Coil Specifics

[costantino]

Hello everyone!

I would like to build a metal detector, first a VLF (Very Low Frequency) and then a PI (Pulse Induction). Therefore, I am searching for an 11" or 12" inch DD coil without built-in electronics. Are there any coils available on the market that are suitable for both modes? If so, could you provide the respective specifications for each coil? For example:

Tx (Transmitter) ---> Inductance (L) and Resistance (R)
Rx (Receiver) ---> Inductance (L) and Resistance (R)
Maximum current that can flow through the coil

Also, if I were to build an 11- or 12-inch DD coil, what would be the optimal specifications for using it in both VLF and PI modes? What are the typical current and power consumption for VLF and PI modes with such a coil?

I have a coil from the Nokta Makro Racer II, the RC29V 11" x 7" Search Coil. I tried to search the internet for something about it but I couldn't find anything, does anyone know what it looks like inside? does it have an electronic circuit inside?

Thank you in advance!

P.S. Please excuse any errors in my English!

[GeoMax]

Hello Costantino,

first of all, PI and VLF detectors are very different in concept. I seriously doubt that you will ever find a VLF DD coil that works just as well in a PI design or vice versa. I would build a PI detector first, as it is easier to build your own coil (mono or DD) there. And in the second step a VLF detector with DD coil.

[Carl-NC]

It depends on how aggressive you want to be on the PI design. An aggressive PI will usually have a TX inductance of under 500uH with extremely low capacitance. VLF coils rarely go below 500uH and don't worry as much about capacitance. But a VLF coil with, say, a 500-1000uH TX coil can be made to work on a PI, but the sampling speed will be limited. As I recall, the old Minelab Explorer coils had a 500uH TX (and 500uH RX, I think) and they might work for both. High frequency VLF gold detectors often use low inductance windings. For example the Goldbug2 TX winding is around 250uH, but the coil includes a resonant cap so it won't work for PI. But other VLF gold coils might.

[costantino]

I found this coil below: Detech 12x10" SEF Coil for Minelab Explorer.

Could this coil be suitable for my purpose?

If it isn't compatible, where can I buy an old Explorer coil that's compatible for my purpose?

Doyou know other VLF gold coil compatible?



Thanks for all Carl

[Carl-NC]

No way to know except to try it.