IDX-PRO+VDI

[Koala]

no did not have the blanket attached to the drain

did not test for phase shift. It hard with everything loose as even moving arm to fast near coil can be seen on the scope and sets the detector off.


Got the coil balanced on a couple of plastic tubs and a small stool to give me access to both side but away from the concrete floor Not ideal as only 4 foot away from a large radiator.

The scope and soldering iron its self causes a bit of interference. Not sure the cable is okay. Its a know brand USB. Even if I touch the cable near the box end the metal detector goes crazy but can't tell if its the wires with the cap's on moving a bit. It's the same type USB as my other coil that's twitchy. Can't do anything about that at the moment as I have no replacement.

New epoxy from ABL (STEVENS) seems to be much better. Takes about 24 hour @ 17C to harden and no heat given off. Seems much harder as well.

[golfnut]

Yes looked good,

With your test did you have your blanket attached to the drain wire?

Did the phase shift? A quick test would be, if you could reject ferrite before - can you reject it in the same knob position on the geb? with the blanket attached. S

[Koala]

Assembled this unit. Showed excellent results. Coil 13 "range on the copper coin 45mm diameter is 60cm. Works steadily. At ground on this coin depth 40cm. https://www.youtube.com/watch?v=xXyIXFg2pKE

Well done looks very good. Looks like you will digging to the center of the earth for them deep finds

[Artyom]

Assembled this unit. Showed excellent results. Coil 13 "range on the copper coin 45mm diameter is 60cm. Works steadily. At ground on this coin depth 40cm. https://www.youtube.com/watch?v=xXyIXFg2pKE

[Koala]

Did not mean potted should read fiberglassed together.

[Koala]

I havnt done the adding space blanket post null. I added a graohite leyer post null once and it carried on working ok, I thing the geb setting point moved a squeak on the dial and it ground balanced better - less falsing.


You will likely see a phase shift and maybe a small amplitude change - but dont know how much.

You could test the effect on a thin ply sheet, with your space blanket over post null - if you got scope.


I do see a null change with potting, and slight phase shift. I guess if you were making them all day you would bias the phase and amplitude one way so it pulls in when potted.


I would wrap pvc tape layer on you coils.
Wrap long strips on your coils, with a drain wiire, leave a gap as in dons tgsl write up., dont let the sheilds touch - phase / test for ferrite reject/ iron reject/ wanted accept and ensure null is < ~300mV

If you can do all that in your shell then pot it and should be good. Steve

results of some experimenting

average measurement on a oscilloscope on pin 6

Nulled but no space-blanket at all mainly 52-54mv but fluctuating wildly from about 40-62mv

Large folded space blanket placed over the middle no change


cut a large square from the blanket and completely covered the coil same 52-54mv but fluctuates is much lower about 50-57mv



While retesting to see if the results were consistent a small corner of the blanked was raised and the fluctuation was much more again.


Is the phase mainly changed by the RX tuning capacitor if so looks like I can ignore untill after its potted and ridged and stable.

[Koala]

can some one please point out witch resistor gets removed for the mr bills sat mod?
thanks

Have you seen this thread

http://www.geotech1.com/forums/showthread.php?19519-Whites-Classic-II-III-ID-and-IDX-Modifications

[gtdavid]

can some one please point out witch resistor gets removed for the mr bills sat mod?
thanks

[gtdavid]

hello,
well i'm finally getting back to my detector build and everything is good but i have very little if no discrimination.
my coil is a fisher quicksilver 10.5

[golfnut]

I think those are good, tesoro use the solvent type.

Ive ued polyester resin applied with a brush it capilliaries in lovely

[Koala]

Too late for this coil but running out of wire are any of the self-bonding wires worth trying

http://www.poyun.com/en/zrqbx_y_1.jsp

one uses solvent the others use heat to set

[golfnut]

My first coil was done in glass fibre - did it on a plastic camping plate. It is heavy it had ally foil wraps. Did it for an early TGSL.

I would like to some done in carbon fibre . as the screen comes free as carbon conducts well.

[Koala]

Thanks for the answers

It's obvious now it's been pointed out it me that I can lay the coils on the bench and null then place the blanket over the top and see if it shifts

Was thinking of not potting the the coils as such or using a housing but laying up with fiberglass direct to the coils to make it rigid

Would be easier to treat them as two separate coils but if I join them first there would be quite a weight saving.

There might be a good reason why I have not seen one done this way before

[golfnut]

I havnt done the adding space blanket post null. I added a graohite leyer post null once and it carried on working ok, I thing the geb setting point moved a squeak on the dial and it ground balanced better - less falsing.


You will likely see a phase shift and maybe a small amplitude change - but dont know how much.

You could test the effect on a thin ply sheet, with your space blanket over post null - if you got scope.


I do see a null change with potting, and slight phase shift. I guess if you were making them all day you would bias the phase and amplitude one way so it pulls in when potted.


I would wrap pvc tape layer on you coils.
Wrap long strips on your coils, with a drain wiire, leave a gap as in dons tgsl write up., dont let the sheilds touch - phase / test for ferrite reject/ iron reject/ wanted accept and ensure null is < ~300mV

If you can do all that in your shell then pot it and should be good. Steve

[Silver Dollar]

Although it true the null is a purely magnetic effect and the shield is for E field shielding
the shield will capacitivly couple into the coils and so change the LC and thus the frequency
and the null. So it is best to shield before you null.

That being said I have to assume the big guys don't as many times the shield is built into
the coil shell so would be completed after nulling. So let me change my answer to - if the
shield is a resistive one (like graphite) it's ok to null first but if it is a conductive one (like
alu foil) then shield first....


And on the subject of frequency. I have read that 12.5 khz is the sweet spot for all around
so I tuned my super TGSL to that frequency.