109 218 THS- 3‘HE INFLUENCE OF SUB-SURFACE GEOLOGY UPON THE PRCPAGATION Cl? ELECTROMAGNETIC WAVES Thesis for the Degree of Mo 5‘ MICHIGAN STATE COLLEGE Clifford J Gibbs I939 THE INFLUENCE OF SUB-SUPEACE GEOLOGY UPON TIE PROPAGATION OF ELECTRO—LLXG-ITETIC WAVES THE INFLUENCE OF SUB-SURFACE GEOLOGY UPON THE PRCPAGAT I OH OF ED1CTRO—lzL1GITET I C WAVES BY CLIFFORD J. GIBBS A TIIES IS Submitted to the Graduate School of Michigan State College of Agriculture and Applied Science in partial fulfilment of the requirements for the degree of EASTER OF SCIENCE Department of Geo lo 5;; 1939 . urn . I :rfll.‘ \ CIGIOWIEDGLEZIETS 'The writer wishes to express his sincere appreciation to Dr. S. G. Bergquist for his constructive interest in the problem and for suggest- ions and criticisms pertaining to the manuscript, to Mr. W. G. Keck under whose direction the problem was undertaken, to the Department of Physics for furnishing apparatus, and to the Michigan Academy of Science, Arts and Letters for providing a research grant to carry on the field work. The writer is greatly indebted to the Radio Division of the Mich- igan State Police for the opportunity to study and to use field intensity data in their possession, to the Consolidated Coal Compang,r of Saginaw for permission to make intensity measurements in their Crapo Mine, and to Mr. W. Fink who assisted in the field work. The writer also wishes to express his thanks to Mr. R. L. Rowe for photography and to Dr. Justin Zinn for checking the manuscript. ices-a He‘d) CCIITEIIWS Introduction ....... . ........................... . ........... Historical. ................. .. ............. ’ .............. .. Local Fading........... ..... .. .................. ... Poor Reception over Large Areas. ................. .. Penetration of Radio Waves.... ................... . Summary. ..... . ..... . .............................. . Theory of Propagation of Electro-magnetic Waves. ..... ...... Tilt of the Electric Vector .............. . ...... .. Penetration of a Radio Wave...... ....... . ........ .. Method of Measurement. ................................... .. Direct Comparison Method........ .......... ......... Indirect Comparison Method.................. ...... . Calibrated Receiving Set..... ..... ....... .......... Apparatus Designed for Experimental Work........... Procedure in Making Field Intensity Measurements... Additional Apparatus... ..... . ...... ..... ...... ..... Field Wonk in the Howell, Michigan, Area................... Description of Area............ ...... .............. Field Work................... .................... .. Experiment in the Crapo Mine, Shiawassee County............ Interpretation of the Howell Survey........................ Survey in the Jackson, Michigan, Area..... .......... ....... Conclusions and Summary.................................... Literature Cited.................. ............ ............. Page 16 17 18 18 18 Fig. Fig. Fig. 10. 11. Ieo’ * usrzm 201.15 Thickness of Glacial Drift in Michigan...... ......... .. Schematic Diagram of the Field Intensity Meter. ....... . Field Intensity Meter.................................. Rod Antenna. ............... . ........... ..... ........... Loop Antenna................ ........ . ...... ...... ..... . Areal Resistivity Map of the Northwest Part of Livingston County............ ..... . ............. ... Radio Field Intensities of W53, Detroit, in the Northwest Part of Livingston County - following page Map Showing Glacial Features in the Howell Area - following page Map Showing the Distribution of Rock Formations in Liic111g&100.0.0000000IOOOOOOOOOOOOOOOOO00.0000... Radio Field Intensity Traverse in the Jackson, Michigan, Area...... .......... .......... ....... ... Distribution of Glacial Moraines in the Lower Peninsula of Michigan....... ............. ......... Page F J N5 (\J (,1 41 43 1. INTRODUCTION The ice sheets which deployed over the Great Lakes region during the Pleistocene epoch left in their wake a mantle of glacial drift covering the surface of Michigan to depths ranging up to 1200 feet (Fig. 1, p. 2). As a result of glaciation, rock exposures, especially in the southern part of the Lower Penin- sula, are extremely rare. The geologist, therefore, is dependent upon well-log data and geOphysical methods for the determination of sub-surface geology. Glacial drift also offers a serious problem to the geOphysi~ cist, particularly in seismic work, as the unconsolidated charac- ter of the material causes marked energy losses. Moreover, in gravitational methods, eSpecially that employing the torsion balance, similar difficulties are encountered, since the pre- sence of large boulders near the surface are responsible for considerable changes in density, and therefore in the recorded value of gravity within the same material. Electrical resis- tivity has been employed successfully in outlining areal geology but is definitely limited in its application to the vertical measurement of rock sections. In view of the limitations placed on the application of geOphysical methods in drift covered areas an investigation of radio reception was made in an attempt to provide an additional 2. ~ coca". no M“ k I Vanna“ - mun-v.- .. e . . .. . , .. W WYM AK MOMMAVI “V .31 Neillfl-‘llagfi2'°. ~IDIQI ' Fig. 1. Thickness of Glacial Drift in lichigan. 30 means of sub-terrane interpretation. This paper presents the results of researches carried out in this particular field. HISTORICAL It is well known that certain localities yield poor radio reception from stations that seemingly should give a good radio signal. Such areas may be divided into two groups; one of very local proportions, not exceeding several hundred feet, and the other of considerable magnitude, covering, perhaps, several hundred miles. In either instance, since the present investi- gation involves primarily the geological aSpects of radio recep- tion, the penetration of an electro-magnetic wave into the ground must be considered. Lgcal Fading!» In the ease of local fading a radio signal has a low intensity or becomes entirely inaudible over a certain area, althOUgh the signal may be strong on either side. Local fading and.so-called "dead spots" in Maryland and Wyoming have been shown by Cloos (4) to be associated with faults and steeply dipping rock contacts when the materials on either side of the fault or contact have marked differences in physical properties, * All fading from man-made causes such as transmission lines telephone wires, steefl.tdxuctures, etc. are disregarded as their presence is easily detectable. . 4. Both of the regions investigated by Cloos are unglaciated and the boundary condition responsible for fading is known to be at or near the surface. It can be postulated, therefore, that in gla- ciated regions, where the geologic discontinuity is buried, the effect, though not pronounced, might be detectable with sensitive measurements and be used geOphysically. Poor Reception over Large Areas.- Poor reception of large areal extent is characterized by a general loss of signal inten- sity. A s an example of this type the problems encountered by the Radio Division of the Michigan State Police may be cited. Prior to 1936 and 1937 communication with mobile units was trans- mitted from only one station, WRDS (1642 kiloqycles, 3000 watts), located at East Lansing. Exceedingly bad reception occurred over » a large area in the southwestern part of the state and in a smaller area in the vicinity of St. Clair, although a good signal could be obtained at equal distances in other directions. In the northern part of the Lower Peninsula the signals became un- reliable as the distance from the station was too great to be covered by a 3000 watt transmitter. No further mention of the St. Clair area will be made as no detailed work has been done in that vicinity. In 1935, E. D. Shipley, under the supervision of R. C. Higgy, both of Ohio State University, conducted a series of field studies in c00peration with C. E. Winans of the Michigan State Police Radio 5. Receiver Division. The purpose of the investigation was to solve certain engineering problems, involving an expansion prOgram, for the improvement of reception in the aforementioned areas. According to the method employed by Higgy and Shipley (8), based upon the Sommerfeld theory, the only ground constant that influences radio field strength is electrical resistivity. Since the ground acts as an electrical mirror in the propagation of electro—magnetic waves, transmitter location sites are chosen where the conductivity is as high as possible. It is the prac- tice in field intensity surveys to run radial traverses from a portable transmitter, record the field strength at given intervals, and than plot the resulting figures in (microvolts per meter) as ordinates against the distance (in miles) as abscissas. The resulting graph may be called an E-D curve. Finally, the ground conductivity is calculated from the data thus obtained. Field studies were made at a number of locations in Michigan; including Lansing, Paw Paw, Benzonia, Kalkaska, Grayling, Roscommon, Mic, Cadillac, and McBain. With the single exception of Lansing, these are situated in either the southwestern or northern areas of poor reception previously mentioned. As a result of the in- vestigations two subsidiary stations were installed; WRDP (1642 kilocycles, 1000 watts) at Paw Paw in the Spring of 1936, and WRDH (1642 kilocycles, 1000 watts) at Houghton Lake in the Fall of 1937. The T-type transmitting antenna at WRDS was then replaced by a vertical type and the power was later increased to 5000 watts. The writer has examined the report submitted by Shipley and has conferred with.Winans relative to the results of their studies. Certain abrupt changes in slope on many of the EPD curves seem to agree quite markedly with formational boundaries. The strata un- derLying the areas investigated are Pennsylvanian and Mississippian in age. The boundaries which seemed particularly effective were those between the following geologic formations; Parma sandstone and the Michigan series, the Michigan series and Napoleon sand- stone, and the Marshall sandstone and Goldwater shale. The glacial drift in the northern area is several hundred feet. If the effect noted on the E-D curves is actually due to the underlying formations then a considerable penetration of radio waves in the broadcast band is implied. It should be noted, how- ever, that the conductivity as determined by a field intensity sur- vey is an average over the depth penetrated and that the absolute depth is a factor that can be ignored from the standpoint of the radio engineer. To the geophysicist, on the other hand, a know— ledge of the extent of penetration is of utmost importance. Penetration of Radio Waves.- According to Eve and Keys (6, pp. 251-252) radio waves in the broadcast band reach to consider- able depths under certain ground conditions. In June, 1926, an experiment was conducted in the Mount qual Tunnel, Montrea1,. C anada. Waves of 411 and 1300 metre lengths could be detected throughout the 3% mile tunnel which has a maximum overburden of 7. 300 feet. Waves of 40 metre length vanished at 1500 feet from the entrance although the overburden was only 48 feet at this point. In the summer of 1927 a similar experiment was carried out in the Caribou mine, Colorado. Broadcast signals of 267 metres from Denver, 50 miles away, were received clearly at a depth of 220 feet, and with difficulty 550 feet underground. It was not known, however, whether the waves came through the rocks, through Openings, or along numerous rails, cables and pipes in the Shaft. Eve and Keys (6, p. 252) state, "In order to remove all fur- ther doubt Dr. F. W. Lee selected the Mammoth Cave, Kentucky, which was entirely free from conductors, which had about 300 feet of overburden, mostly limestone, and was so long and circuitous that transmission through the mouth was definitely proved ineffec— tive. Using a three—hundred foot horizontal antenna in River Hall , morse signals were received from six different longawave stations, while speech and music was made audible with a loud speaker, 300 ft. underground, received from Cincinnati (700 kc., 429 m.) 200 miles away; from Louisville (820 kc., 366 m.) 90 miles away, and from Nashville (650 kc., 461 m.) about 100 miles away. These signals unquestionably penetrated 300 ft. of rock." 8. It should be noted that in none of the experiments involving underground reception has any mention been made of a glacial cover or that the ground conditions differ from those in Michigan. Summary.- Previous research has shown that there are two un- related causes of poor radio reception both of which are geological in character. The first, recorded by Cloos (A) as occurring at faults or steeply dipping rock contacts, is probably the result of reflection and refraction analogous to similar phenomena in light. The second type of poor reception, a general loss of energy over a relatively large area, may occur where formations are horizontal. The latter type can be explained by the theory of propagation of electro-magnetic waves, a discussion of which will be taken up in the next section of this report. Finally, if radio field intensity is to be employed for geophysical interpretation in glaciated areas, considerable pene— tration through the drift must occur. Experiments have proved that radio signals may be received through several hundred feet of rock. Field intensity data in Michigan seems to indicate that a similar penetration may occur in.drift and that the underlying formations may materially influence the signal strength. .9. THEORY OF PROPAGATION 0F ELECTRO—MAGNETIC WAVES A radio wave is an electro-magnetic disturbance of the other which is prOpagated outward from the transmitting antenna with the velocity of light. It consists of a carrier wave which is modulated with sound. Modulation under 100 per cent does not effect the energy of the carrier wave so that in the present consideration modulation may be disregarded. The carrier is a pure sinusoidal wave having an alternating electric field and an alternating magnetic field which are 90 degrees out of phase with each other both with respect to time and to apaCe The carrier wave is plane-polarized. At'a considerable distance from the transmitter, near the surface of the earth, the wave front be- comes approximately cylindrical in form. Ground conductivity causes the electric vector to assume a vertical position and the magnetic vector a horizontal position. The energy of the wave is equally divided between the two fields. There are at least two types of waves to be considered in radio reception. The first, received directly from the trans- mitter, is usually called a ground wave but will henceforth be re- ferred to as a surface wave to avoid confusion with the ground wave as defined by Sommerfeld. The second is reflected from the Heaviside layer and is known as the Sky wave. It will not be” considered in this discussion. 10. If a wire, exposed to electro-magnetic radiation, is oriented parallel to the electric vector an emf is generated. Such an emf expressed in microvolts per meter has arbetrarily been chosen as the unit in field strength measurement. If the earth were a perfect conductor the only attenuation of a radio wave would be the geometric spread of the wave. Then the intensity at a specific point would be given by the formula (See reference 4, pp. 350—351 for derivation)- E0 _-_ KIH/Wr (1) where E is the field intensity K is a constant, depending upon the units chosen I ' is the height of the transmitting antenna W is the wave length, and A r is distance. Since there are losses in transit due to the electrical con- stants of the ground the actual intensity at a given point is equal to Eq. (1) multiplied by an attenuation factor. Several empirical formulas for absorption have been worked out. AOne of the most reliable is that of Austin-Cohen (1, p. 661). The formula takes the form 11. 1 8-an2 where f is the frequency. D is the distance. a is to be evaluated for the particular conditions. The most widely known and used transmission formula of a purely mathematical nature is that of Sommerfeld (13). This is based upon the theory_of a ground wave defined as a wave traveling at the boundary of two semi-infinite media (earth and air) of very different electrical properties. The equation is in the form of an infinite series and because of its complexity was seldom used by radio engineers. Rolf (12) has constructed a set of graphs of the Sommerfeld formula covering a wide range of ground condi- tions which has made the equation more adaptable to field intensity work. A more exact formula was derived by Weyl (15), in which the only assumption made is that the point in question be far enough away so that the transmitting antenna appears as a dipole. It can.be shown (3) that Weyl's formula differs from that of Sommer- feld by exactly the ground wave component. Experiments by Burrows (3) have proved that the ground wave is not present in ordinary 12. transmission and that Sommerfeld's formula and Rolf's graphs are in error in all cases in which the dielectric constant of the ground cannot be neglected. The attenuation factors corresponding to the formulas derived by Sommerfeld and Weyl may be set down as follows (15) - U) H A + 13/2 ‘ (2) A - 13/2 (3) 2 II where S is the attenuation factor of Sommerfeld. W is the attenuation factor of Weyl 00 . A : 1 + rne2in(z + 1r/4) (4) 1'3‘5°'°(2n — 1) n=1 B : (2." x)%e-(x/2)sin 22 +-i((x/2)cos Zz-+ z-+-m/4) (5) 0° C : - X 1-3~5m(2n - 1) (o) xneZin(z -‘w/4) nzl . eria g ZIrZW 0 a z s r/z. ' (7) k - 21s f "These follow from eXpressions given by Wise (16) when the magnitude of k — Zia/f is large compared with unity." (l5) 13. Using the approximate form (6) and substituting (7) the resulting attenuation factor correSponding the Weyl is - w r) C : .2 1.305000(2n - 1)e‘inw/4 Vn(kf -' 218111 (8) (21rrf2)n n=1 where v is the velocity of light. f is the frequency.. r is the distance. 8 is the ground conductivity. k is the dielectric constant of the ground. While the formula may be of some value in showing the manner in which the intensity is influenced by the ground constants it cannot be employed in making geOphysical calculations. It is valid only at a relatively great distance from the transmitter. The conductivity and dielectric constant appearing in the formula are average or overall values for the distance covered and the depth penetrated. It cannot be used, therefore, in evaluating these constants for definite intervals. If it is assumed, as is usual in field intensity work, that the dielectric constant does not change appreciably over a particular region then the intensity for a given frequency and power at the transmitter becomes a function only of con— ductivity and distance. If the intensity as measured in the field is plotted against the distance from the transmitter a change in slope should be apparent where changes in resistivity occur. If the intensity is primarily influenced by material underlying the glacial drift measurements of field intensity should be of value in outlining sub-surface geology. Tilt of the Electric Vector. - If the ground were a per-. fect conductor the electric vector would everywhere be perpendicue lar to the surface of the earth. Hund (9, p. 352), employing the Sommerfeld theory, has shown that a theoretical tilt of the electric vector should exist and that the angle of inclination is a function of the ground constants. He gives the formula - tan T = f[18.1088 I (10) (1 + (kf/18'1085)2)2 where T is the angle of tilt s is the specific conductivity in l/ohm cm. f is the frequency in kilocycles per second k is the dielectric constant 15. From the foregoing it appears that in the field a measurement of the angle of tilt of the electric vector might also be of value in making geOphysical determinations. Penetration of a Radio Wave. - For future reference the following formula, also develOped by Hund (9, pp. 334—335), for the penetration of a radio wave into the ground is given as — H = H e‘bz (9) where no is the field intensity at the surface. H is the field intensity 2 cm. below the surface. 2 l b = BAN/p)? f is the frequency in cycles per second. u is the magnetic permeability, assumed unity. p is the resistivity in abohm-cm. 16. METHOD OF MEASUREMENT If the plane of a 100p antenna is oriented perpendicular to the magnetic vector of an electro-magnetic field the condition for maximum pick-up is obtained since in this position the greatest rate of change of flux occurs. The induced emf under such condi- tions (2, p. 403) is represented by the formula - vi 1' 2waNA/v (11) where V. is the induced emf in volts. f is the frequency in cycles per second. E is the electric field intensity in volts per cm. N is the number of turns in 100p. A is the area of loop in sq. cm. v is the velocity of light in cm. per second. The terminal voltage of a tuned loop circuit because of resonance, is much greater than the induced voltage. The ratio of the ter- minal emf to the induced emf is known as the step-up ratio of the loop. Taylor (14) has described a means of measuring field in- tensity directly. The more common practice, however, is to employ some form of comparison. 17. Direct Comparison Method. - In the direct method a current indicating meter is usually placed in the plate circuit of the i.f. detector of a superheterodyne receiver. The loop is adjusted for maximum pick-up. The deflection of the meter caused by the signal being measured is noted. The 100p is then turned through 90 degrees where theoretically there should be no pick-up. A locally generated voltage of the same frequency as the signal is induced into the loop circuit either across a known resistance drop or by means of a calibrated mutual inductance. Before entering the loop circuit the current is first measured by means of an ammeter and then attenuated until it gives the same deflec- tion on the receiver meter as the signal, in which case the induced voltages of the signal and oscillator are equal. The field strength may then be calculated from Eq. (11). Several difficulties are encountered with this method. Turn- ing the 100p through 90 degrees does not always completely out out the signal. Since the loop is always attached to the receiver the oscillator and attenuator must have perfect shielding to pre- vent stray pick-up. 'The voltages dealt with are extremely small. Friis and Bruce (7) have avoided these objections by placing a calibrated attenuator after the i.f. detector. It is an advantage, however, to have the calibrating voltage and attenuator separate from the receiver, especially in checking against a standard voltage. For these reasons the indirect method is sometimes used. 18. Indirect Comparison Method. - The scheme differs from the direct method by applying the locally generated voltage directly to the terminals of the receiver with the loop-disconnected. In this case larger voltages are used but the step—up ratio of the 100p must be determined. The latter relation depends upon the resistance and reactance of the 100p. Since the resistance may change with climatic conditions, the step-up ratio must be deter- mined at the time of measurement. Calibrated Receiving Set. - This method has the advantage of simplicity and low eXpense since much less apparatus is required. A superheterodyne receiver is employed and a current indicating device is usually placed in the plate circuit of the i.f. detector as in the other methods. The deflection of the meter is a measure of the field intensity when the 100p is prOperly oriented. The plan is particularly good for relative measurements but may be employed for absolute values by calibrating the meter. Apparatus Designed for Experimental Work. - In the present experiment there is no need for absolute values of field intensity and the only requirements of the apparatus are dependable relative measurements and reproducibility of reading under the same condi- tions. In other words, the receiver must be stable and retain its characteristics over a reasonable period of times. 19. A National NC—AA receiver was selected for the experimental work. Referring to Fig. 2, p.20, it will be noted that this set employee a 6K7 tube as second detector and an AVG with the control grid and cathode acting as a detector. In placing a micro-ammeter in the plate circuit of the tube it was noted that modulation very seriously affects the meter. The meter was then placed in the control grid circuit which would correspond to the plate circuit of an ordinary i.f. detector. In this position, not only was mod- ulation objectionable, but the current change from signal to no signal was so small that no sensitivity could be obtained. Finally the meter was placed in the plate circuit of the second i.f. am- plifer. The dc plate current change in this tube is controlled by the AVG and is, therefore, a measure of the field intensity. While no modulation effects were present, the current change was still too small to give the desired sensitivity. To overcome this difficulty a variable resistance, Rp (Fig. 2), was substituted for the meter and the voltage drOp across it measured by means of a potentiometer. The resistance used is small and does not noticably effect the Operation of the set. The only factors likely to change the overall amplification of the receiver over a reasonable period of time are changes in plate current and in "B" voltage. To keep the plate current con- stant, a small variable l-ohm resistance, Ra (Fig. 2), was placed in the "A" battery circuit in series with an ammeter. It was found that with a plate current of about 1.85 amps. small variations in 20. .N .0...— Illl. ‘ll‘l CubuZQFZPFOl >1? —mZMFZ— ”00.0.1.0"; mwkmfi DAME 80.54.83 .28 Euoxw. . 523mm 3702 24545 925:8 21. either direction do not cause appreciable changes in the amplifi- cation. In the field, however, it was seldom found necessary to adjust the current. In order to maintain the Same "B" voltage on the set at all times a voltmeter was placed across the "B" leads and an extra battery and a variable resistance, Rb (Fig. 2), were placed in series with the ordinary supply. While in constant use the "B" batteries polarize continuously so that more voltage must be added to the set by means of adjusting the variable resistance at each measurement. Finally the apparatus was mounted to make it portable as shown in Fig. 3, page 22. Procedure in making Field Intensity Measurements. - The fol- lowing procedure in making a field intensity measurement is em— ployed. Rb is adjusted until there are 135 volts on the set as indicated by the voltmeter. R.p is then adjusted until the desired range is obtained on the galvanometer and this value of resistance is maintained throughout the field work. The receiver is then detuned. The potentiometer is set at .1 volt and the galvanometer brought to zero by means of Rh' Thus the same condition of the apparatus is obtained at each measurement since the only part that changes appre- ciably is the "B" voltage. The signal being measured is now tuned in and the voltage drop across RP measured by means of the potentiometer. The value of intensity recorded is the ratio of the signal voltage drop to the no-signal voltage drop; thus no units are involved. Fig. 30 Field Intensity Meter. N N 23. Additional Apparatus. - For the measurement of the tilt of the electric vector, a rod antenna was mounted on a horizontal axis which may be rotated by means of a dial (Fig. 4, p. 24). A tuned loop antenna was constructed as shown in Fig. 5, page 25, especially for use in checking the direction of the wave. FIELD WORK IN THE HOWELL, MICHIGAN, AREA. Description of Area. - Since the Howell area is only 33 miles from East Lansing, and presents one of the most interesting geolog- ical problems in the state, it was chosen as an ideal place to carry out a detailed radio survey. Another point of advantage lies in the fact that the area is situated within the: surface wave range 0f several large broadcasting stations. In addition, an electrical resistivity survey of the area has already been made (See reference 10). One of the most pronounced geologic structures in Michigan is a large asymmetrical northwest plunging anticline extending from southeast to northwest across Livingston County. The crest of the fold extends through the city of Howell. There is a gentle north— east dip and a mach steeper southwest dip from the crest. Some controversy has arisen as to whether the structure is a normal fold 24. 4. Rod Antenna. Fig. Fig. 5. \ 0 fl Loop Antenna. 25. or whether the steep southwest dip is the result of faulting, as postulated by Newcombe (11). The Goldwater shale of Mississippian age underlies the axis of the structure and extends eastward across the county. 0n the southwest, because of greater dip, this formation is flanked by the Marshall sandstone, the Grand Rapids series and the Saginaw formation in order. The Goldwater shale is responsible for the zone of low resistivity as shown by Keck (10) in Fig. 6, page 27. The belts of higher resistivity are related to the Marshall sandstone, Grand Rapids series and Saginaw formation. The glacial drift varies in thickness from 50 feet on the west border of Living- ston County to over 150 feet on the east side. Field Work. — It was reasoned that an areal intensity survey might provide more information regarding the relation of sub-surface geology to propagation than could be expected from ordinary radial traverse. All measurements were taken on WJR (750 kilocycles, 50,000 watts), Detroit, because this station gives the strongest signal in the area. Several attempts were made to determine the tilt of the wave and in all cases the electric vector was found to be exactly vertical. The survey of this factor was therefore abandoned. The original plan was to use either the rod or loop on a plane table to maintain a level position. In such a set-up the effect of body capacity was extremely troublesome since it was necessary for the observer to be several feet from the antenna while operating the apparatus. 27. *0.— AREAL RESISTMTY MAP 0 TE m PART or um oowrv. anus-us - Luna 0 m u emu-rut. @‘ ! rm 1 . M' um b Fig. 6. 28. The plan finally adopted was to mount the apparatus permanently in an automobile using an ordinary whip antenna 92 inches long. Although the pick-up under these conditions is less than with a 100p the effect of body capacity is avoided and considerable time is saved in loading and unloading the apparatus. Field intensities were recorded at intervals of one mile or less. In each instance a location as free from the influence of power lines, telephone wires and trees as possible, was selected. In a survey of this kind the time variation of the signal must be considered. In the first place a power variation of 5 per cent is allowable at the transmitting station according to regulation although the actual variation is probably considerably less. It has been shown(5) that intensity is influenced by climatic condi- tions, especially by barometric pressure. Therefore, results with much less than 5 per cent error cannot be expected unless a contin- uous record of signal strength is made at one position while the sur- vey is being conducted or the measurements are made under nearly the same conditions. During the survey several field stations were re— peated either on the same day or on a succeeding day as a check. The results Showing this variation with time are recorded in Table I, page 29. Field intensities at the same location are grouped to- gether when occurring on the same day, otherwise they are on the same horizontal line. It will be noted that measurements taken On May 10, 12, and 13 show variations of less than 5 per cent with the exception of those at field stations 15 and 172 which are prob- ably in error. However, all intensities recorded on May 21 are 29. TABLE I. RADIO FIELD INTENSITY VARIATION_WITH TIME. May 10 May 12 May 13 May 21 ' Sta. -Int. Sta. - Int. Sta. - Int. Sta. - Int. (13) 48 . ........... .. ........ (170) 49 (14) 47 ...................... (171) 47 (15) 49 .............. ........ (172) 53 (17) 49::] (63) 51 (18) 49 (64) 50:] (74) 49....... (122) 50 (70) 52 ....................... (148) 52 (66) 54........................ (187) 54 (67) 50 ....................... (177) 52 (130) 48 ..................... (212) 45 (131) 49 ..................... (213) 45.5 (155) 52 .... (214) 47 (156) 54 .... (215) 49 (157) 52 .... (216) 47 (158) 55 .... (217) 51 30. approximately 10 per cent lower than those recorded on either May 12 or 13. This may be accounted for by the fact that an extremely heavy rainfall occurred 12 hours previously. Thunder showers also occurred later in the day and the survey was brought to a close at this time. The complete list of field stations, their locations and in- tensities are reproduced in Table II, pages 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, and 41. The necessity of choosing proper locations with respect to wires is shown by field stations 61, 62, 90, and 91. At 61 a measurement was purposely made with the antenna within a distance of 10 to 20 feet of numerous telephone wires. The car was then driven across the road to field station 62 where the antenna was about 50 feet away and an increase in intensity of 17.5 per cent was recorded. Practically the same situation was encountered at field stations 90 and 91. In general, it appears that from 100 to 200 feet is a safe distance to avoid the shielding effect of wires. The intensities recorded on May 10, 12 and 13 were plotted on a base map and contoured, See Fig. 7, following page 41. 3 1. TABLE II. RELATIVE FIELD INTENSITIES IN LIVINGSTON AND INGHAM COUNTIES Measurements taken May 10, 1939. Field Station Location Intensity 1 Nw.%, NW.%, NW.%, sec.31, T.4N., RBE. 47 2 NW.%, NW.%, uw.&, Sec.32, T.4N., R.3E. 43.5 3 NE.&, NE.%, NE.%, Sec.32, T.4N., R.3E. 47 4 NW.§, NW.%, NW.%, Sec.34, T.4N., R.3E. 44 5 NW.%, Nw.%, NE.%, Sec.34, T.4N., H.3E. 45 6 nw.§, Nw.§, NW.%, Sec.35, T.4N., R.3E. 48 7 NE.%, NE.&, Nw.§, Sec,35,-T.4N., R.3E. 48 8 NW.%, NW.&, NE.%, Sec.35, T.4N., R.3E. 48 9 NE.%, NW.%, NE.%, Sec.35, T.4N., R.3E. 47 10 NE.%, NE.&, NE.%, Sec.35,'T.4N., R.3E. 46 11 NE.&, NE.}, NE.%, Sec.36, T.4N., R.3E. 48 12 NW.%, hw.&, NW.%, Sec.32, T.4N., R.4E. 43 13 NW.%, NW.%, NW.%, Sec.33, T.4N., R.4E. 48 14 NE.%, NW.&, NE.%, Sec.33, T.4N., R4E. 47 15 33.}, Sw.%, NE.%, Sec.28, T.4N., R.4E. 49 16 NW.%, NW.%, SE.%, Sec.27, T.4N., R.4E. 45 17 NE.%, NE.%, sw.%, Sec.26, T.4N., R.4E. 49 18 NE.%, sw.%, NE.&, Sec.35, T.4N., R.4E. 49 19 NE.%, NE.}, Nw.%, Sec.26, T.4N., R.4E. 47 20 NE.%, NE.%, NW.%, Sec.27, T.4N., R.4E. 47.5 Field Station 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 TABLE II - Continued. NE.}, NE.%, NE.%, NE.}, NE.&, NWot. NE.%, NE.%, NE.%. NE.}, NE.e, NEoi. Nw.%. uw.%, NW.%, NW.}, NE.}, NEG}, NIL}, NE.%, NE.}, SE.%, SE.}, Location NE.%, NE.%, Sec.28, T.4N., R.4E. NE.%, NW.%, Sec.28, T.4N., 3.43. NE.%, NW.%, Sec.29, T.4N., R.4E. NE.%, NE.%, Sec.30, T.4N., R.4E. NE.}, NE.%, Sec.25, T.4N., R.3E. uw.%, NW.%, Sec.25,T.4N., R.3E. NE.%, NW.%, Sec.26, T.4N., R.3E. NE.%, NE.§, Sec.27, T.4N., R.3E. NE.%, NW.%, LSec.27, T.4N., .3E. NE.%, NE.%,' Sec.28, T.4N., R.3E. NE.%, ww;%, Sec.28, T.4N., R.3E. NE.}, NE.%, Sec.29, T.4N., R.3E. Nl.%, NW.%, Sec.29, T.4N., was. NW.%, NW.%, Sec.30, T.4N., R.3E. uw.%, NW.%, 360.19, T.4N., R.3E. NW.%, NW.%, Sec.20, T.4N., R., . NE.}, NW.%, Sec. 2 0,T.4N., 3.33. NE.%, NE.%, Sec.20, T.4N., B.3F. NW.%, sw.&, Sec.l6, T.4N., R.3E. NE.%, sw.&, Sec.l6, T.4N., R.3E. NE.&, SE.%, Sec.l6, T.4N., .3E. $3.5, SE.&, Sec.l6, T.4N., R.3E. SE.}, NW.§, 566.22, T.4N., H.3E. 32o Intensity 47 48 45 44.5 50 48 46 46 46 45 46 48 47 45 46 47.5 47 46 47 48 49 46 Field Station 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 NW'I: NE-i, Nw.§, Nwsi. SE.%, SW‘%9 NEot. Nwoi. NW.%, NW-&. NEoi. NE.%, NE.§, Nwoi. sw.}, SE.§, sw.§, NE.§, NE.&, NE'é: NEot. NE.%, T ABLE II - Continued. Location . 4 ’ II, 8001‘ ww.§, .3. c _ 04, I.) 01 q NW W 4, sec. * 14, T.4h., 3.33. SE.§, sw.%, NE.%, NE.&. NE-l. uw.&, NW 1 .4, SW A s .4, ec.l7 , T.4N., 3.4a. NW'%9 NW-é, NE-t. NW.§, NE.%, sw.&, NE.§, NE.§, NB.&. sw.§, Nw.}, NW 1 .4, Sec.2 3’ Tom. , ROBE. NW-l. NE.§, SE.%, sw.&, sw.&, sw.&, BW.&, Nw.§, NE.&, NE.&, NE.&, NW-%, NW.%, NW.%, NW.&. NE.§, NWO'L 4’ Sec.l4, Sec.l4, Sec.l4, Sec.l3, Sec.13, 580.17, T.4N., T.4N., T.4N., T.4N., m, T.4N., R.3E. R.3E. R.3E. R.3E. R.4E. R.4E. 360.17, TOANO, Rom $80.16, Tel-...”. , R0413. Sec.16, T.4N., 3.4a Sec.15, T.4N., 3.43 Sec. 15, T.4N., R.4E Sec.l4, Sec.14, Sec.l4, Sec.l4, Sec.35, Sec.25, T.4N., T.4N., T.4N., T.4N., T.4N., T.3N., R.4E. R.4E. R.4E. Ram. 3.43. 804E. 33. Intensity 47-5 47 47 47 45 46.5 43 47 43 49 46 47 47 45 48 48 4O 47 51 50 51 Field Station 66 67 68 69 7o 71 72 73 74 75 76 Field Station 77 . 78 79 80 81 82 83 84 sw.%, sw.&, sw.%, SE.%, NE.%, NW2. mt. NE.%, SE.&, SM. SE.}, TABLE II - Continued. SW.§, SE.%, sw.%, SE.}, NE.&, NW’%’ NWo-Br. SE.%, NE.&, NH. NE.}, Location NE.%, Sec.23, NE.%, Sec.15, NE.%, Sec.10, NW.%, Sec. 9, SE.&,Sec. 8, SW.%, Sec. 8, SE.%,Sec. 7, SE.%, Sec.12, sw.&, Sec.12, SW.%, Sec.12, SW.&, Sec.ll, 7.311., 7.327., 7.311., 7.311., 7.377., 7.317., 7.317., 7.317., 7.327., 7.311., TOBN. , R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. Re4E. R.3E. R.3E. R.3E. R.3E. Measurements taken May 12, 1939. sw.%, Nw.&, NW.§, s “-2, sw.§, sw.§, NW.%, NW.%, Location SE.%, Sec. 2, NW.&, NW.%, Sec.12, Sac.12, NW.%, Sec.13, NE.&, Sec.14, NW.%, Sec.24, sw.%, Sec.l9, sw.§, Sec.18, To3N., T.3N., T.3N., T.3N., T.3N., T.3N., T-3N., T.3N., H.2E. R.2E. R.2E. H.3E. ROBE. 34. Intensity 54 50 49 49 52 52 52 50.5 49 49 5O Intensity 45 46 46 48 48 47 44 48 Field Station 85 86 87 88 89 90 91 '92 93 94 95 96 97 98 99 100 101 102 103 104 105 Table II - Continued. 37.3, NWoi. Nw.%. NW-i. Nw.%, SE.&, SE.%, NE.}, uw.e, sw.%, NW-é, SW-i. sw.%, .Nw.&, sw.§, sw.&, sw.%, NW.%, 57.3, sw.%, sw.§, sw.%, sw.§, NE.&, NW-%. sw.§, sw.%, NW-i. NE'i‘: $7.}, SW-i. Location NW.%, sw.&, Sec.18, Sec. 7, NW.%, Sec.7, sw.&, NW-i, sw.§, sw.%, NW-%. NE.%, sw.}, Nwot. NW~%. NE.%, sw.&, NW.&, Sec. 6, Sec. 1, Sec.31, 860.31, Sec. 6, Sec. 6, Sec.32, Sec. 5, Sec. 8, Sec.18, Sec.17, Sec.20, 7.3N., T.3N., T.3N., T.3N., T.3N., T.4N., T.4N., T.3N., 7.37., T.4N., 7.317., T.3N., 7.3N., T.3N., TOBN. , sw.l 4, sw.%, Sec.20,T.3N '9 sw.l 4, sw.%, Sec.21, T.3N 0) NW. 3, NW.%, Sec.21, T.3N., NW.1 4, Mai" $80.16, T03“ . O, sw.%, sw.%, NW.%, NW.%, Sec. 9, Sec. 4, T.3N., TO3N.’ R.3E. R.3E. R.3E. R.3E. R.2E. R.3E. R.3E. R.3E. R.3E. R.3E. R.3E. ROBE. R.3E. R.3E. R.3E. R.3E. R.3E. R.3E. R.3E. R.3E. H.3E. 35. Intensity 47 46 46 44 46 40 45 44 48 49 47 47.5 48.5 48 48.5 48 47.5 47 47 50 Field Station 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 NW.&, SE.&, Nw.&, NW.}, sw.&, NW.%, sw.%, sw.}, sw.%, NW'%9 sw.&, NE.&, NW.%, sw.&, NE.&, NW.%, SE.%, NE.%, SE.%, NE.%, SE.%, TAB LE II - Continued. Nw.&, SE.&, NW.§, NW.1 4) NW.%, NW.}, ‘7 SW04, sw.}, SE.§, NW.%, sw.&, Nw.&, NW.%, sw.§, NE.%, NW.%, NE.§, SE.i, SE.%, NE.%, SE.}, Location NW.&, SE.%, sw.§, sw.§, NW-l. Nw.e, NW.%, sw.%, Sec. 4, Sec.33, Sec. 3, Sec.10, Sec.15, Sec.22, Sec.27, Sec.27, SE.&,Sec.27, Nw.%, Nw.s, 7177.}, NW-%. sw.&, NW.%, NE.§, SW‘%3 sw.%, sw.&, NE.&, NE.}, Sec.26, Sec.14, Sec.11, Sec. 2, Sec.36, Sec. 1, Sec.12, Sec.12, Sec.13, Sec.13, Sec.23, Sec.23, 7.3n., T.4N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., 7.4N., T.3N., T.3N., T.3N., T.3N., T.3N., TOBN. , R.3E. 3.33. 3.33. H.3E. R.3E. 3.3a. R.3E. R.3E. R.3E. 3.33. R.3E. R.3E. R.3E. 3.36. R.3E. R.3E. R.3E. R.3E. R.3E. ROBE. T.3N., R.3E. 36. Intensity 48 50 5O 50 49.5 49.5 47 49 49 49.5 50 48 49.5 49 48 52 50 53 53 51 50.5 Field Station 127 128 129 130 131 132 133 134 135 136 137 138 139 140 . 142 143 144 145- 146 147 SE.%, NE.1 4’ SE.%, sw.§, 5E.&, NE.1 4’ sw.&, sw.l 4’ NE.%, NE.%, NW.%, Nw.&, NE.1 4’ 33.}, 37.5, NW.&, sw.%, NE.1 4’ Hw.l 4’ NW.1 4’ NW-t, TAB LE II - Continued. SE.%, NE.%, NE.%, SE.%, sw.%, sw.%, Nwoi, Nwol, NE.%, N737. sw.%, NE.&, NW.%. sw.}, sw.%, Nwoi. sw.&, NE.&, sw.%, Nw.%, NW.l 49 SE.%, NE.1 4’ SE.&, sw.%, SE.%, BE:-L ¢’ uw.l , 4 ’ sw.§, sw.%, sw.l 4’ NW.1 4’ NE.%, SE.%, Nw.l 4, 890.19, T.3N., R.4E NE.%, NE.}, sw.%, NE.1 4’ NW.1 4’ sw.%, NW.§ ’ Location Sec.23, Sec.35, Sec.35, Sec.31, Sec.31, Sec.31, Sec.31, Sec.30, Sec.30, Sec.29, Sec.29, Sec.30, Sec.19, Sec.24, Sec.19, Sec.17, Sec.18, Sec. 8, Sec. 5, Sec. 5, T.3N., R.3E. T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., R.4E. T.3N., T.3N., T.3N., T.3N., T.3N. , T.3N. , T.3N. ’ R.3E. R.3E. R.4E. R.4E. R.4E. R.4E. R.4E. 804E. R.4E. R.4E. R.4E. R.3E. R.4E. R.4E. T.3N. R.4E. T.3N., T.3N., T.3N., R.4E. H.4E. R.4E. 37. Intensity 50.5 49 49 48 49 49 51 50 52 53 53 52 53 51 52 5O 53 53 53 52 53 Field Station 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 TAB LE II - Continued. Measurem ents taken May 13 1 , 939. NE.&, SE.%, NW.1 4’ NW.1 4’ NW .1. 04’ sw.§, NW.l 4’ Sw.%, sw.§, sw.%, NE.4, NE.&, sw.4, sw.§, NW.}, NE.&, SE.%, NE.&, NW.&, NE.% ,9 NE.%, NE.§, ww.l 4’ NW.1 4’ Nw.l 4’ NW.1 4’ NW.l 4) sw.%, SE%, sw.4, 5w 1 .4, SE.%, sw.1 4’ sw.1 4’ Nw.1 4’ Nw.l 4’ SE.%, NE.%, sw.l 4’ SE.%, Location 4 NE.1 4, S€Col7p T.3N., R 4E NW.%, Sec " .21, T.3N., R 4E NW.%, Sec “8 .2 , T.3N . , H.4E. sw.l ” 4, 880.48, T.3N., R 4E sw.l SE.1 4, 380.33, 1.03130, Rots-E sw.l 4, Sec.35, T.3N., R 4E NE.1 4, Sec.35, T.3N., R 4E 4 I NE.l ” 4’ 890.47, T.3N., R 4E sw.l "' 4, Sec.22, T.3N., R 4E NE.1 4, Sec.2l, T.3N., R 4E sw.l 4’ 860.16, TOBNO, R 4E NW.%, Sec.16, T 3N NEOL O ., Roll-E. 4, Sec. 9, T.3N., R 4E sw.1 4, SEC. 4, T.3N., ROAE 38, Intensity 50.5 53 Field Station 166 167 168 169 170 171 172 173 174 175 176 185 186 187 188 NW.%. NE.}, sw.%, sw.%, NW.%, NE.%, NE.%, sw.%, sw.§, SE.&, sw.%, sw.%, NE.4, sw.}, NE.%, NE.%, sw.&, SE.%, SE.%, sw.%, NE.%, sw.§, sw.%, TABLE II - Continued. Location NE.%, sw.%, Sec. 9, Sec. 4, N.w.&, Sec.9, sw.&, NW.%, NE.%. NE.%, SE.%, NE.&, NEo%. NE.§, NE.%, SE.%, Sec. 4, Sec.33, Sec.33, Sec.28, 86c,27, Sec.34, Sec. 3, Sec.10, Sec.15. Sec.15, SE.%,‘SE.%,Sec.15, NE.%, SE.%, Sec.22, NE.%, SW-fi sw.%, sw.%, sw.%, Nw.%. sw.%, SE.%, NE.4, NW.%, SW.%. NE.%, NW-%. nw.%, NE-%. NW.%, Sec.27, Sec.26, Sec.23, Sec.26, Sec.25, Sec.25, Sec.23, Sec.14, T.3N., T.3N., T.3N., T.3N., T.4N., T.4N., T.4N., T.4N., T.4N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3n., T.3N., R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. H.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. R.4E. H.4E. H.4E. R.4E. 39. Intensity 50.5 53 54 53 49 47 53 52 50 50 52 52 53 54 53 55 54 52 55 54 56 54 52 Field Station 189 190 191 192 193 194 195 196 197 198 199 200 201 sw.%, SE.%, NW~%, NE.%, 33.4, sw.%, NW-%. NE.%, NE.%, NW~%, nw.4, NW.%, NE.%, Nw.%, sw.%, sw.%, sw.%, NE.%, NB.%, SE.%, T . ABLE II - Continued. SE.%, SE.%, NW.%, NE.1 4’ NE.%, sw.§, Nw.l 4’ NW.1 4’ NE.l 4’ NW.1 9’ NW.%, NW.%, NE.%, NW.%, NW.1 4’ sw.}, sw.%, NW.1 4’ NE.%, NE.%, Location NE.l 4, Sec.14, T.3N., l NW04, seCOlB, TOBN. ’ SE.l 4, Sec.13, T.3N., Se.A 4, Sec.13, T.3N., NE.l 4, 86(3024, ToBNo, NE.1 1*, $90.24, TOBNO, 1 SW.4, Sec.12, T.3N 0’ 3.. SE.4, Sec.12,T.3N °’ l SE04 , SBColz, TOBN 0’ NW.1 4’ NW.l 4’ NW.%, NE.l 4’ NE.%, NE.%, NE.%, NE-%. NE.%, NE.%, 2». EE.4, Sec. 7, Sec. 6, Sec. 1, Sec. 2, Sec. 2, Sec. 2, Sec. 2, Sec.11, Sec. 7, Sec. 7; SeC.l8,. T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T.3N., T. 3N., R. 5E. T.3N., T.3N., H.4E. R.4E. R.4E. H.4E. 3.43. R.4E. H.4E. R.4E. R.4E. 3.52. 3.53. H.4E. R.4E. H.4E. R.4E. R.4E. R.AE. H.5E. ROSE. 40". Intensity 53 48 48 49 53 53 49 52 52 52 52 52 51 52 50 52 50.5 51 53 49 TABLE II - Continued Field Station Location Intensity 209 NW.4, NW.%, sw.%, Sec.17, T.3N., R.5E. 51 210 NW.4, NW.%, NW.4, Sec.20, T.3N., R.5E. 53 211 sw.4, sw.%, ..i, Sec.30, T.3N., 3.52. 54 212 sw.,, SE.%, sw.}, Sec.31, T.3N., H.4E. 45 213 SE.%, sw.%, 33.5, Sec.31, T.3N., H.4E. 45.5 214 sw.%, sw.%, sw.§, Sec.33, T.3N., R.LE. 47 215 sw.%, SE.%, SE.}, Sec.33, T.3N., 2.42. 49 216 sw.%, sw.&, sw.%, Sec.35, T.3N., n.4E. 47 217 NE.%, sw.%, NE.4, Sec.35, T.3N., 3.43. 51 213 NW.%, NW.%, NW.4, Sec. 6, T.2N., R.5E. 52 219 sw.,, NW.%, sw.%, Sec. 6, T.2N., R.5E. 52 220 NE.%, NE.%, NE.§, Sec.12, T.2N., R.4E. 51 221 NW.4, NW.&, NE.%, Sec.12, T.2N., H.4E. 51 222 SE.%, SE.%, SE.%, Sec.12, T.2N., H.4E. 51 223 sw.%, sw.%,sw.%, Sec.18, T.2N., 2.52. 51 224 _ NE.&, NE.%, NE.%, Sec.23, T.2N., H.4E. 47 225 NW.&, NW.&, sw.%, Sec.13, T.2N., H.4E. 49 I I I I I I I I I II 4 I 1 V _ .\ r ...r ...u.. w 1 my NV . a .4 .. ., .. x. ..., \ «... 7 . . ,I/ o . I \T; “l.\ A‘\ o C efv .fiatfi’. » IIIIII .1... C a. 5 I' F. . 6 N; V c C o no A. . IIIILIJIIIIIIIIIIIIIIIIIIAIIWI _, . _ VI _ w. 7 . V w C I I I I I it. .1 {it ' f z .1; -.—I | __1___-L———-- 1. . $5M D [I lll'l“ YIIIIIII. 2. fl 5‘ ‘ .I III}... 1k§fld A .w A M. .50 1' -____ ‘49 . f 94+ *‘ .LWMILLE‘ fl [I RADIO FIELD INTENSITES OF W J R , DETROIT 0-1.,st '. | .Qny ./-A 1% IN THE NORTHWEST PART OF LIVINGSTON -COUNTY BY C .J GIBBS fl 2 SCALE-MILES 0 I939 RSE. RAE. R38 EXPERIMENT IN THE CRAPO MINE, SHIAWASSEE COUNTY An interpretation of the results obtained in the field inten— sity survey in Livingston county is not possible without some idea of the depth penetrated by the radio waves. Although this can be worked out theoretically it is advantageous to have experimental verification. The only way to accomplish this is to take under- ground measurements in mines, caves or tunnels. The Crapo coal mine, located about 1 mile west and 2 miles south of New Lothrop, is one _ of the few places in central Michigan where such a situation is possible. The mine is approximately 190 feet in depth. The over- burden consists of glacial drift, mostly boulder clay, and Pennsylvan-- ian shales. All of the overlying material has a low electrical re- sistivity. On May 20, 1939 the field intensity meter was taken into a drift of the mine to a position approximately one half mile from the shaft. vAt this point the only metal present was a 2-inch iron pipe used as an air line. It was impossible, however, to pick up any radio signal although WJR gave a field strnegth of 41 at the surface. If Eq. (9) is solved for the depth at which 99 per cent of the energy of the wave has been absorbed the resulting form is — z = Jae-2 (P/f)% <12) 43. Placing p : 9°1012 abohm-cm., a good average for glacial drift. f : 750,000 cycles per second (WJR) 1 . z : fig; (90.107/75)2 = 2530 cm. - “5.9 m. In other words, 99 per cent of the energy of WJR's signal should be theoretically lost after penetrating only about 85 feet of glacial drift. INTERPRETATION OF THE HOWELL SURVEY. From the results of the preceeding experiment it may be con- cluded that variation of intensity must be influenced mainly by the presence of glacial drift and by the character of the topography. Fig. 8, following page 43, is a detailed map showing topographic and glacial features in Livingston County. In observing the contour map showing radio field intensities, (Fig. 7), the most striking feature is the fingering out of the contour lines in the direction of wave propagation. If the ground traversed by the wave were per- fectly homogeneous the contours, or lines of equal intensity, would be a series of concentric circles. The center of curvature would be located at the transmitting station of WJR situated at Trenton, several miles south of Detroit. The result obtained shows a definite departure from ideal curvature due to shadow effects, produced at particular points where energy subtracted from the wave ..pt .....w.,......._. .3 nu .- » o .r. 9 e. I .5 \ ....“ a... . l‘.‘ c a .. .. . .... ~ V» p 1.. .. . .0 .... - I \I. H _ III", p . . Y . l . . O 2.. .... o a . I . a .. . . . w .‘ . < ‘ » N J .I . i I. .... c u J .. , . , , .1 . é u . . «g h - _ gr...» _ ‘ ‘1 . . ....1 .. . II. .. I. v 2 O raw ‘ n , ..n . .. _ . 5,- . r... . u . w . - , . r m. . J l x r . ... . ...r..1 I. . m . a a .. . .. w. .K/ . :1: . | u h .../Um. _. .. . .. _ . r, . . i (L .. . . 71‘ p. o I « . , . n. I l 1 ,. May . .2 h . ...-7| .. . . -m .. .I. .. .. . . , 1. . . . g . I x .... . .../I - ......) . . . . .2 . . - o 2 . . . . . , . u A. .o r ..L _ ~ _ _ § .u E I A . . _ . 5 a . . :2... L . I. . p . ~ 0 . 1 « Iv!!! . . . 5 t. o ‘ . 2 ov . g o . M L l . . a l a T m" w .. . . . . I. i a... .2. a - .... 1... 1V... . . - . Yb.- '4... . . Q s I. x A Iv. .V‘I a I . in ..u u. 6 . . . .. s . r . f. O n. . mu . . . . . g p..\ . r A ... .. m . . .... . _ ,. .. r . . . . 4.. r .. . . , r .. . . ._ I / ... . . . . , ..= . . ; . fl ._ . . l \ . a. . . . .1. q 55*». AN m pl 0. . L. _ .. . . 26.3. . x. w u . . E . .. .1 ..l . “ ...«o v. 4 .r. .1 faring?“ ......a . ... m . a. _ . . ‘ .. p Y _ .fib U . 1 u m . W . . ... Q. .. ....._b~ ...... n .\.\w..‘>...lup J . II. . r o u . I . I o. . \\ J c. 1 V ...“. ... . ... . z .t . O . r - r ... 1 .. ... .. r“ . . o: t . a" n... m s I I\ no lg. . ................/.o ... . . , . ......2 _ Id ...“. I ”um MAJ“ u — I ... I .\ I J . NUCH ” _ . _ J \ . a . .JVI o . ix... 1 p. . «ab... m Y‘VIVW) .. u n)... ‘ W V...“ m n. c o 9.. ......h .. . .. a ... new... m ... . n ... v .y ' .tI l\ . I” — I ‘1“ I ”"1 1 J ., . J‘. ..... .. ... ... . ..s. J . 34:1."9’ . s V .. mu. ... . . I l I “1. r _ . . .. a 2...._......... ...... .1 . ,. . . . a .. we ..‘no a . . m « .nn. .: . _ - W. . . .... . ... . 4. a 1 I. c . .. ...; . ......q‘. . . . , 4 I . a; ... . .- . 1. .. ... . ..q I. .. ..I. II. a Ii. .0 .IIQIIrlol w II a . . L . .. . ._ . A ... . ”2V _ . o . ... ... - v . B _ . . J .. .u 1 . .... W I.‘v.. I 0 .— . V .- \ 1 K. O. 2. ‘8 n ... . . '11. . .. r. h . ,. u. I .. . II.. . . u . A .. .o o i. . ,. ... ( o . n 6 < 1 TI. . ... ...: 2... 5%.... .2; Q . ... . , . 'v 2.05 . U . c 2 ...: _ 1 .. h 2;... ... I . . c . ' ~ ~ .I _ ... - ... ..1. . 0.... . . m.. u ” .... ... u n .. .....2.....:......... ..w. . .o ... . ..... rafwmnxegr ... . “...—Moo...“ ....w; .a». “....n IIA. ...rumnz‘ .. o . . ... v. . ... // . Ills... . . . «I ...f I: _ i L . .u _ .. .f . ... ..." .. . A . L o. . v. o»..._... ...: .... x. _. ..._. .... .u. .. .I . a .. n . _ _. .. . G. 0. .... .. ... f . . a _ . ... _ ... m o . . . . . ..... 1.7 .. . ............ . .1 .. .. . . . 0 2 .. O. a J F. ‘fi ; A o . I. . 0 MAP SHOWING GLACIAL FEATURES IN THE HOWELL AREA. ESKER E M A K OL‘TWASH PLAIN TILL PLAIN MOR AINE 44. causes the contours to be bent backwards. It will be noted that the 47.5 contour which extends through Cohoctah and Conway Townships shows a configuration similar to that of the 50.5 and 53.5 contours extending through Howell and parts of Handy and Oceola Townships. There is a wide belt of high intensity extending from southeast to northwest across Howell Township. Figure 8 shows that this belt is directly in line with a large strip of till plain situated southeast of the city of Howell. This till plain has a more gentle relief than the moraines flanking it and is beset with numerous lakes and swamps. Since till plain is largely boulder clay, which in this case is well 'saturated with water, the electrical resistivity will naturally be low. Theoretically the combined effect of low resistivity and level topography is conducive to good propagation, low absorption and high field strength. The belt of high intensity is flanked on either side by zones of lower field strength. The readings recorded in section 13 of Howell Township and section 17 of Oceola Township, about three miles north of the city of Howell, show a marked drop in signal strength, suggesting that absorption has occurred near these points. Again referring to the glacial map it will be seen that this particular ' area lies directly behind a large esker and several kames in sections 17 and 18 of Oceola Township. Low intensities nay be produced by eskers and kames in several ways. In the first place, these 45. features are composed largely of stratified sand and gravel, materials of high electrical resistivity which causes electro-magnetic losses. On the other hand, eskers and kames have elevations higher than their surrounding areas and may act more or less as a shield. This latter property would be true of any marked elevation in the path of a radip wave o Another belt of lower intensity extends from the southeast part of Handy Township in a direction about west-northwest. The glacial map shows an extensive area of moraine to the southeast of this zone, including a prominently large kame upon which the State Sanitarium is situated. These features produce a marked shadow effect similar to that associated with the esker and kames referred to above. It may therefore be stated that the field intensity pattern obtained in the northwestern part of Livingston County is the result of glacial and topographic features and that the underlying bedrock produces no perceptable influence upon the field strength. The absence of tilt which should theoretically exist in the electric vector is not easy to explain unless a high dielectric constant is assumed. This might be permissable on the basis that the water table is high in the area during the Spring. However, since the assumption of a value for this constant without experimental 46. verification is not justified no calculation involving BO. (10) will be attempted. This inconsistancy of experiment with theory de- serves further investigation. Since the glacial drift in the Howell area averages about 100 feet in depth and no influence of underlying rock is apparent it would be of interest to run an intensity traverse across a formational boundary where the surficial material is very thin. Referring to Figs. 1, page 2, and 9, page 47, it will be noted that conditions of this nature occur in the region extending south and west through Jackson. On the basis of these considerations the following and final part of the experiment was conducted. SURVEY IN THE JACKSON, MICHIGAN AREA." On May 24, 1939, a radial traverse was run on WJIM (1210 kilo- cycles, 250 watts daytime), Lansing, starting in the southwest cor ner of section 28, Brookfield Township, Eaton County. On approaching the region of Marshall a fading and severe hum of the signal was noted. The hum was definitely associated with telephone wires, although the effect was not noted in other areas. A location was chosen where the noise level was no longer objectionable and the fading was found to be caused by an interferring station which could not be identified. 47. \ 0 8 £8 5 u P 9* t E Ho GHYON I 0 R . L A " n: L " ”5 5 ”PER \ DOMINION or CANADA ’ : ONVO £1. 3 0‘ m €13 3;? t . s ~ - CIBJ _ n“ V vat ‘ “‘v‘ Iv‘, . flat; “file 0,1. /_.4 .. {a s c GHQ IRON Q r I ‘ ~ 8 '\ K‘ ”00 IN ‘ OICKIN SN ACIINACI . ‘ \.‘ "t Cnnmvtt N o A o ‘ | _ ‘I. ..boaf-‘an‘ QmmcmV 1 LEGEND . " 7 ° PB8ISYLVLNIAN ‘ _ 3’. .... CKBO . 1. P - COO-l “OSIWOO >‘3/D. I f Degzsoufi ISL 6‘ uxssxsszrrxu [..- I ' ile- llichigan formation .- /" oiic M inn-Marshall sandstone ,—' ‘9 S \T Mc- Coldwater shale: g 5% iinm \ lb- Antrin(3erea ss ' / ‘ (a... Bodford..m).ls'orth. o i b ‘% Lusum oscooA Q 1 Antrin Ih ' / h C mum ! g u [t xroa ISSAUK sco-uow ' o h an. Traverse limestone / DI- Dundee limestone ' U " u , ‘0 nir-Dotroit River dolomite ! \ fif SA< osctou cunt ouosw ’9’ m 1 SIIDRIAI ' e *0“ Sn—Iackinac limestone :/ I 1" m 9° Bl-Salina salt i m utcosu mama mourn SN-Iviiagaran dolomite line. i “m ° msc 8-811‘11'1“ stone \ ‘ “out,“ 5" oamvxcm “3 Helium onArIOT OIL-Richmond ls. a. sh. .. .’ OCT-Trenton 1s. 8- 601. 5A \II’X’ 3“ °‘ L t 2:.» ' oww '. '75' V CLINTON Qndiermansville «101. a ss ‘ i "a 3‘" CMBRIAN v i mum elm-Lake Superior ss : “um ' I" no“ :6“ L m i wt PIE-WAN .I ‘ ' srcun Ak- Keseenawan ss a lava ' . m mu w m Ah.- Monian.slate..sch1st :1 “it?! "M m 1 CANADA lid—Laurentian granites l r’ . ADC-leewatin schists " cm " Jame" n % '/ Jesus __ ,./ LAKE ............. -— ' N B—;"N—" "“ "....-O 106'- """' ERIE GDLOGIC MAP OF HICHIGAN Generalised tron Publication 39 MICHI GAR GmIDGICAL SURVEY Figure 9.—Map showing the distribution of rock formations in Michigan. 48. Later in the day a similar traverse was attempted on WIBM (1370 kilocycles, 250 watts daytime), Jackson, starting at a point north of Burlington, Calhoun County, but again fading, due to an interferring station, necessitated abandoning the survey. Finally on June 5, 1939, a radial traverse was made on WJR starting at a point one-fourth mile south of the corner of sec- tion 14, Butler Township, Branch County, and following a line through Litchfield and Moscow in Hillsdale County. The results of the sur— vey are shown on the accompanying graph, (Fig. 10, page 49). It will be noted that a marked change in intensity occurs around Litchfield but that in the vicinity of the approximate location of the boundary between the Marshall and Goldwater formations the curve in particu- larly smooth. Therefore, it is concluded that the irregularities in the E—D curve are caused by the presence of the town itself and by topographic and glacial features rather than by the underlying bedrock. Inasmuch as no topographic map of the section is available no comparison between the relation of intensity changes and t0pogra- phic expression can be definitely worked out. However, the character of the glacial material changes appreciably along the traverse and intensity variations may be accounted for in part by changes in the electrical prOperties of the ground. Another source of variation is the possibility of taking measurements slightly off the exact radial from the transmitter. In the latter case pronounced lateral V.’ r , Y . v v v _ I? ' . A A A e o e .e A e ‘— e e a _u A e A A . . . . . . . _ . .. I A A i—e 1 o A A A-.~ e ‘ "'1‘ ¢ a-e o e - s A A - A' o -— . A A - to—O-=—-v o o * - a e -A - .7 Q A A A . A I A . . . A A - ._ . , . , s— C - I A i 6 q I —e 0 -e . — s I - . A . _ , a. L .___.__._.-._ v . 4..--_._.__. g b 9 s I A A e A e v A o e A A e . q . A - A A a — e - s o . A A A o a e 9 e . Q Q . I b a Q A . . I . . A q 0 . . s l a 0 O I ‘ D V O l O i A I D o I O Q I A p . . U ... D C C 0-. C D Q .— . t O T O I 0 ' ' . U ' I D Q ' O C I A O a ‘ - A D l . I A . 9 d e a 9— _o o a e - I I - v A o a A o A . A 4 A _.—..—. ..——.——.-«———o—o—o—§.-.— e-__ ..-—- —fi-——-d—.—. -l 8 a q a e 9— 6 ' q - I 0—- I s e e e o o O - y g .' . A . g . o o . e A e d A l 1 . a } A s . A—. J -e - A I 9 A s 0 - ~ - o A . I A o A e A p - C A n - - O a . e O o O I o A u o 0 A 0—; e e e e 0 I a a . e I t u a - o I s l - e A I A. e I ' n A s . o . . . . ' d g . A e - A - A A I A A e. _— . n—_-.——.——I—-. — ..-_ _—.—.——_o A..— ——————o—-—- "."_——1 7 e — .4 o e A . A I A . _c— v .. u . .4 A A A A A . . ._— O 1 < _ A-A e A I e A . e o e A A A O A A A A A A A I A s Q a o o e I l u - e 7 q, - . < . J . ~ . y - - I s _ . 7— . D-C - -o n—e A I -- e—. L - -.—.———.— - T—oo—o—o 9- — . . I I I r V l - L4 4.4—” +_.L-.._ --_._ - . . .- . » Or.—‘ —. . Q . A . A . A . . A . A A - I a . I + l ’ - ‘ K i I ...fifl..--_. _ . —..-- _T_._._—.._.__.__—_. _— . ___._ -- .._—._ —=. __ l--.._.. A ... —._ .__4 6 _ . ——, . < - o < e A - ‘ n A s I s e - n , s ‘ ~ — _ I » _ _ . _ y~ . -. - .A , A ‘ . . I . . . , A A - A A q A - - - - - o a < —. -— .. e— - O . . 4» ‘i - I ? ..—-—— -¢ —-. ——--o---—e—c—,—--o—~- - - k—o—a~ —9——o— -<—~ - —o -- —a . .-. - -e— -ie —.< .—e——. a A...— A —.-.—e.—.—.—. —-—————4 7.. >__ _ . _ _- . , . . _ . , , . y _ . . i . I.;-.i.. ... ,. . .. - .. ...-..... .. i . I A A - ~ A —¢ . o A . ,_ _ A - A - A ‘ 1' , |. I ‘ f _ g , . .' . , .' _.._._4__. ., ___._..._._.__.'--'.-. -..—.... ‘_._ _. ._ .. ---..- ._ ,_. -. -- - . ..-. ._ .--..._ '._....l.--. ...an -.._._._ -.. .....- ._-__. 5 b , - - A i ‘ . i _- . . . ., - _ — ., - e — . , . . - . . ,_ _- V- o J _—~ .— -— i I J i . 5 . . . i i . , V -*—o— —'————.- — .... -q_—p——.- —_—.———.——.—. —- u— 0 .—.—.—.—- ———o— —.——-.—.——_——_.—o— - .—. -—1 . - 0 ~- A o e- A i I ’ -e— — . ' . — ‘- a--- e -:' -A — V — .- . _ _ ... 5 -= a . ,h _ . I E 3 ' > . - . Eieldlntmsity Sdrfiega__-. _3_._._ .-_~_‘_;_-__.---._'_;_'____-_.__-'_=, .'r*, 1”:.f1"'i:;f 7‘- Across Contac_t_ of . — . 1' .4: .'° ' : t. ~l—0 ~ A . . A . . - Wwfifl 0—0.“... .-—1 0 via 81' OI'IBfithRS - ' s A A - > I . ' . . 7A . . A y A - A -— , . A A ' - a 0 - A . A A A A . A n - I. A A A A o . A - - A . l i . — —.—. —- — -0 p e . . _.,._-—.. . . A A - A I -e- A e - l I—u—9—._-——_.._.-._._._-__-_.__-,_._ _ .__¢,__—.—A——-_—A__-_.‘ - — _ ._ - - .4--_. _....-..A -.J. I -—_.__.—__-—.—_.—.. -~ ...—-....._-_..-.._.___ ..4 3 ‘ - - : ~ - e . . . A A .— . - . I \ — A A A A . A . V v 0 t , l V —'- _ - A s . i— —_.—g. ~—--‘.—.._.-s._.__.__._-—.—-_———.——-—--.—n—.--... — - - o g -—p— V - .- --_ ---—.-—-—-- —n- D . a -- _.--4——+—-——¢—1_-.-~———..—— .- —. ..—A .. ._ 1- -~— -. V -e— . -._. - \ ~ . . ~ v . - 0 Q - - 0 . A A i . ' I - 1 A . . v .— - I » . - A. A . - ..-.— _ A A . . I . _. A . - . ..__..r_-_ A v A—‘ -—+ . _, -..-p—g__—-—-——Q--—. --—. -—_1.u —_. o u “-9- - e ...__. _ . - --—.—-..- 9 cu. - -. .—.—.——.—.—-o—.—--.—. “—0— . ' V O A D A A . . s e A . . . . . . A — . , 0— O s - ' . A - L . A o ._..__.-o —. -——- I. fi { O - C D o I 9 C U ‘— Q I I r s A « I A . A A . A v I - A - .. ' O o A — — e - s v. e u. . e - Q A _e s A .__. ...-*_.-.—__-_ —.—— ..-—.--“ ...__._____ I 7 Q ‘ — O O - ‘ o —_s A 0 Or a A O 7 - A s A e < . A I o u 1 . I A A O . e- A . A A A 1 A y . . . .- A A ‘16 ,‘ - v—e—- I e s A A . < . . . I . O u a - '— _—. -—.—. .. ‘ .---—— —— 1' —¢- 0 O - . ' .c u A e , | I l g I d —. - c a a a - A . s A A e o e A A .. A v . e u -o A v e e— v 0—0 o e e ' e l g 1 .- — -- A e~ 4 o g ‘ . A . A . e A A . .-I 0 g . -a n a - | v — s v I A A A I A -_- a I - A - A A C A A A A 1 e- . A - A A —e A e - —— I ..- - r a O - s e A v o A ' A e - o e o e e e s s e s A - v e e A O V e l . l A e - y o 6 o q A e e e l—o— I - - - - er - A e e A A I o A - A o o A I e —e A o A s I— I l L 1-0 - 0 O I .7. s A s s O -— e e e 1 A s A a ~ -0 I e V A e 4 A A I e a A A -e a o e e 0 ~ I I . I . I ~ 1 Q o I v e e e o I A v o D O a A I A A - l i A s A q o i A ‘1 -4 , v ‘ l _ g I L l l 1 fi— w v ‘v v v I ‘V I , , i I . I —o '-'-O-O . . A I p e e 9 A..— A e o s s e e a i A A - I A a o O . O'- s 0-. . --s t 0 0 -~ I 9 l 0 I v ' I ' I I I I —0-6 s O -1 o -< —o t I Q t 0 ~ 0 O - O o a 0 l I ' 9 ' I-‘ ‘-- I s s I e A s 9 e- —o y e t v 0 e 7 o a A . - , i I ' I | | i I h—f—‘— fi—H—Q-o e o 1 A a A A 4- - a -e--o —e e a A I—» c v a a e o-+ A A e I I I . - . . A o A A-a—o-o -Q A 9A 0 g~e- V e A -——1 i , I I l . ' I Q o 6 A : e 1 0—. o e - A 4 o 0 a $ .-6+t I A I o d o . I «— 5——~»— I A s A A . o A v s o e 0-. e e A- O o e l—«— -4 ' I I I I y L I | I “g l L A l i . 1 ' l ' l 1 L 1 I x A A A q ._ — C A . a—o4~ . _ . _. A 0 . . A A . . . 4, -..4 ‘ - A A -o ' A > A —9 - - - s a A . o A o A v 4 A . i A . A A A . A A A ' A . A , . . . — o _. e A 0- . ' A . . A a A V V o n I _ ‘ 9 A u o A o 0-. A - A _ . I . - A a . - . A e l - I - . - - A A A. A A v I A e—A 5—9 v 0 s 0 - v . a A I A A A l —A —e a-- A-e A e - - '. . - - . o-.‘. A ' - A L _. g§ ...—......” . .__- ...—...“.... . _'. _-_._. _.__._. 1 Ii 8 O - v e n e l o e I A A e s -e I s a A A - ‘ 4 <-A A e A i q ~ —0 s 1 I . A . - - A A A y D . e A A A t c Q A - a e- e t o 4 A < A A A A A ~ A - A c-e A A A —- . . . . A o A . - A A - A -. A -—-1 I e A e I A A A I . I—l . A I A - . A . . . . A y A _o A e— .- A O . i - i . A A i 1 A . _.__ _ __ . . l A i A . l t . . v r v i-A A A A 0 A o A . A Q A A A . D A .~A ' A A I— - I .—. c e . A 1 A A A A A A - f A . A- o g . A A A O 1., . A h u U A — . I ' p 6 1 l ‘ e e s e . A - g o e I e A - l - w o n A ‘ A A _ . A - - I» 9 0-4 A I 2 A 1 - A A o e I A A i s e... A e A A a A o D A A p p e A . u e—o I I A w 4 L 0—. ——-—.— — —.-—-.———1 —~ fi 0 . -‘-—-4 6 - s A a A - . I — - . A a . .- A A - b v » . .. I . .....-.i, I l ...1 . A A I . . —. . . , . _- _ -—‘ ‘~ 1 A , v .— O l ‘ . A A; A n _ -..... . _ -. - .... --....— ._._... ..-—..—-- .._‘- —o—-.—o—— A A . _ , - s —-e ‘ . O A“: o A t b C O ‘ O I O . O s s v — e A e——d —O a . e.o e A A s l—o'. A I A I ~ A 1 O O . s - — —- - if o»t—: A A A v -e e e O - e o s A 0 0A0 0‘0 9 I s l -o n A A I .a 0—. I ~ A - I A Q A o A A A . A b . A e . e '7 ‘10 O A e—e I e A e ‘9’. r: I A O o - - s ' A ‘ —} §-—-e-+ a-AJ . A A A A O . l ' A l >_4—- .»—.__._I , A I 7—9 I I 4 — A H - Q—O— _ 4 - ~ I i. ,i , v I< r u.— < 0 - s O 1 A I v A A I. , 9 o , A - . v - A q A e- s u e A o A s A -- o + A . v» i . A V a A v ‘ r ‘ v 3 ‘fi ‘ 3 ‘ ‘ “ —. _.....-. -a ‘ _— — e——A—~—A e —-.—A—.. —— - ...—o—no— .-4—4—o—c ¢——. - _-_...—.—_..__.....-.q. -6 e o o a A A s A e— . - e A . . . A . - . A - A A y s O Q a I o o I I 0 u e e a - A A A . . g A A A _ o v e o 0 s l O s v o - I - A — A A Q ‘ e A o A A A A A e D a e s - o . o I A A ? A e 9'. A I A A A _.—.-u-—. — . , .—-— ‘ _.._.-- -—_.__-....——.—--.— o—-——--—>- 0—4—- 0— -—-——0 -D-’— 2 Or 0 0 ~ 0 0 s A A - I I A A A 9 A I A . e A . A o A A A -+— o 1 A 0 e A - ~ g e I - o D A I A >7. A Q . l e s e e . A u A I . . . A ‘ ; ‘ ‘ 7 -——-- « q —. _._..—.—-__.._.. .—q——.—.——c—_.. .._.—._—.. W—. ..——_A I—/- o O o A a s t l - e -c- Q A A A q A =3 -e A A . . A - I - A O A .. . .Gmtact: cc v A . - O Q ‘ o e a e 1 e s A e e o ‘ o s A ‘ 0- re. ..e g c 1mg; 0; A . e . 1 . ”f . § I A A A A - o A I A—A Q A e e A l . e u A . ' ' ’ v I v v 4 a O‘-¢‘-fi—I ....—. no. —_. .—_... . .———. ..-...n- -._-_A—-Ao—o— _:—'fii- In. ——A. O O 0- O 0 ~ I - I A a O Q _ e a A u s e A o — . A - Iv s v I ‘ A e + ' A o o . A i A v o d -A i - ~A 9 e A A A A A - 3 - A A A A I A A e A A A A o >- v 1 —‘V f 0 O o -; I A s Iv : O b 0 e- i O A O A 1 v - - t d . A A s A A A A ~ . e a A A e A n e A A A A o I i . A. s A s I I 0 e e e e e o O I A e . e I A A A . . I A . I A A , u g e A - A e A A e . i 1 f i, l f 4 A —. .. .-—— --—._- ..-— .n— _._A- — -. - ..g'o —.—_ ... - —._.—.—4-.—--.-. . .._.-.. F-.. . ' I so 0 - I e s a e A e I A I . e .- A e e A - A A o - A a o O A A I e 0 +—:0 o-o e~o s n e a s 0 . I . o e e I s A ~ - A A . s b A e a e . p e e e plug...I_1_I... . .. .. .. . . .. . .... . .. 10 111-n W1 1 " 'Bastanceimmiew' -' "(iliiiiiii‘n 4 i O .l 2 3 4 5 6 7 8 ‘9 10 ll 12 13 14. 15 16 l7 l8 )— i_. Fig. 10. Radio Field Intensity Traverse in the Jackson, Mich. Area. fi—v A - -.;..o--. 3 I A ...—L-.. A A A A A A A A A A o b .- : o—o A A— A —l -. A _ A-A . A ._ _A . . A . _ r. . A — A .- - _, - \ r A I_ o o A A A A -A— A ~—o A 5 A o o o A . I I A A o - . A . A . A —..I -. A -. A A L A.._._.—. . A A .-o A ~ A I ' - - A A T 1 i Y <.____¢ _ __ -—. A -A.————.—.-.—- -. -— .- o——-‘-—-—-———o-—~—A—c '———Q-—o—o—o—-_ .9 A._;I.. A A O A . o $ . A O .9 ... A-—.. . . A A . A , A + A ' A - . A. A A .A— ‘ A—o— A . A . A A —c - b- A' A ' A A , A — A A A A o A A - A A A A p—n o 9— o A A A - ‘I J I A A A o I - o A A ' A A A A- A A A A L—- A A- A— o A A A a 9" A A A -- Q.- A A A - _I A . I A . - A . , .L—p—fi—‘fi—o “...—.th —.—-..‘—.—o—Q—o—q -.—.——-—o __A I—“-——.--.--' -——— -—._——. -—o—o—--..—__.—- .A—-.— .—.-~—_._.._. 8 —A o o a . l A » I A A A A I A c A A ' — I ‘ A -- I A ‘ - A A A A l 9 o I A A 5 A 9 o . 0 A A A I I o 0 A A A o A A - A A - - A A A .. . . , 0—6 A I A 0 -o— o A ' . A A o I c A O A I c - I Q g I a - I ~ ~ 0 . o o o o D .-_I 0 A A A A A o A A A A A A q A q - x A A A A . A A A A I A A A A I l Y fi .- —--—— ——¥ 7 -, A- o O A A 1 A A A A A I . A A - A A - A o . . .o - A A O - o 0 o o A . A A . A A o - A A I u -- A ;: o I .'_— I A — A A _. . . . I . . . I o 0 0 A .' A-v A c —O —A A -:~ 0—‘ 'o—b o ' - y- .-- ‘ A . A - - A A A ' I . A I l L . ' v ‘ ‘ 1 v | I I4 I-.. H_.—*_. ‘4-1 A ----. ‘ 1 A ‘~. 4- -. _— ‘—A— A A A A A Q D a . A A _ A O A , - , _ .' I I ' I . ' A L + _ _._.._ _._.._._._. J .A_._...-.-._A . --.—.... ...-.A— A ..-.-...—_._--——-_._.__... _-.—.— ._ ._. 6 . . . A. _ A A A A . 4.. A _A ;-A A , - l A - - . - y C - 0 I ‘ o - O ' r - I ~- ' __ ‘v' . .- . , . A A . V . _ I — I a———.—---—— -_~_,_—. ..—.—. .. _ i - A . ....-. 7 __.--._—.—__ =.__ . A ---A A. . - - __ . ..- . "i -_ ,- J —n =_..—.-._.----—. . -.-._A..—_-A -.._ -_ .— A A_-« _ _. A t . L _ _ , A, I i -...~ - - . A . . . - A A i .-.-Q— —- A A A . . I A f I . A Y A >- ‘ A . o - A . - - A _A , I . - o A ' A . A A A —- A r A I . . -— — A - A . ,_ _. , ' 4 ... J I r , ,_ . . I - . -_ v - . . _ _ . _ — .-. I M‘—‘- -— V i ----..— —.-_ n-.. —-— *- ——.-— L—_. -. ¢«-A—._ .- .-.— - ..—_- H— * _Q— .— ..—. ”...—‘fi— *— -_. —————._._A_ —A 5 _ 4 I. . A ' _ _ ._ . . A A . A A - _ , P A A —o A . A '- — A . A L A #— . -o———.—-—-o —.—.— --._ O. _— A A - . . I A — - _ ._ A - A A . I A A A -.-——A—-..—-——A—.—.——n—o—o— ——.—-5 ___—.._.._A— n— ——A I A A _. , __- .-A A A _ _ . . ., . _ A A -A - A — -A A A A A A I — o o I- ~A v~ 5 _ A —- A o - <5 — ‘ — A A A A . 083- _r g - —g A . A A ._ ._ . _ . A . A. _ -A~, - . . .- ,-I-_J_—-I——- ‘ . — A .— . .A I - 7- - . - I A A A A T _ —. A - .- -. .—. v- = c.— _ — __ — - ._ . . , » vTa GI' or filon ‘ ' ‘ - A A A A A - _’ - - 4 , ;. A- .. . . -.I . . A . . A A | . - I A - L A A A -~ _. -1- A A ~ A - A - -_-_ .g .— A I A . .A A A A . A —A A . A I . —t-- - O- I A ~A A A A o .- .-_.—, - ..-- — o -- I A . A- —< - a A- A -— _ - A — A A A . g . o A . ‘i—--¢—-—$-- . ._.— L.__.__A.-_—-_A -_ _‘—_L—_.—-.— -. A— ._-_._ . _.-A-_-...-- . L i l 1 i 1 5 ; ? V 3 - .. . v ~ < — - A A A u A . a 1 - O A — A f . A A A . A . - - » - A A A 1 . . ,- -- ... . . t A . - "-1——.'—‘-°—. A— .—.——"-——r_——-—_.-- -— —. . —¢_A ..I —- -1 -_-o .— 0 - A —---o- A --.—A— — n. u —- -_.. --.—-.—a n -—+. . A 7.. _-t_ . , I. ..._.__A -A, __ . - A . A . . - . A - 7.. . -- . A .. - A _- f.‘ A A - | - A . v -‘ o 7 . _ . ..-.- _ -- > . .A 3 . A . A A A A -—o————$——A— — _._.___i — -—._—$_.- _ .._._L -- 1_--.. , ... A _—— C o -— -—A — A - —-A—._. - _A - _——_ ... - o— ._..-._A-.-- - -._._._._.. .0— . _ I ' - . A 0 ' o o A A . A A . A A I ‘ -— A A '0 A I I ~ 0 O O ' C I O U i Q — . A . A A A o - _ A A A O a O A A - -v 0 I o O A-o . O I —A - l - 1 A - . A A A A _ A A I — 0 ‘ C D C D I -. —‘- O ‘ § 0 I , : I - - t , — 6 o A A A . —A A A o 6 A-. A A I I- - o - q . I A o o o-q O A O I o —v—A A I T I I --A_A A A a O o o—‘- f A A A I i A ' -A t - l >-—r—€--$+ o . l-o Q I A l I A 0 A I I 1 I PJfi—f—P- Q q o g a o l I A A I I j I ' I _A A A 6 A A A A I - A A . A v . ' ! | I E p , A A f 1 A . I __ I A A 1 L L I -‘———T I o - A AA - A . l A ~ A I A A A A A A . ' A A A o A o 4 .. o I A . O . A A . A A A A . A A A . A A - A A . A A A A a A A - A o - - - f r A A I - a- C — — - ‘L - A A I I . -A —-- o— A A A - - - - — - A ‘- + V ——..__A_ - _..——n———A— _— _._-___-.._-—.—.——.—.——b—A_—o — .- A... .. —-—--~‘9 . O—Q- -. o O < I A A --.- A . . A I A I A - - o o v Q q .a 9' -. A q A A . A 0 I ‘- 0-1 n A I v o -o 4— A o A ~ A A A A o O - , 0 I — _a— A—.——.—¢ L J- + A f ‘L +¥r : ‘-O ' i Q . I - I o — D I . 0 a I I O 1 Q T 4, ¢ A 4 9 Q I a A A - o 0 0 Q I o o 0 I - I o—A—I t ‘é_.+ — A t A ' A . A A A A A I o I -I o '1 9.4 ‘ A A A -—a 1 A - A o A o A A —O b A —~ 1 . # Y .._..—— --— A-fi, A 5 wA V ; = A A i 7 J ‘ 0-. I D A A A A A . A l A A 4-. A ' - I O I I 0—9 +- I y .—+.—J ‘ y ‘ o A ~ A A A A A A A A A . A . - I I I ‘ O I— 0—1 0 fi 0 Q A - ' . - - . A . A . . A A . .L A "1 «hi. -. ~ , . ~ _ ‘ . I l . .——-—.—.—. .—— —._. v 1 4 O A n A “v4 ‘7 4‘ A A 4 A . —4A——o—— ‘ --.- . 1 V ....._._-— A—--¢—_— -. - .—- .- r-—AA b-AA . . - A 4‘ ¢ A _ -_. '4’ . . A . ‘4" ‘ ...--.-_A ...- — _A— . —— .— - _— _‘A--—.—o--._ ,.___._ A 0 1 O I I I 411 J , . . - . ._ . —A to- ~ . I *- - y A 0- 0 . A V I O O I A“ —--— f A 0-. A A - A I . A A - A .‘ .. . A A _4- , o I . I I I A A ' -. _ I A 40 A: A- A I - - A —. Y A I I r, g . A L A *0 A c—-¢ o A O A A A A I Q 6 9 O 0 o I i o -- ‘ Q 4 O C 0 .— ._.- 1 A l I ' I ‘4‘. f-o o 6 o o A A A . ‘ 0-? O rug—0 o 1 A A A : . 30 A A A A I A A ' A A . A A _.A , L ._.' .--f.. , . v - , I ‘ ' I O A A-q _L- OE , A _- -_-_A_- . A , A . . ‘ -a I 0 - - A 1 1 . A_ - . ---. __AA-d- . . ._ .. .-.—---..-._._._..--_. -__._..___...__.-. b... . . . A A . . A A - - ~ A A - A A ~ L - A A A Q j—- A A . A A A A A I A- H4 4 I }< -‘ A - A A A -.. . _I-, »_¢ ‘ 4 A _i . ‘ . - -- . A - A A 4- 1 I O —o— —o - -—. ——.-—.-¢—-_¢.—A A .— A4—4——- .-- -.-— o—o— o—a—A—P—a—A- - - — I- '9 .4 0-4—4 1 L I I A A A I, A H 9 A v A ' o I . A . A - A A - O O D—Q A A A I v 1 l A . A A . A A A A.— I A . A I - q o 4 A A A A A A A .I . . — A . A A . l A A 4 v A ..-. .- _-—- —--_—..__ -.. A - ..-.._—.._. ‘- .-. -_.—. -.-,.,_.__._.__.- A.-—_A-. 4—4- 4—4 A A . A A I A A A A A A o A o A ' A A A I A A - ' ' A A A A A A - I 0 c A A A A A I I - o - A 1 A A A A - A A A o ' o .I O- I 0 —A r o ' .‘ 1 ‘ —. n . h-—.---——o—.—. -— .-. ... - g I in 0-. ‘——-—Q—-— 2 A- —>- A A A A A A A A . A !- o-I I A I 1 I A I 1 A . A . A A A . A A A >— ‘ I Q A I A I A . A A A A A A A A A L—f v v 6 O O 0 A o A o- A A A A . A A . v I o -o I I J Viv r -—_-—._._. o—a——-—--—.—-- ...—o L r v - I O o A ‘ A A A A A q- - - . A A A A - o - o A O I — A o I A A A A 0 Ace . A - , I . A A A A . lfi—l A A A vi 0 A o ”a g A o e 1- 0 0g cmg o ' ' ' ' ' ' -}-I I . . .. A- A A A . O A A . A A A . -I A » A A A v f t v v v i ‘ v i v A g g | V —*—‘Y— —H--—p—-o-~ u---.-.—A—o—_——..—A—.——.— . ———-.—J- A 6 A A o A g A A A A A . A . A A A . A A A . . A I A A - 0 o A A O ‘ I 6 a l I 6 i A O A O 0 I I O Q A ' A Q a A o O A v a ' I o A I O A I I 0 l 0 0 v 0 O ' - .0 $I'f9—d-o—y 0 —O—Q‘?.O|~4 -' oo-A-A |~ AA AAA. A AAA Ago... A AAA-Aoooooo. ‘ l . I L— A A A A O l A A—. f A A 4 A A A A A A A A A v A A A A A A A A A . A A o A A A A A A . A l ' . .- 1 v v v __v_+ i A __ ... .——- .h— — u. u —_ ' AAQ—u—o -—.—- g ._ g o -_._—o- I u-o-—. —-A—o—-o -- O .-'—— —— —.—.-< I I—0 A O A A z A A 0 ~ A o A A A g A ‘ o A A A A A A A A I A A 6 A A A A o O >— o o a A " o .—o A .-c 1—D A A A I - I A v A A - A A A I A u A . A A A y o A A A A A A > A I—qL 0 q -1 o . o A A . A o n O 0 A1 - I A I Q I a . 0 O o C I I v I l a U 1 A fi- ~~[v-T—Brstancq (In-filled) " "'°"""1’I11 IO 1 l [I 1 r; l I U 1 L 11 l i A A. A ' AAA—A A A I L L 1 A l l I l 1 I I I T 111 012 789101112131415161718 Fig. 10. Radio Field Intensity Traverse in the Jackson, Mich. Area. 50. changes in field strength such as those shown on the areal map of Livingston County may be encountered. The conclusion is reached from results obtained in the Jackson area that even in regions where the material overlying bedrock is relatively thin: that field strength changes are primarily the result of surface effects and have no significance geophysically. FIELD IKTEXSITIES IH BRAHCHnAED HILLSDALE'CCUYTIES Field Station 1 2 10 11 13 14 15 16 17 18 19 2O 21 TABLE III Measurements taken June 5, 193 Location HE.i, Sec.14, c.5s., :E.;, Sec.13, T.5$., .;.fi, Sec.18, T.ss., sw.§, Sec.9, T.SS., NE.4, Sec.16, T.53., sw.;, Sec.10, T.5$., SE.$, Sec.10, .55., SE.%, Sec.11, T.58., ss.;, Sec.12, T.SS., sw.i, Sec.7, T.58., sw.g, Sec.8, T.5S., 33.3, Sec.8, T.SS., 53.4, Sec.9, T.58., sw.g, Sec.11, T.SS., ss.fi, Sec.11, T.ss., SE.i, Sec.11, T.ss., Ln.%, Sec.7,. T.SS., NE.%, Sec.8, T.SS., KE.%, Sec.9, T.58., NE.§, Sec.11, T.SS., Ln.%, Sec.11, T.SS., NB.%, Sec.12, T.5$., R. 4"”. R.4W. R. 4.1". R. 4W . R.3W. R.3W. Intensity 24.0 27.0 29.6 30.0 29.0 31.6 32.6 33.5 33.7 33.0 34.8 37.0 34.0 41.9 51. : Lower Peninsula of Michigan. (A ft» r Luv" 1'" Q. L) 52. CONCLUSIONS AND SUMMARY. Wayl's formula (Eq. 8, page 13), for the attenuation of radio wave shows that the geologic factors influencing field intensity are conductivity and dielectric constant of the ground. On Fig. 11 is shown the distribution of glacial moraines in Michigan. These features, composed largely of unstratified drift, are interspersed with till plains, consisting mainly of boulder clay, outwash plains, eskers and kames, made up principally of stratified sand and gravel. As a result the surficial material in Michigan varies considerably in its physical character and, therefore, in its electrical properties. This lateral variation in the ground constants is responsible in part for changes in radio field intensity. In Summary, theoretical and experimental studies of radio re- ception which have been made in the areas of Michigan covered in this report prove definitely that the mantle of glacial drift together with topographic features are the controlling geologic elements affecting field strength of radio Signals in the broadcast bani.‘ No influence of underlying bedrock was encountered since the pene- tration of the radio waves is apparently limited to a depth much less than the average thickness of the glacial drift in most areas. 53- ---—- / . x \‘17 .J‘ {3* Hal .uVI, T Fig. 11. Distribution of Glacial Moraines in the Lower péninsula of lichigan. ; . I) Q 0' ‘ 2’ '