PI (Pulse Induction) versus VLF (Very Low Frequency) SAND SHARK versus TIGER SHARK

Underwater Detectors

by Rusty Henry, Service Manager

PI (Pulse Induction) versus VLF (Very Low Frequency)

Maybe the title of this article should just be SALT WATER VERSUS FRESH WATER! The problem with that, however, is its very seldom a “cut and dry” decision.

The obvious answer, if money were no objective, is to own both a SAND SHARK and a TIGER SHARK and have the best of both worlds. However, I know what it’s like to have to buy tires and groceries and pay bills at the same time, so I am going to try to help any perspective customers to narrow their choice down to a single machine.

The more obvious advantage of the TIGER SHARK is its increased versatility due to its superb discriminate mode.

Even though the SAND SHARK is strictly an all-metal detector, it has a distinct advantage around (or in) salt water due to its superior stability.

However, I have seen guys do remarkably well with the Stingrays and Tiger Sharks at the ocean and on the other hand, some PI users (by ignoring the blip-blip signals of nails, wire, hair pins, etc.) can still clean up at a fresh water lake!

Before making a decision based strictly on salt water searching versus fresh water (or land) searching, perhaps we should look at some of the more subtle differences between Pulse Induction (SAND SHARK) versus VLF (TIGER SHARK).

The first thing that comes to mind is the ability of a VLF machine to respond to tinier metal objects than the PI is capable of. Therefore, if finding very fine gold chains, or perhaps a gold stud from pierced earrings or a tiny little gold charm from a charm bracelet is a high priority, then you are definitely leaning toward the TIGER SHARK.

Before jumping to a final decision based on that, let’s consider the area you might be searching for these items. If you live in the Midwest, where there are many fresh water lakes and the only time you have an opportunity to search at the ocean is on an occasional vacation, then your decision is an easy one—the TIGER SHARK. But what if you live right on, or very near, the ocean and have the opportunity to search there often, especially down in the wet sand at low tide and especially after a good storm.

When it comes to working successfully down in the wet sand at the ocean, the new SALT WATER MODE of the TIGER SHARK can significantly improve its performance in that area. However, it still can’t compare to the stability (and consequently – success) of the SAND SHARK when searching down near (and especially in) the salt water. This is because wet salt is conductive and a VLF unit which transmits from one set of windings and receives from another is adversely affected. The PI unit which “pulses” and receives from the same set of windings is not affected by conductive salts or mineralization.

Even though the SAND SHARK is not capable of competing for the absolute tiniest of metal targets (especially with the 10½” coil) any normal-sized ring or other piece of jewelry is no problem. Certainly this also includes all coins, but we all know that “coins are just something to keep you interested while you’re looking for the next piece of jewelry.” Also, keep in mind that before Tesoro’s original Stingray VLF, no one was finding fine gold chains with an underwater unit anyway.

To carry this one step further, how much good is it for the TIGER SHARK to respond to even tinier metal targets, if when working in or near the salt water there is so much noise from the conductive salts that these targets get masked out? You can always lower the sensitivity of the VLF models to get more stability but then that will cause losses as well due to loss in depth.

Another way of putting this is that the PI unit may appear to have less depth and sensitivity initially, but when you consider that it is able to retain all of this through all types of ground and conductive salts, the end result is many times an increase in depth overall when compared to the VLF in these adverse conditions.

I have found very small, thin (pinkie finger and birthstone-type) rings down in the wet sand at low tide with my SAND SHARK and many items that I know I would have not found if trying to control a VLF unit in that environment. I have even used a Pulse Induction-type unit successfully in a gold nugget searching situation taking advantage of the fact that it is not bothered by the otherwise troublesome mineralization, but I’ll admit that I did not find any matchhead-sized nuggets or smaller…only about pea-sized (about 1 dwt.) and larger.

The added weight and clumsiness of an underwater metal detector as compared to good top performing lightweight land-based units has never made using an underwater detector that attractive to me for either nugget hunting or coinshooting. Most detectorists will opt for a good lightweight (and usually less expensive) model for the land hunting or searching in the dry sand “blanket area” on the beach and use their underwater unit primarily in the water. But, if you have been considering a submersible metal detector, I will say that whether it be a Pulse Induction or Very Low Frequency unit, an underwater detector is the easiest detector there is to pay for over and over in finds. The TIGER SHARK would definitely come closest to being an “all-around” detector and the obvious choice away from the ocean. However, for extended salt water use, I simply have to recommend the more specialized SAND SHARK.

It is my sincere desire that anyone, after reading this article, will not be disappointed with their choice of either of these units and be happy and successful taking advantage of the strong points of that respective underwater detector.