karelian

Sorry about the dove in the background, a little bit of native wildlife intruding.. Just the Tdi Sl, followed by the standard machine with Anderson shaft and finally the modified Pro. Threshold and target response from a 1 grain gold ingot, just to flesh out some detail.

RickUk, I suspect that there are a number of factors a work that determine depth between the machines. First as a simple air test, with the ground balance OFF, we are focused only on threshold and sensitivity. Ground conditions are usually a huge factor.. but in air tests we can dismiss this, for now. This will play a big part in the later in ground testing..

So the modified Pro has a smoother threshold, making it easier for us to distinguish target response. Secondly the more pleasant threshold makes for a more 'pleasant' detecting experience, less concentration required, less fatigue etc. Finally I believe there is a small but noticeable improvement in sensitivity. Combining all of the above the machine could be regarded as outperforming the standard machine, by a small margin in regards to depth, but significantly more pleasant to use. Finally the modified unit can advance the gain a little further before it becomes a bit unstable. Not sure if it is the modifications or a common variable between all Tdi Pro detectors.  Rare to find detectors that settle gain on the same point on the dial. I had two XL PRO machines and they were identical, but one could push gain a little higher than the other, with almost identical depth and sensitivity..  question remains unanswered?

After years of using the standard Pro my brain is hardwired to 'work with' the warbles and I can easily distinguish target reponses. I work at a certain sweep speed which I believe is optimal, lots of coil control, know my machine and more..  I am immune to the warbles, others could easily find them distracting to say the least. Another reason why I have a Tdi Sl as a loaner machine, light and balanced, decent performance with the battery upgrade and that super clear and stable threshold..  Our detectors are what they are, so it is up to us to work out how to get the most out of them, normally we have to adapt to the machine since machines cannot adapt to our way of doing things.

The modifications on this Tdi Pro are I guess a way of fixing what many would regard as shortcomings in the standard machine and to some extent they have been successful.

Same test as above, changed the coil to the Jimmy Sierra Digger 14 x 8 mono, by Miner John. Gain was less this time, only got the standard machine to 5 and the modified machine to 7. Suspect coil size plays a part in this.

Standard Pro got 1 grain 8cm,  0.5g gold coin 31cm, Half Sovereign 42cm.

Modified Pro        1 grain 9cm, 0.5g gold coin 33cm, Half Sovereign 45cm.

Both machines with ground balance OFF, pulse at 10, conductivity on ALL.

So a pattern of behaviour is showing, the modified machine has a smoother threshold, it allows a couple points of extra gain and has a fraction more depth. This pattern seems consistent regardless of the size of target or size of coil used.. It will be a while before the next test. In ground testing on the goldfields, weather, fires and other factors will determine when.. hopefully soon.

Mike T, performance is one thing but that smoother threshold certainly makes the modified unit more pleasant to use, if using headphones to drown out the sounds of the oceans, wind etc, it can make all the difference in terms of concentration, ability to pick up on small variations in audio or whispers etc.  

The Tdi Sl has a beautiful steady threshold hum, music to my ears, with the 16v battery pack there is still a small performance deficit.. but it is a fun, super light and a well balance machine to swing.

On the standard unit I sometimes turn threshold to just silent, makes for more pleasant experience with headphones on the beach, with a small loss of performance. 

Tested small gold sensitivity and ability on porous gold using Coiltek Tdi 6" mono coil.  Both machines were tested on the one grain ingot, the modified unit beat the standard unit by 5mm or half a centimetre. I suspect the smoother threshold makes it easier to pick up the target response but even taking that into account it was marginal. The quartz infused and partially porous gold sample is a challenge for PI machines, from testing I know the small Coiltek Tdi coil and the Sadie will pick it up. The standard machine managed 4 cm whilst the modified Pro came in at 5 cm, marginal but still a 20% advantage. The unstable threshold works against the standard machine, I only record target depth as that which is repeatable and in my mind stands out as a target.. Threshold seems to be key here, actual sensitivity is very close, just a small fraction in favour of the modified machine. Also the ability to advance the gain or sensitivity before instability was checked. A clear advantage to the modified machine. Where the standard machine peaked at six, I got the modified unit to eight. So the threshold component transcends into a bit more gain, an advantage in detecting whispers, with a bit extra sensitivity. Tested were conducted with the same battery in both machines, same time and location etc. These were air tests to determine sensitivity and threshold only. One final air test to follow before actual ground testing in the goldfields. 

I'll do better next time, titles would be nice. Clearly first machine is a Tdi Sl, second is the modified Pro followed last by the standard Tdi Pro with Anderson carbon fibre shaft.. The modified machine clearly has smoother audio than the standard machine which exhibits that atypical warble.. more to come..

phrunt, the answer is the modified unit is a goner, long term I'll keep the standard machine, regardless of the results. The reason is I know the history of the standard unit and have looked after it since near new. I can vouch for its history etc if I ever decide to sell.

Do you keep the car with service books and history, or the one with an aftermarket turbo..... 

I've been asked to do a video showing the differences in threshold, I'll show the Tdi SL, modified Pro and standard Pro. It won't be very exciting but it may be informative.. At least I used a DSLR, external Rode microphone and a decent Miller tripod.. no music, just threshold hummmmmmmmm...

The passing of a friend unfortunately has led to me taking ownership of a modified Tdi Pro. My machine is mounted on an Anderson shaft and is factory spec. My old mate had his machine modified to smooth out the threshold and to add some sensitivity. The specifics related to the modifications are not known by me, other than that they were conducted by 'Luke'..Oz Digger.. This happened some time ago. So the modified machine is probably not a keeper, I don't want two Tdi Pro machines.. The opportunity to do a comparison cannot and should not be ignored. 

My intention is to focus on small gold performance, the threshold smoothness, the ability to use gain, basic performance and handling characteristics  under different circumstances. The machines will use the same fully charged battery pack, same coil, same targets, same test location and conditions on the same day etc. Trying to minimise external variations. I'll start with the usual useless air test. Later I'll follow up with in ground testing on the actual goldfields in mineralized soil. Test coils will be with a small coil and a large coil. Targets will be gold only. The 1 grain ingot, the half gram gold coin, a half sovereign gold coin. Some real small sub gram nuggets to see how small we can go.. There is a process involved so I'll take my time and do it right.  Any specific questions or suggestions, speak now or forever hold you peace.. I'm only doing this once. Once it sold it will be too late to revisit.. 

All the best.

Joe klecz just google 'neoprene arm rest covers', also search ebay, should get lots of results. I just got them off ebay years ago, just checked and there are lots of different dealers online..

I agree and fully recognise Jim in Idaho that your Tdi Sl has been modified and that it is an excellent performer. I am not entering the realm of modified units, just talking about stock machines.

Due to a good friends passing, I have two Tdi Pro machines, one stock standard and one modified. I actually prefer my own machine which is not modified, its mounted on the Anderson rod. My old friend had some work done to make the threshold smoother and add some extra gain, not sure of the details. I can say the modified Pro is hotter on the beach and my machine is better on hot ground. I'll get around to selling it soon, after I have finished playing with it. 

It's frustrating  but I will get rid of it as 'not working for parts', simply because I don't know what the heck was done to it and I refuse to sell machines any other way if I have questions about their condition. Probably why I don't entertain modifying any of my own machines, apart from that 16 volt battery pack... works well..

Look forward to a Tdi Pro standard vs Tdi Pro Modified comparison before I get rid of it.

All the best.

Jim in Idaho, I have used my Tdi Sl with battery boost now for a while, there is a significant improvement. The reality is that the Tdi Pro will beat the SL for depth under all ground conditions, under all circumstances. The 16 volt battery pack narrows the margin but if depth is the only criteria then the Pro wins. If ease of ground balance and battery power and life are included then the Pro increases the margin significantly, particularly in difficult ground conditions. As the owner of both machines for years, that is my experience. A Tdi Sl using the lower 12 volt battery or the Whites rechargeable packs provided with the detector is way behind in depth.

I did a quick comparison between different voltage on a Tdi SL, then compared the results using the Tdi Pro. Machines had a Whites Super Pulse 220 coil fitted. The Tdi Sl machine ran with gain or max, the Pro had gain on 5.

12.34 volt Tdi SL  1 grain gold ingot  6cm,  half gram gold coin 24cm, Half Sovereign 32cm, US Quarter 27cm

16.48 volt Tdi SL                                   8cm,                                     26cm,                             35cm,                       30cm

Tdi Pro,                                                   8cm,                                      27cm,                            36cm,                        33cm

In my experience the worse the ground conditions the greater the margin in favour of the Tdi Pro, not gospel just my experience.  No expert but I suspect the ground balance system of the Pro and the filtering on the Tdi Sl both play a part. The depth comparisons  above do not tell the whole story. A super light  and beautifully balanced Tdi Sl with upgraded battery is not a bad thing..

The reason I have an Sl is because of the very light weight, it is great for kids and old people, the battery system allows air travel, that beautiful smooth audio. It is a great loaner detector for family and friends. If depth is the main criteria then the Pro is it. I like the Tdi machines for their flexibility, great on the beach, good for coins and relics. They have decent performance on the goldfields, a great all rounder. The dedicated gold prospector is probably much better served by Minelab's superb line of gold machines. An individual who likes to do a little of everything like me can find excellent value in the Whites. There is a strong argument for a second hand Tdi Pro, rebuild a few new battery packs, a great value.  

I have been asked by many people about this, just expressing an opinion based on my personal experience. 

All the best.

This combination eats up large areas fast, perfect for the beach. Large coins like the Australian 50c come in up to 14 inches, which slows me down a bit because I have to dig so deep. Again a very well behaved coil. Isn't upset by salt water or wet sand, EMI has yet to raise its head.. full gain on Tdi Pro possible on two out of three locations visited.

High winds made for a short beach run, early days. Very good coil, I'm very happy with depth and sensitivity. 

Loves beach junk, bottle tops, aluminium in all it's forms, ring pulls, etc A real beach cleaner.. Tried three different beach areas, really comes to life in the low junk sites. Small coves, smaller beaches, no kiosk but a yacht club, good dollar coin areas.. not too much rubbish.. I'll give this combo a good run over the summer and take it into the goldfields later in the year.. So far so good.

If circumstances demand on the beach  I can fine tune to find 'gold'. Problem is if I knock off small iron, I will loose other targets like Australian $1 and $2 coins. Depending on the area I normally dig everything when using the Tdi in wet or damp sand and swap to a VLF on the dry sand which helps is trashy areas.  On the goldfields I dig everything, no exceptions..

On the beach when needed I can disc small iron by  setting pulse around 13 to 14, the ground balance between 5 and 7, conductivity in LOW.. play with the machine using a small piece of iron to fine tune the settings. Using these setting the 18 x 6 mono still hits well on gold. The one grain ingot does not respond at all, the half gram gold coin looses 2cm or less than an inch, from 22cm to 20cm. Half Sovereign, a solid little gold coin goes from 34cm to 31cm, good signal very clean while ignoring small iron.. So yes the Tdi will let us disc small iron and still hit gold with a loss of roughly 10% depth. Not forgetting the 18 x 6 hit a one grain gold ingot at 5 cm and failed to detect it at all when set up to ignore small iron. 

Most targets are shallow or under 20cm or 8 inches, so the 18 x 6 will still hit well if setup to ignore iron whilst covering large areas fast. The option to target gold items is worthy of exploration, the coins barely pay for my fuel..

On the goldfields  I just leave the delay at ten, do a normal ground balance and switch conductivity to low. Away you go, very smooth and steady in the worst ground.. no boot tacks... nails or small bits of rusty flakes.. Aluminium  foil is another story.. But again I will loose gold over a certain weight... the idea of going over a monster nugget and missing it means I usually leave conductivity in ALL, unless specifically targeting small gold. At least the machine gives us a choice. Again the Nuggeteer coil works well on the Tdi at all settings.

Just started with the useless air test, pleasantly surprised that the Nuggeteer  18 x 6 mono is very stable and quiet. No EMI issues at all in an area with mobile phone towers, WIFI, an EMI hot zone, whisper quiet and smooth operation. So far so good. Balances well on the Tdi Pro, just adjust shaft length and it floats nicely.  Build quality is good, coil mounting points are solid and appear durable. Coil cover is a good fit. Sensitivity is very good and the preliminary air test indicates decent performance is on offer. In the next day or so I'll give it a good run on the beach etc. Weather is a bit wet and wild, much appreciated actually..

Tdi Pro air test, gain was 10, ground balance off, conductivity in all, pulse set at 10.  

Australian $1 coin     37cm  - 14.5 inches

Australian 5c coin     30cm  - 12    inches

Australian penny       36cm  - 14    inches

Australian 3 pence   30cm  -  12   inches

Half Sovereign           34cm -13.5 inches

0.5g gold coin            22cm -  8.5 inches

US 3 cents, Buffalo  34cm - 13.5 inches

US Quarter                 28cm -   11 inches

Whites Buckle           51cm  - 20 inches

It did not go unnoticed that I was able to advance the gain on the Tdi Pro fully, without issue, very stable. I'll attempt simple discrimination when ground testing, eliminating fish hooks, hair pins, nails etc Interesting to test depth under those circumstances..

The main game being coverage, large expanses of beach.. depth is secondary, so far so good. Seems to hit hard for 80% of its depth, only fading on targets for the last 20%,  5cm on a grain gold ingot is decent for a coil this size. Tested a  flat 0.3 gram gold nugget and it hit hard out to 15cm or six inches. It hit hard on a 1.6 gram nugget out to 25cm or ten inches..  I look forward to  gaining more experience with this coil. In ground performance and beach experience to follow shortly.

Karelian

Just arrived in the mail, Nuggeteer 18 x 6 mono, mounts nicely on the Tdi pro using a Minelab lower rod. It is weighty at 1 kg but easily balances on the Tdi Pro, just don't have any metal in your shoes..

When the weather clears I'll go down to the beach and give it a good run. Useless air tests, test garden results and beach run results in the very near future.. karelian

Nuggeteer 18 x 4 mono has arrived, I'll give it a good run to see how it performs. I am hoping to add it to my favourite beach coils, the Jimmy Sierra Digger 14 x 8 mono by Miner John and the 12 duel field from Whites.  Ground coverage will be good, weight is just over a kilogram at 1014 grams so should balance well.  Interesting to see how it performs in regards to depth and also when using the TDI machines limited ability to tune out small iron. I am happy to just  tune out fish hooks and hair pins and dig everything else.... Karelian

BT-168D battery tester, again best found on Amazon or Ebay. Should be under $10. 

Pelican 1050 case with aa insert. Amazon or Ebay should give you start. Like all Pelican cases it is weather sealed and solid. I like it because it holds 40 cells and it keeps the dust and dirt out. I can empty the box and wash it in the sink, then just leave it outside to dry. 

Karelian

The Garrett A2B was typical of machines available at the time. They had a meter, operated as VLF/TR, ten turn ground balance made it easier in hot ground. Solid metal construction, lots of batteries and a bit of weigh. Lucky if it balanced well and more often than not the handle blocked the meter. We have come a long way folks. I take the old girl out when I feel nostalgic and when I know other detectorists will be around. A great conversation piece and it does not go unnoticed.. It has brought back a lot of memories and made me new friends.. 

I used one of these when I was 17 years old. Rich pickings back then, way way back then... A lot of younger detectorists  may not know what a Garrett A2B is or looks like. Goes back to the old Groundhog circuitry, 15khz, VLF/TR, adapted for hot ground with a ten turn ground balance, tone control for audio. A good reputation here in Australia for finding gold. Before Minelab became king and before Pulse Induction became the main game.. This was found nearly unused, a real 'Closet Queen'. Seller told me he lost the battery tray not long after he got it, sat in the closet for nearly three decades... Karelian

On 7/25/2018 at 5:24 AM, phrunt said:

yes show the Garrett, I want to see it!!!
 

Some images to answer the question..

Forgot to mention PM Coils also produced a limited number of coils for the Whites GMT, possibly other brands and models such as the Infinium , Scorpion Stinger etc. They were happy to experiment, that willingness to 'have a go' is sorely missed, since no current coil manufacturers have yet stepped into the possibly very profitable gap left by the Bigfoot. We can all dream can't we?  Karelian

Sadly Pm Coils is out of the game, for a while they made a Scarab 18 x 14, Nuggeteer 18 x 6 in mono and AI, 12 x 4 mono and AI. There was also an 18 Tarantula, it's in the photo, two coils shown with funny shape.  Jimmy's T-foot as an 18 x 5.5 duel field would be the ideal beach coil. Don't know how many Razorback Beach Hog's were made,  a real beach sweeper.  Only rarely spot Nuggeteer coils on the local Australian classifieds, very reasonably priced compared to the 'bigfoot' coils I sometimes see advertised in the USA. Paid $60 for the 12 x 4 AI and $175 delivered, for the 18 x 6 mono. (Australian dollar roughly US 70 cents.)  I'm interested in how the big 18 x 6 mono balances on either the Pro or SL, it was classed as a 'patch finder' coil.

These coils seem well put together, quality feel and solid. The coil cable is quality, also durable and the coil cover fits well. The Nuggeteer GPX coils already used Litz wire, so I'm looking forward to testing that 18 x 6.  A bit wider than the genuine  'bigfoot' but the same length so on a pulse machine depth should be interesting. 

Karelian

Now what I really wanted from this style of coil is something like a 'bigfoot' for the beach. My current beach coil is the Jimmy Sierra Digger 14 x 8 mono coil made for him by Miner John. Well balance and light with a good footprint it is a winner.

I've given up trying to find a bigfoot coil for either my MXT or XL PRO machines, too old and rare plus the prices are a bit high.. A nice Razorback Beach Hog would be great but again too rare and hard to find in Australia whilst   perfect for my Tdi machines.  As luck would have it I am waiting for a Nuggeteer 18 x 6 mono to arrive. Not my first choice but for this style of coil we have few options and opportunities are not to be missed.. Coverage is the key goal, decent depth but not too much... if nothing else it should just eat up large areas fast.. Full review to follow..

Karelian

I've had this coil for quite some time, but it was packed away and forgotten. It was purchased for A$60 because I was intrigued.

It is the anti-interference version. Measures 12 x 4 and uses the MInelab lower rod.

Weight is decent, build quality is good. Performance in the field still remains a mystery as I've yet to use it. I gave it a quick air test just to see how it behaved on the Tdi Pro.

This version has a hot spot in the centre of the coil which appears very sensitive to small targets at shallow depth. Seems to hit fairly well at shallow depths but doesn't have much punch for the deeper targets. Test garden results on coins would give real world depth on coins between a solid hit around 15cm or 6 inches and fading fast past 20cm or 8 inches. 

Useless air test with ground balance off, gain at max, in ALL, frequency in the middle, pulse delay at 10.

1 grain was               7cm

.5 gram gold coin  16cm

1/2 Sovereign         23cm

Us Quarter              23cm

Aussie Penny         25cm

Whites Buckle        33cm

So in summary it hits hard on small and shallow targets, the centre of the coil is a hot spot for sure.. Fades fast as depth increases, the big Whites buckle just managed 13 inches.

Since I managed max gain on the Tdi Pro in an EMI hot zone, the Anti-interference feature seems to work ok.. One of the things I like about the Tdi machines is the ability to plug in all sorts of coils, never know if you don't have a go..  My Tdi SL is highly resistance to EMI and the Pro less so but still very good. This coil could make more sense mounted on a Minelab around electric fences and mobile phone towers.. etc.

All the best,

Karelian

I like the Whites battery tray system, but it requires me to 'test' each one of the eight AA cells as I load the tray. My father was an electronics technician and when gadgets failed his first question was always the same.. 'Did you check the batteries.?'  In my experience he was on to something.  Ok, the Pelican AA battery holder may be excessive, but the cheap tester is well worth it and I have a 'system' in place which means failures are rare.  Cheaper ammo boxes keep AA cells well sorted, clean and protected whilst ready for use. Most of my machines run on AA cells, I also use them on GPS, radios, torches, battery banks etc. I buy 'bricks' of bulk AA cells, quality but cheap, new technology some with ten year cell life. Too many cheap and nasty cells out there so it pays to be a bit fussy about what we 'feed' our expensive toys..

All the best, Karelian

My MXT has given years of valuable service, the 24k and GMX have made a credible argument for an upgraded nugget hunting VLF.

Must agree the new slimmer and flatter coil on the 24k is a big move in the right direction. Don't like to criticise the 'old girl' but the Shooter 6x4 and Eclipse 5.3 were always a bit 'chunky' and the move to the 'slimmer' design would be most welcome.. Every little bit helps when hunting for the specks..

The higher frequency in the GMT made it hard work in 'hot'  Australian ground, so I found myself happy with the MXT. Looking at the images you can see the MXT has a practical limit when it comes to detecting small gold in hot ground. Smallest gold found was 0.15 grams, half of which was gold. Time and technology move on and the GMX Sport has sparked my interest as it opens new options. Looking forward to its release.

I've been able to exercise some restraint in regards to buying the 24k, the lack of 6x4 dd has helped a lot plus the ability of my MXT to fill the niche to a reasonable extent.  The addition of waterproofing which doubles as weather and dust protection is a big bonus. The promised coils package would seal the deal...  Pulse Induction technology dominates nugget hunting in Australia for many good reasons. Their remains in my view a credible argument for a capable VLF as part of my nugget hunting arsenal. A waterproof high frequency VLF would expand my crevicing and panning toolkit.  Lot of smaller gold left, hard hit areas continue to produce the fly specks.. it is the bigger bits that are more elusive. The 24k looks good and all the reports are interesting. The GMX offers just that little bit more..  

All the best,

Karelian