Metal Detector Field Test & Review - Prospecting With the White's PulseScan TDI Pro
By Chris Gholson
From Page 36
November, 2010 issue of Lost Treasure
The year was 1950 and the United States was in the midst of a craze believed by some to have been even larger than the gold rush of 1849. While some searched for gold or silver, most prospectors could be found walking the desert listening to the clicks and pops of their Geiger counter.
Uranium was on everyone’s mind and with good reason. The government was guaranteeing $3.50 per pound of recoverable uranium oxide and a bonus of $10,000 for the discovery of new high-grade deposits. Successful prospectors were being paid over $150,000 per month!
Two of these hopeful uranium hunters were Olive and Ken White, Sr. Most Geiger counters required headphones. This concept did work, but, as Mr. White discovered, it proved problematic in rattlesnake country. He eventually developed his own design and approached the leading manufacturers, but was rejected.
Rather than throwing in the towel, he decided to manufacture them himself at a rate of one per day. His products were well received and within seven years he had 65 employees.
Then, in 1958, White’s was thrown a curve ball when the government announced they would no longer buy uranium. The future of this growing business was uncertain until a former dealer from Tombstone, Arizona, persuaded Mr. White to build him a metal detector.
On his first outing with the new detector, the dealer found a Spanish spur, several artifacts, a large piece of silver, and a few coins. The results of this successful field test were published along with Mr. White’s name and address.
Ex-uranium hunters and hobbyists alike embraced his detector and once again the orders started pouring in. This marked the beginning of the White’s Electronics we know today.
The newest addition to their product line-up has been dubbed the PulseScan TDI Pro and is a high performance pulse induction detector with improved depth penetration and enhanced ground canceling abilities.
Those familiar with the White’s brand may be wondering about the differences between the original TDI and the TDI Pro. At a glance the two models look similar, but improvements have indeed been made.
Building upon the success of the original model, the White’s engineers, in conjunction with Eric Foster of Oxford, England, were able to take the TDI a step further. The most significant changes have been the addition of a Volume control and a dual Coarse/Fine GEB control.
Seasoned White’s users will also notice that the three colored LED lights found on the original TDI have been replaced with a single LED. The TDI Pro has eight controls. These include: Pwr/Gain, Pulse Delay, Fine, Coarse, Threshold, Target Conductivity, Frequency, and Volume.
The Pwr/Gain knob turns the unit on/off and is also used to adjust the Gain. The level of Gain selected will definitely affect the way the detector responds to metal objects. A higher Gain will improve both depth and sensitivity, allowing the user to find deeper and smaller nuggets.
However, in areas with high mineralization or external interference, too much Gain can be detrimental. In these places a high Gain will cause the detector to become unstable, more chatter in the Threshold will be heard, and overall performance will suffer.
A higher Gain is always more desirable, but not if stability is sacrificed. Therefore, the operator must choose an appropriate level based on the ground conditions and amount of interference present.
As its name implies, the PulseScan TDI Pro is a true pulse induction detector. When turned on, it transmits a pulse into the ground and then, after a very brief time delay, samples the signal coming back (or the received signal).
This is the real magic behind the PI machines and why they are able to ignore most of the ground mineralization that plagues conventional metal detectors.
The Pulse Delay knob allows the user to adjust this sample pulse delay by altering the time between the end of each transmitter pulse and the start of the receiver-sampling period.
Pulse Delay is measured in microseconds (uS) and TDI users can set the delay anywhere between 10-25 uS (10 uS is the lowest setting, which samples as close as possible to the end of the transmitter pulse).
A low setting gives the highest sensitivity to all objects regardless of conductivity. As I discovered during my field test, a setting of 10 uS was optimal when chasing gold. Higher settings can help reduce the effects of severe mineralization and minimize signals from low-conductivity targets.
Obviously, if you are searching for nuggets this would not be good, however, a setting closer to 25 uS may improve the response from high-conductive targets, such as deep, silver coins or buried treasure.
The Frequency knob is used to counteract electromagnetic interference (EMI) by making small adjustments up or down the transmitter pulse rate. Interference can be recognized by a constant warbling or oscillation in the threshold. The most common sources of EMI are power lines, microwave transmissions, electric fences, lightning, or other nearby metal detectors.
These disturbances in the Threshold can cost a person valuable targets, so be sure to experiment with this control if you feel EMI is affecting the detector. The TDI Pro has a frequency range of 3.25 to 3.37 kHz pulses per second.
The Threshold knob adjusts the continuous background hum heard while the detector is on. The purpose of the Threshold is to provide your ears with a steady reference point making it easier to identify weak responses, which are often small or deeply buried targets.
The level of Threshold a person chooses is largely personal preference, however, with the TDI, I found a slightly elevated level to be best as it tended to mask some of the spurious background EMI chatter.
The Volume knob increases or decreases the overall loudness of the audio. Turning it up or down will influence both target responses and Threshold level.
Again, like the Threshold, the level of Volume is largely personal preference. I would suggest a level loud enough to ensure that weak targets are heard whilst ensuring that this level is not overly fatiguing to listen to for hours on end.
While they are separate knobs, the Coarse and Fine controls are actually interrelated and their settings will greatly affect the way the TDI behaves. In order for a detector to work properly it must be able to cancel out the negative effects caused by naturally occurring ground mineralization. The most common culprits in gold-bearing regions are iron oxides. If a detector is unable to accomplish this, it will sing like a set of bagpipes and a lot of good targets will be missed. This is one area where the TDI Pro excels.
By using the Coarse and Fine knobs to perform a “ground balance,” the detector will ignore this mineralization and only sound off on metal targets. The process of proper ground balancing is too lengthy to describe here, so I will condense by saying that the Coarse knob is used to make major adjustments while Fine is used to make minor ones.
The Target Conductivity toggle is one of the features that excited me most. Simply put, it allows the user to select whether they want to hear only low-conductivity targets, only high-conductivity targets, or both.
Low-conductivity targets, which produce a high-pitched tone, include gold nuggets, lead bullets, and pull-tabs, etc. High-conductivity targets, which produce a low-pitched tone, include nails, wire, and coins, etc.
If the toggle is set to Low, only low-conductivity targets will be heard. If the toggle is set to High, only high-conductivity targets will be heard. If the toggle is set to All, both low and high-conductivity targets will be heard.
In order to test the nugget finding abilities of the new TDI, I took a drive to one of my favorite patches in central Arizona. I chose this area not only because it has been good to me over the years, but also because the soil and hot rocks present offer a good representation of the typical mineralization encountered in the goldfields.
The only drawback was that my testing was done in July. With daytime temperatures reaching 115 degrees, I would have to get an early start. By five a.m. I had reached the patch and was ready to put the TDI through its paces.
The first thing I did was turn the unit on and set the Gain in the halfway position. Next, I selected All on the Target Conductivity toggle. Then, I set the Pulse Delay to 10.
And, finally, I adjusted the Threshold to a steady hum and set the Volume around the 11 o’clock position. Interference was not a problem, so I left the Frequency control alone.
With those settings out of the way I was ready to ground balance. As expected, the balance was way off and every time I pumped the coil above the ground I received a strong response. My first attempt at balancing took a few minutes, however, after playing with the Coarse knob and tweaking the Fine knob, the TDI purred along like a kitten.
Like all detectors, it moaned a bit over the worst stretches of ground, but overall I was impressed with how it handled the iron-rich environment. Most of the hot rocks that screamed on my VLF detector were completely ignored by the TDI, and only a few of the largest lumps of ironstone produced a noticeable disturbance.
Ground balancing this detector is not hard, but it will take some practice. Push yourself to become proficient at it and check the balance periodically throughout the day. Remember ground balancing is vital to your success, as the settings you select will have a dramatic impact on your ability to hear targets.
By 10:30 the desert had really heated up and all I had managed to find was a handful of modern day bullets. Not wanting to abandon ship without at least one nugget in my poke, I began wading through the worst of the sticker brush and scanning the soil around the roots.
At long last a high-pitched tone beneath a Cat Claw bush caught my attention. After peeling back three inches of the bright red dirt I caught a glimpse of my first TDI nugget. My clothes got tattered and my arms got scratched, but the new half-grammer was worth it!
The following morning I decided to head for higher ground where the weather would be more agreeable. At 6,000 feet, test site number two offered cooler temperatures and plenty of shade from the pine trees. This area had not produced much gold for me in the past, but I knew it would be an excellent spot to experiment with the Target Conductivity.
The gulch I hunted was directly beneath some old hardrock gold mines. What gold I had found here was very rough and often locked in quartz. The ground was mellow and easily balanced out, but what it lacked in mineralization, it more than made up for with trash.
The tin cans, rusty nails and scraps of wire left behind by the old-timers were almost as plentiful as the pinecones! It had always been a nightmare to work, but I had a hunch the Target Conductivity would be a big help.
Once again, I started with the Pulse Delay set to 10 and the Target Conductivity set to All. Within moments I was greeted by a symphony of signals, most of which were low tones. I dug a few to satisfy my own curiosity and indeed found them to be chunks of iron trash.
After an hour of listening to low tone after low tone I got fed up and switched the Target Conductivity into the Low position. The difference was immediate - all those annoying low-pitched signals simply vanished.
Natural gold is almost always alloyed with other base metals such as silver or copper. Because of this, most nuggets behave as low-conductivity targets. The fact that nearly all nuggets register as low-conductivity is actually a good thing and here’s why.
The most common trash encountered on the goldfields is composed of iron. The folks at White’s took full advantage of the situation by designing a control that would cause high-conductivity items, like iron, to produce a distinctive low tone.
For me, this is a very exciting feature because the user can opt to ignore high-conductivity targets and focus only on those of low-conductivity.
By the end of the day I had added two more golden treasures to my collection. One was a quartz/gold specimen found on a bank below the diggings, and the other a rough nugget found about a quarter mile downstream. Both gave off a high pitch and were easy targets for the TDI.
While I give a huge round of applause to White’s on the effectiveness of this feature, I am sure they will be the first to admit it is not 100% foolproof. No discrimination system currently is. I discovered that other items, such as lead, pull-tabs, boot tacks and small pieces of tin, would also produce a high pitch.
Despite this, I found the Target Conductivity control to be an incredibly powerful tool with a high level of accuracy. It will undoubtedly save prospectors much digging and frustration and increase their odds of success by quickly eliminating a bulk of the trash targets.
I would suggest that until a person becomes confident in its operation they should dig all signals at first. I would also suggest that if you are hunting in an area known to harbor large nuggets (over 1-ounce) I would certainly think twice before dismissing a low pitched signal as a piece of ferrous rubbish.
Something else worth mentioning is that the ground balance (GEB) can be switched off with the Fine knob, turning the TDI into a straight pulse detector. This will increase depth penetration, but target variability will be lost. I will say that if you are able to turn off the GEB, then chances are you are not detecting in an area likely to contain gold.
Virtually every goldfield I have visited around the world has contained moderate to high levels of mineralization, so chances are the GEB will need to be activated. Perhaps the beach would be one area worth trying with the GEB off.
My time in the field with the TDI left me feeling impressed. Not only did I score nice pieces of gold, but the machine itself was fun to use. I compliment the manufacturer on the improved ground balance system, Target Conductivity feature, and the rechargeable lithium-ion battery pack.
I was glad to see a 12-inch coil supplied as standard equipment. This mid-range size offers good sensitivity, coverage and depth penetration, not to mention it is lightweight and waterproof.
The fact that the TDI is also compatible with a wide range of aftermarket coils, namely Nugget Finder, was also a huge bonus.
If I had to list any dislikes, it would be that the coil is not supplied with a skid plate. Also, after several hours of use, my hand began to hurt. The stiff, oval design of the handle is hard on the palm and on I would recommend a different shape or perhaps the addition of more padding.
The unit itself is nicely balanced and easy to swing, but the control box is cumbersome. If the weight and size prove problematic, one nice thing about the TDI is that it can be hip-mounted; a feature not found on many other pulse machines. By simply moving the box to the hip, the operator can dramatically reduce the overall weight and should be able to detect longer with less arm fatigue.
As you can see, my list of pros far outweighs the cons. The TDI Pro is a serious contender in the world of pulse induction detectors.
It offers solid performance, a mild learning curve, a decent retail price, and is produced by a company with a reputation for building quality products in the USA!
For more information, visit www.whiteselectronics.com, or call 1-800-547-6911. Be sure to tell them you read about it in Lost Treasure Magazine!