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To all interested parties: While I had possession of the console #6 communication set, I decided to not only test this unit, but run further tests on that passive eighteen hydrophone array. I needed an amplifier that contained both the pre-amp and 18 watt amplifier to make accurate test results. Here are my conclusions: (1) The hydrophone selection unit that used stator brushes to select the desired hydrophones for monitoring worked very well. I am going to shelve this unit in storage for possible later testing and use. (2) At one point in the early evaluations of the first six hydrophone passive array, I made the statement that not all hydrophones were equal. Once again, I have found this to be true. As I trained thru the hydrophones and compared that which was heard, the output from each varied not in relation to the sound source I had provided (a submerged sonar beacon), but rather as to the individual piezo element that made up each hydrophone. It would seem that minute variations of many factors determine how loud of amplification can be obtained from each hydrophone without adjusting the gain and volume of the main electronic enclosure.(wire resistance, solder connections, piezo construction, ect) * The way I see of overcoming this shortfall would be to install a preamplifier circuit dedicated to each hydrophone and adjusting them all to a set gain level. I have neither the money nor test equipment to accomplish this task. This would also require periodic adjustment as the electronics would age. Another thing is that although these piezo elements were housed in a plastic cup, most if not all directionality was lost once the air filled resonance chamber was omitted. Seems the HBH-2 hydrophones were more directional than first thought. I even attempted to better channel the sound by installing styrofoam cups but to no avail. Due to the complexity and large size of this array, it is being scrapped. The use of one or two hydrophones seems to be the best and simplest way for these little boats to hear there way around. If you plan on using an array of hydrophones, even if used in a limited area dedicated passive search, use a preamp for each hydrophone and adjust the gain to be simular. In this way once the contact of interest is best recieved, your probably listening the the hydrophone that best picks it up. David Bartsch Get free photo software from Windows Live Click here. |