VLF METAL DETECTOR VS. PI METAL DETECTOR
A VLF (Very Low Frequency) metal detector is a single or multi-frequency
machine that consists of a continuous sine wave. The sine wave(s)
goes down and into the ground to find a metallic target, and once it does, the
machine charges the target releases an eddy current and sends a signal back.
A common misconception for these machines is that you cannot get depth out of a VLF metal detector. That is not true, as long as a VLF machine is properly set up and you are using the right detector in the right conditions with the right coil, you can absolutely get depth with this machine. Yes, a VLF detector can have an advantage on shallow very very small targets, on and off of bedrock. As long as you can keep it stabilized, ground balanced, and the sensitivity is set properly,
this can help you find some of the smallest gold pieces, many in the
grain over gram range.
A PI (Pulse Induction) I guess that my best and easiest description of PI metal detectors is a machine that talks and then listens. Unlike the VLF detector, a PI machine is not a continuous sine wave it is pulse, on off, on off. These machines will do better than VLF in most highly mineralized soils because it’s measuring
the speed of the signal decay of the target and the ground around the target. However, there are places like low mineralization deposit areas where your PI machine will simply just not work to its fullest potential and in these places, you are better off with a VLF machine, and vice versa. For example, if you have excessive cold or hot rocks and or weird salts, there have been times when a VLF detector has been outperformed by a PI machine.
HOW DOES FREQUENCY WORK IN A VLF DETECTOR?
The higher the frequency, the closer to the surface the
machine works to find smaller targets. The lower the frequency,
the deeper in the ground the machine will go to find
larger and more conductive targets. It’s not the case that one
machine or frequency works better than another, it depends
on the conditions and the ground that you’re detecting coil size and your tuning. Frankly, for me when I head out detecting, I have a VLF and PI with me and I do recommended that you carry both types of machines, if you can, to be prepared for all of the varied conditions and the ground to change and to get the best results.
WHAT IS A HOT ROCK?
One of the most common questions received in the metal
detecting industry is, What is a Hot Rock? Hot rocks are
magnetic or have metallic properties that are higher than the
surrounding ground. No matter what, it is seen as a target
to your machine which can be disrupting if you don’t know
how to properly mitigate them. Keep in mind, hot rocks will
never be 100% avoided, but there are ways to reduce the
number of hot rocks you come in contact with.
DIFFERENT TYPES OF MINERALIZATION
There are two types of mineralization most associated with nugget hunting. First, there is high mineralization within the ground, where the ground
itself is hot and can contain hot rocks or cold stones. The
second type of mineralization is moderate or benign, where
there is less mineralization in the ground. Many people confuse
hot mineralization for hot rocks, but these are two different
things. Moderate or benign mineralization can also
contain hot rocks, and it’s actually this combination that can
cause the mitigation of this to be very challenging. Another
misconception is assuming orange soil is always hot. It’s
very possible that if you see orange soil, it’s most likely hot.
However, it could just be a red iron pigment. It’s important not
to immediately jump to that conclusion.
WHAT ARE DIFFERENT TYPES OF COILS
Three Different Types of Coils
1. Mono Coils: A mono coil is designed for a PI machine
and is a single winding which puts a concentric pattern
into the ground. You will always be able to get more
depth with a mono coil, but it is also more susceptible to
ground mineralization noise and it will be affected by the
ground mineralization itself. Using a mono coil, you have
to be very aware of what your overlap is. The second part of
the Mono coil question is when to take the Mono off and go
to a Double D coil. That answer is simple, when you can no
longer detect with a Mono is when you go to a Double D.
2. Double D Coils: Double D coils work for both PI
and VLF machines. Double D coils have two back to back D-shaped
windings inside the coil. At all times the coils are transmitting, and
another receiving across the plane of the coil. The Double D coil design is like
a knife blade that goes into the ground down the center of
the coil. These coils are great at handling mineralization
where it essentially takes the ground mineralization and distributes
it all the way across the blade lessening its effects.
3. Concentric Coils: The third type of coil is the concentric
coil. Many people think concentric coils are the
same as mono coils however, that is not the case. Mono
coils are built for a pulse induction machine using one winding
whereas concentric coils work with VLF machines by
using two separate windings one send one receive. Although they are similar in
design, they work for two completely different ways for two
completely different detectors.
Coils are measured off of a round coil configuration.
That being said, there is really no difference in size, only
in shape. For example, a 14x10 coil will have the same attributes
as a 12-inch coil. Why are there two different kinds
then? The key difference here is that elliptical coils work
extremely well in difficult areas in between scrub bushes and rocks. If you are still trying to wrap your head around that, here is a simple way to make
sure you choose a coil size that is different from what you already have:
Length + width = X ÷ by 2 = the size of the coil.
Take a 14x10 coil for example, 14+10=24 ÷ 2 = 12.
You have a 12-inch coil.
DISCRIMINATION ON GOLD DETECTORS
There is no truly accurate nonferrous discrimination on gold detectors
and discrimination for gold is dangerous. Iron discrimination
is really the only type of discrimination on a gold machine
and at best, this discrimination works “kinda.” Trusting
these signals is dangerous and can lead to missed gold,
so do your best to operate your machine to the best of its
ability without assuming anything. Even with the best iron
discrimination, you should dig these targets until you know
for sure they are ferrous junk, understanding that if there
is any wavering in the signal of another target that sounds
“almost the same,” it has to be dug.
EAST VS WEST
Many people assume that the West is a better place to
go gold prospecting, but this isn’t completely true. The key
differences between the two locations are the gold mineralization
area, with the West containing a lot more open ground and it is hotter ground.
That being said, there is a gold belt that runs from the north eastern United States all of the way through Alabama. Plus there is a lot more glacial gold in the eastern US. Although geography is going to be different, gold is gold, and the best place to look for gold is where it has been found before. The biggest issue with both the
West and East is going to be finding accessibility and being able to find that line and stay on that line. However, western states were developed to be able to go prospecting, mining, and staking claims which is why these states are known to
have easier access.
WHAT SHOULD YOU LOOK FOR
WHEN PROSPECTING WITH AND WITHOUT A DETECTOR
With gold panning, 99.9% of the time, wherever there is
gold there is black sand. However, this cannot be reversed,
if you find black sand that doesn’t mean there is definitely
gold in the same area (although it is possible). The most
important thing you can do before gold prospecting is to
understand your surroundings and the area you will be hunting.
1. Think like gold! “If I were 19 times heavier than
the same volume of water, where would I go?”
2. Understand the streams and the water dynamics or
the deserts around you.
3. Take a look at the overall geology. Look closely at
what is easy to see then deeper to see what others miss.
4. Take notice of any big trees or massive boulders that will change water flow.
5. Don’t forget about the inside bend, but also keep in
mind there are so many things that can change the way gold
drops out of the flow.
6. Do your research beforehand.