Cable locator

[Davor]

If so, are you planing to built such a circuit and experiment with it?

Eventually, in a way, yes. I'm thinking of engaging the existing detector in a 2 box configuration, and also as a completely passive device, where the upper coil (otherwise 2 box Tx) would receive air signal, amplify it to binary level, and use it as a reference for lock-in operation of the existing Rx. In such case it would operate a lot like the devices in this book, only with the benefit of lock-in amplifier. It should work, but I have no idea how good.

I'm about to make a detector that will cover upper VLF, and lower LF, and I'm also examining some alternative approaches. So 2 box is in fact only one of the possible solutions. IMHO 2 box will become much more sensitive with a meaningful lock-in amplifier.

[ivconic]

Eventually, in a way, yes. I'm thinking of engaging the existing detector in a 2 box configuration, and also as a completely passive device, where the upper coil (otherwise 2 box Tx) would receive air signal, amplify it to binary level, and use it as a reference for lock-in operation of the existing Rx. It should work, but I have no idea how good.

I'm about to make a detector that will cover upper VLF, and lower LF, and I'm also examining some alternative approaches. So 2 box is in fact only one of the possible solutions. IMHO 2 box will become much more sensitive with a meaningful lock in amplifier.

Similar to Cscope 33XD...

[Funfinder]

Sounds like a professional task but I'm shure you can get some successful results.


The most important thing will be to get useful field-strenght-compare-outputs because the distortion or changes of the from far away coming
radio waves will result in field-strenght-changing magnetical-pulse-polarizations. Make shure therefore that your detector is vertically or horizontally
good balanced while walking so the coils don't change their total position for more than 5°.

The coil ground distance also will matters alot while using such weak foreign waves.
Of course a 2box design with its own little radio transmitter will be much more stable then.




btw. the whole topic reminds me on those youtube radio-metal-detectors DIY manuals:

www.youtube.com and serach for: am radio metal detector

this here works by coil-detuning if a metal object comes near
http://www.youtube.com/watch?v=VXIhxoqCliE

If such an AM radio contains already a signal-strenght-meter it could be used directly with some modifications.


and this here is really interesting:

it shows the EMFAD GPR output:
http://www.youtube.com/watch?v=8pPvZdL88Ik
The burying procedure goes til 4min30 and after this you can see the EMFAD software results.

and here you can find alot EMFAD info in german language:
http://www.schatzsucher.de/Foren/arc...x.php?f-6.html
Seems the EMFAD exists already since 15 years or even longer.
And even the treasure-hunters in Germany had their problems with it:
"sometimes the EMFAD receives signals, sometimes very bad and sometimes not at all."

And the price for a new EMFAD in the year 2000 was 27.000 deutsche Mark (ca. 13.500 Euro)
So with some "Hombrew-EMFAD" really alot amount of bucks could be saved.


Davor, perhaps it also would be good if you can find a way to send the data of your detector to some Laptop.
For the beginning even a simple oscilloscop-programm feeded by the soundcard line-in or mic could do the job.
Or even more simple - some sound-recording software so afterwards the signal-strenght over some longer time-line is visible.

If working with such "fragile" and weak detection-signals a good output will improve a lot.
Even a row with 20 LEDs already would give a good range of different detection signals.


Have fun and listen while experimenting to some cool radio music!

[Funfinder]

this post here is also interesting:

http://www.schatzsucher.de/Foren/showthread.php?t=24479

orig. in german, translated below by google:


Long wave radio
Hi,

I had read in some forum about long-wave detection.

World receiver, strong transmitter antenna on the ground and in failure, there is a cavity.

Nonsense?
Practicable?
References?
DEFI is offline Reply With Quote
Old 28.04.2006, 13:11 # 2
Hobbyists
Commander


Avatar hobbyists

Joined Feb 2002
Location: Dortmund
Detector: SC 625, B.J. 1944
Posts: 4,249


I've already thought about it, but discarded because the process is too difficult for laymen provides interpretable results.

Of voids and metal parts arise as interference, which lead to an increase or decrease in the measured field strength contours of a larger bunker can be distinguished bad because this change in field strength varies across the object, and also still can be overlaid fading phenomena in the main signal.

And otherwise is not every radio and each antenna, the radio should be able to receive as the DCF77 time signal transmitter, which is particularly suitable for a turn-off loss of control and field strength haben.Als antenna selectively tuned external ferrite or frame-antenna to the time signal transmitters for these things.



But here is the matter certain people who are more knowledgeable than me so ...
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Old 28.04.2006, 14:04 # 3
ORIGINAL
Knight


Avatar ORIGINAL

Joined Sep 2002
Location: Lago di Baldino
Detector: eyes, hands and ears
Posts: 332


Physically, the right. But difficult in execution. The LW radio reception has particularly during the day a fluctuating field strength. The geological reflections therein go well. Better results should result in the evaluation of the frequency shift. This requires a separate long-wave radio source should be moved quickly across the grounds. Difficult remains the direct ground wave so strong shield that does not plug up the receiver and the interference can be taken ...
Are there commercial probes fuktionieren so?
My 2 cents
Gina
__________________
Greeting Gina

[Davor]

There is more to a signal than just amplitude, and there is more to a hobby than unloading insane amounts of money just to see a nice picture on a screen in 64k colours. I just can't imagine myself roaming the nature while ogling the PC screen all the time.

I'm not into ruining some people's business and I simply won't barge into someone's niche with my version of their equipment. Also any kind of ridiculous oversizing of simple wearable portable equipment is a big NO for me.

As for LF and detecting big "things" in the ground, my recent interest is in mineral hunting, and those tend to grow in veins, and especially in voids, so there you have it. And places I wish to investigate are not a least bit friendly with cumbersome oversized equipment with odd antennas jotting allover the place. It just must be compact, and interface must be human.

[Funfinder]

You're right but I prefer results and facts, so pls tell us in 1 or 2 months how it goes or ask specifical questions if you need help.

And personally I wouldn't care if others want nice displays and spent many thousands of dollars for such kind of technology.
btw. that EMFAD not just has display but also audio-ouput so you can walk and listen without tablet, laptop, netbook etc

And prospecting minerals with such detectors - I don't know. Must be very strong veins at least; better with the eyes.

[Davor]

Again, 1 or 2 months is not my timeframe. This is my hobby, so far.

As for veins, yes, they tend to come in kind of pattern, but nice crystals grow in voids or geodes that don't. I have no idea if this is going to work, but I know a few people willing to invest some serious labour (and a few pounds of dynamite) to reach these.

[bernte_one]

ok here is first part of the 77,5 khz passive locator

[Funfinder]

@ bernte_One
The PCB lauyout looks real good.



@ Davor
I was interested in collecting minerals already as a child. Many days I spent at canyons and gorges to collect special stones, brought by glaciers or which can be found directly there. Walking over scree- and gravel slopes, climbing mountains.

Most of the times metal-detectors won't bring you much further here as long as you don't check out old gold-mines with them for overseen veins etc. but with detectors that can find cavity you also will find special high-mineralic stones and meteorites.

If you wanna find large stone-druses which contain rock-crystals (quartz) with special cavity detectors it may work.
The usual way is to look for flourid- or chlorid-sand outside of the closed rock-walls. But it depends of the content of the rocks there (granite, gneiss, slate) and the size of the little cave if such a detector can sense any difference from the outside. Sometimes those are very small cracks and sometimes they are filled with clay or sand.

For usual sites the strenght of the mineralic ground will have not enough difference, but ore-veins in limestone may have, there you also can find silver.

afaik geologists are using special detectors (also seismic) for prospecting but most still is by investigating the different stone-layers or geografic conditions.
For mineral-finders the usual way is to check out the already existing info (what places or regions are good) and hunt there.

For you could be interesting a location with given up mines - some time ago I saw a report from the Kosovo where the remainings of very old gold mines are still visible.
Here you could be able to locate old tunnels, wells and drains incl. old tools and ore-stones from the mine. But in the mountains of Croatia or north in Carinthia, Austria in
the Alps also is such stuff to find and the good thing is: many of those lost mines are far away from any villages or people, some are even 3500m sealevel.
I have a book called "Gold-treasure-chamber Alps" which is full of stories and info about such old gold- and other ore-mines - many of them were buried for 500 years
under snow and ice. For alpinists today it is very interesting to climb such montains and check out the old tunnels and remainings of those high-mountain-ranges with metal-detectors.

btw. some mines and caves in Croatia also have been used in 2nd Worldwar to get rid of the bodies of the enemies, so be careful you don't find bad surprises...
There are islands on the south dalmatian coast where you don't wanna know whats left in the caves. But the more danger can come from the mine itself -
depending on the bedrock and how stable the mines are built this stuff can kill persons, even by poisoned gases.

Personally spoken I've been - also with metal-detector - in several mines. It's really cool and adventurous there. Found already over 10 chisels and other stuff.
With basecap and LED front-lamp, with T-shirt and some jeans, no problem, you don't need the complete mine-workers-outfit incl. plastic helmet and stuff,
but sometimes it needs some climbing skills or rubber boots. War bunkers and tunnels are also interesting, but depending on the concrete and other factors
it can be quite dangerous there or you may find not really harmless war remainings there. Some may have been used to hide treasures, but most of them are empty.

If they say that the longwave under good conditions can penetrate 100 meters into the ground, it also may work inside such mines or tunnels, to find blocked ways etc.

but it seems that detectors using very short waves from 30-300 MHz also are able to penetrate the ground up to 15 meters.
The russian Loza and the german easyrad (which is a quite priceworth GPR) are working on this frequency, using 2 dipol antennas which have around 1,5m distance.

And if its the same as with the usual metal-detector cavity distinction by ground-balance-values, it will not work if the ground is sandstone or other low-mineralic-stuff,
because that way the contrast-factor "empty cave" versus "ground" is too weak to see changes there of the EM-field.

Higher frequency allows higher resolution but the penetration depth for shure will be not very good - but for ca. 5 meters depth it may be good enough, if the ground or
the walls of the mines are just medium mineralized.


Now you have the full info and you can pick the best way. Good luck and don't get lost in some old treasure-mines! I wanna see some long-wave devices first and hear how they do.

[Davor]

Thanks for the heads-up

[bernte_one]

next part
tone and optical exit part


p.s. thats my second design with sprint layout 6 i´m totally a noob in this case

[bernte_one]

i found a seller for those stuff
http://www.metageo.de/pages/produkte/vlf-geraete.php