IB pinpointer

[dbanner]

Sometime ago, following Carl's description of the Whites TRX pinpointer IB coil arrangement, l was looking for a simple circuit to adapt for an IB pinpointer.
I came across a Garrett patent for a hand held IB detector design, which I thought maybe could be the basis of an IB pinpointer based on the TRX coil arrangement.
There doesn't seem to be component values though. But it shouldn't be too difficult to render component values on to such a simple schematic so long as an operating frequency is chosen. The rest of the values can be inferred and are very much standard.
Any thoughts? Perhaps later on, a microcontroller can be integrated into the design.

[Skippy]

It may be worth a look at this Polish discriminating PP design:
https://www.geotech1.com/forums/show...387-PINPOINTER

I have yet to get around to building the pp electronics, as I haven't finished off the design/construction of an IB stacked concentric coil assembly. Stalled since Feb last year, I must finish it off. It's designed to work on my 13kHz Fisher F75 , if it's acceptable on that, it should be good for the simple pinpointer circuit.

[dbanner]

Carl quote-
" I don't recall exact parameters but I think the TRX had 100 or so turns on the TX and several hundred on the RX. The RX wire was pretty thin, maybe 35-36 awg. Coil spacing was probably 1/2" or so. Don't recall the number of reverse windings, maybe 5-8. The coil assembly was slid inside a short piece if 1/2" fiberglass tubing (made by the same company that made the White's lower rods) and potted with epoxy. After complete assembly of the circuit+coil, a piece of shield tape was maneuvered on the coil tube to tweak in the IB and affixed. Again, I don't recall the kind of tape ". End quote

5-8 reverse windings to achieve something close to a balance seems quite a small number of turns. I get the impression that the shield tape was to fine tune the final null, don't know.

Guess I will have to try to make it to have a sense of what it takes, but it appears to be straightforward enough, no magic.

[dbanner]

Here is the schematic for the discriminating pinpointer design referenced by Skippy in post #2.
It seems to use an active (self oscillating) buzzer. Looks rather simple.

The coil implementation seems to be the biggest hurdle. Maybe I'll have a try at building this circuit.

[dbanner]

The advantage of the TRX coil arrangement is that the tx magnetic field is better focused and the field of detection is sharply uni-directional, aligned with the tip instead of all around and to the sides. This makes for increased detection distance and faster and better pinpointing. Here is a video which demonstrates this effect.
https://m.youtube.com/watch?v=GWarO1Zy9QA

[dbanner]

First I will build a simple Colpitts oscillator for the TX and try to balance the coil according to Carl's description.

[dbanner]

There is a video demonstrating the Polish pinpointer vlf, showing also the coil construction.
But I am suspicious, what appears to test good on the bench, suddenly you wave it around in the air and it beeps away like a drunken canary.
From the video, It does appear to be stable.
https://m.youtube.com/watch?v=Rm8DJFXxBCQ

Objective here is to make a good probe for a vlf machine.
This little circuit facilitates some testing of the coil arrangement. There is a layout.
Interestingly, the coils don't appear to be wound on any ferrite rod. Not sure.

[dbanner]

Here is Sunray probe switch box. Looks like a 3PDT toggle. Seems kind of old school.

[Skippy]

Here's a few more images related to the Polish PP, including coil construction data: