THE UNIVERSITY OF MICHIGAN'RESEARCH INSTITUTE ANN ARBOR STUDY OF INPUT CIRCUITRY OF DIRECTION FINDER SET AN/TRD-4A Technical Memorandum No. 77 Cooley Electronics Ieboratory Department of Electrical Engineering By: C. E. Lindahl Approved by: H. W. Farris Project 2899 TASK ORDER NO. EDG-10 CONTRACT NO. DA-36-039 sc-78283 SIGNAL CORPS, DEPARTMENT OF THE ARMY DEPARTMENT OF ARMY PROJECT NO. 3A99-06-001-01 July 1960

TABLE OF CONTENTS Page LIST OF ILLUSTRATIONS iv LIST OF TABLES v ABSTRACT vi 1. INTRODUCTION 1 2. DESCRIPTION OF THE INPUT SYSTEM 1 3. ADCOCK ANTENNAS 6 4. MEASUREMENT METHODS AND CALCULATION PROCEDURES 10 5. BASE-LOADING RESISTORS 18 6. TRANSMISSION LINES 18 7. ELECTRICAL GONIOMETER GO-5/GRD, SER. NO. 179 20 8. TRANSMISSION LINE-RF SWITCH COMBINATION 22 9. RECEIVER INPUT IMPEDANCE 22 10. SUMMARY AND CONCLUSIONS 24 DISTRIBUTION LIST 25 iii

LIST OF ILLUSTRATIONS Page Figure 1 Block diagram of input circuitry 2 Figure 2 Plan view of antenna configuration for low (0.5 mc to 10 mc) and high (8 mc to 30 mc) frequency ranges 3 Figure 3 Base-loading resistor diagram 3 Figure 4 Electrical goniometer GC-5/GRD 5 Figure 5 Electrical goniometer GO-6/GRD 5 Figure 6 Circuit diagram of RF switch in goniometer operating position 6 Figure 7 Input impedance of AN/TRD-hIA low-frequency antenna 7 Figure 8 Input impedance of AN/TRD-4A high-frequency antenna with base resistors 8 Figure 9 Input impedance of AN/TRD-4A high-frequency antenna without base resistors 9 Figure 10 Th~venin equivalent of a linear antenna 10 Figure 11 Block diagram of north-south input system 12 Figure 12 Linear, passive, bilateral network 13 Figure 13 Equivalent circuit of two-wire transmission line 16 Figure 14 Summary of transmission loss calculations —transmission loss vs. frequency 17 Figure 15 Base-loading resistors —transmission loss vs. fre_ quency 19 Figure 16 Transmission lines —transmission loss vs. frequency 19 Figure 17 Electrical goniometer GO-5/GRD, ser. 179 —transmission loss vs. frequency 21 Figure 18 Transmission line —RF switch combination —transmission loss vs. frequency 21 Figure 19 Input impedance of radio receiver R-390/URR 23 iv

LIST OF TABLES Page Table I Transmission loss as a function of frequency 18 Table II A, B, C, D parameters and transmission loss as a function of frequency (transmission lines) 20 Table III A, B, C, D constants and transmission loss as a function of frequency (goniometer) 20 Table IV A, B, C, D parameters and transmission loss as a function of frequency (line-switch combination) 22 Table V Receiver input impedance as a function of frequency 24 V~~~~~~2

ABSTRACT A study is made of the input circuitry of the radio direction finder set AN/TRD-LA. This circuitry consists of the antennas, the antenna connecting cables, the goniometers, and the transmission lineRF switch combination connecting the signal goniometer to the receiver. One objective of this study is to determine the effect of each component of the input system on the power finally delivered to the input impedance of the receiver; hence, transmission loss calculations based upon experimental measurements were made for each of the components. In conclusion it can be said that the overall transmission loss could be decreased significantly by matching impedance levels throughout the system. vi

STUDY CF INPUT CIRCUITRY OF DIRECTION FINDER SET AN/TRD-4A 1. INTRODUCTION A study was initiated concerning the input circuitry of the AN/TRD-4A direction finder, namely, the antennas, the antenna connecting cables, the goniometers, and the transmission line-RF switch combination connecting the signal goniometer to the receiver. The reasons for this study were twofold: 1) to become familiar with the AN/TRD-4A operating as a direction finder; and 2) to study those components which are critical factors in determining the equipment sensitivity. The methods used in the study and the results obtained follow. One of the objectives of this study was to determine the effect of each component of the input system on the power finally delivered to the input impedance of the receiver. 2. DESCRIPTION OF THE INPUT SYSTEM Figure 1 shows a block diagram of all the components of the input system of the TRD-4. The Adcock antenna system consists of two vertically-polarized U Adcock antennas placed as shown in Fig. 2. Each U Adcock antenna consists of two monopoles erected over a counterpoise used to establish a satisfactory ground plane. The spacing between the monopoles and their heights depend upon the frequency band to be covered. The low-frequency band covers from 0.5 me to 10.0 mc; the high, from 8 me to 30 mc. The

NORTH BAS E-LOADING TRANSMISSION FROM GONIOMETER ANTENNA RESISTORS LIIDADRIVE MOTOR SOUTH BASE-LOADING TRANSMISSION LO ANTENNA RESISTORS LINE SIGNAL TRANSMISSION RF TRANSMISSION GONIOMETERLNESITH LIE ECEIE ANTENNA RESISTORS LINETCH LINI WEST BASSE- LOADIN ~JG TRANSMISSION ANTENNA RESISTORS LINE FIG-1 BLOCK DIAGRAM OF INPUT CIRCUITRY

DIRECTION OF ARRIVAL OF RADIO WAVES ASSUMED IN THIS REPORT N N W E W E 33' ) t, (- ee'-lo" + + — S I I I s 33' L 18-10"- a) LOW FREQUENCY RANGE b) HIGH FREQUENCY RANGE FIG.2PLAN VIEW OF ANTENNA CONFIGURATION FOR LOW (O.5MC TO IOMC) AND HIGH (8MC TO 30MC) FREQUENCY RANGES TO ANTENNA I 20 f TO TRANSMISSION LINE oon FIG.3 BASE- LOADING RESISTOR DIAGRAM

required spacings of the antennas for these bands are shown in Fig. 2. The height of each monopole used in the low range (0.5-10.0 me) is 29 feet with an antenna top-loading disk on each. In the high range (8-30 mc) a height of 22'-4" is used. The base-loading resistors are located in an antenna coupler unit fastened to the base of each monopole. The circuit diagram is shown in Fig. 3. It is understood that the purpose of these resistors is to damp-out antenna resonances which cause bearing errors. The matched transmission lines connecting each monopole to the signal goniometer consist of 170 feet of RG-13A/U coaxial cable. Two types of signal goniometers are used. The type GO-5/GRD electrical goniometer is used in the frequency range from 0.5 mc to 10 mc; the GO-6/GRD, from 8 mc to 30 mc. Figures 4 and 5 show the circuit diagrams of these devices. The purpose of these signal goniometers is to combine the signals from the antennas in such a way that the output consists of only two side bands with the carrier signal suppressed. After the resultant goniometer output is passed through the receiver of the direction finder and the signal is demodulated in the azimuth indicator, the bearing of the incoming wave can be determined. The transmission lines connecting the goniometer to the RF switch and, in turn, the RF switch to the receiver, consist, respectively, of 2-foot and 3-foot-5-inch pieces of RG-22B/U coaxial cable. The RF switch is used to switch from a signal goniometer mode to a single-loop operating mode and vice versa. Figure 6 shows its circuit diagram when switched to the goniometer operating mode.

R401 R405 R402 500 <51 <500 J 401 L401 J402 " I NT401 J40 R403 I UNLESS OTHERWISE SHOWN, RESISTORS ARE IN OHMS, CAPACITORS ARE IN UUF. 2. SWITCH VIEWED FROM KNOB END ADGOCK FIG.4 ELECTRICAL GONIOMETER GO- 5/ GRD R RSOI 5 R505 < R502 750 51 <750 J5K01 501 JSO2 S O SJ50S3 R503 T501 _ K0 O: 750'Ao_ K5 01 ROTARY TRANSFORMERJO 750 R508 L503,N. 4 1 UNLESS OTHERWISE SHOWN, RESISTORS ARE 4 OHMS, CAPACITORS ARE IN UUF. 10 PS 2 SWITCH VIEWED FROM KNOB END 51 S501 S SENSEI FIG.5 ELECTRICAL GONIOMETER GO-6/GRD ~T501 K501~~5

FROM GONIOMETER (a TO RECEIVER GONIOMETER FIG. 6 CIRCUIT DIAGRAM OF RF SWITCH IN GONIOMETER OPERATING POSITION. 3. ADCOCK ANTENNAS The impedances of both the low- and high-frequency antennas were measured, and the results are shown on the Smith charts of Figs. 7, 8, and 9. Since the base-loading resistors are connected physically to each monopole, an impedance measurement was taken with and without the loading resistors connected. All impedances were normalized to 74 ohms, the characteristic impedance of the RG-13A/U connecting cables. An equivalent circuit of a linear antenna can be derived by Thevenin's theorem. Such an equivalent is shown in Fig. 10, where Za equals the antenna impedance as measured above and V equals the open-circuit voltage across the antenna terminals when an electromagnetic wave impinges on the antenna. In order to relate the voltage, V, to the electromagnetic wave, we can define the effective height, h, of the antenna which equals the ratio of this voltage, V, to the magnitude of the electric field intensity, E, where V is in volts and E is in volts/meter. It is 6

IMPEDANCE OR ADMITTANCE COORDINATES FREQUENCIES ARE IN IMPEDANCE OR ADMITTANCE COORDINATES o WITH BASE RESISTORS MEGACYCLES / SECOND ~MEGACYCLES /SECOND 0X WITHOUT BASE RESISTORS T0. ~ ~ ~ ~ 03o. 3 d~o /0.o s 3 o.: a-,'. CY q" 2~ 2. ~b g o- 0.0 000 q'%000 COMPONENPT INDUCTANCE OCOPONF Zo= 74iN, o 3.0~~~~' 0~~~~~~~~~~~~~~~' b0~~~~~~~~~~~~~~~~~~~~~~~~~~ o~~~~~~~~~~~~~~~~~~~~~~~~~~~~/; oO./o!c' LOW FREQUENCY ANTENNA. -P o 4.0;3, ~~?d'c~~~~g`~ ~~~~~~~ o~~~~~~~~~~~~~~~~~~~:7.~~~~~~~~~~~~~~~~~~~~~~~. ~-~~~~ Y 1JoCY0 2 o~~~~~~~~~~~~~~~~~~~~~~~~~~ s- 0 Cy f 00 0 8 (p co o, N 9 7~~~~CNTE r1Ct 71$VO 7,N-1 P.13 33 16 25 JN 14 1AMEACHR FI. NPT IPDAC F ANTD 4 a D~~tT~.CE COMLOW REQUENCY ANTE N NA

IMPEDANCE OR ADMITTANCE COORDINATES 0.12 0.813 ~ j o./ or o q r,,, c, O,,. O,...,... 0 A FIG.8 INPUT IMPEDANCE OF AN/TRD-4A HIGH CFREQUENCY ANTENNA WITH BASE RESISTORS. / o,o.... FREQI II I I UENCa 2 Y I I II R E S ISTORi. FREQENC ANENN WIT BAE RSISORS

IMPEDANCE OR ADMITTANCE COORDINATES 0.12 0.13 OAO 0:l 0.3 ~)' S ^ s R AD IALLY SC ALE PARAMETERS I Z sS' B a o ~ o 3 q w o i N _ o o o 0o;,,0~o 2, \~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ \'-~~~~~~'P n F | 0L~~~~, o o' o ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~eo~ FREQUENCIES ARE IN MEGACYCLES/ SECOND FIG. 9 INPUT IMPEDANCE OF AN/ TRD-4A HIGH FREQUENCY ANTEN NA WITHOUT BASE RESISTORS. ZO o=: T46 o~O P 00oQ:" 0~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'$ 0~~~~~~~~~~~~~~~ o" o S~~~~~~~~~~~~~~~~~J~~~~~~cZ; o~~~~~~~~~~~ o p O~~~~~~~~~~~ 1ot'' fil a% 00 -3, & 2 00'd o FIG. 9 INPUT IMPEDANCE OF AN/ TRD-4A HIGH FRQUNY NFN AWIHHTRAFRF.1 onR(

ELECTROMAGNETIC 7 WAVE I,ZA tv t f vt FIG. 10 THEVENIN EQUIVALENT OF A LINEAR ANTENNA. assumed that E is vertically polarized. The best way to determine the effective height is to measure it experimentally if suitable field-strength measuring equipment is available. However, this not being the case, this report treats only the input system components following the antennas. 4. MEASUREMENT METHODS AND CALCULATION PROCEDURES The results stated were all obtained by the measurement of various impedances. From these pertinent impedance values, calculation procedures were used to obtain the desired result. As stated above, one of the objectives was to determine the effect of each component of the input system on the power finally delivered to the receiver input impedance. In order to do this, certain assumptions had to be made. These were: 1) all components are linear within their normal operating ranges; 2) the transmission lines between the base-loading resistors and the signal goniometer are selected so that their electrical characteristics are identical, as are the base-loading resistors themselves; 3) the monopole antennas are identical; 4) the base-loading resistors are resistive throughout the 10

frequency range used; 5) the north-south, east-west, and output terminals of the signal goniometer are balanced with respect to ground; 6) the transmission line-RF switch combination between the goniometer and the receiver is balanced with respect to ground; and finally 7) the receiver input is balanced with respect to ground. The above assumptions were verified within the experimental accuracy of the measuring equipment used. The input system can be divided into two parts, the north-south system and the east-west system. Throughout all the measurements it was assumed that a signal was arriving from the north as shown in Fig. 2* The signal goniometer rotor was locked in such a position that its output would be maximum when a wave arrived from the assumed azimuth angle. Under these conditions the voltage developed at the goniometer output by the east-west U Adcock is zero; hence, we need consider only the northsouth antenna system. Since the east-west and the north-south systems are identical, analysis of only one of them is necessary to determine the system behavior. The system analyzed is shown in Fig. 11. In order to determine how power is transmitted from the output of the antennas to the input impedance of the receiver, one must first know how each ccnponent of the system alters this power transfer. One way of doing this is to measure experimentally the open- and short-circuit impedances of the comnponents and then from these measurements calculate the A, B, C, D parameters of each component part. The A, B, C, D parameters are defined by the following equations describing the behavior of the linear, passive, bilateral network shown in Fig. 12. 11

I5 TRANSMISSION LINES ZA F I r —— I —-1 ) z~~~~~~~~~ A~~~~~~ 14 I a 12 _ _ _ _ _ _ _ I~~ I,, r........,.~ E -I I 5 3 v ~ ~ ~ ~ ~ ~ ~ ITRANSMISSION T SIGNAL LINE-RF ZR RECEIVER E4I AT BT CTHOT P S EM F5' T T3GOIOMTE 2 SWITCH I n,~~~~~~~~~~~~~~~~ G I E R COMBINIIVAT ION ~cr~ I C.,, D Zn I VS-BASE LOADING RESISTORS F II II.1 OKOI O OT-OT NU YTM

Est AB,CCD tE 1 2 FIG. 12 LINEAR, PASSIVE, BILATERAL NETWORK. Es = AER + BIR (1) IS = CER + DIR (2) where ES and IS are, respectively, the voltage and current at the sending end of the network and ER and IR are, respectively, the voltage and current at the receiving end of the network with the assumed voltage polarities and current directions. The A, B, C, D parameters can be found from the image impedances and the image-transfer constant of the network. These quantities, namely, the image impedances and the image-transfer constant, can in turn be found merely from open- and short-circuit impedance measurements taken at both the sending and receiving ends of the network. The following equations were used to determine the A, B, C, D constants from open- and shortcircuit measurements of each component: ZOC1 = open-circuit impedance looking into end 1 with end 2 open-circuited. ZSC1 = short-circuit impedance looking into end 1 with end 2 short-circuited. ZOC2 = open-circuit impedance looking into end 2 with end 1 open-circuited. ZSC2 = short-circuit impedance looking into end 2 with end 1 short-circuited. 13

ZI1 = image impedance looking into end 1. ZI2 = image impedance looking into end 2. e - image-transfer constant. zn 1 ~Zocz Zsc (3) ZI2 = o2 zSC2 (4) = tanh1 ZSC = n + OC1 (5) ~z 2 zCl zoo1 A OC1osh- (6) z12 A = / I coshe (6) i ZI2 D - A coshe (7) B = Z/1 ZI 2 sinhe (8) C - sinhe (9) The following steps necessary to determine the A, B, C, d parameters are listed in summary: 1) Determine experimentally the open- and short-circuit impedances looking into both ends of the network. 2) Calculate the image impedances from Eqs. (3) and (4) and the image transfer constant from Eq. (5). 3) Then calculate the A, B, C, D parameters from Eqs. (6), (7), (8), and (9). After the above has been done, we can determine the transmission loss caused by each component of the transmission system from the equation: 14

Re(ESIS) Transmission loss = 10 log10 - (in db) (10) Re(ERIR) where Re( ) indicates the real part of the quantity within the parentheses and I equals the conjugate value of the complex current. To apply the above theory to the system shown in Fig. 11 after the receiver impedance has been measured and the A, B, C, D constants for each component calculated, a voltage, E1 is first assumed. Then, knowing ZR, we can calculate I1. From the A, B, C, D parameters E2 and 12 can be found. Equation (10) is then applied to find the transmission loss caused by the transmission line-RF switch combination, and so on until the antenna terminals are reached. The transmission lines between the signal goniometer and baseloading resistors and the resistors themselves deserve special mention. Essentially they are in themselves unbalanced devices. However, the two transmission lines will be considered together as being one balanced component; likewise, the resistors at the base of the north and south antennas will be lumped together for the purposes of analysis and will be considered as being one balanced component. If we know the A, B, C, D constants of an unbalanced device, we can calculate the constants, At, Bt, Ct, Dt, of two of these unbalanced devices connected in a balanced configuration. Indeed, it can be shown that At = A, Bt = 2B, Ct = C, and Dt = D. A word should be said about measuring balanced impedances with respect to ground with an unbalanced radio-frequency impedance bridge. A two-wire transmission line can be represented as in Fig. 13. Since Z= Z2 in the balanced case, only two different impedance measurements need be made to determine Z1 and Z3. From these measurements we can calculate the

FIG. 13 EQUIVALENT CIRCUIT OF TWO-WIRE TRANSMISSION LINE. equivalent balanced impedance from A to B. This equivalent balanced impedance was the one used above in all the mentioned calculations. First, A is shorted to B and the impedance measured from this point to ground, G; call this impedance ZABG. Next, short B to ground, G, and measure the impedance from A to ground; call this impedance ZABG. It can be shown (ZAB.G) (ZABG) that the impedance between A and B, ZA-B = 1 ZAB-G- ZA-BG Clearly, the determination of the transmission loss of each component in the input system is a long and laborious process, but it has some rewards. By knowing the A, B, C, D constants of each component, we can calculate how the component will behave when placed in an entirely different system. Also, two devices designed to perform the same function can be compared by knowing the constants of each. The constants calculated above for each component are tabulated below under the appropriate headings, and the transmission loss calculations are summarized by the graph of Fig. 1l for the low-frequency range from 1.00 to 10.0 megacycles. 16

22.0 20.0 18.0 TOTAL TRANSMISSION LOSS - 16.0 Z 14.0 n 12.0 f BASE-LOADING RESISTORS Mn 12.0 0 -J o 10.0 Fn 8.0 6.0 TRANSMISSION LINES 4.0 GONIOMETER GO-5/GRD 2.0 TRANSMISSION LINE -RF SWITCH,COMBINATION 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 FREQUENCY (IN MEGACYCLES / SECOND) FIG. 14 SUMMARY OF TRANSMISSION LOSS CALCULATIONSTRANSMISSION LOSS VS. FREQUENCY 17

5. BASE-LOADING RESISTORS The base-loading resistors were assumed to be resistive throughout the frequency range used. The A, B, C, D constants are: At = 1.4, Bt= 400, Ct = 1 X 103, Dt = 1 The contribution of the base-loading resistors to transmission loss as a function of frequency is given in Table I and shown graphically in Fig. 15. TABLE I TRANSMISSION LOSS AS A FUNCTION OF FREQUENCY Fre qu ency Transmission (megacycles) loss (db) 1.0 7.44 2.0 9.27 4.0 5.70 6.0 5.37 8.0 16.99 10.0 8.39 6. TRANSMISSION LINES The A, B, C, D parameters for the transmission lines and their transmission loss as a function of frequency are given in Table II. A curve of transmission loss vs frequency for these transmission lines is shown in Fig. 16. 18

12 m3 aII ao 9 un 8 cn3 0 7 - I z 6 5 (1) cn 4 E (1 3 Z: 2 I0 t 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 FREQUENCY (IN MEGACYCLES /SECOND) FIG.15 BASE-LOADING RESISTORSTRANSMISSION LOSS VS. FREQUENCY 3.0 z 2.0 VC) 0 -J z _~ 1.0 zE I0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 FREQUENCY (IN MEGACYCLES / SECOND) FIG.16 TRANSMISSION LINESTRANSMISSION LOSS VS. FREQUENCY 19

TABLE II A, B13, C, D PARAMETERS AND TRANSMISSION LOSS AS A FUNCTION OF FREQUENCY (TRANSMISSION LINES) f Transmission At = Dt Bt Ct loss (db) 1.0 lo0 4 0.0938/ 58.20 147.6 /90.20 6.74 x 10-3 /90.20 2.0 1.146 0.985 /180.50 27.8 /254.50 1.27 x 10-3 /25.5.0o 1.394 0.938 / 1.59o 5.0 /79.20 2.465 x 10-3/ 79.20 6.0 1.761 0o859 /183.20 78.0 261.5~ 3.47 x 10-3 /261.5 8.0 1.967 0.759 /.2.4 /83.20 4.49 x 10-3 /83.2 10.0 2. 2 0.648 188.0 1.8 /26. 5.245 x 10-3 /26.50 7. ELECTRICAL GONIOMETER GO-5/GRD, Ser. No. 179 The A, B, C, D constants and the transmission loss of the goniometer as a function of frequency are given in Table III. A curve of transmission loss vs frequency is shown in Fig. 17. TABLE III A, B, C, D CONSTANTS AND TRANSMISSION LOSS AS A FUNCTION OF FREQUENCY (GONIOMETER) f Transmission A B C D loss (db) 1.0 1.277 2.58 /-1.200 87.5 86.600 43.3 xo103/-85.640 1.861/1.960 2.0 1.872 2.51 /-0.390 1169 87.960 20.54 x103/-82.12 1.775/ 4.930 4.0 4.55 2.49 /-4.650 317 82.560 9.27 x10-3/-76.940 1.580/ 8.850 6.0 5.37 2.24 / 0.710 1461 /89.1 0 5.02 x103/-60.9 0 l1.41/19.010 8.0 7.14 1.974/ 0.55 1574 /88.4 o 2.87 o/-39.2 o 1.228/ o30.45o 10o.o 9.5 1.620/1.450 1732 /88.1 0 1.809x10-3/- 3.70 1.069/47.950 20

9.0 8.0 7.0 0 Z n 4.0 z 3.0 < I: 2.0 1.0 o I I I I I I I I 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 FREQUENCY (IN MEGACYCLES/ SECOND) FIG.17 ELECTRICAL GONIOMETER GO-5/GRD,SER. 179TRANSMISSION LOSS VS. FREQUENCY a 2.0 z C') 0 -J z 1.0 0 c) z 0 0 I I I I I I I I I I 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 FREQUENCY (IN MEGACYCLES/ SECOND) FIG.18 TRANSMISSION LINE-RF SWITCH COMBINATIONTRANSMISSION LOSS VS. FREQUENCY 21

8. TRAINS1ISSION LINE-RF SWITCH COMBINATION The A, B, C, D parameters and the transmission loss of the lineswitch combination as a function of frequency are given in Table IV. A curve of transmission loss vs frequency is shown in Fig 18. TABLE IV A, B, C, D PARAMETERS AND TRANSMISSION LOSS AS A FUNCTION OF FREQUENCY (LINE-SWITCH COIMBINATION) f Transmission A B C D loss (db) 1. 0o.587 11001 0.13 5.53 84.6 1.588x10-3 /22.59 0.999 0.350 2.0 o.814 0 993 /0.470 12.39 86.690 1892x10-3 38.650 0.995 /0.630 4.0o 0.715 0.972 0.810 25.7 /88.180 2.79 x10-3 59.22o 0.970 /1.570 6.0 0.870 0.931 0.480 37.75 89.38 3.785x1o0-3 /66.76 0.936 3.320 6.0 1.337 0.877 1.700 49.8 /89.87~ 4.76 x1o-3 /73.450 0.886 3.40 10.0 0779 0.801 2.290 61.1 900 5.71 x10-3 /76.950 0.830.25~ 9. RECEIVER INPUT IMPEDANCE The receiver input impedance was measured in the following way. First the entire DF system was connected as it would normally be used and a test signal was transmitted at the proper frequency. The receiver was then tuned to the test frequency, the antenna trim control adjusted for maximum output as indicated on the carrier level meter, and the RF gain control was set to position 8. Impedance measurements were then made at the input to the transmission line-RF switch combination with the receiver connected. At the time of taking these measurements the input signal level 22

IMPEDANCE OR ADMITTANCE COORDINATES FREQUENCIES ARE IN BASE RESISTORS MEGACYCLES / SECOND 0.12 0.13 0.9 36 0,14,~~~~~~~ "~O.~k O. I$ 09-~ ~ ~ ~ ~ ~ ~ ~ ~~~~~9 z 10.~~~~~~~038 03 o.!O~t~o: 390.36~L~LN 0 0 0 ~j:ce*J 0.2 o ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > o ~ ~ o C OPNN COPOEN TO~ / ~:~~~~~~~~~~t ~~~~~~~~~~40 60 Pd o~~tk0 o~~~~~~~~~~~~~~e~~~~~~~~~~~~~ o o c o i3/~~~~~~~~~~~~~o r 8 V't A f FIG.~~~~~~~~~~~~~~~~~~~~~~~~~~r 19 1INU IIIDAC y'RAIO RCIVE 0 P O: c~~~~~~~~~~~~~~~~~~~~K 0c ~;J /J~/~V)~~I~~t~V t~rXKK~\ X /1K XXY;~~ XK)O)CC\ \ pi o p I IX \~J h" O~~~~~~~ 0 i i - R-390/URR 230

to the RF bridge was adjusted until a reference voltmeter connected to the plate of the AGC amplifier tube V509 read 15 volts or below for each impedance measurement. Since all the characteristics of the transmission line-RF switch combination were known, it was a simple calculation to find the actual input impedance of the receiver. The results are tabulated below as a function of frequency and shown graphically in Fig. 19. TABLE V RECEIVER INPUT IMPEDANCE AS A FUNCTION OF FREQUENCY f ZR 1.0 18.25 - j36.4 2.0 68.7 - j71.4 4.0 113.2 - j32.2 6.0 139.6 + j 5.61 8.0 77.1 + j85.4 10.0 75.1 + j28.3 10. SUIMARY AND CONCLUSIONS As a summary of the transmission loss calculations, Fig. 14 was plotted. This shows the cumulative transmission loss as a function of frequency and shows graphically the relative effects of the various components. Clearly, the base-loading resistors are the largest contributing factor to the overall transmission loss. Another observation that can be made is that if care were taken to match the impedance levels the overall transmission loss could be decreased significantly. 24

DISTRIBUTION LIST Copy No. Copy No. 1-2 Commanding Officer, U. S. Army Signal 27 Commander, Air Proving Ground Center, Research and Development Laboratory, ATTN: AdJ/Technical Report Branch, Fort Monmouth, New Jersey, ATTN: Senior Eglin Air Force Base, Florida Scientist, Countermeasures Division 28 Commander, Special Weapons Center, Kirt3 Commanding General, U. S. Army Electronic land Air Force Base, Albuquerque, New Proving Ground, Fort Huachuca, Arizona, Mexico ATTN: Director, Electronic Warfare Department 29 Chief, Bureau of Ordnance, Code ReO-l, Department of the Navy, Washington 25, 4 Chief, Research and Development Division, D. C. Office of the Chief Signal Officer, Department of the Army, Washington 25, 30 Chief of Naval Operations, EW Systems D. C., ATTN: SIGEB Branch, OP-347, Department of the Navy Washington 25, D. C. 5 Chief, Plans and Operations Division, Office of the Chief Signal Officer, 31 Chief, Bureau of Ships, Code 840, DeWashington 25, D. C., ATTN: SIGEW partment of the Navy, Washington 25, D. C. 6 Commanding Officer, Signal Corps Elec- 32 Chief, Bureau of Ships, Code 843, Departtronics Research Unit, 9560th USASRU, ment of the Navy, Washington 25, D. C. P. O. Box 205, Mountain View, California 33 Chief, Bureau of Aeronautics, Code EL-8, 7 U. S. Atomic Energy Commission, 1901 Con- Department of the Navy, Washington 25, stitution Avenue, N.W., Washington 25, D. C. D. C., ATTN: Chief Librarian 34 Commander, Naval Ordnance Test Station, 8 Director, Central Intelligence Agency, Inyokern, China Lake, California, ATTN: 2430 E Street, N.W., Washington 25, D. C., Test Director-Code 30 AT2N: OCD 35 Commander, Naval Air Missile Test Center, 9 Signal Corps Liaison Officer, Lincoln Point Mugu, California, ATTN: Code 366 Laboratory, Box 73, Lexington 73, Massachusetts, ATTN: Col. Clinton W. Janes 36 Director, Naval Research laboratory, Countermeasures Branch, Code 5430, Wash10-19 Commander, Armed Services Technical In- ington 25, D. C. formation Agency, Arlington Hall Station, Arlington 12, Virginia 37 Director, Naval Research Laboratory, Washington 25, D. C., ATTN: Code 2021 20 Commander, Air Research and Development Command, Andrews Air Force Base, Wash- 38 Director, Air University Library, Maxwell ington 25, D. C., ATTN: RDTC Air Force Base, Alabama, ATTN: CR-4987 21 Directorate of Research and Development, 39 Commanding Officer-Director, U. S. Naval USAF, Washington 25, D. C., ATTN: Chief, Electronic Laboratory, San Diego 52, Electronic Division California 22-23 Commander, Wright Air Development Center, 40 Office of the Chief of Ordnance, DepartWright Patterson Air Force Base, Ohio, ment of the Army, Washington 25, D. C., ATTN: WCOSI-3 ATTN: ORDTU 24 Commander, Wright Air Development Center, 41 Chief, West Coast Office, U. S. Army Wright-Patterson Air Force Base, Ohio, Signal Research and Development LaboraATTN: WCLGL-7 tory, Bldg. 6, 75 S. Grand Avenue, Pasadena 2, California 25 Commander, Air Force Cambridge Research Center, L. G. Hanscom Field, Bedford, 42 Commanding Officer, U. S. Naval Ordnance Massachusetts, ATTN: CROTLR-2 Laboratory, Silver Springs 19, Maryland 26 Commander, Rome Air Development Center, 43-44 Chief, U. S. Army Security Agency, Griffiss Air Force Base, New York, ATTN: Arlington Hall Station, Arlington 12, RCSSLD Virginia, ATTN: GAS-24L 25

UNIVERSIV OF MICHIGAN 3 9015 03483 1480 DISTRIBUTION LIST (Cont'd) Copy No. Copy No. 45 President, U. S. Army Defense Board, 61-62 Commanding Officer, U. S. Army Signal Headquarters, Fort Bliss, Texas Missile Support Agency, White Sands Missile Range, New Mexico, ATTN: SIGWS46 President, U. S. Army Airborne and Elec- EW and SIGWS-FC tronics Board, Fort Bragg, North Carolina 63 Commanding Officer, U. S. Naval Air 47 U. S. Army Antiaircraft Artillery and Development Center, Johnsville, Guided Missile School, Fort Bliss, Texas, Pennsylvania, ATTN: Naval Air DevelopATTN: E & E Department ment Center Library 48 Commander, USAF Security Service, San 64 Commanding Officer, U. S. Army Signal Antonio, Texas, ATTN: CLR Research and Development Laboratory, Fort Monmouth, New Jersey, ATTN: U. S. 49 Chief of Naval Research, Department of Marine Corps Liaison Office, Code AO-4C the Navy, Washington 25, D. C., ATTN: Code 931 65 President U. S. Army Signal Board, Fort Monmouth, New Jersey 50 Commanding Officer, U. S. Army Security Agency, Operations Center, Fort Huachuca, 66-76 Commanding Officer, U. S. Army Signal ReArizona search and Development Laboratory, Fort Monmouth, New Jersey 51 President, U. S. Army Security Agency Board, Arlington Hall Station, Arlington, ATTN: 1 Copy - Direcotr of Research 12, Virginia 1 Copy - Technical Documents Center ADT/E 52 Operations Research Office, Johns Hopkins 1 Copy - Chief, Ctms Systems Branch, University, 6935 Arlington Road, Bethesda Countermeasures Division 14, Maryland, ATTN: U. S. Army Liaison 1 Copy - Chief, Detection & LocaOfficer tion Branch, Countermeasures Division 53 The Johns Hopkins University, Radiation 1 Copy - Chief, Jamming & DecepLaboratory, 1315 St. Paul Street, Balti- tion Branch, Countermore 2, Maryland, ATTN: Librarian measures Division 1 Copy - File Unit No. 4, Mail & 54 Stanford Electronics Laboratories, Stan- Records, Countermeasures ford University, Stanford, California, Division ATTN: Applied Electronics Laboratory 1 Copy - Chief, Vulnerability Br., Document Library Electromagnetic Environment Division 55 HRB-Singer, Inc., Science Park, State 1 Copy - Reports Distribution Unit, College, Penn., ATTN: R. A. Evans, Countermeasures Division Manager, Technical Information Center File 3 Cpys - Chief, Security Division 56 ITT Laboratories, 500 Washington Avenue, (for retransmittal to BJSM) Nutley 10, New Jersey, ATTN: Mr. L. A. DeRosa, Div. R-15 Lab. 77 Director, National Security Agency, Ft. George G. Meade, Maryland, ATTN: TEC 57 The Rand Corporation, 1700 Main Street, Santa Monica, California, ATTN: Dr. J. L. 78 Dr. H. W. Farris, Director, Cooley ElecHult tronics Laboratory, University of Michigan Research Institute, Ann Arbor, Michigan 58 Stanford Electronics Laboratories, Stanford University, Stanford, California, 79-99 Cooley Electronics Laboratory Project ATTN: Dr. R. C. Cumming File, University of Michigan Research Institute, Ann Arbor, Michigan 59 Willow Run Laboratories, The University of Michigan, P. 0. Box 2008, Ann Arbor 100 Project File, University of Michigan Michigan, ATTN: Dr. Boyd Research Institute, Ann Arbor, Michigan 60 Stanford Research Institute, Menlo Park, California, ATTN: Dr. Cohn Above distribution is effected by Countermeasures Division, Surveillance Dept., USASRDL, Evans Area, Belmar, New Jersey. For further information contact Mr. I. O. Myers, Senior Scientist, telephone PRospect 5-3000, Ext. 61252. 26