Cortes Field Test

by Michael O. Smith

I've owned and used Tesoro detectors for years, so when I received the new Cortes for field-testing, I couldn't wait to get started. The box was smaller than I had expected, nice for packing/shipping. The unit has three poles that interlock by button snaps, and the S-shaped pole has a padded armrest with the battery compartment underneath. This compartment holds two AA battery packs of 4 batteries each. They pop in by simply compressing one end. Just forward of the armrest is the control box. The most notable difference is the meter display. Another obvious difference is the slightly elliptical, 9 X 8" concentric, spoked search coil. I had already used a similar coil on another detector and knew that this was going to be a great asset for the Cortes.

I was pleased to see how comprehensive and thorough the instruction manual is, since I was about to jump into uncharted waters. The first day it was raining cats and dogs, as we say in the South, and I was homebound. So, I read the manual twice, through and through, carefully following the one, two, three's and A, B, C's of Cortes' operation. I was encouraged by the ease of these instructions and the predictable results I got.

The specifications for the Cortes include a built in 2-1/4" speaker on the back of the housing, with louvered openings that help keep out dirt. This is also where the 1/4" headphone jack is located. Headphones are a must since they not only accentuate those faint fringe signals, but also help extend life to the batteries. After 30 hours of field testing I decided to change batteries, even though I still had 1/4 of the battery graph left on the meter.

The detector operates at 10kHz and has an optimum operating range from 30 degrees to 100 degrees and from 0 to 75% humidity. It has the option of interchanging a variety of coils, as well as previous Tesoro 5-pin uMax and Series II coils. One of the features I like the most is Tesoro's lifetime warranty. I have taken advantage of it more than once. What a plus! Weight? How about 2.98 lbs. I hunt all day with such a light machine.

The basic features include four operating modes: No-Motion, All-Metal; Sum Discrimination; Silent-Search Discrimination; and Notch Discrimination (narrow & wide). The discrimination mode is factory-preset ground balanced. The All-Metal mode is a manually ground-balanced mode with adjustable threshold level. The two Notch modes have factory preset widths. The Sum Discrimination mode provides improved target identification by averaging signal information and utilizes a 9-tone audio ID. There is a backlit display, high or low, for hunting in dim or no light situations. The digital display identifies targets in three ways: Displaying numerical, alpha characters, and a bar graph. It shows the probable target depth (best suited for coins) and battery life remaining. The meter works in all modes simultaneously, and also makes it easy ot tell whether the target is iron or other metal.

The meter shows basic groupings of likely targets as follows: Iron and foil; nickels and pull-tabs (round and square); zinc cents and screw caps; copper cents and silver coins. However most of your attention will be on the bar graph which shows how much signal is in each of these categories, and most important is the number of the target response with 0 being iron and 95 being silver. There are a few tricks on some of the variants you get with iron, but usually it reads as 0. The Sum toggle has 9 tones that correspond to the 9 bar graphs, which allows you to get a cleaner signal from your target and also adds the dimension of a tone-related identification. The basic tone response/quality of the machine is still the same as with previous Tesoro detectors.

I actually relied on the sound more than any other identification feature. In All-Metal, you get a louder and wider signal the closer you are to the target. This being said, the meter number and bar graph help break the tie on whether to dig or not. It is also tremendous fun to second-guess your target before digging it up - sort of a personal contest between you, the detector, and reality. With experience you will be right most of the time, especially in recognizing targets as ferrous or nonferrous. The two usual exceptions were when the meter read 95 but had multiple bars lit up, and less often when there was a high ID number and no bars lit up. It does not take long to figure these readings out.

To use the Sum switch, you simply push the toggle to the left and move over the target with a 2-3" sweep, and as the sound becomes one tone you will also see the bar graph settle down to one or two bars. At this point your reading is better defined, and the ID number is usually accurate. Most often you will be able to identify the target without the help of the Sum feature. Again, if it sounds good from at least one direction, dig it. Remember that the bar graph and depth are set for coins; as well as any modified coin or artifact can vary your readings, so identifying it as a good sound , or a target response on the meter, is the only excuse you need to dig.

The notch feature has a wide and narrow setting. Narrow will phase out pull-tabs and Wide phases out pull-tabs and Zinc cents. Remember that you can lose some gold rings at these settings. The central portion of the response graph allows a wide separation between metals and helps separate nickels, rings, and pull-tabs more accurately. When Discrimination and Notch is being used, the meter will still indicate what the target is and how deep. This is an outstanding feature. As you can imagine, phasing out something while still being able to know what it is has advantages. Also, being able to see that you are in an iron-rich area without getting a positive signal from iron truly helps you pick up on home sites or areas of concentration.

When you use All-Metal mode, you should ground balance the machine first. The procedure is very simple. All you do is lower your coil straight down from about 10" to 1" above ground. If the sound increases, lower the ground balance by turning the knob counterclockwise. If it increases, turn it clockwise. There is no need to reune, just repeat this operation until there is no change in tone. The only trick is finding an area free of iron to ground balance on; however, this only takes a minute or less. The other modes are preset and require no ground balancing. All-Metal gives a little extra depth, a more accurate reading, and requires no motion, which helps with pinpointing. Again, the meter will work in All-Metal and show what the likely target is, thus allowing you to leave the iron and pick up all the other targets. This, too, has its uses, as when you are trying to find a new site in a wooded area, or are looking for those ultra-deep targets in a worked-out site. Sometimes the meter will give a response even when there is no sound indicating such targets. In the Discriminate mode, there is a red "Boost" area on the sensitivity control that goes beyond 10. In areas of low mineralization, I have found that I can go full Boost, which means higher gain and greater depth. Also, I have encountered no instability except around some type of electrical interference.

Enough basic information. The next thing I did at home was to gather a wide variety of test targets such as artifacts and coins. I air tested these and had my wife, Sue, write down the readings from about 6". I have included the results along with this field test. I must note that there is some variation due to different soils, humidity of the soil, the orientation of the item and its mass and distance from the coil. A good idea is to learn the likely response from distinct groupings. For example, the civil war Minie ball is around 70; a 2 cm lead shot, 75. This will give you an idea of what to expect, especially if that is a likely target in your area. In contrast, a zinc cent is 77, so if you use the wide notch setting to miss that pull-tab or zinc cent you may also miss the Minie ball, or a Spanish 1/2 real, which reads 75.

Always remember that there is overlap in readings from coins and various relics. Most U.S. or larger foreign coins, as well as thick copper/brass, tend to read higher. Most .22 shells read about 7-9; foil and small aluminum reads very low, around 2-7; shot gun shell readings may be anywhere from 18 to 43 depending on the make and size of the shell, as well as orientation. Shot at 2 cm is 75, 1cm is 41, and 1/2 cm is 22. This machine is so sensitive that I actually picked up a positive signal at 2-3" on a #8 shot, 1mm the Gereral Service eagle read in the 55 range. A thin gold ring was 6-12 and a 2 cm brass flat button was 64; however sideways it was 30 to 50, depending on the angle, thus reflecting potential variations in readings - another good reason to Cortez with finds. Finds made by Nathan Spalding dig if it sounds good or is other than iron. Now let's take a look at what this machine can do in the field.

I started with some open areas, as I wanted to keep things as simple as possible during initial testing. I have some locations which, for all practical purposes, are worked out, but still have deep targets remaining. Most of these produced rich finds in their hey-day. Of course, when I do find something, I want a reasonable chance of it being a nice relic or coin. Of the seven sites selected for this evaluation, six were in that category, and one was new. It presented a 50' section of firebreak and the corner of a field. It was, however, pre-Revolutionary War… more on that in a minute.

Site #1 was an area of couple of open fields next to a bluff. This area was well worked, but with each new machine I had tested it produced deeper or more difficult finds. Anything found here would represent an improvement in depth or sensitivity. At the end of the day, I had four deep .50 caliber round shot, eight flat buttons, a nice 3 cent piece, a 2" escutcheon plate from furniture, which was 10" deep, and about 10 other targets. One surprise was a coat-size, two-piece eagle "I" button with 50% gilt. This was most encouraging, so now it was time for a different type of site.

Site #2 was a wooded area, mostly pine trees with a moderate amount of undergrowth and moist sand. Here I found 14 flat buttons, most of where were 6-10" deep. To my surprise, I found a Georgia state seal button. Unfortunately it was bent, and part of the back was missing; nevertheless, I had found a confederate button.

I had never found any Indian trade items along the Georgia coast, but this was about to change. I found a brass arrowhead and a Spanish button from the 1500s. This was remarkable since the first settlement of the U.S., San Miguel de Gualdope, 1526, was less than a couple miles away. I also found a handful of varying sizes of shot and few other items. We had previously found relics there from the 1700s through the late 1800s. I have found a number of Colonial silver thimbles, but was pleasantly surprised to unearth an ornate silver one from the mid 1800s.

Site #3 was dry and sandy, with a lot of cactus. It had been a fairground in the 1920s, but we had found no more Wheat cents on the last several trips. It was littered with trash, and that too was a problem, especially an endless number of .22 short casings. These gave a reading of 6 and I was able to ignore them without fear. Closely observing the meter, I got a "quarter" reading of 95, which turned out to be a silver quarter. Next came a Mercury dime dated 1943 and two Wheat cents, one of them a 1910. I also found a Mercury wing skate charm that read 30. I knew that this should be a good target and it was.

Site #4 was a semicleared area, an old home site that had yielded some Confederate buttons long ago. I had searched a number of times, hoping to find one more, but did well to get two or three flats. Next to a big tree, my friend and I searched again, as several of us had done about four times this year. In the same area I had found a round shot three months earlier. I got an iffy signal at 6" that read 65. I could not believe my eyes… a beautiful GMI button! My first. That one button would almost pay for the detector. I also found the trigger guard of a large Colonial blunderbuss at about 12". I was surprised at how many small shotgun pellets I was finding. This reassured me that I was missing very little. I like to use the crisscross and circle method of pinpointing, mentally computing exactly where the center of the signal is. The small circle of the coil is the most acute pinpointing area of the coil. Just before leaving, I got another good signal at 6" that read 60. It was an eagle "I" cuff button, or so I thought. When I got home, I discovered that it was actually an "R" with some of the gilt remaining.

Site #5 was new, but within 100 yards if a Colonial home site we had hunted heavily. It was a firebreak along a bluff. The home site was recorded as c.1735, but we had never found any buttons earlier than the revolutionary war. In the firebreak and on one corner of the field, I found a 1723 British copper in Very Fine condition and an 1838 Spanish half real, plus a lot of flat buttons. A couple were a type from the late 1600s and early 1700s. One 3" piece of flattened lead gave me a good signal at 16" and read 80. This was in pure, moist sand. Needless to say, I was no longer worried about depth. The other surprise I had from this site was a field-made pewter button with a dogwood flower on it, a design attributed to British lieutenants, buttons just prior to the Revolutionary War. What a great find, and one that will have to be added to future button books. This button was 8" deep, and read 20, and is solid and 1 cm in size.

Site #6 was one I had not visited for about ten years, and the pine trees were now big. Here I found a nice Indian trade tomahawk and another Indian trade item, bronze and in the shape of an eagle's talon. I also found a 1772 half real and a beautiful bronze candlestick from the 1700s.

Site #7, the last, was a "mixed bag" area that again had been largely worked out. Here I hit a little spot that I guess had been missed before. I found four escutcheon plates and two drawer pulls from the same piece of Colonial furniture, two Indian brass tinklers, and the front brass fitting of a flintlock gun. One other surprise was a 1 cm pewter eagle button from 1811. I was sure that we had worked this area out.

At this point, I felt very confident that I had covered most of the conditions needed to offer an informed evaluation of the new Cortes.

As with any new machine, there are a few things that might be improved to suit the individual. I have a vision problem with contrast and glare, so for me a bigger display screen and glare proof glass would be better. Also, I found that going through thick woods could pull the battery door open. The batteries remained tightly in place, though. A different catch might be better. Finally, I like the black search coils instead of white, but those were the only changes I would consider. I did have some trouble in heavy iron areas when I set the discrimination above iron and used the notch. I lost some depth and had trouble picking up a good target next to a bad one. That being said, I was most impressed with the performance of the Cortes in these conditions and at different settings.

When I set up between minimum and iron, I could tell that a target was iron without digging, and also if it was a good target, even next to a piece of iron. This did not seem to influence depth or the quality of the signals. In conclusion, I was most comfortable hunting at this discrimination setting and listening for any good signal, from at least one direction. If the sound was good, I planned to dig but still spent a little time trying to identify the targets by the meter readings for depth and ID number. This was a lot of fun. If it was possibly iron, not reading as 0, I worked the meter for a while to help make the final decision to dig or not to dig.

The new Tesoro Cortes is a very versatile detector and light enough to swing all day. The batteries could last as long as 40 hours, and over 30 for sure if you are using headphones. There is a wide range of hunting settings to use with this machine. When I hit one area of wet salt marsh where I was getting back some false positive signals, I backed the sensitivity back to 8. The result? No more disturbance, just smooth performance. I placed an ordinary plastic bag over the detector during a rainstorm and had no problem with it operating erratically. In areas with heavy concentrations of pulltabs or .22 shells, the target ID number and notch features saved me a lot of time and backaches. A number of times I dug good signals that I would not have otherwise, due to the meter readings. Finding occupied areas in the woods was also very easy, and I cannot say enough about being able to determine target depth and identity in All-Metal mode - a major advantage. As for price, I probably paid for a couple machines with the finds I made during these field tests.

I would highly recommend the Cortes to anyone who has some good sites and wants to work them for all they're worth. You will find it easy to use, with a lot of options and little room for disappointment.

* - Reprinted with permission from Tesoro, "Metal Detector Information" - 22nd Edition

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