vMch vdll exclude power and low-frequency radio signals. The use 

 of the preamplifier was to increase the signal-to-noise ratio of 

 the receiving system and to provide the utmost sensitivity possible. 



The receiving transducer is a type MI -2 mine hydrophone and, 

 although no information was available concerning its use of frequency 

 response, it appears to be suitable over the 20- to 40-kc. range. 

 It consists of a Rochelle-salt array, about 3-1/2 inches in diameter, 

 which, when considered as a piston, would have a useful directivity 

 pattern at these frequencies. It is fitted with a large flanged 

 pipe, capped at one end, which contains the 6AH6 cathode- follower 

 amplifier. In use, this assembly is suspended over the stern to a 

 point just below the ship's wake. 



Fig. 6. Telemeter transmitter and receiving hydrophone 



MECHANICAL DESIGN 



Telemeter Case 



This consists of a 5~l/4-inch-inside-diameter (I.D.) steel 

 cylinder, 27-1/4 inches long with a l/4-inch-thi ck wall. The inside 

 surfaces of the ends are machined and ground. A l/4-inch relieved 

 lip on each end has been machined to prevent damage to the 0-rings 

 during assembly of the instrument. There are also three anchor 

 points on each end of the case for attachment of L-shaped clamps to 

 retain the end caps. 



End Caps 



(a) The end caps are machined from cast brass blanks . 

 caps are 5-3/4 inches wide on the 3/8-inch -thick flange and are 



The 



10 



