to wave height. The d.c. analog should be 0-5 volts at 1 milliampere. 

 Lower signals will attenuate longer period waves excessively. 



Bias signal amplitude, held constant by a constant voltage harmonic- 

 neutralized transformer, is passed through a resistance-capacitor filter 

 to further improve the wave form before it goes to the recording head. 



The recorder is designed to use Minnesota Mining and Manufacturing 

 Company No. 428 magnetic tape 1/4 inch wide, on 1,250-foot reels. One 

 reel of tape will record continuously for about 3 weeks. The tape speed 

 used is one-half inch per minute. In normal recommended operation at CERC 

 recording wave stations, the magnetic tape recorder operates continuously. 



Tape-recorder engineering design data was not available regarding the 

 slowest speed that could be used. The minimum tape speed, tape-head gap, 

 and bias frequency, needed to record 2-second waves in the field had to 

 be developed in the CERC laboratory. 



To provide a section of tape long enough for analysis on the CERC 

 spectrum analyzer, a recording must be at least 20 minutes long. While 

 a 20-minute record may be analyzed, a 24-minute record is recommended. 



The recorder has a built-in calibrating signal (sine wave) with a 

 period of 4 seconds. This signal, usually recorded for 30 minutes twice 

 each day at 10 a.m. and 10 p.m. local standard time, is used to check 

 recorder operation and to standardize input to the laboratory spectrum 

 analyzer. The amplitude of the calibrating signal is adjustable to 

 provide the same signal on the magnetic tape as the full-scale signal 

 provided by the wave gage. The calibrating signal is programmed by a 

 timer plugged into the recorder chassis. A switch is provided on the 

 front of the tape recorder to permit the user to place the calibrating 

 signal on the tape at his selection. This signal must also be 20 minutes 

 or longer. 



The recorder does not have an erase head; magnetic tape used must be 

 free of all recordings prior to use. When ordering, specify that tape 

 shall be of virgin quality and free of all test recordings. Tape should 

 be shipped in steel cans to aid in avoiding magnetic fields while in 

 transit. 



Numbered, small, adhesive markers must be placed on the section of 

 tape that is directly over the tape head when the tape is installed and 

 just before it is removed. Additional markers should be similarly placed 

 on the tape at significant times. Markers should be logged, listing the 

 exact time of placement and any pertinent comments. These markers and 

 the data logs are the only means of identifying the time of recorded 

 wave data; their importance cannot be overemphasized. 



Two meters are incorporated in the recorder to adjust and monitor 

 its operation. One has a zero center pointer, and indicates the ampli- 

 tude of the waves at the tape recorder. A meter movement of 400-0-400 



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