Whats In Your Coil?

[strick]

6 hours ago, phrunt said:

Thanks as always strick, these are great to get, I'd love to see some more GPX 6000 coils, namely the Coiltek's, any of the Coiltek's really, along with the mythical NF GPX 6000 coils if they ever come out.  Nugget Finder just keeps refusing to answer me when I email asking if they are going to be semi-spiral or bundle wound, I assume because they're bundle wound like the Coiltek's and that's not good for marketing.

I have the small coiltek I’ll take a pic soon...

strick

[strick]

For @phrunt   sorry for the delay..  Coiltek 10x5 GPX 6000 and Nugget Finder 12x7 GPX 6000 hope this helps. 

strick 

[The Pest]

This truly is a fascinating eye opener.... I'm surprised how many of the coils have small circuit boards inside.... The wine-dings in some of these is not what I would expect to see.... not that I would open one or anything 😉

[phrunt]

Well, that's interesting, they're both semi spiral! They've done a fantastic job quieting them down over the stock coil then.  Now I certainly have no need to rush out and buy the NF 12x7", I figured if it was semi spiral and the Coiltek was bundle I'd want the NF, but seeing they're both the same I'll stick with my Coiltek 10x5, it's the smaller of the two so should be the most sensitive.

The Coiltek appears to have neater windings.

@The Pest the small circuit boards are often there to prevent aftermarket coil manufacturers making unapproved coils.  😞

Thanks very much @strick

[dsb]

2 hours ago, phrunt said:

I figured if it was semi spiral and the Coiltek was bundle

is the coiltec 10x5 concentric? i don't see the Double d crossover?  Semi spiral and bundle, i'm clueless. what do they mean?  thanks.

[phrunt]

1 hour ago, dsb said:

is the coiltec 10x5 concentric? i don't see the Double d crossover?  Semi spiral and bundle, i'm clueless. what do they mean?  thanks.

Sorry, yes it's confusing, spiral is another way of saying flat wound where the windings (wires) are laid out flat with each wire next to the other, and semi spiral they layer one layer of windings on top of another laid out flat but taking up less of the coils surface area being doubled up, a few reasons for this and I guess having it fully laid out flat could make the coils hyper sensitive and saturate on ground too badly for the GPX 6000 being such a sensitive detector, they worked very well on the 4500/5000 though.

The GPX 6000 coils such as the Coiltek 10x5" are traditional mono's with just one winding transmitting and receiving and laid out flat with multiple layers, a compromise between fully flat wound and bundle wound.

Bundle wound the wires are all bundled together like a rope, a little less sensitive but bundle wound coils tend to have hotter edges with the field of detection concentrated at the edge of the coil. 

Concentric has an outer transmit winding and an inner receive winding in loops, some cases two inner receive windings depending on the detector.  Concentric coils can be (Spiral) flat wound or bundle wound too. 

I'm sure someone could explain it better than me and hopefully will, I hope this helps clear it up a bit though.

Each coil type has its advantages and disadvantages.

[LRM]

On 6/24/2019 at 3:29 PM, strick said:

8. Fisher Gold Bug two  6"

 

Anyone happen to know what the values of the resistor and capacitor that are inside the GB2 coils? Can't bring myself to sacrifice a coil just to find out but I would really love to know!

These xray images are incredible.

[gef12]

gathering from a look in .. these are bundle flat wound simi bundle would say ..

as you suggested - well the minelab ones are ...

cheers

vktek

 

[gef12]

3 minutes ago, gef12 said:

gathering from a look in .. these are bundle flat wound simi bundle would say ..

as you suggested - well the minelab ones are ... GPX6K

cheers

vktek

 

 

[phrunt]

I love to bring this thread back to the top because it's one of my absoute favourites, however today I was stumbling around cleaning up my desktop on my laptop and I found 2 photos I'd saved strick had done of the Coiltek 10x5" and NF 12x7" for the GPX 6000, and something stood out to me I hadn't noticied initially.  I always thought the Coiltek had a much neater wind of the wires but that wasn't it, it was the twisted wires from the chip to the start of the windings.

As you can see Coiltek twist them, Nugget Finder has a bigger length and just let them run.

So why do we typically twist wires?  By twisting wires that carry an equal and opposite amount of current through them, the interference and noise produced by one wire is effectively cancelled by the interference and noise produced by the other. A twisted pair also improves rejection of external electromagnetic interference from other equipment.

So, anyone with coil making experience have any idea why they've twisted them and what benefit it may have in this coil situation? I'm looking at you @Geotech 🙂

I personally think the Coiltek 10x5" is much better than the 12x7" for EMI, I just put it down to it being a smaller coil but maybe there is more to it?  When we are all chasing the tiniest hair of improvement in performance could this be part of it? 

Sorry Coiltek if I've revealed one of your secrets 🙂 Seems a lot of effort to twist a wire for no reason.