MD coil Q Inductance and frequency

[goldfinder]

Any IB/VLF MD gurus out know what is the best coil inductance (I) and coil Q would be recommended for max depth and max detection capability for nugget detecting. ??

Also, best frequency range. ??

For example, what is I for Minelab and Tesoro Lobo Super Trak. ?

Any help, hints, etc. greatly appreciated.

I am working on a nugget shooter with PIC control and PIC signal processing on the detection side. I'll post design if it works well.

Thanks in advance !

Goldfinder

[Geo]

Any IB/VLF MD gurus out know what is the best coil inductance (I) and coil Q would be recommended for max depth and max detection capability for nugget detecting. ??

Also, best frequency range. ??

For example, what is I for Minelab and Tesoro Lobo Super Trak. ?

Any help, hints, etc. greatly appreciated.

I am working on a nugget shooter with PIC control and PIC signal processing on the detection side. I'll post design if it works well.

Thanks in advance !

Goldfinder

Different frequency for Gold, Silver, Copper etc!!!!!!
So, there are a lot of parameters to calculate the coil inductance

[goldfinder]

Gold !

I said "nugget shooter". As in gold nuggets.

I know there are a lot of parameters. So what is the equation or heuristic to figure this out?

Goldfinder

[Carl-NC]

Generally, the higher the frequency the smaller the gold you can get, and the more sensitive to ground mineralization. Lobo ST runs at 17.5k, GMT runs at 48k, Gold Bug 2 runs at 70k.

The higher the frequency the lower the inductance you need to use to stay below self-resonance. There are ways around this but low inductance is by far the easiest.

Try 20kHz and use 1mH for both the TX and RX coils.

[technos]

I have noticed that most nugget detectors (at least the most popular) run in the 17KHz to 25KHz range. The problem with the higher frequencies is that you will sacrifice depth. But perhaps that's not an issue for the area you would be working.

[goldfinder]

ballpark inductance ?

Generally, the higher the frequency the smaller the gold you can get, and the more sensitive to ground mineralization. Lobo ST runs at 17.5k, GMT runs at 48k, Gold Bug 2 runs at 70k.

The higher the frequency the lower the inductance you need to use to stay below self-resonance. There are ways around this but low inductance is by far the easiest.

Try 20kHz and use 1mH for both the TX and RX coils.

Great answer Carl - thanks much. I'll give it a shot. I have a spreadsheet to do coil comps and also does Q and capacitance. Computes inductance a couple ways as a check. If anyone wants a copy I can send it to you and you can put on your site.
Goldfinder

[miqui]

I am working on a nugget shooter with PIC control and PIC signal processing on the detection side. I'll post design if it works well.

Thanks in advance !

Goldfinder

Is it possible you post the design now to try to help, maybe we any idea aboutthe design.

thanks ,
Miqui

[miqui]

Any IB/VLF MD gurus out know what is the best coil inductance (I) and coil Q would be recommended for max depth and max detection capability for nugget detecting. ??

Thanks in advance !

Goldfinder

I thinkinking to work in a nugget detecting too

Thanks,
Miqui

[goldfinder]

Great answer Carl - thanks much. I'll give it a shot. I have a spreadsheet to do coil comps and also does Q and capacitance. Computes inductance a couple ways as a check. If anyone wants a copy I can send it to you and you can put on your site.
Goldfinder

Thanks Carl - is that milli henry by any chance? micro henry is way small. for an 8 inch coil that computes out to 1 turn; whereas, a 49 turn coil is about 2 milli henry or 2000 micro henry.

Goldfinder

[goldfinder]

PIC VLF machine

Is it possible you post the design now to try to help, maybe we any idea aboutthe design.

thanks ,
Miqui

Miqui,
I am going to use the "Matchless" IB/VLF design for a basis. A PIC will drive a mosfet to drive the transmit coil so I can easily control frequency, timing and it allows me to also different voltages and current on the xmit coil. On the output side I'll have the receive coil input to a preamp and amp with capability to control level. That will feed into an PIC uC which will have some of my jim-dandy signal processing software.

Beyond that I have no real design detail. Mostly a cut and try once I get the front end working. Scarborough had a basic nice design with 90% dept and detectability wrt some decent commercial MDs. I have the design in my head but not on paper.

When I get further along I post results. Don't hold your breath as I am a little slow but will get there.

Goldfinder

[Qiaozhi]

Thanks Carl - is that milli henry by any chance? micro henry is way small. for an 8 inch coil that computes out to 1 turn; whereas, a 49 turn coil is about 2 milli henry or 2000 micro henry.

Goldfinder

1mH means 1 milli-henry.
1uH means 1 micro-henry.