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#1

Dan79
Member
Joined: 10 March 2016
Posts: 30
Member
04 August 2020 04:10 pm

just upgraded from the tdi pro to a gpx5000 and was wondering if i can use my tdi miner john coils on the gpx. As i have four of them from a small folded mono up to a 20 inch. Just figured i would ask just on the off chance they would work
Thks Dan.

#2

grubstake
Member
From: Perth, WA
Joined: 20 October 2014
Posts: 2,579
Member
04 August 2020 04:42 pm

I'm pretty sure from memory that the answer is no, but here's the contact email for the bloke who can give you a definite answer:
1minerjohn@gmail.com

This is his webpage, which is still pretty bare since he was burnt out in a Californian wildfire 2 years back:
https://minerjohndesigns.com/


Where it is, there it is.

#3

PhaseTech
Phase Technical
From: Adelaide, SA
Joined: 29 May 2014
Posts: 2,042
Phase Technical
08 September 2020 07:47 pm

Did you hear anything back Dan?


Agent for Minelab, Nugget Finder, Nokta & Makro, Quest, Detech, SteelPhase - Phase Technical Website

#4

Dan79
Member
Joined: 10 March 2016
Posts: 30
Member
09 September 2020 01:56 am

nahh i got no response. I think i wil play it safe and stick with the gpx coils.

#5

BigL
Member
From: Cowjahaveapoop
Joined: 04 March 2018
Posts: 153
Member
09 September 2020 08:35 am

https://www.detectorprospector.com/foru … s-tdi-pro/

according to these guys it seems the Mono coils are interchangeable

Last edited by BigL (09 September 2020 08:37 am)

#6

davent
Member
Joined: 01 September 2015
Posts: 3,019
Member
09 September 2020 01:52 pm

No read the posts again, the TDI can use the after market GP, GPX coils, but the GPX can’t use TDI coils. I was told this also when I bought my first PI which was the TDI pro oz

2 users like this post: grubstake, mxt sniper

#7

BigL
Member
From: Cowjahaveapoop
Joined: 04 March 2018
Posts: 153
Member
10 September 2020 07:18 am

.. right you are Davent, need to get my eyes checked argh

Seems odd though, they say you can use aftermarket GPX coils on the TDI but not the other way around, doesn't make sense.

#8

grubstake
Member
From: Perth, WA
Joined: 20 October 2014
Posts: 2,579
Member
10 September 2020 09:10 am

I've located a pretty definitive comment from the late Reg Sniff on Whites TDI coils vs Minelab coils:
1599688498_minelab_vs_tdi_coils.jpg

Source: https://nuggetshooter.ipbhost.com/topic … ack-coils/

When Miner John first took over Razorback Coils and was still selling under that name as well as his own, he produced separate ranges of coils for Whites TDI detectors and Minelabs:

1599689182_miner_john1.jpg
1599689182_miner_john2.jpg


Where it is, there it is.

2 users like this post: Ded Driver, mbasko

#9

BigL
Member
From: Cowjahaveapoop
Joined: 04 March 2018
Posts: 153
Member
12 September 2020 08:46 am

a coil is just that, a coil. If its parameters fall within those required by a detector, then you most certainly can use it. Obviously any chip and or coil dampening (in the coil itself) needs to be factored.

I make my own coils and what I can tell you is, there is more than just meeting the required coil inductance. When I bench test coils, I have 5 other parameters I measure, all of which impact the detector/coil combination performance. All detector designs have coil parameter sweet spots, if the coil meets this then you have an ideal world... if not then you are running the detector in either a capacitive or inductive reactactive state, on a performance front this has good and bad points but more of a concern is you can damage the detector

So with all due respect, if the TDI coil parameters meet those required by a GPX, then go for it

#10

mbasko
Member
From: Central West NSW
Joined: 27 January 2015
Posts: 4,508
Member
12 September 2020 11:00 am

BigL wrote:

So with all due respect, if the TDI coil parameters meet those required by a GPX, then go for it

I think you've missed the point of what Reg said?
A coil made to suit the ideal parameters of the TDI's is outside of the ideal parameters required of the GPX.

For whatever reason (likely being single channel, manually adjustable pulse delay etc ) the TDI can accept a lot of GPX coils (it won't run them all well or with others pulse delay may need increasing to run ok).

The late Reg Sniff wrote:

Now, when it comes to coils, the TDI is forgiving but works best with coils made for the TDI and not ones made for the ML's. 

My understanding is the GPX series with MPS, DVT etc. needs more rigid coil parameters.
I was told awhile ago that putting a TDI coil (or other out of spec coils) onto the GPX might be a risk of possibly letting the smoke out? Not sure how true that is though I would not personally be prepared to risk it for a coil that will not offer any performance gains.


Everything we use comes from mining or farming.

1 user likes this post: EVIE/BEE

#11

BigL
Member
From: Cowjahaveapoop
Joined: 04 March 2018
Posts: 153
Member
12 September 2020 03:26 pm

mbasko,

I understood Reg's point, but it does leave the door open for debate.

Regardless of coil brand, most PI coils are built around ~300uH. A coil is nothing more than a tank circuit, you will find the parasitic parameters near consistent across all PI coil brands when you've ~300uH.

Add the coil cable and you now have a completely different ball game, get the coil cable combo right and your good to go... and I'm not talking about wiring configuration either, so be warned! If your coil & cable combination is out of tune for the PI, then you'll blow smoke.

MPS, DVT or whatever really has nothing to do with the coil, they are time domain; transmit cycles & receive algorithms (number crunchers).

Give me any ~300uH coil (PI or VLF... whatever) that has no dampening or chip and I'll make it work on a GPX without blowing smoke. It may not be the best coil but it will work

Last edited by BigL (12 September 2020 03:36 pm)

#12

mbasko
Member
From: Central West NSW
Joined: 27 January 2015
Posts: 4,508
Member
12 September 2020 08:47 pm

BigL wrote:

mbasko,
Give me any ~300uH coil (PI or VLF... whatever) that has no dampening or chip and I'll make it work on a GPX without blowing smoke. It may not be the best coil but it will work

No offence but what's the point of that then?
I'll stick to using & recommending coils made specifically for different detectors for the best performance, which is what most would be after, not just whether it works in some form?

In a thread on Geotech Carl Moreland says TDI coils have a higher resistance than GPX coils & while they work peak current would be less.

This leads me to believe that for optimal performance Minelab GPX specific coils require a lower resistance than that of TDI coils.
Less current to me = less target inducing eddy currents & a less intense electromagnetic field?

"The stronger the current, the more intense is the magnetic field."


Everything we use comes from mining or farming.

1 user likes this post: davent

#13

BigL
Member
From: Cowjahaveapoop
Joined: 04 March 2018
Posts: 153
Member
12 September 2020 11:55 pm

It may seem pointless using any coil that is "relatively" inferior, but companies do, they call them anti interference coils.. give n' take.

The GPX series handle low coil R input, this benefits the coils current charge (ohms law)

Last edited by BigL (12 September 2020 11:58 pm)


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