DEMPI Aurora

[Funfinder]

YES!!! I made it! *laugh*

And for luck we have here enought PI specialists,
but you have to deal now with strong MHz pulses.

[kt315]

your MHz's will be consumed by upper layer of ground. you do nonsense, as always.

[bernte_one]

looks like a simple non linear junction detector, but designed for coins only

[Andi68]

Schematic please

[Funfinder]

Don't listen to KT, he's meanwhile on some weired Pseudo-Science-Trip! *laugh*


First I wanna introduce you to the name: DEMPI means:

Directional-Electro-Magnetic-Pulse-Induction

Aurora is the mythologic goddess of dawn.
https://en.wikipedia.org/wiki/Aurora_%28mythology%29
I chose the name because of the powerful eddy-current aura
the DEMPI creates - which shine a light into the dark.
Comparable with the aura while a total eclipse of the sun.


My initial idea was to use something "EMP-Weapon" style *laugh*
but such a very strong EM-pulse would be not directional and needs
a huge amount of energy, especially over a longer amount of time.

The main important point is the directional antenna!
Magnetic loop antennas aka MD-coils are already
directional - but as we all know: not good enough!

As we see with GPR, MHz frequencies of course
can still pentetrate the ground!
Especially when the radiation power will become
concentrated and reflected.

Its stupid to think that MHz won't penetrate
through stuff otherwise you couldn't listen
to FM radio inside of a house. These waves
even go through brick-stones so also not too
extremely mineralized soil should be a problem.

But the plan is to make first intensive in-air tests until
the coin really is detectable from 1 meter distance and
next we can improve the power, the frequency and of
course the soil-penetration!

What's needed is a PI circuit but it must bursts
short pulses of very high power MHz energy!
Instead of releasing the pure current into the
coil, the power first gets transformed into MHz.
The rest ist pretty PI-style but of course the
RX-ferrite antenna will have an extra circuit
so it's safe from overloading.

The main question is if we will get the CE-certificate
for this super-detector! *laugh*
Depending on the frequency it works like a military jammer! *laugh*
It also can overload sensitive radio-equipment if the dish
points at it. Yeah, its like a litte EMP-weapon but this is not my fault,
we need strong enough directional pulses to create tough eddy-currents.

Now what frequency?!
I would say the higher the better but at least it must be high enough
so it will be reflected by the ca. 30cm-50cm dish. So I guess at
least 100MHz or something.

btw. the trick is pretty simple: To compensate the high frequency
we must use strong enough power!
With 5kHz we can use 50mA or whatever but with 500 MHz
this would vanish in thin air.

That's why we use PI and it will be All-Metal without discrimination.
Because we can't send a steady wave with such a high energy.

One thing is already now clear: In air the DEMPI will work 100% like
a charm and a coin in 1 meter distance is simple, because even
with usual MDs we can detect it already at 50cm.

The main challenge will start when the prototype is ready and
we make it deeper and deeper for all kind of different soils!

This project will bring the dusty-rusty PI-technology to a new shine!
If I would be a PI enthusiast I would be already now fanatical and
excited because this is now a whole new world of improvements!

I'm excited because of my invention but of course until we have the
first real working Dempi-detectors, this might still takes 1-2 years.
It depends on how fast someone is able to built the needed MHz-
pulse-generator and the receiver-circuit.

Of course for MD-companies who are building PI-detectors like
Minelab this is childs-play but we will have our own project here!
Or do you wanna wait until they built it and sell it for 10.000 bucks?

The simplest method would just modify a powerful PI-circuit
by adding the transmitter MHz stage. Don't know if we have some
interested ham-radio tinkerer here, but such transmitter-circuits
are not complicated anyway. I built a simple one already as a kid.

We will see! Don't be too euphoric, it will work but yet we don't
have it! *laugh*

btw. this detector will be fantastic for gold-nuggets because of
its "super" high frequency and very directional antennas.
It might be possible to find them even by a handheld-device
when they're not too deep.

And NO, this is not a LRL! But the LRL-dreamers would like to
have the DEMPI when it finally exists, thats for sure! *laugh*

[bklein]

Try Googling "flat top current pulse" and you'll get some pretty interesting reading on creating high current DC pulse drive circuits.
Maybe it is easier than you think?

[Skippy]

And here is the coin it can easily detect at 1 metre:


Your detector does resemble a NLJD device, so I recommend protective clothing when using it, particularly for your eyes.
http://www.elvira.ru/en/production/n...et-36-english/

[bklein]

Upside down Tesla coil?
Won’t detect very well underwater...

[Funfinder]

Some funny replies, for luck we will need no lead-protection clothes and
the gold targets must not that huge to be detected from 1 meter. *laugh*



The main question is pretty simple:
What creates the best strong feedback pulse!

We also could detect some coin at 10 meters with radar-antenna
by simple wave-reflection in air but this is not the goal. *laugh*

OK, those through wall scanners even operates with microwaves
and all the smartphones and WiFi routers also go by microwaves
through soldid structures as long as they are not metal-shielded.

btw. as shield we also can try some diamagnetical foil in combi
with aluminium, because we wanna detect the magnetical pulse.

Too bad we can't use directional induction balance, that way
we'd have discrimination, too. Perhaps its possible through two
different EM-pulses which "imitate" for a very short time the
two coils of a usual IB-detector - but this is pretty complex.

Anyway, the goal will be directional metal detection, or do you
wanna work in 20 years still with all those half-directional
pseudo-deep usual coils?!

So our main concern is:
How to induce strong eddy currents from a greater distance
and afterwards being able to detect or receive them.

btw. we can receive GPR-satellite signals also without Sat-dishes! *laugh*
but with TV-satellites this is not possible.
Using 1GHz "microwaves" is the question how good they pentetrate
the soil compared with 100MHz. More directional the 1GHz are of course.

And for a small handheld device I guess some 15-20cm dish would be better,
for the "direct to soil"-coil 30cm or even 50cm is OK for really good results.

btw. what kind of crap are these usual dipole GPR antennas?!
No wonder they are not deep when they radiate into all directions! *laugh*

Using kilometer-long waves (5kHz) in combination with a small 15cm coil
to detect 1mm tiny gold-nuggets is the same absurd! *laugh*
Every radio-ham expert will facepalm beause of such non-fitting antennas! *laugh*


What I would find really interesting is a chart where we see the relation
from wave-lenght compared with penetration-depth concerning all kind of different
materials and soils (using the same amount of radiation energy) !!!

as example something like the following, but this is just guessing:

10KHz --- 1 MHz --- 100MHz --- 10 GHz

in air:
no difference at all

dry sandy soil:
40cm --- 35cm --- 30cm --- 25cm

clay soil, hot rocks:
40cm --- 30cm --- 20cm --- 10cm

This we have to test and how to adjust the power!
But what in the end counts is just anyway that our directional ferrite
antenna will receive even the weakest radiating eddy-currents.

btw. this would be even an improvement for usual PI-designs.
Using more sensitive RX-antennas, instead of the usual "lame" mono-loops.


ps: a cool experiment would be to detect metal from distance by little tin-can wifi-antennas.
I have no idea if we can bring the internal chips to do this. However these wifi-transceivers
don't have much field-strenght but they are pretty sensitive concerning signal-reception.

[bklein]

Rather than a detector that finds pop cans >3 feet deep, many users want the option to detect small gold and I?m told you need to do it within 6 microseconds. So what is your goal for targets?

[Funfinder]

Only 6 uSeconds? For such a high power energy burst?
Well - I'm flexible concerning targets. Tune it for gold-nuggets first
will accelerate the development but also finding relics or coin-hoards
100% deeper will be very good.


But before we begin at all there is one important question to solve:

What kind of eddy-current-style does a strong MHz pulse causes?!

This is the crucial question because we must first know for what we are searching for,
what our directional ferrite antenna has to pick up.

Usual PI are almost like analog EMP weapons, they cause one strong DC pulse -
high current, high voltage per Meter, and then the decay curve is measured.

Its the damped sine wave, I put it already on the above posted picture:
https://en.wikipedia.org/wiki/Damped_sine_wave

But such EMP pulses, also caused by flashes at a thunderstorm,
are everything else than directional and they are causing a broadband
radiation distortion in many frequencies. Same as old car spark-ignition
systems which "jammed" nearby television-receivers.

Wikipedia writes that PI "magnetizes" the ground by strong DC voltage pulses
https://en.wikipedia.org/wiki/Metal_...ulse_induction
and next we have that computable sine wave decreasing,
which is different if a nearby metal consumes some of the voltage and
produces eddy-currents itself.

But we will not work with single DC high voltage pulses because they are
not really directional. So the main important question is:
What kind of eddy currents do we get if we use strong MHz pulses?!

Induction balance MDs are producing 5-100kHz so we can guess already
what structure these eddy-currents are having or producing.
Thing is we have to receive them from a far further distance, from some sort
of "EM-reflection" which is created by our pulses. Yes, it has a bit radar-style,
with the difference that we will find metal within other "reflecting" materials.

This is simple because mainly just metal produces eddy-currents and
sends them - non-directional - back to us.
Perhaps its simple because the decay-curve with MHz pulses is the same as
with plain poor DC EMP pulses.

But its not just about that damped sine wave:
The find will become a little transmitter itself through our MHz treatment.


We will solve this problem very fast because this is the usual GPR-technology.
https://en.wikipedia.org/wiki/Ground-penetrating_radar
(...) detects the reflected signals from subsurface (...)

This was exactly already my initial idea! Just not by continous EM-field - it would
be possible if you wanna have some 5kg heavy Lipo battery on your back *laugh* -
but by powerful directional MHz pulses !!! Perhaps 5 per second or something like that.

Another quote from wiki GPR which I did read before, so I could invent the DEMPI Aurora:

GPR uses high-frequency (usually polarized) radio waves, usually in the range 10 MHz to 2.6 GHz.
A GPR transmitter and antenna emits electromagnetic energy into the ground.
When the energy encounters a buried object or a boundary between materials
having different permittivities, it may be reflected or refracted or scattered back to the surface.
A receiving antenna can then record the variations in the return signal.


Metal objects of course have a very different permittivity as the surrounding ground.
This is also important:
"The electrical conductivity of the ground, the transmitted center frequency,
and the radiated power all may limit the effective depth range of GPR investigation."

Yes, the radiated power .... It will be really juicy! *laugh*

[Funfinder]

I've found some frequency charts here:

http://www.usradar.com/about-ground-...radar-gpr/faq/

100 MHz	20ft (6m)	60ft+ (18m+)	Tunnel @ 60ft (18m) depth 2ft (60cm) Pipe @ 20ft (6m) depth
250 MHz	13ft (4m)	40ft (12m)	3ft. (90cm) Pipe @ 12m 6in. (15cm) Pipe @ 13ft (4m)
500 MHz	6ft. (1.8m)	14.5ft. (4.4m)	4in. (10cm) pipe @ 4m 3/16 in. (0.5 cm) hose 1.8m and less
1000 MHz	3ft (90cm)	6ft (1.8m)	3/16 in. (0.5 cm) hose @ 3ft. (90cm) Wire mesh, shallow
2000 MHz	.5 ft. (15cm)	2ft. (60cm)	Monofilament fishing line

[Funfinder]

I wonder if its possible to skip all this complicated frequency-manipulation-stuff
by adding just directional antennas to the usual MD designs.

Directional means that we point the antenna exactly to a metal object - evtl. 5m
away - and the TX and RX coils are powerful or sensitive enough to find a signal!

How directional are cylindrical antennas? MD loops are flat but will "cylinders"
create some super fantastic directional electro-magnetical pulses?

But I guess if it would be so damned simple, we would have already since a
very long time super deep detecting MDs with cylindrical search-coils.

However good ferrite antennas for sure will be super directional for RX and
the TX antenna doesn't matter much, als long as its powerful enough and
reaches a good distance.

btw. if found this info:


http://www.pcte.com.au/images/pdf/Pr...rmeters%29.pdf

This primary field reacts with the electrical and/or magnetic properties

of the target which responds to it by either modifying the primary

field or, as a more general and more accurate description, generating a secondary

magnetic field; one way or another, the effect links back into the coils in the

search head (sometimes the same coil as the transmitting one, sometimes a different one),

and induces an electrical voltage in the receiver coil(s).


Inducing eddy-currents means creating a secondary EM-field source object for
a short time. We know this field is weak and it loses per square-calculation
more energy the further away is the receiver. Especially because the
eddy-currents are everything else than directional.

So all whats needed would be a high directional ferrite antenna to catch
those REALLY far away eddy-current-EMagnetical-radiations?!
Comparable with the small but highly effective ferrite antenna of an AM-radio.

At least this would be the simple solution - if it works:

Usual MD coil creates strong EM field by pulse induction etc,
ultra sensitive ferrite-antenna receives weakest eddy-currents!


Also worth reading:
Loop and cylindrical antennas act different when they contain a ferrite core:

http://www.hard-core-dx.com/nordicdx...op/amloop.html

Because the ferrite, not the loop coil, is the primary object concentrating flux
from the received station, the ferrite bar antenna is most sensitive to stations
broadside to the ferrite bar, not the loop. The longer the ferrite bar, the more
flux it can couple into the loop.

This means that the cylindrical magnetical loop RX antenna either has to be
positioned flat or: directly pointing at the target, but then without ferrite core.

And perhaps eddy-currents are also detectable with the following:
https://en.wikipedia.org/wiki/Radio_direction_finder

[Funfinder]

OK, your brains seems to be a little bit overloaded through the amount of
informations *laugh* but don't be afraid - this project starts very simple:

For the beginning we will see the ground as if it would be dry desert-sand.
The only thing what counts for now is that we'll reach a great directional distance!

Were are the super PI-specialists? Am I in the wrong forum or what?
Do you want me to leave and sell my project to some company?
If you can't value this fantastic opportunity good enough.

But I'm doing the brainwork anyway, so I don't care if you participate from it or not.
What comes around, goes around... or something like that.

Of course I would be happy if I could present you already the final ready solution
but its not so simple, since over 30 years no one was able to built a directional MD,
besides these not mentionable LRL-liars!

I still think the first solution is the best one! Very strong directional MHz pulses are
causing inside of the metal-object still very strong eddy-currents.
Forget about this whole GPR stuff with polarized waves and sh*t.
The only thing what we need first is a nice feed-back signal from metal.

And this is not a dream! The directional antenna will have a gain-factor of 10x - 50x
compared with what we have so far! And don't believe that 10 turns of a 1m PI coil
will be able to receive deep and weak feedback signals good enough.

Its simple anyway: Because no matter of analog DC or MHz:
We will listening for the magnetical feedback pulse of the finds eddy-currents -
which will work with a good fitting directional antenna of course much better.

[Funfinder]

These are other forms of directional detection:

https://en.wikipedia.org/wiki/Active..._scanned_array
https://en.wikipedia.org/wiki/Phased_array

but not useful enough for our task - besides as source of inspiration.

What still counts of course always will remain the signal-noize-ratio!
This means that when we are using a strong directional EM-pulse
also the "pseudo-metalic" ground starts causing "eddy currents".
But you know this from powerful PI detectors already anyway.

Of course this can vary concerning which frequency is used.
Even pure magnetometers get distorted by mineralized soil
and those have already a pretty wide detection distance.
But first we can't care much about mineralized soil or this
project is finished before it even really has started.


What would be your wishes? Give me some input:

Do you wanna walk over desert-sand with a small
handheld-directional-MD and be able to find 5 meters deep coin hoards?

Would it be good if it has a display with graphical output?

What is the limit of the weight so its still comfortable to use?

How narrow the directional beam should be?

These are all engineers-questions we better know before we can start
so afterwards everyone is at most satisfied with the end-results.

btw. I guess there exists already devices which produce short
strong MHz pulses - we just have to find them and adapt them
for our own purposes. *laugh*