Bad Ground

[WM6]

Thanks for your all efforts to educate members here, mikebg.

What if H1(f) and H3(f) not differs in shape?

[mikebg]

Thanks for your all efforts to educate members here, mikebg.

What if H1(f) and H3(f) not differs in shape?

WM6 my efforts are directed to colleagues in Russia because they are physicists, not familiar with theory of signal processing.
The phrase "H1 and H3 not differs" means that there are no eddy currents in the soil. If this is so, then H1 and H3 have the shape of the GND signal received by REF coil, ie we can calculate easy the shape of H2.
I will post description of equipment for measurement of H1 and H3. Unfortunately I can not test OZ bad ground because my test equipment needs about 16kg soil. Now I'm measuring all avaliable (not Australian) soils.

[WM6]

Unfortunately I can not test OZ bad ground because my test equipment needs about 16kg soil. Now I'm measuring all avaliable (not Australian) soils.

Maybe you can find even worst soil than one from OZ in your neighbourhood Anatolia.

This is from Wiki:

"The old term for the mineral is magnesia. Stones from the Magnesia region in ancient Anatolia contained both magnesium oxide and hydrated magnesium carbonate as well as iron oxides (such as magnetite). Thus these stones, called Stones from Magnesia in antiquity, with their unusual magnetic properties were the reason the terms magnet and magnetism were coined."

[Sergey_P]

T – target (T=(Tx*t)(t),is convolution)
G-ground (G=(Tx*g)(t), ..)
T and G – a stochastic process (or random process)
S=T+G - received signal

[mikebg]

Maybe you can find even worst soil than one from OZ in your neighbourhood Anatolia.

This is from Wiki:

"The old term for the mineral is magnesia. Stones from the Magnesia region in ancient Anatolia contained both magnesium oxide and hydrated magnesium carbonate as well as iron oxides (such as magnetite). Thus these stones, called Stones from Magnesia in antiquity, with their unusual magnetic properties were the reason the terms magnet and magnetism were coined."

Thanks WM6! You are great Webfinder.

[ishtar hunter]

Buy Jeohunter and you do not need to experiment anymore.

yes i have a geo hunter and it's very good for bad ground .

[WM6]

yes i have a geo hunter and it's very good for bad ground .

Problem is, that we do not need bad ground, we need gold (or at least silver).

[mikebg]

Problem is, that we do not need bad ground, we need gold (or at least silver).

To WM6 and all other Webfinders.
We will find gold and silver even buried deep in the bad ground.

The measuring equipment, which I'm using now to measure bad ground is complicated, expensive and operates too slowly becase uses primitive principle. It can measure until 2MHz, but it can not operate in the field. My measurements showed that there is nothing interesting for bad ground properties at frequencies above 20kHz. As you know, the TX of most conventional metal detectors operates below 20kHz.

I need colaborants to find in the WEB and to test all free available softwares, which use the soundcard of PC to measure frequency response, impulse response and THD (total harmonic distortion). Many radio and audio amateurs use laptops for such measurements.

I wish to involve many participants of the forum to measure spectral characteristics of targets and soils at audio frequencies (below 20kHz).

Soon I will post the sketch of a cheap and simple sensing equipment which everybody can build to measure responses of very bad ground with a laptop. For measurement of targets and small amounts of ground, you can use laptop and the sensing head sketched here in post #18. The head needs only two shielded cables for connecting to headphone and microphone jacks of laptop. I think there is suitable software in the WEB.

[WM6]

Soon I will post the sketch of a cheap and simple sensing equipment which everybody can build to measure responses

.

No more sketch, dear mikebg, please, post complete working schematic.

Left sketch to TV show.

[ishtar hunter]

Problem is, that we do not need bad ground, we need gold (or at least silver).

Geohunter3D is a turky proudact and I have geohunter & it's performance to detect non-ferrous metal in bad ground is very good and you can easily balance in bad ground & Land mine, yon can see this site http://www.makrodetector.com/?t=Jeoh...id=127&setLg=1

[WM6]

Geohunter3D is a turky proudact and I have geohunter & it's performance to detect non-ferrous metal in bad ground is very good and you can easily balance in bad ground & Land mine, yon can see this site http://www.makrodetector.com/?t=Jeoh...id=127&setLg=1

I know that it is from Turkey, as you, and maybe this is reason for your promotion.
I believe that one can detect something with Geohunter too, as by most of detectors can, but investment in Geohunter will not be refunded by findings in one whole life. Therefore I see no reason to throw money away for such "hi-tech" toy, which do not exceed the actual performances of say $50 SurfPI kit.

[mikebg]

I need colaborants to find in the WEB and to test all free available softwares, which use the soundcard of PC to measure frequency response, impulse response and THD (total harmonic distortion). Many radio and audio amateurs use laptops for such measurements.

I obtained results with phase error trying to use the soundcard of my PC as metal detector. As you see, the phase of bad ground changes in too wide range, which is impossible in theory.
My computer shows two drawbacks at collaboration with the software HOLMImpulse:
1. The soundcard can not examine bad ground at frequencies above 7500Hz.
2. The microphone amplifier in soundcard operates with AGC (Automatic gain control). The settling time for gain reduction is about 4 seconds, ie my "metal detector" operates allways in motion mode.
I have two questions:
1. How to make the soundcard to examine frequencies up to 20kHz?
2. How to disable the AGC of microphone amplifier?
Does anyone know the answers?

[taliesin]

I obtained results with phase error trying to use the soundcard of my PC as metal detector. As you see, the phase of bad ground changes in too wide range, which is impossible in theory.
My computer shows two drawbacks at collaboration with the software HOLMImpulse:
1. The soundcard can not examine bad ground at frequencies above 7500Hz.
2. The microphone amplifier in soundcard operates with AGC (Automatic gain control). The settling time for gain reduction is about 4 seconds, ie my "metal detector" operates allways in motion mode.
I have two questions:
1. How to make the soundcard to examine frequencies up to 20kHz?
2. How to disable the AGC of microphone amplifier?
Does anyone know the answers?

Is your sound card built into the motherboard of your computer? If so.You could buy a cheap second hand slot in sound card and disable the agc on it's board.some old cards used bigger components easier to work on.

[taliesin]

try this page mike

http://realcare.intervoice.com/voice...sf_FAQ.html#Q7

[Aziz]

Hi Mike,

don't use the microphone input. Use the stereo line input.

Microphone input is often restricted (band limitted) to the speech frequency range (max. 8 kHz). It has a high input impedance and has a high gain, which is very very noisy. Mic in is usually mono channel.

Well, some "incompetent hardware *******s" implement a low pass filter on a high quality high sampling rate sound cards (low-pass fc << nyquist frequency). I have one sound card, which has a SR of 96 kHz but the bloody ******* allows me only 20 kHz bandwidth (I can not see the 20-48 kHz range even if I sample with 96 kHz).

And we have some "incompetent software *******s", which don't allow the high SR (96 kHz). Some of them even can't make the damn software stable & reliable.

Not every sound card is convenient.
Aziz