Geotech

I'm gonna head over this week and try to get that answer.

I know what you meant, I feel much the same way. The SL was supposed to be a re-boot of the TDI effort. The TDI was difficult to manufacture, it had (I recall) 14 trim pots. The SL had 1 trim pot. The SL suffered a slight depth loss but was more stable. The board was designed to be put in either the SL box or the big TDI box with Lithium power. The intent was an upgrade that had both depth and stability. The board also fit the Beachhunter waterproof box and I built protos for this but it was rejected by mgmt. I hinted at this on the forums and eventually someone (Tom?) picked up on it and released it. There were also extra components on the board to implement ground tracking and a couple of other features. So there was a plan, it just didn't have priority. And the retirement of Dan Geyer left me as the only guy who could (or would) work on it.

The TDI-SL was purely a development for Africa. The intent was a simple AA battery system and sub-$1000 price tag. Some were built and sent to Africa but it didn't catch on, so the SL was released for domestic sales. I argued hard for a sub-$1000 price tag but lost. If you look at the PCB on the SL you will see some unstuffed parts that were for future development, including auto ground track. But then I got onto truncated half-sine and the performance was so much better that I completely abandoned the TDI platform. The reason half-sine never saw the light of day is because, for 3 years, I was diverted to developing a security walk-thru which, after I finished the project and even built a production line, was canceled. There is more to the walk-thru story I may tell one day; it is probably the key reason White's failed.

Thanks for the insult Reg. I wasn't questioning Howard's technical abilities, from everything I've heard about the QED it is a very capable detector and Howard did a good job with it. But I do question his business acumen. Sitting on a forum, bashing the competition, and repeatedly daring them to sue you was poor etiquette at best and outright stupidity at worst. And he reaped his reward. I suspect that White's could have done an admirable job selling the QED and Howard could have made a nice chunk of money while moving on to his next great idea. I'll note that Bruce is not sitting in his garage building detectors to sell, probably he's in his walk-in vault counting his money. It's ironic that things could have worked out differently for both Howard and White's with some better applied judgement.

The guy you saw detecting at OSU would have been Bob Canaday. He did PCB layout and my office was next to his. Wonderful guy, he died very suddenly a year and a half ago. He was the key tester for White's, nothing went to production unless Bob said it was ready. After I left, that policy changed. I used to occasionally meet Bob for breakfast at Sharon's and asked him about the MX Sport debacle. He said he was not asked to test it, instead they had it tested by outside people. Had Bob tested it, it would not have had all those initial problems. The front office guy was probably Steve Howard. Steve's a nice guy and means well but sometimes he makes bad assumptions and can be a little abrupt with people. I think if you had reached Mark things would have turned out differently.

Steve Howard? I suspect he's still there.

Actually, he'd rather take nothing than take any less than 75% of value. And I doubt the Chinese would pay for anything at all. They'll just start using the White's name & logo without paying for it.

6 years ago White's was a single decision away from a very different outcome. But it's company with a long history of missed opportunities.

I keep wondering, who? I can say with confidence it ain't FTP. Minelab was interested 10-12 years ago, but I can't imagine they would still be interested now, they are so far beyond what White's has. Garrett now has the Apex platform to build off of, so not much there for them, either. Nokta/Makro? It would be a huge stretch for them to want a US manufacturing facility, and there is again not much IP that would interest them. I do know that a price I heard for selling the company 10 years ago was about 10X the real value, and I suspect that will be the case now. I will be surprised if there is a whole buy-out, I expect it will end in a big auction.

I started there in 2008 and already a former intern had been hired on as full-time. I brought in another intern and also hired another former intern. I suspect you simply didn't reach the right person. The front office was sometimes not cognizant of engineering needs, you'd need to get all the way to the Engineering manager (probably was Mark Rowan at the time).

This is 100% on Howard, not White's. I also tried to work with him but he was excessively obstinate. I told him his behavior was gonna get him sued by Minelab and there was no way I would risk putting White's in the middle of that mess. And I was right. So Howard had 2 opportunities to work a deal (and even avoid a lawsuit) that would have made him a small fortune. You're feeling sorry for the wrong people. The family was very much the root of the problem. Lots of people tried to steer the company away from the rocks but with no success. I was still there at the start of the MX Sport, I argued against the mechanical design as being way too bulky but a big pod and 8AA batteries were must-haves, along with that "White's sound" (bonk-bonk). No, the people to feel sorry for are the employees, who were the best bunch of people I've ever worked with.

If that was ~8 years, it was not over royalties. It was over behavior.

Even including warranty repairs, the White's repair center always made a net profit for the company. So they may either keep it open or pass it off to someone else. One thing about White's is that it is located on Kenny's home property. The buildings and content don't have to be cleared out, and small portions can be kept running at little or no cost.

Actually, a big problem was that they hung onto the distributor/dealer model for too long, and when they finally decided to go online & big-box they just didn't have the people and structure to do it right. Same with Tesoro. The USA survivors (FTP, Garrett) embraced online & big-box. The issue with "not listening to what the market wanted" was really "not having the people to execute it." White's has exceptionally little value for FTP. None of their models except maybe the GM-24k would be of any interest. The truncated half-sine patent I wrote is the only one I consider to have value, others either have little value, are easily circumvented, or are near expiration.

There were a lot of problems, starting with the family. They never had a high opinion of engineers and thought they could be easily replaced as needed. And one particular engineer with an outsized ego had a knack for either getting other engineers to leave (like me) or for getting them fired. IMO, the downhill run started when Mark Rowan was let go. The V3 barely survived that, most of the rest did not. I thought the company could coast a while longer selling the models they had. The MXT & GMT (and derivatives) are quite good. But that was pre-Equinox, which suddenly made all those products overpriced. And the cost structures at White's don't support cutting prices in half.

This was very unexpected, I thought they had another 5 years just coasting. White's had a lot of problems, but I gotta say that in all the jobs I've had the past 40 years, the 6 with White's was by far the most fun.

Platinum rings are like gold rings... they can be all over the conductivity range depending on size, thickness, & alloy. Generally you want to hunt in all-metal whenever possible. Use Tone mode when there are a lot of nails or when you get tired of digging clad. Use Mute mode when there is so much iron it's too noisy (like, say, a beach fire pit area).

I'm the one who approved the "no target hole" claim, based on my understanding of what "target hole" means. It has been discussed extensively with the TDI to mean any target conductivities that fall into the GB notch and are therefore not detected. I assumed that the same definition has applied to Minelab models, though admittedly I have not been engaged in many Minelab discussions. If I'm mistaken, then we can certainly change the claim to better match accepted terminology. Like you, I'm really opposed to introducing bogus redefinitions of widely-accepted terms just for marketing purposes.

The traditional subtraction GB design subtracts the outputs of 2 channels to eliminate ground. That is, ground cannot be heard, ideally at all. That also creates a hard notch in the target conductivity range, whereby there is a hard notch where a particular target (or small range of targets) cannot be heard. Traditionally, targets on the low side of the GB point produce a high tone, and on the high side they produce a low tone. But right at the GB point particular targets produce no response at all. In the AQ the GB subtraction is modified to no longer produce a hard notch. Therefore it can no longer provide a true GB function, but it also doesn't hard-notch targets, either. In Tone mode as target conductivity approaches the transition point from the low side, targets respond with a high tone, then progressively you start hearing some low tone mixed in. Right at the transition a target produces equal amounts of high-low tone. Higher conductors eventually produce a low tone. But nowhere should any conductivity produce a hard notch in the audio response. That is what "no target hole" means. Now, you can switch to Mute mode and any low tone responses are eliminated. This means that, around the transition point, targets produce a broken high tone audio. Targets above the transition produce no audio at all, and you can certainly call this a massive target hole but that's not within the spirit and normal definition of what is meant by a target hole. In Tone mode, the AQ lets you hear all targets and you can decide whether or not to dig them. With a target-hole detector, particular targets are simply not detected. On the salt issue, there is no salt rejection mode other than pulse delay. At 7us you can definitely hear salt but even then I found it reasonably manageable, at least in wet salt sand. In active surf I think I had to back off to 8us, and in deeper water it may need to be higher still. There are limitations to what the AQ can detect at the very lowest conductivities, but that again is not in the spirit and normal definition of what is meant by a target hole. Much like it cannot detect a ring at 3 feet; that's not a target hole, it's a fundamental limitation.

Ditto from me, Monte.

I've been reading through Dimitar's patent today. It uses a square wave (voltage) transmitter which produces a triangle wave current. When the coil is non-ideal (due to resistance) the triangle wave becomes slightly exponential, especially at lower frequencies. The patent describes an analog correction process after the preamp that compensates for this. Then it describes a the possibility of multiple demod stages (I/Q pairs), each with a preceding notch filter. One demod pair has a notch filter for ground, the others have different notches for different target responses. That's as far as I got, these things are tough to read. I fell asleep twice. Bottom line is, the Tarsacci is 100% continuous-wave VLF. It is NOT sinusoidal like most single-frequency VLFs, but the demods are continuous-time just like SF-VLFs so it does not use time-domain demodulation like BBS/FBS. However, the preprocessing before the demods is done in time-domain fashion, so overall I would call it mixed time/frequency domain. I have to admit, I've not seen things done quite like this. My own developments have included square-wave drive designs and I've considered coil compensation methods but at this point I've pushed it into DSP. But I understand exactly what Dimitar is doing there. The ground/target notching is more interesting to me and I think I know what he's doing but I need to keep reading. Congratulations to Dimitar on a different and clever solution. Too bad FTP didn't hang on to him.

It used to be that simple, but not any more. I have personally designed & built a detector that does both. At the same time. I assume it still exists, somewhere in the engineering attic at White's. But otherwise your post is very valid.

Here's the equation I came up with for an effective diameter: Using nominal dimensions the 5x10 is 6.32 and the 7x11 is 8.35, both remarkably close to GB's numbers. To add to Jason's post, increasing coil diameter has a double effect, both on the TX side (which Jason covered) and on the RX side. The two are similar, in that curvature of the B-field limits the effectiveness of the coil depending on diameter vs target size. If the target is small enough, its eddy B-field presents both the positive and negative flux to the RX coil, resulting in cancellation and no detection. But right at the edge of the coil, geometry works in your favor and you can detect it. Eric Foster made a chart of coil size vs optimum detection depth: "Here are the curves I have used for many years. The range reaches a maximum when it is equal to the radius of the coil. Coils larger or smaller than this optimum will result in less range. To show how this works, along the bottom axis you see coil diameter, which is obviously 2 x the radius. So for an 11in coil, if we go up the vertical scale to A, we have 5.5in. Also note the diagonal line and the series of ever increasing semicircles. Everything to the left of this line shows increasing detection range up to the maximum where it intersects the line, then decreasing range to the right, where the semicircles are shown dashed. If a certain metal object is just detected at 5.5in with the 11in coil, then going larger in coil size will cause a reduction (going down the dashed side), and going smaller in coil size will have a similar effect. Initially, it won’t be much, i.e. going from an 11in to an 8in coil will only make 0.5in difference but below 4in diameter, the range will drop rapidly. Now, suppose with the 11in coil, you can detect an object at about 12.5in (B on the vertical scale. This indicates that the coil is not an optimum size for that particular object. If we carry on up the curve (direction of arrow) we can see that by using a 20in coil, we could gain another 2.5in (C). The curve peaks at 15in with a 30in coil. But the extra inch gained hardly makes such an unwieldy coil worth while. Other factors come into play of course. The curves assume that the number of turns and the coil current is the same in all cases; which it isn’t necessarily. For the same inductance value, a smaller coil has more turns, which counteracts to some degree the loss in range. Also a smaller coil will pick up less electromagnetic noise, earth’s field noise and ground effect, which make for a smoother threshold. The end result is, that with a small nugget that can be detected at between 5 and 7in with the 11in coil, so that it is on the top part of the curve, an 8in coil may well give a similar range. That is not to say that smaller coils do not have other advantages. Small coils and probes are very useful in rocky areas or searching in undergrowth. They have less drag too for water hunting, and less pickup from mineralised soil or conductive sea water plus better signal separation on close or multiple objects. One other point regarding PI, is that the small object sensitivity is largely determined by the sample pulse delay. If an object is so small, or thin, or made of high grade stainless steel, such that all the signal has decayed before sampling takes place, it would not matter how small a coil you made, it would never be picked up. Eric." Jason, I'm curious what FEM software you were using. - Carl Edit: Thanks (Steve, I presume) for embedding the chart, I've deleted the link. Didn't occur to me that the link only works for Geotech members.

I wish I knew...

My preference is to keep the location a secret. Place a capsule there with a log book and let people keep searching. If anyone finds it, they can add their name to the log and keep the secret. Kind of an ultimate geocache, but without the GPS coordinates.