Prospecting with the White's PulseScan TDI Pro
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.
Some of the more successful prospectors were being paid over $150,000
Two of these hopeful uranium hunters were Olive and Ken White Sr. Most
Geiger counters of the day required that the operator wear 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 manufactures, but was rejected and
told his idea was impossible. Rather than throwing in the towel, he
decided to manufacture them himself at a rate of one counter per day.
His products were well received by the community and within seven years
he had sixty-five 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 now 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 whites
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 the following: Pwr/Gain, Pulse Delay, Fine,
Coarse, Threshold, Target Conductivity, Frequency, and lastly 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
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. They work hand-in-hand and their settings will greatly
affect the way the TDI behaves in the goldfields. In order for a
detector to work properly it must be able to cancel out the negative
effects caused by naturally occurring ground mineralization found in the
soil. 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 tremendous amount 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 actual 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. For a full description of this process please
refer to the instruction manual.
The Target Conductivity toggle is one of the features that excited me
most about the TDI Pro. 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, pull-tabs, etc.
High-conductivity targets which produce a low-pitched tone include:
nails, wire, 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 offered a good representation of
the typical mineralization encountered in the goldfields. The only
drawback was that my testing was being done in July; probably the
hottest month of the year in Arizona. With daytime temperatures often
reaching 115 degrees, I knew I would have to get an early start. By five
o'clock AM I had reached the patch and was ready to put the TDI through
first thing I did was turn the unit on and set the Gain in the half-way
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 eleven 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 located directly beneath some old hardrock gold
mines. What gold I had found here was very rough and often still locked
up 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 was
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 at
this trash infested site.
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 were well aware of this and 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 altogether and focus only on those of
low-conductivity; which is exactly what I did.
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 that they 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 a few 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 twelve inch coil supplied as standard
equipment. This mid-range size offers good sensitivity, coverage and
depth penetration, not to mention it is light weight and water-proof.
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 the fact 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 future models 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. It would be nice to someday
see the TDI put into a digital form with push-button controls and an LCD
screen and do away with the bulky metal box.
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
right here in the good ol' USA! For more information on this product,
please visit the manufacturer’s website at www.whiteselectronics.com, or
call them at 1-800-547-6911.
* All rights reserved. Not part of this article shall be reproduced or
transmitted in any form or by any means, electronic or mechanical,
without written permission from the author.