spectrum output from the Kay vibralyzer. The 

 high sweep rate of the CTFM sonar operating 

 at short range indicates clearly the rate of 

 bursts of data. It is possible that A j and 

 Af could produce double signals suchas those 

 indicated, but for the sweep rate of 34 ms. 

 and the range of the diver, this double signal 

 is impossible. The first return at 1,800 Hz 

 occurs for the diver at a range of 14 feet 

 (4.3 m.) which agrees with his observed po- 

 sition. The second signal can only be accounted 

 for by reverberation between surface and 

 bottom. 



U.S. Naval Ordnance Test Station 



A trip to USNOTS, Pasadena, at the invitation 

 of J. Vetter and R. Davis, resulted in an 

 analysis of a portion of one of the Doppler 

 tape recordings made at the Mission Bay 

 Yacht Club pier. A lengthy discussion with 

 the personnel at USNOTS indicated that 

 extractions of signals from the returns would 

 not be easy and would require considerable 

 process analysis. A day was spent at USNOTS 

 using their playback equipment and recordings 

 of fish returns from Mission Bay. The time 

 required to analyze these portions of the tape 

 became uneconomical. 



Slow Scan Analysis Technique 



A rapid means of analysis therefore was 

 attempted with a narrow band Hewlett-Packard 

 low-frequency wave analyzer and the test 

 configuration indicated in figure 8. This tech- 

 nique made use of intensity nnodulation of a 

 CRT (Cathode Ray Tube) and produced an 

 image suitable for photographic integration. 

 For the first time intensity-modulated signals 

 were integrated to improve the signal-to-noise 

 ratio of the recorded data. The dynamic range 

 of this technique was limited by the CRT, 

 and therefore the output was confused by large 

 noise impulses. A sample of a typical photo- 

 graphic output is included in figure 9 to indicate 



Figure 8. — Slow scan panoramic spectrum analysis block 

 diagram. 



Figure 9. — Slow scan panoramic spectrum analysis from tape loop input. 



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