Coax for duel field coil

[Reg]

Hi Herb,

Here is a little different concept for a dual field mono coil I built that seemed to work fine. It is different from the Whites design since it uses only one coil formed into a figure 8 concept but then modified even more.

What I do is this, I build a coil larger than the housing I will use (step 1). I then squeeze the coil into something like a lopsided figure 8 (step 2) and then twist the top part one half twist to form the 8 (step 3). I then fold this smaller coil back into the larger one (step 4) and ultimately elongate the inner coil (step 5). This allows me to use a DD type housing such as the Hay's 11" by 9" design. The larger coil fits in the outer ring while the smaller coil fits in the inner center elongated zone.

Attached is a simplified drawing of the steps I mentioned. Hopefully, it will make sense.

The idea of this design is the larger coil is used for finding deeper targets, while the inner coil will be more sensitive to smaller objects closer to the surface.

Reg

[Reg]

Hi Herb,

I am not sure what you mean about a dual field coil. If this a mono design having two coils, then those coils are connected in series and a simple mono coax will suffice.

Now, if you are referring to building a DD or concentric type coil, then yes, you will need a good dual coax type of wire.

The best wire to use for a DD coil is the S video cable. The problem is, finding the best that works well and this does not mean the most expensive.

I personally use the Mogami dual coax (S Video) for my DD coils. However, one could try different S Video types to see what works best for them.

Now, as for the dual field mono coil much like what is build by Whites, this is different since it mimics a mono coil in design.

Keep in mind that Whites has applied for a patent on this design so any building of such coils can only be used by you and not for sale.

Right now, I have not seen Whites design so I don't know just what steps on their toes. I do know I have built a couple of different designs and they both work well.

The idea of a dual field mono coil works well for a coil that has the capability of a mono coil for depth but still has better sensitivity to small objects, much like a DD coil is capable of doing. So, it works best when trying to nugget hunt where one is trying to find both deep gold and very small gold.

I personally prefer a single coil design for coins and larger objects. I feel there is a slight depth advantage to the single coil design on the larger stuff, but I really haven't done that much comparison either. What little I have done sort of points that direction, though.

Now, as for coil connections, I posted those over on the TDI forum, but will do it again here also.

I hope this has at least answered part of your question.

Reg

[PVGOLD]

Hi Reg and all
I am looking for some advice and information about coax for a duel field
coil ie what type. I have read that S video cable will work. I would rather not
use two lengths of standard coax. Is there a certain brand that is best to use? The coil I'm building is for a TDI so I am also looking for schematics
for the 5 pin connector and wiring within the coil itself.
Any help will be greatly appreciated !!

Thank You

Herb