VLF vs PI depth !

[Funfinder]

Many people here have PI and/or VLF detectors, even selfbuilt.


Now please letz forget just for a single moment about discrimination and focus on depth only.

What are your experiences so far?

How much percents the PI goes deeper with the same coil size?
Important: A DD coil with 30cm outer diameter counts as the same like a 30cm mono PI coil even if the DD consists of 2 slightly smaller coils. AND: if tested in medium mineralized soil.



The Minelab GPX 5000 with 30cm Mono-PI-Coil (no disc) seems to be able to find best low conductivity coins in medium mineralized soil - the test video shows such smaller coin at around 35cm / 1ft plus. But perhaps only for a trained ear that can recognise the smallest changes in detetection signals and while searching real slow and carefully.


Is your PI really deeper at all than a VLF / TR / IB? Or does it just wastes battery-power?

Or do exist some general test results already about this topic?

[SVEN1]

My home built PI's will give a slight increase in threshold at 36cm when passing a large man's wedding band under the coil air testing. I can not hear this change when hunting in the water or on the beach as the threshold is not 100% steady due to ground conditions that change. But, there are times I might hear it if ground conditions are stable? I haven't actually buried any targets yet to see how deep I can penetrate our local sands which does contain black sands. My water scoop with a magnet attached always has a fuzzball of black sand sticking from it.

From the way my PI is calibrated, it discriminates out most small foil but, still picks up the small gold rings. I actually like using the PI more than the VLF, hate digging the small foil.

Next time out I should bury some coins and rings and see how deep the machines will actually detect the target. I don't think any of the coins found today at the beach were over 5"-6" deep. But, did get signals from targets deeper than 12 inches that I did not dig down to as they sounded like larger pcs. of iron. I am not sure how much deeper my PI's will go vs. a higher end VLF machine, haven't had enough actual hunting time on it. I did make a 7" search coil that almost air tests as well as the 10.5 coil pictured. The 7" coil is fun to use but, the 10.5 covers more ground. i am still working on slowing down my swing and keeping a steady rhythm from side to side without stopping at the end of each swing

[Funfinder]

@ SVEN1
> threshold is not 100% steady due to ground conditions that change

Shure, but this is the final sensitivity or signal vs error-signals.


Perhaps this question looks too cheap for all the many readers or writers of this forum but I am still looking for answers!

Here must be a person with PI and VLF that have same coilsize!
So do us all a favour and tell us your experiences.

Until this happens I'm simply assuming that PI indeed just is
a waster of battery-power with bad disc and extremly detection-
errors if it comes to high mineralized ground.

I know already information of professional PI-detector producers
that write that their PI with 50cm mono-coil will detect only huge
coins and not any deeper as a VLF.

The only advantage if it comes to depth may be the more
practical because more lightweight 1m frame coil consisting
just of 25windings instead of 100 to 500 a "real" detector
would using for such a difficult task.

[Waikiki_Sweep]

Multi-frequency

Looks like you forget third kind of detectors: Multi-frequency
Check out last one: Minelab CTX3030
I saw it working. Almost 2 ft. for nickel in air.
Incredible depth in ground and strong target ID.

I believe it will bit both PI and VLF for the depth.
But in salt water people told it little bit noisy.

[Funfinder]

Minelab CTX3030 should be Multi Frequency P.I. with 25cm coil?!

Mod. Pirate Black Devil from Bulgaria for 250 Euro also seems to
can do this - VLF induction balance, 25cm coil - of course in air.

PI in air is absolutly an "unfair" test situation because PI
sends out very strong impulses and receives much better
feedback EM in air than in soil. This is almost radio transmission.

Is this already the proof that PI has 0% depth advantage?

Any info about how compete diving MDs for salty sea water?

[Mechanic]

HI Funfinder,

How do you explain this then, in Australia up until 1995 all manner of vlf detectors were used to find gold in the goldfields. By 95 gold was becoming extremely difficult to find because every man and his dog had been over the ground. In 95 Minelab released the sd2000. This saw the goldfields open up again people were finding nuggets again and big nuggets at that. Sure a vlf might get better detection depth in air vs a pi, but put it on some hot noisy ground and the pi(provided it has a good ground balance system) will eat the vlf for breakfast

Cheers Mick

[sido]

Just to add to Micks reply.

Here in OZ (Goldfields) there are two layers of mineralization present than affects detectors in general. One the surface layer just beneath the soil and another deeper layer down a foot or so.

Both VLF and PI will see past the first layer, but where the PI excels is past the second layer, therefore being able to excite and detect targets that a VLF is unable to do so (basically cannot penetrate past the second deeper layer)

SD2000's, being Pi performed the best with a compromise of not having discrimination ability.

Now in neutral soil or mild mineralization, that is a different scenario and this is where a VLF may come even to PI performance on those particular soils with the ever help full of having discrimination ability.

Cheers Sido.

[Funfinder]

Great, at least the hopefully constructive discussion has started
and we have some gold-hunters from Down Under here.
Because those should use the most P.I.s at the gold locations.


So far the only thing is proofed that a detector with the same
EM-field energy will penetrate the same distance, no matter if
P.I. or VLF.

Or a VLF would be even better, if it doesn't works with a
groundblurring and extremly E-smog sensitive motion-circuit.
But alot treasure-hunters want it the most easy way possible
because detector itself and digging is heavy enough...

PI with discrimination exists already for a long time and it
still has not become a breakthrough in MD evolution.
If PI really would be so much better, it has beaten
VLF for a long time now already.

Especially since 5 years where high current LiPo packs are
available for a good price, providing enough PI energy.

Are all those Gold PI detectors not completly different,
and this explains why they are better than VLF for this task?

They have little 15cm coils for better small nugget detection,
instead of discrimination the circuit can fully concentrate for
the soil conditions and the frequency is adjusted to gold only.


And the same with the huge 1m frame detectors:

Would be really interesting to compare the Jeohunter with its
1m x 0,7m coil with a 1x1m frame P.I. in high mineralized soil.
I'm shure the Jeohunter is deeper because it uses much more
inductivity compared with those louse 25 PI windings, even if
the PI may use much more peak voltage pulse energy.

The count of windings of the PI is very limited because
of the timing - more windings need too much time to
establish a strong EM field and the breakdown of this.

You just have to read some of those PI 1x1m depth infos from
the websites of those who sell them - not really convincing!


We really have to test this very exact and serious so finally we
have some clarity and the simplest test would be the following:

What detector with the same coil-size beats the Minelab GPX 5000?


- 30cm mono coil for the GPX, up to 30cm coil for VLFs
- little to medium coin, low conductivity
- high mineralized ground that varyies every 3m slightly
- same distance coil ground
- coin buried at an area of 10x10meters, location unknown
- best possible sensitivity settings for all used detectors
- weak e-smog sources nearby

I'm hearing already ivconic that will write that his Deus XP
with large coil (sorry, but it is over 30cm ) will beat the
GPX 5000 with ease, because the XP even finds a 0,1mm
coin of 1cm diameter buried vertically at 30cm depth.

But this is no joking now - if someone has the GPX 5000
plus the Deus XP or he has a friend or knows somebody
with the needed detector we may have a chance to get
those tests and more important: finally clear testresults.
The Minelab GPX 5000 of course must use a 20cm mono
coil or some coil with the same size the Deus XP also uses.

[satdaveuk]

HI Funfinder,

How do you explain this then, in Australia up until 1995 all manner of vlf detectors were used to find gold in the goldfields. By 95 gold was becoming extremely difficult to find because every man and his dog had been over the ground. In 95 Minelab released the sd2000. This saw the goldfields open up again people were finding nuggets again and big nuggets at that. Sure a vlf might get better detection depth in air vs a pi, but put it on some hot noisy ground and the pi(provided it has a good ground balance system) will eat the vlf for breakfast

Cheers Mick

Your so so right Mechanic, Im suprised because this been a tech forum and air tests are still talked about like you get in the kiddy forums.
Air test are a joke and at the very least boreing, if I see another utube air test will pull my hair out, they prove nothing apart from that they can detect metal in the air, which is no good to man knor beast unless your looking for metal in the air, which we have eyes to do that, so know benefit at all.
Theres never been a problem detecting metal in the air of some great distance since the late 1800s using bog standard BFO format, ive built detector in the past using a MW radio as the pick up which got me well over 12" using very few common parts, so wheres the big deal.
The big deal is getting distance under are earth amongst all the crap thats bouncing the signals all over the place giving us false readings.
Going back to your question which is a worthy topic, the best Ive recorded with a old copper penny was 18" in pasture land with VLF which was a whites DFX, disc mode, but keep in mind I use my own custom programs, very little disc and dig almost everything, and also bare in mind that very same coin in a different location could be more or less depth .
The problem im facing with PI over here in England is there not much good for pasture as we have so much iron in are soils due to thousands of years of farming, beach not had much experience but will be testing the Mnipulse3 next month in cornwall .

Regards
Dave

[sido]

Consider this too....Pick a ground with higher mineral content and test a VLF's performance compared to a PI (same coil sizes etc...). The PI will out perform the VLF for reasons as stated in my previous post.

The higher the mineral in soil, the worse the VLF will perform in respect to depth penetration. The PI will see deep targets that the VLF will not.........

Look at it another way, Minelabs best VLF, BBS, FBS whatever they call them, seldom you will see anyone using them in high mineral grounds (goldfields). Great for mild ground conditions (parks, dry sand etc..., also good depth and discrimination in these conditions.

Air testing is a waste of time, In fact you can air test the latest GPX5000 and you would think something is wrong with the machine, why, because the VLF will probably air test better......in saying this where it counts in performance is on real soils and all types for that matter.

Sid

[Woody.au]

It is the way the P.I excites the target that gives it better depth capability, P.I detectors are mainly very low in operating frequency compared to vlf detectors. The higher the operating frequency the more pronounced the effects of ground minerals or conductive salts impeding the rise and fall times of a sine wave and via magnetic viscosity of ground minerals reducing the effectiveness of high frequency signals penetrating deeply. The P.I needs to be looked at differently by the way it increases magnetic flux into an object over a longer time period than just hitting a deep object with the very small residual of a sine wave. I have tried various detectors over the years, (since 1980) also some home brew creations. Nothing beats a Pulse Induction detector for outright depth in any soil, including sand. In laymans terms one can look at ground as a big resistor that is frequency dependent on the amount of energy it absorbs, the more transitions over a given time period the more energy is literally turned into heat. There are also other factors such as phase distortion and other strange effects.

I should add that the first P.I detectors where very long pulse type detectors that had on times say from 200us to 1ms These detector went very deep on large targets, now the new detectors run from 15us to 60us to get more samples per second to increase sensitivity to very small Gold at the expense of larger deeper targets. The secret to getting as much depth out of a P.i is to keep the current flowing into the coil and continuing to increase and turn off the detector at the point of maximum current and shut it off fast.

[Davor]

Actually, the only advantage of PI is omitting the fast decaying soil response from Rx reception by means of a delayed sampling. At VLF this would be equal to notching out the ground vector + and - several degrees (as if it was that simple ).
I can imagine such VLF system, and in case you overdo with notching ground and more degrees beyond, you lose discrimination ability, and it becomes deaf for small gold ... oops, we already have that with PI

[Funfinder]

one question first:

What are the problems if a small VLF DD coil want's to work
properly inside of a large PI coil? Using different frequency of
course and distance minimum 30cm between the coils.



ThX for the new interesting info.
If PI notches out ground or exactly spoken the area from small
gold to light medium mineralized ground the main problem is:

lack of full detection capability and enough sensitivity to
distinct between the slightest "colors" of mineralisation

We must not forget that 1 liter of mineralized soil has the
same EM interaction structure as a small plate of iron
(haven't tested the total exact values yet)

That's why real successful and deep detection always
has to do with HIGHEST POSSIBLE CONTRAST-FACTOR !

PI sometimes is like digging up the flower bed with an excavator.

PI with long powerful pulses (0,1 sec) shure will work just
fine for very deep large targets - but only if the contrast is
high enough to the surrounding ground - even by size or by
kind of metal (as example aluminium in high miner. soil).


We must not forget ONE thing:

VLF creates a steady EM field like a transmitter with
carrier frequency! All kind of frequency, amplidute or
attenuation effects / shifting is detectable that way -
for the benefit of very high contrast factor.

btw. that's the reason why VLF can work with such low
energy radiation fields and the circuit is fast enough for
such "games" like motion-ground-blurring or real time
soil condition adjustment etc.

Accu powered coil for PI would be unthinkable.

But because disc doesn't matters with PI the most
sensitive Pinpointers could be created - border sensitivity
devices with shifting sound frequency. Of course those
Pinpointers have to work with Li-Po packs and not with
alkaline 9V blocks that are expensive and lasts just a few hours.


In the future the MD producers will not have a chance
if they don't provide a much more sophisticated ground
analyses technic. As example there could be some small
segmented satellite coils that analyze the ground conditions
much more detailed and compute a picture of the below
radiation patterns. The best idea therefore would to use
a spiral-coil with 10 different circuits and each one from
very small to very large diameter gets compared by the
detectors firmware with the others!

I doubt this would be possible with PI, but a bunch of
small PI coils with slightly shifted timing could be used
to form a 3x4 grid and the electronic compares them
and sums the whole signals up somehow.


btw. I've seen some of those PIs in Australia in action.
Perhaps it was a Minelab, maybe not - but they detected not
only special single very hot hotrocks but also many many
iron junk parts. Shure those find some nature gold, but not
in the form of fine sand, just upwards a certain nuggets-size
and most of the time only if those nuggets are directly near
the ground. PI in high mineralized soil will penetrate maximum
15cm for usable distance, because the gold-nuggets are not
that huge that you will detect them 35cm / 1ft. away - such
bonanzas are extremly rare. You can get them in Nome, Alaska,
5m below the sealevel in the water, but also buried, above the
layer of clay and hard bedrock.

[bklein]

I was hunting a local beach with a CTX-3030 and hit an area with a ton of coins. All nickels and pennies, little or no quarters. I found only one ring - but my first (yea).
There were so many targets I looked like a digging fool. I came home and looked at all the coin and realized it is all newer stuff but heavily corroded and coated with a brown coating. I have no use for it - a lot of it even if cleaned would be unusable. So I masked out the pennies on the CTX and went back the next day. Even though masked out I could see the pennies were still there and nickels too. No rings this time. A guy on a forum was saying that the black sand layers there were masking out the rings under them. His surfmaster DF was finding rings. Is this the story or did I just not have the coil over the right spot? (or someone beat me to them that day) With the DF would there be a way to tell a deep target (ring) from one of the shallow pennies?