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I recently gave an underwater sonar beacon system a try. There are two units you see advertised, the "Dive Tracker" and the "Dive Track". The former unit works OK, but the receiver is prone to flooding (a user I know has sent his back twice). The latter unit appears to be well designed. The beacon and receiver look like medium sized flashlights. The company RJE international also makes a unit called a "Mark Track" which has a 1000' range as opposed to 750' of the Dive Track. The Mark Track also has a variable pulse rate so you can use two beacons at once. Both beacon and receiver use a standard 9v transistor battery. Duration with alkaline battery is 10 days for the beacon (20 with lithium) and 24 (48) for the receiver. Procedure is to attach the positively buoyant beacon with a 5' or so line to the anchor line, a part of structure or to a lead weight. You twist a magnetic switch to turn on the beacon and turn on the receiver to see if it is operating. The receiver has a 1" red LED bar graph on it's side. When searching for the beacon you scan left to right with your receiver. When you are within 180 deg. a single LED lights up to show you it "hears" something. Keep sweeping back and forth until about half the LEDs light up. Aim it at the strongest signal and when all LEDs suddenly light up, you are locked on and pointing directly at the beacon. I swam away from the beacon to try to loose the signal. I got to the point (after heading out into the sand for quite a spell) where I could not get a lock, but I was able to get a general direction good enough to eventually get a lock-on. It worked better if I pulled up to 6 or 8' off the bottom. Why would I want one of these things? The main reason is that I hate wreck reels. It would not be so bad if all you had to do was to deploy the line, but eventually you have to reel the damn thing back in. This forces you go over the same ground you went out on, a waste if you on a lobster hunt. Another reason is that it is a pain to do an area search over the sand if you are on a dropped gear hunt. This is a breeze with a beacon. Maybe the thing will eventually pay for it's self and turn an otherwise boaring dive into something interesting. Afterall you can only go to the friggin Morgan so many times, and you know there are some goodies laying out there in the sand waiting to be found. Beacons are no good for penetration and they could fail on you so I carry a reel and a bag anyway for rigging a ascent line. The sonar beacon cannot be seen through wreckage, but it can reflect so as to give you a tangental course back to the beacon. I trust my ability to navigate in low vis so that most of the time I am 90% sure of where I am. This unit takes care of that last 10% which gives me a nice, warm, fuzzy feeling when it's time to find the up line. Jim
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