IDX-PRO+VDI

[Silver Dollar]

I tried aluminum foil on an earlier coil attempt and found it reduced the signal significantly so
I tried a centertapped RX with no shield but that was noisy. The next coil I tried some metal
screening like you use on you windows I figured that would shield but not reduce the signal
but it was a minelab style coil with 1mh TX and 14mh RX and it was too noisy too!

Next I bought a Deep Search Tesoro coil off ebay and it works and is nice and quiet but
has low detection depth. It is center tapped and uses graphite in the coil shell. I think the center
tap reduces the signal quite a lot. So a normal coil with graphite is my current idea for a good
coil.

I just got a Fisher 440 super big coil off Ebay. It's huge! 11.25" across. I'll have to measure it to
see exactly what I bought. It was only $16 shipped so I figured I couldn't go wrong!

Here's the info. I get 12.6 mh on the two sides but 10 mh on the top 2 and 3.2 mh on the bottom 2.
A picture with the schematic and readings displayed;

[Koala]

Barry just a thought but want salt corrode you copper drain wire

Silver Dollar in testing no matter how I connect a metallic shield of any type causes a noisy coil. Does not appear to be the way to go. Quick and dirty test with carbon and cardboard is 100% better.

Space blanket does shield from near charges but falses as soon as it touched anything except dry sand.

[golfnut]

the spray Henrik used is good.

[Silver Dollar]

I've had some trouble with my homemade coils being noisy and am thinking
the superglue melted the insulation on the magnet wire. I used some wire
from an old TV degaussing coil and noticed the physical change in the wires...

[hoadlies]

Well finally give up shielding with a space-blanket and alloy sheet. Can not make work tried connecting it many different ways tried two layers of insulating tap wires in different ways different cables nothing works.

In desperation I got a piece of card and spread a carbon PP3 battery insides over it and tapped a tap wire to it. Well even though it's only over the bottom and does not fully cover the coil it works reasonably well

Well spent two weeks try to shield my coil and have found many ways that don't work.

Don't know how people get the space-blanket to work mind you there are lots of build configuration like in a metal enclosure or plastic

Have to make a better shield now and finish the coil. Does mean I now have a spare RX and TX wound.

HI KOALA & ALL,,, SEEM"S Like you have tried many shielding methods ,, When I built my IDX coils I used carbon-graphite mix ,using nitro-cellulose clear for the base .. they seem OK ..

Since Using that mix ,I have been told a better formula !!!that is to use a water based undercote paint- or cieling w/based paint use graphite, battery paste & ''SALT'' aim for 50-100ohms per inch ..
I have not tried that myself as yet but will on my next coil ..
When I did my DD-coil I set the coil with super-glue then Wrapped Ordinary insulating tape ,Then 2x wraps of ''Micropore]] hostpital tape [available at any Chemist], I used a copper-wire around the edge of the windings Leaving a gap of about 5mm,& use only one end for grounding..[ then applied the graphite mixture ,& then another wrap of Micropore tape ,,& then it was coated with apoxy-resin into the coil housing ..
The Micropore Tape is Strong ,sticky-backed & porus ..Very Good stuff & cheap ..

WAITING to Get-out Metal Detecting ,finished my Second-hand 4WD toyota 4 runner [made a ROO-bar & a Tow-bar ,BUT.ITS Been BL*&#Y RAIN & COLD for weeks now [Need some Sunshine HA.Haar..]

I,,HAVE MY IDX,M/L F1A4,& my WHITES GMT 3 ,all waiting to go,,Made 3x picks using Leaf-Spring from cars& wooden handle..
Just need to see a small piece of that Yellow Stuff ???..

CHEERS TO ALL FROM ,,OZ,,,,,,,,,,,,,,,BARRY..

[Koala]

Well finally give up shielding with a space-blanket and alloy sheet. Can not make work tried connecting it many different ways tried two layers of insulating tap wires in different ways different cables nothing works.

In desperation I got a piece of card and spread a carbon PP3 battery insides over it and tapped a tap wire to it. Well even though it's only over the bottom and does not fully cover the coil it works reasonably well

Well spent two weeks try to shield my coil and have found many ways that don't work.

Don't know how people get the space-blanket to work mind you there are lots of build configuration like in a metal enclosure or plastic

Have to make a better shield now and finish the coil. Does mean I now have a spare RX and TX wound.

[paku]

ok thanks bro

[seadoggy]

i need help about setting VDI
how to Setting the VDI

I set up my IDX as follows:
1) set up P7 in approximately middle position;
2) set up ground balance by VR1;
3) moving in the front of coil a piece of aluminum foil and turn VR3, I find the situation where the foil starts discriminating;
4) Turn the 5K pot of VDI-board until a zero reading at approximately the same small piece of aluminum foil.
regards

[paku]

i need help about setting VDI
how to Setting the VDI

[Koala]

My homemades show lots of noise. One has center tapped RX and no shield, the other
Has metal screening as a shield. My original Tesoro brown coil works great and is wired like this;
[ATTACH]30694[/ATTACH]

The 2 shields are connected and used as the TX minus. RX minus is tied to shield in the coil housing.
Some say this isn't the best configuration.

My Deep Search is a bit different. The RX is center tapped (center point goes to TX minus) and the
shield is totally separate.
[ATTACH]30695[/ATTACH]

I have tried different wiring schemes too on my homemades and haven't gotten satisfactory results jet.

The Deep Search has weak volume. It responds similar to the Brown one (strong volume at close range)
but just sounds smaller. I was looking for the volume control on the other coil to turn it down and on this
to turn it up. Not really sure what causes that it seems to be duty cycle of the audio??

Pity can't try that on the IDX as TX is -V and RX is GND

[Koala]

Right tried a few more things but no solution

Tried alloy foil over RX no difference

Tried alloy foil over RX and spaceblanket over TX

Tried homemade coil on original Classic I still not working

[Koala]

Hi i want to build this project i already maked pcb but i cant find in my country this circuit lf347 can i replace it by tl074 recorf to datasheet are same thanks br!

looks like TL064 is know to work

http://www.geotech1.com/forums/showthread.php?18990-IDX-Pro-troubleshooting&p=148566#post148566

[salim]

Hi i want to build this project i already maked pcb but i cant find in my country this circuit lf347 can i replace it by tl074 recorf to datasheet are same thanks br!

[Silver Dollar]

My homemades show lots of noise. One has center tapped RX and no shield, the other
Has metal screening as a shield. My original Tesoro brown coil works great and is wired like this;


The 2 shields are connected and used as the TX minus. RX minus is tied to shield in the coil housing.
Some say this isn't the best configuration.

My Deep Search is a bit different. The RX is center tapped (center point goes to TX minus) and the
shield is totally separate.


I have tried different wiring schemes too on my homemades and haven't gotten satisfactory results jet.

The Deep Search has weak volume. It responds similar to the Brown one (strong volume at close range)
but just sounds smaller. I was looking for the volume control on the other coil to turn it down and on this
to turn it up. Not really sure what causes that it seems to be duty cycle of the audio??

[der_fisherman]

See what your saying. But seeing as I have two coils here that work properly I am guessing the problems I am having are my own doing with my homemade coils. Would like to know how the factory coil is wired as there is high ohms between both TX and TX and shield and the connector is also connected the the shield (is that just a short from the shield pin or separate in the coil end)

High ohms between the two shields is exactly what is usually needed (though what you wrote is a little ambiguous!). Then they will be "linked" to that central earthing point ONLY when plugged into the control unit. (assuming that I correctly understood your post!)

If your search head has low ohms between the two when not plugged in, you have probably found your problem(s)....
Generally speaking:-
There should be no contact between either coil and either shield.
There should be no contact between shields in the search head, though they may be linked in the plug. If so, you will need to separate them before measuring.
There should be no "loops" anywhere, that is, no link say between shields at the search head and the plug or control unit.
There should be no links in the head between the coils.

Some professional search heads have caps in them, which must be taken into account when using on your own control unit.....I am not clever enough in this to have a personal opinion with any validity on this point....sorry.

regards

Andy