CaptJohn said:
Whats the diff between the Sand Shark and the Tiger Shark. Is Sand Shark a PI only great for salt water, How is it for Fresh water, and the Tiger is something else, what type water is it better for, can it do well in both salt and fresh? Is one better on land than the other. I'm in need of a Good Salt Water and sand machine, that will also do a fair job in fresh water. What about coils is the 10" worth 25 bucks over the 8" coil. Kellyco has has the 8" Sand at about $602 and The 8" tiger at about $636. How do the coils float or don't, under water? Any tips from any owner of either one would be helpful.
Hi CaptJohn! The "Tiger Shark," is a VLF machine built for FRESH- water. The "Sand Shark," is a PI machine built for SALT- water.
Very Low Frequency (VLF) and Pulse Induction (PI) metal detectors.
A "VLF" or very low frequency type metal detector, works extremely well on dry sand and in fresh water. It does not work as well in saltwater, or on wet ocean-water beaches. In highly conductive saltwater conditions pulse induction, or "PI," metal detectors excel. The VLF metal detector sends 4,000 - 90,000 radio waves per-second into the ground. When the radio waves hit something conductive - like an iron nail, gold ring, coin or aluminum pulltab, a magnetic field sets up around the object and a particular signal frequency is transmitted back to the detector's receiving coil. VLF metal detectors have the ability to "discriminate," or tell what type of metal they are seeing by "reading" the return signal frequency. An iron nail for example, has a different frequency than a silver coin. The processor in the metal detector knows the difference between the two, and can be set to remain silent when seeing the nail.
However, the radio waves bounce off everything that is conductive in the sand or water. This is why VLF detectors must be "ground balanced" to work effectively in highly mineralized soil, or on highly conductive saltwater beaches. You must tune or adjust the machine to see through the "fog," or white-noise created by the salt and iron in the sand or water you are detecting. Unfortunately, this usually leads to a loss of depth and stability.
A pulse induction or, "PI" metal detector, sends out hundreds of electric pulses-per-second, rather than thousands of radio waves. While PI metal detectors do not have the ability to discriminate between different types of metal, their powerful pulses go much deeper than the VLF signal, and eliminate the problem of mineral conductivity. A pulse induction detector measures the decay rate of the electronic pulses it sends out, and looks for anomalies. The strong electronic pulse is not conducted by the salt in the water or the iron in the black sands.
Think of a Navy ship "pinging" with its sonar for an enemy submarine. If there is nothing in the water the "ping" just continues on and fades out at the same measured rate. If the submarine is there, the signal decay is interrupted and bounces back to the sonar operator on the ship. Most successful ocean-beach detectorists, own both types of detector. The land-based VLF unit is preferred in the dry sand blanket area because you can use discrimination to knock out iron and still achieve superior depth without loss of stability. The pulse induction machine is used on the wet ocean- and black- sands, as well as in the surf.
Do some more homework on the right machine for you!
