EQUIPMENT AT MOUNTAIN LAKES 



73 



r^" 



HETEROOYNE OSCILLATOR 



DETECTOR 



TUNING 



OSCILLATOR 



747 KC 



"~l 



variable: 

 frequency 

 oscillator 



650 TO 500 KC 

 (650 -f) 



FREQUENCY 



OSCILLATOR 



650 KC 



MODULATOR 

 BUFFERS 



AMPLIFIER 

 ATTENUATOR 

 650-(650-f) 



=d_l_ 



.J 



NOISE GENERATOR CIRCUIT 



NOISE 

 GENERATOR 

 WIDE BAND 



•*-*- 



650 KC*IOC 



BAND PASS FILTER 



(FOR TUNING) 



650-0 15 KC 



OR 



650*3 KC 



BAND PASS FILTER 





I RECORDER I l"T """ 



it! 



Li 



THTRATRON 

 CONTROL 



BAND PASS 



FILTER 

 12 C WIDE 



AMPLIFIER £Ji...___ _________^-_— r 



01 T0I50KC \ ^__ ^__^ Y 



— ' MONITOR ! 



CONVERTER | 



I I 



POWER AMPLIFIER " 



01 TO 30KC 

 AMPLIFIER 



0.3 TO I50KC 

 AMPLIFIER 



U 97 KC 



MODULATOR 

 74 7-650 KC 



MODULATOR 

 (650-tl-tf 



I 



DETECTOR CIRCUIT 



94 TO 100 KC 



OSCILLATOR 



97 KC t 1' 



I 



MODULATOR 

 97 KCtf'-97KC 



POWER 



ATTENUATOR 



AND LINE 



BRIDGING 



NETWORK 



Pi 



ER TRANS- 



I 



30 A 



TRANSMISSION 



MEASURING 



SET 



'V I 

 r 



CATHODE 

 RAY 



OSCILLOSCOPE 



f- 

 H 



DE BAND Ai 

 0.01 TO 130 KC 



mplifier] 



PART 2 



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v Y~ 1 PART I 



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MITTING BOOT 



^1 



IMPEDANCE, MATCHING 



COILS, PADS AND 

 WATTMETER CIRCUIT 



SWITCHING CIRCUIT 



j SWlTCHIN 



I n" 



R RECEIVING 



X 



jL. 



-BALANCED COAX LINE BETWEEN PIER BOOTHS 



I COUPLING AMPLIFIER, DC 

 SUPPLY CCTS .CALIBRATION 

 SIGNAL CIRCUIT 

 I SWITCHING CIRCUIT 



■4, 



TERMINAL 



NOTE -BROKEN LINES INDICATE ALTERNATE CI RCUlT ARRANGEMENTS 



TO PROJECTOR 



FROM HYDROPHONE 



Figure 7. Block diagram of 15 c to 150 kc System 2. 



of 135 ohms, which corresponds to the impedance of 

 the coaxial transmission lines to the piers. Adjustable 

 135-ohm attenuators, designed to carry the full power 

 to the amplifiers, are connected in the output circuits 

 to supplement the amplifier gain controls, to stabilize 

 the output impedance, and to improve the amplifier 

 signal-to-noise ratios. The amplifier design and the 

 use of output attenuator pads permit a 55-db margin 

 between signal and amplifier noise. A bridging net- 

 work of 30-db loss at the amplifier output terminals 

 allows a 30 A transmission measuring set, described 

 later in this section, to be used for monitoring 

 purposes. 



Transmission Lines 



The 135-ohm insertion loss of the combined trans- 

 mitting, receiving, and pier booth cross-connecting 

 lines does not exceed 0.25 db at 150 kc, which is too 

 small to require any correction for line attenuation. 



Balanced coaxial lines (Figure 11 A) are used for 

 signals from power amplifiers to coupling booths on 



the piers, return signals from pier receiving booths, 

 for linking transmitting and receiving booths, and for 

 interconnecting the various systems. The four-wire 

 groups marked "quads" are used for controls such as 

 relay operation, intercommunication, and indexing. 

 The requirements to prevent cross talk are severe, 

 as is indicated by the difference in outgoing and in- 

 coming levels that may exist. For instance, the hydro- 

 phone level in the receiving line may be as low as 

 10— 16 watt, while the power supplied to a projector 

 over the transmitting line may be 150 db above this 

 level. In order not to affect the measurements, the 

 cross talk must be lower than the received level by at 

 least 15 or 20 db, which requires a margin between 

 the transmitting and receiving apparatus of nearly 

 170 db. In addition to the use of coaxial cable, other 

 precautions tending to minimize cross talk have been 

 observed, such as a minimum spacing of 6 feet be- 

 tween all transmitting and receiving lines, and care- 

 ful attention to the laboratory grounding system as 

 described later in this section. 



