I did some air tests tonight using the needles received from Nupi (plus a small square of aluminium cola can - 5mm square). The bottom line is that none of the detectors I tested could detect any of the needles.
The detectors used were:
Laser Hawkeye
Garrett GTX1000
Nexus Credo
Tesoro Bandido
Minipulse Plus
Crossbow Classic PI
Prototype PI
Only the Hawkeye, GTX1000, Credo and Bandido could detect the small piece of aluminium can.
However, I'm not surprised that the PIs were unable to see it, as they're designed for beach and relic hunting. The prototype PI has a bipolar transmitter and an 8us sample delay, and even that was unable to detect it.
VLF detectors are generally more sensitive to small metal targets than PIs (which rely totally on detecting the eddy currents in the target). Since the target is very small, the eddy currents have substantially died away before you can take a sample. Whereas a VLF detector continuously stimulates the target, and is able to receive a stronger signal than the PI. On the hand PIs can have a distinct advantage in mineralised ground, and don't lose as much depth between an air and a field test.
For detecting very small targets, a VLF is definitely the best choice (if the ground is not mineralised) probably with a high TX frequency, and a small coil.
Nupi - Thanks again for the needles. They will make some good test targets for future projects.
The detectors used were:
Laser Hawkeye
Garrett GTX1000
Nexus Credo
Tesoro Bandido
Minipulse Plus
Crossbow Classic PI
Prototype PI
Only the Hawkeye, GTX1000, Credo and Bandido could detect the small piece of aluminium can.
However, I'm not surprised that the PIs were unable to see it, as they're designed for beach and relic hunting. The prototype PI has a bipolar transmitter and an 8us sample delay, and even that was unable to detect it.
VLF detectors are generally more sensitive to small metal targets than PIs (which rely totally on detecting the eddy currents in the target). Since the target is very small, the eddy currents have substantially died away before you can take a sample. Whereas a VLF detector continuously stimulates the target, and is able to receive a stronger signal than the PI. On the hand PIs can have a distinct advantage in mineralised ground, and don't lose as much depth between an air and a field test.
For detecting very small targets, a VLF is definitely the best choice (if the ground is not mineralised) probably with a high TX frequency, and a small coil.
Nupi - Thanks again for the needles. They will make some good test targets for future projects.
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