Concentric coil for IDX

[golfnut]

For reference, This coil is a DD and the coil diameter is 9.75" - the shell is 10"


I did a fresh airhead test too..

This was 7" compared to the 5" in low mineralised soil - using the same GEB and Disc, Sens, Thrsh positions.

Don did your have your Disc fully opened up during yout test bed vids ? ?
S

[dfbowers]

I generally set my disc to reject hot rocks and small nails. I need to accept thin brass like military buttons.
I will give 1/2" lead balls and coins a try in the test garden.

[golfnut]

Got to borrow a trident 2 on my testbed.


The depth of this was the same as my IDX - could see 5" down target but not 6"....


What was odd it did see deeper targets with its PP function - is it normal that the tesoro PP is more sensitive than the Disc mode ???


Didnt make sense to me..


S

[golfnut]

Concentric for my IDX. Considering the sheild - I did some graphite test samples to get the ohms/square, my aim was around 10kohm/sq.



I did three duplicate samples to get an average. Used copper tape for edge terminals. Made patches in square shapes for the ohms/sq resistivity measurement.


Also did circular sample on plastic carrier.

Water based black paint from economy store (wilkinson uk )

One part synthetic graphite (Graphite trading Co UK ) - 3 parts paint - - - by mass.

I did the three samples at the same time, from the same mix, the mix was agitated fully to get the graphite for each delivery.




Ovened at 80C for 1hr then measured resistance at the copper connections.

Cell 1 10.5kohm
Cell 2 open cct
Cell 3 open cct

Left overnight repeated measurement

Cell 1 8.5kohm
Cell 2 open cct
Cell 3 open cct





I was a little dissapointed with the random nature of the reliability shown with my test.

Looking further, there are areas on the defective cells where I get a low reading, but alas it is not continuous across the test piece.

The circular disc on plastic was open circuit.

Need a way to deliver the grapghite payload so all of the grains touch.
The other thing is Im nervous the paint adhesion to the shell will be weak and my coils complete with potting will flop out one day !!

S

[dekoratör]

hello
rx coil and cap if we connect the tx circuit,
could we see rx frequency on dmm?

sorry bad english.

best regards...

[golfnut]

Yes, you can use cap and Rx coil to resonate on Tx osc - if you know the cap value you can de-embed the L value.

S

[golfnut]

Epoxy and 25% graphite

Redid the paint test using epoxy.

Three open circuits!



Need a recipe !

S

[dekoratör]

Yes, you can use cap and Rx coil to resonate on Tx osc - if you know the cap value you can de-embed the L value.

S

thanks...

[dekoratör]

Redid the paint test using epoxy.

Three open circuits!

[ATTACH]24271[/ATTACH]

Need a recipe !

S

try black liquid shoe polish
respects...

[ashefr10]

hello, I would like to know about the pdf is mentioned 35 turns or 70 turns for Tx and I would like also the values of Tx and X-ray and winds intermediate for a head of 27 cm (10" ). thanks

[Davor]

As far as I know, the PDF gives detailed description of the coil, and the inductance is not that critical. Just follow the description and confirm the results with inductance meter. A multimeter with inductance measuring should be fine.

BTW, seadoggy successfully tested graphite with white glue (Polyvinyl acetate) compound for shielding purposes. The resistance is about 100kohm/cm of a track on paper.

[Dixix]

Question About Don's pdf

I would like to build a concentric coil for my IDX.
I have read the instructions in Don's very good pdf. (Thanks Don, for the valuable informations!!!!)
Ask a question about the following sentence:

..."For the tricky part - When the bucking coil is wound around the Rx coil opposite direction from the Tx coil, the frequency goes up by about 60Hz, so 1 turn or 2 will have to be added to the Tx coil to bring the frequency back down to 6.59kHz. "...

If I have understood correctly,
first assemble all with the capacitors and then measure...?
So the TX coil with a long wire end, so I can even possibly add one or two turns?
Sorry for my slowness...

Dixix

[golfnut]

It does not matter about the frequency shift. I ran mine at 12kHz with no drama. S

[mohandes]

hi don and another guru
i ask this ? before and Mr gulfnut answer to me but my cc coil dont work. i do it like your pdf.
JUST I CHANGE 19cm to 20cm of diameter for TX coil ( so i change 1mikro farad to 470n+470 and get 6.58kh )
but it is very bad no nulling and not detecting ,why ??

[dfbowers]

Yes, you must add capacitors to allow resonance. You can then adjust frequency by adding a turn or two. I can't say why a particular coil cannot be nulled. I can only document what I did to put a concentric together. I would feel better if my results could be reproduced.
Hopefully some of the videos I posted on youtube are proof that the recipe in the .pdf works...