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     PADI's Advanced Scuba Course should be seriously considered by every certified diver. The various components are designed to extend the knowledge and experience that an Open-Water Scuba diver has. At Deep-Six it is an inexpensive way to continue diving, as well as a way for a diver that has not been diving for a while to get back into it.

     As explained elsewhere, there are just 5 dives that have to be completed for a diver to become Advanced. Two of them are core dives and are required. The other 3 are elected by the diver. Follow this link to obtain complete information -> Advanced Courses

     The following information is used for specific dives. A diver working on Advanced Scuba may be referred to this chapter to enhance their knowledge about a specific dive.

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     It is quite simple to understand how a metal locator or detector works. Most use electromagnetic fields to locate metallic objects. Electromagnetism comes in a variety of forms such as light, x-rays, radio waves, etc. Some electromagnetic energy is at a very low frequency such as radio waves, and some is at a very high frequency such as gamma radiation. There is an even lower frequency than radio waves and that is electrical radiation. It travels at the speed of light, as do all of the types of electromagnetism, but it should not be confused with electricity. However, when electricity travels through a wire it emits electrical radiation. That is why your radio emits static when you drive under a high voltage wire.

     The very low frequency metal detectors (VLF Detectors) have an outer coil of wire that has alternating electrical current traveling through it. Electrical radiation is emitted from that coil of wire at right angles to it. If that radiation hits a piece of metal a pulse of electrical radiation is emitted by the metal but has an opposite polarity. A second smaller coil in the detector detects that pulse and registers it on a meter, with sound, or by light. Different metals change the electrical field in different ways so some metal detectors are manufactured to tell one metal, such as iron, from another, such as gold. They are discriminators.

     The Beat Frequency Oscillators (BFO Detectors) emit higher frequency radio waves. They also have a receiver for radio echos. Metals change the frequency of the radio waves and the metal locator detects those changes.

     Pulse Induction Detectors: These metal detectors have a single coil of wire. Direct current is pulsed out at rapid intervals. So, the very low frequency electrical radiation is emitted in pulses and is distorted by metals. This distortion is picked up between pulses and that is why only one coil is needed. The detection depth is greater but the ability to discriminate is usually less.

     Magnetometers: These have a great detection range sometimes measured in thousands of feet. Also, they are quite expensive when compared to the other types of detectors. They are able to detect only iron and steel objects. Magnetometers are able to measure the magnetic field of the earth. That field is distorted by iron or steel.  Just as a compass detects and lines up with the earth's magnetic field, if you bring a piece of iron near that compass it will deflect because of the change in the magnetic field. A steel shipwreck will deflect the magnetic field of the earth and that can be measure quite effectively by a magnetometer from quite a distance. 

Click here to get further information on Advanced Courses

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     Being a diver since 1954 and teaching scuba since 1956, I do have some thoughts on the "buddy system." Most of my underwater life has been spent diving with no real buddy. There have been some occasions where I was diving with someone that would provide needed and correct assistance, but it has rare.
     When an instructor conducts a training dive for his or her students there is no way most of them, if not all, would be able to recognize a problem or know what to do about it. Yes, we emphasize mouth-to-mouth while performing an in-water transport, but to get the student to realize there is a problem with the instructor is really a stretch. Although I do not make an issue of that with the other divers, it does place self-rescue as a top priority.
     Most of the time when diving from a boat for pleasure (not instruction), a buddy check is rarely done. It's almost like nobody wants to be "a boss" or suggest the other diver makes mistakes. I have seen divers enter the water with no weight belt or pouches, with their BC hose unattached, or a tank that was used for a previous dive. And underwater the buddy system sometimes fails. There are dives when the "buddy" lags behind in low visibility and gets out of sight. Usually the 2 divers end up diving alone (horrors) until the SPG suggests it is time to surface. Forget the "search for 1 minute and then surface to reestablish contact".
     I do a lot of recovery for guests at a popular resort in Lake Mohonk, NY. They drop wallets, cell phones, cameras, glasses, and jewelry into the lake. The bottom consists of muck and leaves at 40'. The temperature is 40 degrees and the visibility is about 2'. If I dove with a buddy it would be a disaster. Most divers would not be able to descend feet first until they are about 10' from the bottom, invert, add air to the BC so minor finning keeps the diver inches from the bottom while the search and recovery is made. Without training even the best divers may end up crashing into the muck creating a scene similar to Enwitok. Goodbye to the pocketbook or earring.
     I do not want to give my students the impression the buddy system leaves a lot to be desired. They check their buddy with easy-to-remember steps. They are instructed to check the air supply, the BC connection, the weights, and then to give a "walk around" before entering the water. They do this for all the pool and open-water dives. But they are also made aware they should do a self-check. They should check to be sure the air is on, put on the BC, look at the SPG and press the BC inflator (if the SPG drops the tank is not on, if there is no inflation the BC hose is not firmly attached), and then put their hands on their weights and/or belt. The divers are made aware the self-check may be the only check that is done in the real world.
     Back in 1954 there were no divers for me to buddy with. Being a kid I made my own scuba and dove in a lake in upstate NY. I remember the absolute thrill of being able to breathe underwater. That 50-year-old impression is still as vivid as if it occurred yesterday. I had no thoughts about being down without someone else. It was just too exciting, and I see that excitement in many divers descending in the pool on scuba for the first time!

     The above buddy system comments were transmitted to the Editor of Dive Training Magazine in April 2010.

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