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Which Of These 3 Coils For Underwater Work?


Tony

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On 7/11/2020 at 6:03 AM, Tony said:

I have decided to finally swap out my big 12” Dual field coil on my TDIBH for something smaller. The purpose is to use in the water.

I have some pros and cons with each model so feel free to add any ideas you have.

  1. Coiltek Platypus 12x8. Waterproof, epoxy filled. Maybe too long on the 12” side which sees the most water resistance
  2. Detech 8” Mono. Foam filled so more buoyant but not too worried as 2/3 the size of the Dual Field coil. Good size. Waterproof.
  3. Garrett 8” Mono coil. Waterproof, epoxy filled. Good size. Suitable for lower delays?

Have you seen this old thread?

Maybe more has been learned since then, but from what I've read, White's made an effort (and a successful one, apparently) to build the TDI series to be compatible with Minelab PI coils (which includes Coiltek and NuggetFinder 3rd party aftermarket coil manufacturers).  At least that seemed to work for mono coils, not necessarily for DD coils.

Other manufacturers' coils, such as Garrett's -- maybe not.  Carl seemed to think at the time of the linked thread above that some modification would be necessary for optimal operation.

It appears (and this is partly my experience but also others' experience from similar experimentation) that coils can turn out to 'work' on products for which they were not made.  But also, 'work' doesn't mean operates optimally.

I never finished my experiment of getting a Garrett Infinium LS 10"x14" coil to run on the TDI/SPP.  I found a solution for my buoyancy problem -- adding weight to the White's TDI Superpulse 150 (mm = 6 inch) mono.  That was a fun project but the results (subsequent performance) were just so-so.  I do think the Garrett coils (Sea Hunter you show, and Infinium open coils -- same housing but different(?) windings) would be a much better ergonomic solution if the electromagnetic properties are compatible or could be made compatible for optimal performance.

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Here is how detech 8" coil is sealed. I was thinking to open the coil and fill it up with the epoxy, but for the moment decided to glue the protection to ensure better sealing, just in case.

If the cable gland is sealed properly, I don't see problems.

20200712_210408.jpg

20200712_210347.jpg

20200712_210335.jpg

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11 hours ago, Skullgolddiver said:

You're inspiring me Tony!

I 'm wondering if the 8" AQ1 coil  can match the needed inductance

Not sure......I think stock AQ1B coils are wound for higher delays. Maybe email the company.....ask for Colin.

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6 hours ago, GB_Amateur said:

Have you seen this old thread?

Maybe more has been learned since then, but from what I've read, White's made an effort (and a successful one, apparently) to build the TDI series to be compatible with Minelab PI coils (which includes Coiltek and NuggetFinder 3rd party aftermarket coil manufacturers).  At least that seemed to work for mono coils, not necessarily for DD coils.

Other manufacturers' coils, such as Garrett's -- maybe not.  Carl seemed to think at the time of the linked thread above that some modification would be necessary for optimal operation.

It appears (and this is partly my experience but also others' experience from similar experimentation) that coils can turn out to 'work' on products for which they were not made.  But also, 'work' doesn't mean operates optimally.

I never finished my experiment of getting a Garrett Infinium LS 10"x14" coil to run on the TDI/SPP.  I found a solution for my buoyancy problem -- adding weight to the White's TDI Superpulse 150 (mm = 6 inch) mono.  That was a fun project but the results (subsequent performance) were just so-so.  I do think the Garrett coils (Sea Hunter you show, and Infinium open coils -- same housing but different(?) windings) would be a much better ergonomic solution if the electromagnetic properties are compatible or could be made compatible for optimal performance.

I did have a good read of that thread. No absolute guarantees of optimal performance but I hope to find out soon enough.

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23 hours ago, pjrough said:

 

Tony, good luck with your project.

Can I ask you to make a good photo if the PCB front side?

Can you also show where the headphones were plugged to?

 

I still have to decide whenever I will go for piezo or dynamic head speakers for my TDI project. But it nice to compare PCB, so I can track where to plug the piezos.

 

Here are two different pcb's older is from 2011 and newer is from year 2016.

20180307_175228.thumb.jpg.94c9254b1ff3bebfa24b305abee9db69.jpg

20200712_121725.jpg

Board attached. Headphones go into the SPEAKER socket. Down the bottom (short side) and just off to the right of centre.

A3408EA5-D26B-4B0C-A795-2AEC2A741EEF.jpeg

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Thanks, Tony.

Can you tell me there  "volume" pot goes?

...whites uses the same amplified sound source for low impedance speakers and for piezos. It is good to know. Will check if I can see any difference in circutery.

By the way. TDIBH is quite loud. But there is a way to switch stock piezos to speakers headphones. Potentially it will help to differentiate low "whisper" targets.

The idea is the same to OBN Excalibur mode, but here we can use low ohm speakers, so there are plenty of options.    

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The VOLUME socket is just to the right of the SPEAKER socket.

You are right.....the volume isn’t lacking on the TDIBH !

Not sure if the photo is clear enough.....took the photo indoors as it’s wet and gloomy outside.

 

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On 7/11/2020 at 9:04 PM, RickUK said:

I use the 8'' Garrett Mono coil on my 'Crossbow' pulse works exceptionally well,also have the 14x9 coil as well,both work well but the 8'' is my favourite out of the 2.Very good depth and also good for smaller targets like jewellery etc.

Rick

Did you have to modify the Garrett Sea Hunter 8” coil on your other detectors?

 Thanks Tony 

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1 hour ago, Tony said:

Rick

Did you have to modify the Garrett Sea Hunter 8” coil on your other detectors?

 Thanks Tony 

Tony the only thing that was changed and i will admit it was not me that changed it but the coil plug was changed so that it worked with my 'original' Crossbow Pulse,the designer and builder of just 13 Crossbow machines was George Overton who with Carl own Geotech1 forum,i bought the coil beand new from a Dealer who had a sale here in the UK,i approached George asking if this Mono coil would work and the challenge was accepted.He changed the coil plug which is basically straight forward after working out which terminals to use on the plug,one other thing i will highlight that he also did was i think he added some resistor just inside the control box which connected to the terminal this was so that the coil and control box could wok together in harmony for a better way of putting.I could find the exact details and calculations that George Overton used and the exact same alterations had been done when he also got the 14x9 SeaHunter coil up and running as well.......both work exceptionally well but my favourite is the the small 8'' SeaHunter Mono coil.

If you need any other help/advice or what ever dont be afraid to ask,i mainly use the Crossbow Pulse as a hoard/relic hunter as the design of this machine was originally made for depth on largish items rather than say fine timings for small gold jewellery.For small gold items i use my TDI Pro and especially my Mirage Pulse with a small 5.5'' Mono coil which i also did at one time have on my Crossbow.

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Thanks Rick for your reply.

I just want to make sure that whatever I choose works well.....I don’t need 10uS in  the rough saltwater....more likely closer to 20uS to keep my sanity. The Coiltek Platypus is out because they are no longer made. I’m considering the 8”Detech Mono....it is foam filled but being just 8” will be okay, plus I can run a rubber weight to keep it down. I feel the Detech will work optimally without any modification. I’m still waiting to hear from Eric to see if he has a suitable coil. So maybe some uncertainty with the Garrett 8” ?

Appreciate the info

Tony

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