PimentoUK

Hmm, the 'clear' ones seem different, and usually seem to have fewer use cycles.
Keep searching for the brown ones, probably these?

toastabags

gold toastabags

The "toastabags" are described as food-grade PTFE in some listings, I've edited the post to show this.
Even a 10cm ( 4 inch ) square would make a fair few washers, definitely enough to share out with your detecting friends.

I've no idea why the sheet is 'envelope brown' ... my Tygavac sheet dates to the mid 1980's, and it's the same colour as that sold today.

One other possible washer material ( untried ) is polypropylene sheet. This is sometimes used for plastic bottles, like shampoo. Check your toiletries, kitchen cleaning products, etc for PP markings. This is a 'relative' of PTFE, and shares some of its slippery nature. A single washer cut from a bottle wall will fit under the nut without any space issues.

Yes, that's the stuff. But a quick scan of eBay USA suggests small quantities/samples are not available, the cheapest seller I could find listed at 7 Dollars ( plus a few direct-from-China listings ).
There is an alternative, that should be OK : toaster bags. Try searching for:
"toaster bag" ; "toastie bag" ; "toastabag"; "non stick toaster"; "grilled cheese toaster"
These are often sold in small boxes or 2 or 4 ( in the UK ), very cheap:
toastie bags
US ebay:
toastabags US

They are likely something that you could buy in a store,( rather than online Amazon/eBay etc ), looks like a two pack for 3 or 4 Dollars should be possible?

The specs for the "50 times reuseable" ones state they're food-grade PTFE, and from the photos, they seem to be the same stuff; pale brown with a woven pattern.

One thing I notice with my Equinox coil fixing bolt/nut is that it's very stiff to turn. I assumed it was mostly friction, and not much to do with applying compression to the clevis washers and coil ears. It makes no sense for it to be that stiff, when the coil ears are vulnerable.

So I decided to experiment with some PTFE/teflon washers underneath the head of the bolt and nut. These are cut from a thin sheet of PTFE-coated glass fabric. My sample came from the composite industry, Tygavac branded stuff that's used when autoclaving glass/carbon fibre items. However, it's widely available these days for a variety of less exotic uses, including heat-sealing. There's sellers on eBay offering small quantities at low prices. Some sell 10cm square sample pieces for a dollar or two. Search for:

"PTFE heat sheet" or "heat press sheet"
and look for brown-coloured stuff.

Cut it out using a sharp knife and scissors. I stuck on some masking tape, so I could mark out the cutting lines easily. A pair of compasses could be used to draw two circles, or use the nut as a template to draw round.The central hole is 8mm ( it's an M8 thread ), outer diameter is 27mm.

You really only need one washer, under the nut, if you can ensure you don't tighten the bolt, only turn the nut ( my recommended practice ). Nut and bolt heads are near-indistinguishable, so, if you pass the bolt through from the cable side of the coil, then the nut will always be on the easily accessible non-cable side.

Does it work ? Yes, there's a big drop in friction, I actually feel like I'm tightening the bolt, rather than just wearing away plastic. I'm sure I am less likely to over-tighten the bolt as a result.

Attached picture of my set, for guidance.

I'm pretty sure that only two pins are needed, the 0 Volts ( ground ) and the +5 V. The two data lines are simply left unconnected. And it shouldn't be too hard to work out which wire is which ... they may even tell you in the owners manual ?

If that happened here in the U.K, the clean-up would be easier, as the majority of our 1c-equivalent coins ( 1 pence ) are steel, plated with a lustrous layer of the finest copper. So a magnet would do a good job of 'sweeping up'. Hopefully it would be completed before they turn into brown bubble-surfaced garbage.

I'l explain by example:
Take a look in the "Detecting coins and relics" sub-forum.There's a recent thread titled "Cashing in clad".
If you click on "Cashing in clad" it links to the start of the thread.
Clicking on the "2" button takes you straight to page 2.
Clicking on "8 hours ago" ( below "PI-Man" ) takes you to PI-man's post, the last one in the thread.

It's just bitten me, too. Doesn't seem to like links to external websites, turned my entire post red, said I have to wait for approval ..

Hmmm, tricky questions, and setting off my "uh-oh??" alarm too.
The EBL PP3 batteries are 600 mAh. That's what every seller states they are, and it's what their website say, too:
EBL PP3 Li

So if you've seen some claiming to be 650mAh, I'm getting suspicious they are fakes/copies.
Yes, there are now other brands of two-cell Lithium PP3's, and some claim, and may actually be, higher capacity. I'm sure it's possible to squeeze a few more mAh in the box. Trouble is, EBL seem a good brand, and they've been making these PP3's for a while, now. All these other Chinese 'brands' I've never heard of ...
Now.. the AA cells. You got me worried as soon as I read 3300mWh. This is the warning trigger for wierd and wacky stuff. Sure enough, I think you are referring to these things:
Lithium AA

The answer is a big NO. They consist of a lithium cell, ( about 800 mAh capacity ), with some magic electronics board** integrated in the package, to drop 3.7V down to 1.5V.
They are not what you need, they produce electrical interference, and need a special charger.
You just need plain old NiMH ( nickel metal hydride ) rechargeable cells. Any old crepe will do, they will outlast the PP3 easily. Even AAA cells would be OK, as many of them are 900 mAh+ capacity now. You might even have some suitable AA's at home, or maybe a trickle charger for them. I use some pretty low spec NiMH's in my Fisher F75, they still run it fine.
If you in the market for some AA rechargeables, however, the best brand is generally considered to be Panasonic Eneloop. There's a few 'flavours' including the LSD / Low Self-Discharge type, which stay charged up for months on end.

** Buck mode switching regulator

Quote:"I hope it´s interesting for you too"
Unfortunately, these tests are almost meaningless. Half of the 'depth' difference you are seeing is caused by the larger search-coil on the Legend. I assume you have the LG30, 30cm x 23cm ( 12" x 9" ), and your G2 clone has the 11" x 7" bi-axial clone coil? If you had a larger coil for the clone ( a proper brand one ) you would find the air 'depths' increase.

In-ground testing is the best way to sort out what works when comparing multi-frequency vs. single frequency.

[What would probably be more interesting is a comparison between the Teknetics G2+ and this TX850, with original search-coils, and with genuine Tek coils.]

I would suggest the Equinox, purely based on the cost of the two machines. Just buy it, get out hunting, and you'll eventually work out if there would be any benefit to upgrading to the Manticore at a later date.
All detectors "pay for themselves" at some point, but the Equinox is going to achieve this more comfortably, and it will be just as fun and rewarding to use whilst doing so.

A bit more detail would help, here.
Are you trying to create a Hyperlink to a thread on here.... but you specifically want it to link to the very last post in the thread, not the start of the thread, or any specific individual post within it? This may be what you're wanting:

For the last post in a thread:
https://www.detectorprospector.com/forums/topic/23160-greetings-from-australia/?do=getLastComment

You can get this link by right-clicking on the time of the last post, below the name of the last poster.

For a specific post:
Here's Valens Legacy's reply post:
https://www.detectorprospector.com/forums/topic/23160-greetings-from-australia/?do=findComment&comment=246242
If you look at the thread , at the top of his post you'll see "posted June 9". Right-click on that, and "Copy Link Location" and paste it into your new post.

Hope this helps you, and maybe helps others too, as they're not the most obvious things.

A promotional video for the D2-based two-box machine:
D2 hoardhunter

No experience of the Mark1 machine ... but know my electrics.
The reason that two 9V batteries ( in parallel ) are suggested to replace 6 x AA, is related to current draw, and battery life. One alkaline PP3 may have adequate capacity, but still may not respond well to heavy current demands.
If you use NiMH rechargeable PP3's, they usually have rather modest capacity ( about 180 - 280mAh ) , so you would still likely need two in parallel.
One alternative solution: Use Lithium PP3 rechargeable batteries. EBL seem a good brand. They have two lithium cells in series internally, plus some charge regulating etc electronics. They have a decent capacity ( 600 mAh ), plus can handle higher discharge current rates with no troubles. So only one of them would be needed to substitute the 6 x AA's. The EBL PP3's are commonly sold as a 'bundle' of two or 4 batteries and the 'special' charger.

On the 8 x AA's side: One PP3 and two AA's is a bit ugly, plus the AA cells will outlast the PP3's by a significant amount. I guess weight is the intent of this battery replacement exercise. 8 x AAA would be an obvious solution. A rechargeable pack of 9 x AAA NiMH cells ( or 10 cells ) would also be an idea, though you would have to make / improvise a charger ... not too difficult if you have electrics skills.
Open up a PP3 NiMH, you will typically find 7 small cylindrical cells ( probably 1/3 AAAA ). A bit of surgery to remove 2 cells changes this to 5 cells. Modify two PP3's like this, and you have essentially two 6 Volt PP3's , giving the required 12V when run in series. Again, some simple custom charging arrangement would be needed.

More advanced solutions:
Make a custom 3 cell lithium rechargeable pack to replace the 12 Volt / 8 x AA pack. Electronics skills are definitely needed here, as you will need a 'battery management system' ( BMS ) circuit board to ensure the cells charge up evenly. These are easily found on eBay, 5 dollars or less. But the charger needs some thought. The cells themselves could be rescued from 'used' disposable E-cigarettes ( Vapes ). You may have friends/relatives who use these, ask around.

A small handheld metal detector may help locate it if you're sorting through boxes. Us detectorists use a device known as a 'pinpointer' or 'pinpoint probe'. They are essentially custom versions of electricians cable-finders / plumbers pipe-finders for finding nails / electric wires in a building.
If you own, or can borrow from friends/relatives a cable-finder, it may be of some use.
There are some cheap pinpointers available these days, look on eBay.
Alternatively, the 'Security Wand' type of metal detector, used by security guards to check for knives etc on people, can also be used, and there are some cheap versions of those available.

I'm not totally in agreement, Simon.
I think the issue you're overlooking is this:
To take something average, and make it a bit better, doesn't increase the manufacturing costs much. To take something high-end, and make it a bit better, means it will cost much more.
Example:
To make a 250 Dollar mountain bike 500g / 1 lb lighter, you just need to change some plain steel bits for plain aluminium, and it would then be a 275 Dollar bike. To make a 2500 Dollar bike 500g lighter, you need to start swapping high-grade aluminium with carbon fibre, and swapping cromoly steel with titanium, and you have a 3000 dollar bike.

The Manticore coil may only be modestly higher in performance than the Eqx, but that could come at a price.

Quote:"Minelab proved with the Vanquish they can make Nox coils a lot cheaper than they do"
Yes, it's true that they are very similar. The electronic pre-amplifier in the V is not made to such a high spec as that in the Eqx ( not such a low-noise design ), which may make a dollar or two difference. But .. the design work, and manufacturing know-how that went into the Eqx coils, has carried over to the V coils 'for free'. Sales of the Eqx have more than paid for the R & D etc costs, so producing a slightly toned-down version is easy.

" .... and then the X-Terra[Pro] comes out and further reassures us we are being taken for a ride"
X-TerraPro coils are not made to the same standards as Eqx/V coils. They only have to work at 5kHz to 15kHz, so they don't need fancy expensive 'pseudo-Litz' multi-strand wire, probably just a single solid enamelled wire, or maybe bifilar/trifilar winding of thinner wire. That would save a few dollars. The pre-amp is probably cheaper ( maybe not such a low-noise design, and it won't have the bandwidth needed to amplify 40 kHz signals ), plus it wouldn't surprise me if it doesn't have any security chip in it at all. And it's probably not nulled to to the same standards as Eqx/V coils, which saves manufacturing time.

Quote:"The Manticore coil? No reason it should cost much more than an Equinox coil, except for Minelabs "If the detector costs more, charge more for the coil" history."

I'm sure this IS part of the pricing strategy.
But ... the Manticore does have more electronics inside it. It almost certainly has some accelerometer / rate-gyro inertial sensor to measure sweep direction / speed. And the Manticore coils operate up to 50 kHz ( IIRC ) rather than the 40kHz of the Eqx, so it's likely the coil windings may be built to more exacting standards. And the fine-tuning of the mechanical assembly ( nulling the coil ) may be done to a higher standard. The multiple stiffening ribs also point to them trying to achieve greater stability. Plus they have to recoup the extra R & D costs they must have spent on the coil.

Quote:"I never liked the T2/F75 ... because of the single-button interface"

They could've done more with the interface, especially considering it's really a two-button interface. But the rotary encoder's button is lamentably under-used. On my F75 [early model] the sole function I recall it had was as a 'cancel' function when setting up a notch pattern. I'm sure this was never even mentioned in the User Manual. As I rarely had need for notching of any kind, I never used the 'cancel' button.
It did serve a secondary function - pressing it 'woke up' the interface. One use of this was if you were wanting to switch between 'Disc' and 'All-Metal'. If you left the menu cursor at the top of the list, you could switch between Disc/AM by rotating the encoder one click cw / ccw. But the processor has a time-out, so this function doesn't stay working. Pressing the encoder button 'wakes up' the processor, and then the encoder will function as Disc/AM select.

My 'plan' was to automate this action:
Rotary encoder rotation can be simulated. Intercept the two quadrature signals, and pass them through XOR gates. Then "one click cw" or "one click ccw" can be done easily. The remaining 'logic' comprises timer functions to activate "encoder button push" , followed by " encoder rotate" , plus a front-panel push-button to trigger the action, toggling back and forth ( or 'press and hold' to toggle )
In practice, it would all fit in an 8-pin microcontroller ( Microchip PIC / AT Tiny etc ) , so there would be hardly any hardware, all software.

[[ sorry for off-topic ]]

Quote:"One thing I might add is a mineralisation meter, like on the Fishers. Not sure if that was mentioned."

Yes, I posted some thoughts earlier in the thread about using the '88' display to show mineralisation level:


earlier post

Anecdotal evidence seems to suggest the single-frequency modes on the X-Terra Pro perform better than the similar modes on the Equinox, particularly on a wet beach environment.

It seems likely the Equinox had most of it's R&D put into multi-IQ, and the single-freq modes were provided as an 'easy to include' addition. Whereas the the X-Terra Pro only has single frequency modes, so no doubt some design thought was put into their operation.

SO, it would be nice if any Equinox update could include improved single-freq modes, based on X-TerraPro "know-how".

There is a larger coil made for the GB2, similar shape to the 6", but about 10" long? Perhaps it may be worth looking out for one of those.
As they are official Fisher products, there's a good chance they have geometry that's deemed correct for the machine. Putting a round 15" DD on a 72 kHz machine, for example, may just prove disappointing ( big coil says 'big targets' , 72 kHz says 'small targets' ).

You should register with the Geotech1 Forum, where you will find an abundance of info about coil building:

Geotech1 forums

Unfortunately, the GB2 is one of those "difficult" coils. The combination of high operating frequency, and internal components ( tuning capacitor etc ) , and the fact no-one seems to have reverse-engineered one, means your chance of success are low.

I think the GB2 is not the best choice for beach detecting, due to its high operating frequency, and inability to handle the electrically-conductive salt-water sand. It would be better to buy a new machine dedicated to beach hunting, preferably with some degree of water-resistance as a feature.

Quote:"It is [an assumption], but only to a very small degree, because the ground was encompassing most of the field with each coil tested."

I've no idea what "encompassing" is defined as, I would assume even with the coil pressed on the dirt, it would only encompass half of the field, the half below the coil.

But anyhow, I've located some ground pickup measurements I did on my Fisher F75 11" x 7" DD coil. This behaves much like a 7" coil ( long, narrow coils tend to have their characteristics dominated by the 'narrow' dimension ).

Assuming your 'standard' coil height is 1 inch, and you state the 11 inch coil was raised 2.5 inches above this, to 3.5 inches:
I'll convert that to 25mm and 87mm metric.
My measurements show a ground signal level of:
25mm ... 7.6 mV
87mm ... 2.8mV
that is a drop to 37% of the signal at 25mm height.
I would expect an 11 inch coil to be less affected proportionally by such height changes than a 7 inch one, so perhaps a 45% to 50% drop would be an estimate? This then permits a target signal 45/50% weaker to be picked out. This roughly equates to 15% more target depth ( ie coil to target depth ).

Quote:"The raising of the coil ... wasn't a "significant" flaw, as the vast majority of the field below the coil was still in the ground for each coil."

That sounds like a very hand-waving guesstimated assumption to me. Not backed up by any technical measurements taken on a real detector, or any ( difficult ) mathematical modelling of search-coil behaviour.

Like anything technical related to detector operation, the truth is never straightforwards. Ground signal does drop off as the coil is raised .... but not anywhere as severe as the target signal drops off. And when a coil is very close to the ground, the ground signal behaves rather unexpectedly, and can actually 'plateau' or fall in level. But ... the phase angle of the ground signal also varies too: raise the coil 20 inches, you'll get a huge phase shift from 'ferrite-like' to 'salt-like'. It's really the "wobble" in ground signal that causes trouble to a detector. Some perfect uniform flat ground, and a perfectly swept coil, would give nearer air-depth results.

If you're comparing different size coils, are you comparing them at the same height? Would it be more correct to compare a 10 inch coil at 1 inch height, to a 5 inch coil at 0.5 inch height, for example? Or do you keep a fixed 1 inch, as that's how you would use a coil in real world hunting?

It's also worth noting that EMI pickup is coil height dependant. It seems that the ground provides some degree of shielding, perhaps it depends on whether the EMI is vertically or horizontally  polarized. 

How coils pick up a target signal, how they pick up the ground signal, and how they pick up EMI, is a complex issue. And it varies from one machine/manufacturer to another. So it's important to state that this is a test of the Legend. Plus, it's probably wise to state what revision of firmware it's running, as performance could well vary as a result of this ( in the past and for future revisions )

Regarding:"I don't see how a preamp in the coil, or a 'security chip' in the coil, would affect the coil's susceptibility to EMI and ground impedance"

The pre-amp DIRECTLY affects pickup of targets, the ground, and EMI.
So for example if a 5 inch coil has a pre-amp gain of 20 , and they make a 10 inch coil with a gain 14 ( ie. 0.7 x the small coil gain ), then:
The larger coil will likely pick up about 2.5 times the EMI, multiplied by 0.7 = 1.75 times total. So it still picks up more interference, but not as bad as would be expected ( based on typical 'simple' detector behaviour ).
Likewise, the larger coil picks up a stronger ground signal. This is part of the reason the manufacturer may choose to make the pre-amp gain lower.

And on the subject of ground signal pick-up:
Quote:"By saying "going deeper", I meant I could raise the coil by that amount off the ground and still get a good repeatable tone."
This shows up a significant flaw in your tests. If you raise your coil, not only do you reduce the target signal, you also reduce the ground signal. Considering a primary function of the detectors circuitry is to pick out the  ((target)) signal from the ((target plus ground)) signal, changing both target and ground signal is not equivalent to changing just one alone ( by burying the target deeper ).