recorder at a receiving cluding a seismic recorder at a receiving location 2,418,116 13 ' for recording on a single trace said impulse and seismic waves after travel through the earth, an 14 bination of a transmitter for generating and radiating a single electromagnetic carrier, a ?rst ampli?er and gain’ control means for producing ampli?er including an amplifying tube operable variable gain of said ampli?er during the period upon creation of said seismic signals for ire-y of recording of seismic waves, demodulating 5 quency.-modulating said carrier, a second amph means responsive to the .frequency modulated ?er having an amplifying tube operable by voice carrier for applying to said ampli?er. and recorder ‘ _ signals for amplitude-modulating said carrier, a a signal representative of said impulse, means gas tube normally biased to a non-conducting operable by said signal for initiating operation of condition, a ‘single source of supply for the anodes said control means, said demodulating means 10 of said amplifying tubes and said gas tube, circuit including‘ signal-limiting means for preventing connections for operating said amplifying tubes operation of said recording means by amplitude with their cathodes substantially at the same modulation of said carrier, means operable im potential as the anode of said gas tube, a re mediately after said geophone signal produces sistor, means connecting said resistor in series said frequency modulation for ‘so biasing said 15 circuit relation with said gas tube and for con-_ ?rst-named ampli?er as to prevent further fre >. necting it in the grid circuits of said amplifying quency modulation of said carrier during the tubesfor the development, upon current ?ow period of recording of said seismic waves, and ' through said resistor, of a negative bias to pre means for rendering said biasing means ine?’ec vent conduction of current by said “ampli?er tive thereby to render e?ective said frequency 20 tubes, and means operable within a short time modulating means for subsequent modulation of interval after creation of said seismic waves for said carrier. ' rendering said gas tube‘conductive thereby to 5. In a system for geophysical exploration in ' > produce said negative bias. which seismic signals produced at a shotpoint EARLEY M. BHOOK. are recorded at a receiving location, the com- 25 ROBERT W. OLSON.