karelian

Jim in Idaho, I am sure 'Reidman' did a five cell battery pack for the Tdi Pro going back a few years now. I'll just do the simple version with a five cell holder, nothing fancy. Works well for me to be able to remove the batteries and swap out in the field and better for the cells since I use a quality smart charger. I can used protected 18650 cells, don't have to worry about over charge or discharge.. Yes I will have to do another comparison test, the extra voltage demands it. Again I think the combination of a modified machine with the higher voltage battery pack is about all I can think of when it comes to maximise depth potential.

I'll complete 'playing' with the Tdi Pro modified unit by making a five cell battery holder. I've used the standard 8 cell White's battery and I have made a 'emergency' four cell battery holder. I will expand to the five cell holder and give it a go. Not the first to do this so I'm not too worried about damaging the machine. Should be around 21v hot off the charger and give an honest 18 plus volts most of the time. Just plan to combine a two cell and three cell holder into a single five cell unit, pretty simple. Just an expansion of the earlier 4 cell holder. The Tdi Sl likes a little extra voltage so I'm keen to see how the Pro works with a bit extra.. A modified Pro with upgraded battery voltage, about as far as I can go with this machine I think..

The standard Pro machine with the Sadie coil with quick ground balance on video, then switch to Low and finally the Digger 14 x 8 in All and Low. Just shows that sometimes ground noises cannot be eliminated, just managed... All the best.

The location used for this comparison between the two Pro's is German Gully near Fryerstown in Victoria. The ground is very hot, has been worked and surfaced in areas. Produced nuggets, iron stone and hot rocks in quantity. Ground moisture is very low, very very dry. Test results were only done with the Sadie coil, I have included old results done years ago at a different location with the standard Pro. Soil moisture during the 'old test' were much higher, I am thinking that and the different locations explain the different results. Old test, 1 grain gold ingot 6cm, half gram gold coin 21cm, gold half sovereign 27cm. Standard 1 grain gold ingot 9cm, half gram gold coin 16cm, gold half sovereign 21cm. Modified 1 grain gold ingot 11cm, half gram gold coin 17cm, gold half sovereign 21cm. So the modified unit has a small gold advantage, smoother threshold , all else being equal.. Video to follow shortly.

Due to time restraints and excellent prospecting weather, I only compared the two pro's with the Sadie coil mounted. I did use both with the Digger 14 x 8 and the Nuggeteer 18 x 6 also, but not for testing, just looking for gold.. The location of the tests is shallow ground heavy in ironstone and hotrocks. Beautiful colour quartz and lots of red earth.. Both machines were stable, ground balanced well and suffered equally. The Sadie coil was stable but transmitted a bit of ground noise on both machines, both were good in ALL conductivity but excellent in LOW. No differences here. The big Digger coil was very good in All conductivity and superb in Low, much quieter than the Sadie coil on this location. The previous gain advantage the modified machine enjoyed on the beach and in air tests, did not show up in ground tests. Both machines managed gain around five or six, no clear differences here.. Again threshold was smoother on the modified machine, apart from this they operated in the same fashion and behaved the same out in the field. More information and videos to follow shortly..

It must be said that you can run the Tdi Sl with ground balance 'OFF' when using the small Tdi 6x4 coil. I tried it in a very quartz infused open cut, worked very well. Tried again in an area with iron stone and hot rocks, no joy since it is very noisy and picks up all the hot rocks etc but ground balance was easy and once set up she ran very quiet and smooth in this location. I will upload a link later since I did shoot a bit of video with the SL without ground balance, then with ground balance etc. One location pictured shows the Sl on a log in an area cleared by fire..

On the road...

Dug the coil out of storage, mounted it on the Tdi Sl and all is good to go. Just feels weightless mounted on the Tdi Sl, this rig is super light and well balanced. The lighter battery pack helps also. I could swing this thing all day. Also looking forward to heading out into the goldfields, all has been organised for early in the new week. All the best.

I knew I had read this somewhere, taken a few years to get around to doing this, looking forward to trying it out. I have used the small 6 x 4 Tdi coil but it never occurred to me to try it with the ground balance off..

Never managed to find a Razorback 'Piglet' locally, so jumped on the Whites made 6x4 Tdi coil. The Tdi coil uses the Whites 6x4 housing used on the 'Shooter' coils. Images tell the whole story. I'm hoping that the small footprint will have much less ground affect and allow me to avoid the ground balance. Worth a try..

Jim in Idaho, in the last threshold target response video I had the Sadie on the SL, the standard pro had the 14 x 8 Digger and the modified unit had a Super Pulse 220. I'm taking the Sadie and Super Pulse 220 coils into the goldfields plus one larger coil, probably the 14 x 8 Digger. So we have one small, one medium and one large. Targets will be the one grain gold ingot, the half gram gold coin and the gold half sovereign. I will bury the targets and will choose the same location as previous tests. The ground effects will be significant and will tell the real story. I'll test using a pulse setting of ten, normal ground balance, then repeat tests in both Low and All conductivity. On a side note, I'll take that small Jimmy Sierra 6 x 4 Tdi coil out as well, just interested if it will allow me to run with ground balance OFF in hot to moderate ground, just curious..

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