pulse code modulation were available. Command and control channels were available for 

 functions such as picture initiate, video gain, contrast, etc. Relatively inexpensive broadly 

 directional (70 deg at 3 dB down) transducers were used for both sending and receiving. 



During tests off Hawaii CUTLINK demonstrated its capability for transmitting video 

 acoustically. Two-hundred-line FM analog pictures were successfully transmitted from both 

 200 and 1300 ft. An image of the vidicon target was transmitted from 15,200 ft. The pub- 

 lished examples of video imagery shown are quite good; however there were some problems 

 with line synchronization, ghost images, and granulation. These were attributed to multipath 

 interference from a bottom-reflected ray (Ref. 3). The pioneering accomplishments of the 

 CUTLINK system attracted much attention, and it received an award from Industrial Research 

 magazine (Ref. 4). 



Another development that had a strong influence on our SUBSAT tests was the 

 development of amateur radio slow-scan television (SSTV). In 1957 a student at the Univer- 

 sity of Kentucky, Copthome MacDonald, realized that it would be possible to transmit video 

 over voice-grade radio frequency channels. His paper describing the design and development 

 of the first amateur SSTV system was awarded the 1958 National AIEE (now IEEE) first 

 prize. Since 1958 amateur SSTV has progressed to where it is a commonly used mode of com- 

 munication and employs the standard format shown in Table 2. During this period successive 

 generations of relatively inexpensive commercially built amateur SSTV equipment using this 

 format have become available. The earliest equipment, both privately and commercially built, 

 used charge-storage vidicons as cameras and cathode ray tubes with slowly decaying phosphors 

 as monitors. The present state-of-the-art is to use conventional fast-scan cameras and moni- 

 tors and to use scan converters to go from the slow to fast and fast to slow formats. The 

 latest scan converter designed for the amateur market, the Robot Model 400, features all 

 solid state scan conversion, with each TV frame being completely digitized and stored in 

 memory. This scan converter was used in the SUBSAT tests. 



TABLE 2. AMATEUR RADIO SLOW-SCAN TV FORMAT. 



Number of Scan Lines 



Number of Horizontal-Resolution Elements 



Aspect Ratio 



Time Per Frame 



Horizontal Sweep Frequency 



Vertical Sync Burst Duration 



Horiz. Sync Burst Duration 



Sync Subcarrier Freq 



Black Subcarrier Freq 



White Subcarrier Freq 



120 

 120 

 1:1 

 8 sec 

 15Hz 

 30 msec 

 5 msec 

 1200 Hz 

 1500 Hz 

 2300 Hz 



Bit Rate 7200 baud 



In another recent acoustic television experiment Conrad and Moffet (Ref. 5) used a 

 Model 400 scan converter and a parametric sonar to transmit slow-scan video over a hori- 

 zontal path. The purpose of this experiment was to show the feasibility of transmitting 

 video over a long horizontal path in a shallow (i.e., 600 ft) lake, a path which is prone to 

 severe multipath from surface and bottom reflections and multipath from multiple refracted 

 paths. The transmissions were successfully accomplished using two primary mixing frequencies 



