DD coil for Minipulse rev c

[wes0008]

I brought a Minipulse rev c kit from SilverDog last week and I would like to have a DD coil made before I start to make the kit but I'm not completely sure of what to do! I would like some advice on making the coil including specific specifications and I would also like to know if I have to make any changes to the kit in order to use a DD coil, as the instruction manual off the mini pulse rev c feed only mentions a mono coil. My prospecting target will mainly be small pieces of gold. I also have a local electronics shop who have enamel coated copper wire ranging from about 0.2mm all the way up to 1.5mm in diameter. If anybody could give me some advice that would be much appreciated!

[Silver Dollar]

Have a look here to see how it is done on HammerHead; http://www.geotech1.com/forums/showt...the-Hammerhead

You generally do not want to use magnet wire to make a fast PI coil (DD or otherwise) and you need a fast coil
to find small gold. So look for some stranded tinned wire instead. You might start with 300 uh for TX and 450 uh for RX...

[wes0008]

Is there a particular coil size that you would recommend?

[Qiaozhi]

... as the instruction manual off the mini pulse rev c feed only mentions a mono coil.

See Fig. 7, page 13.
The wiring for a balanced coil is shown there.

[wes0008]

Oh yeah! Thanks Qiaozhi! Has anybody got any further advice?

[Silver Dollar]

Well generally a small coil sees small targets better but it would depend on
where your searching and the size of housings available. I might make a 6"
or 8" for small gold...

[wes0008]

I think I might try an 8" coil over the 6" just for a little extra depth.

[Silver Dollar]

I've made a 6" "OO" coil for my Bandito and found it goes deeper than a "DD", it about
matches a 12" concentric. I'm looking to try some smaller ones to see how small you
can go and still get good depth. If a couple of 3" or 4" ones can match a 8" I'll be happy!

[wes0008]

Does the OO coil have good target isolation?

[Silver Dollar]

Not sure what you mean? The "DD" is a bent "OO" the "OO" works the same only better.
The circle is the best shape for a coil...

[wes0008]

I suppose the OO would have the same or similar target isolation then.

[wes0008]

I wonder what a double eclipse or double rectangular coil would be like?

[wes0008]

See Fig. 7, page 13.
The wiring for a balanced coil is shown there.

I don't understand where the tx and rx ends go, do they connect to the unused pins on the plug and the tx 1 and rx 1 solder points on the pcb? A picture of "fig. 7" is below.

[Qiaozhi]

I don't understand where the tx and rx ends go, do they connect to the unused pins on the plug and the tx 1 and rx 1 solder points on the pcb? A picture of "fig. 7" is below.
[ATTACH]31343[/ATTACH]

The TX wires connect to PL2 pin 2 & PL2 pins 1/3.
The RX wires connect to PL4 pin 2 & PL4 pins 1/3.
This is shown on the left-hand side of Fig. 7.