Tejon air test vs. the CZ

[Anonymous]

Well, I got my Tejon yesterday afternoon and while I haven't had time to test it out in the field yet (that comes later today), I have run some air tests on it to compare to my main detector, a Fisher CZ7a.
I'll post my first impressions and initial field tests later but want to share what I've learned about the Tejon so far.
First of all, I'm primarily a coin shooter and my unstable soil here requires that I go very deep (10"+) to get even moderately old coins. The CZ does a great job but I was looking for something with similar performance but that was a little lighter in weight and handled iron a little better.
Anyway, with that preamble out of the way, let me get on to the air tests. Now, I know that air tests have their drawbacks but they can be instructive (IMHO) for getting a feel for the potential differences between detectors.
In all of the tests, I pulled out all the stops to get absolute maximum distance/"depth." That is, I set ground balance, sensitivity, volume, etc. to give the best numbers. My targets for the following tests were clad coins ranging from a penny (copper and zinc)to a quarter.
<STRONG>Tejon</STRONG>
(In all of these tests, I got the deepest readings with the ground balance fully counterclockwise.)
All-metal mode---
The threshold tone on my Tejon is a little squirrelly when set at the factory setting of around 1 o'clock. In fact, to best detect whispers, I had to set the threshold at about the 10 o'clock position, and I still couldn't get a nice steady tone...it still tended to waver, so I had to listen very closely. Sensitivity in this all-metal mode was in the "max boost" "square" but not quite pegged; pegging it resulted in slight chirping.
Here are the distances that I could clearly detect a change in the "whisper" of the threshold:
Quarter: 15"
Dime: 13.5"
Nickel: 14.5"
Penny (copper): 14.0"
Penny (zinc): 14.0"
These are very impressive depths for any detector but especially for a Tesoro.
Since I am a coin shooter, I was interested in the effect of the discrimination circuits on depth so I first looked at the main discriminator.
Main discrimination ---
Here I set the main discrimination at the "I" in "Foil" to accept nickels; a position I would normally use in coin shooting in the field. I also had to back off the sensitivity setting a bit from the max boost range to a setting of "10."
Quarter: 11.5"
Dime: 10.0"
Nickel: 9.5"
Penny(copper): 10.5"
Penny (zinc): 10.0"
As can be seen, kicking in the main discrim circuit knocked off about 3"-4" in depth compared to the all-metal mode. Nonetheless, these depths are very respectable and are about 2"-3" deeper than my original Bandito.
Of course, after the main discrim indicated that I probably had a coin, I'd want to click in the "alt discrim" circuit to see if it was a "high coin."
Alternate discrimination ---
This control I had set in the "SCAP" range to accept zinc pennies with a "broken" sound and all other coins with a nice solid signal. Other controls were the same as the main discrimination test.
Quarter: 9.5"
Dime: 8.0"
Nickel: no signal
Penny (copper): 9.0"
Penny (zinc): 8.0" (broken signal)
As you can see, as expected, there was another slight loss of depth as higher levels of discrimination were dialed in. The alternate level of discrimination resulted in a loss of another ~2" of depth. Still, being able to ID high coins out to almost 10" is impressive and would likely satisfy virtually all coin shooters.
So in conclusion, if there were a perfect correlation between air testing and field testing (and I know that there isn't), it would appear that coins could be detectable out to 15" and ID'ed as coins in the 8"-12" range...not bad at all.
Of course, since my main detector is a Fisher CZ7a, a class of detector "known" for its depth and prowess as a coin shooter, I was interested in comparing its performance to the Tejon.
<STRONG>"Fisher CZ7a"</STRONG>
I also pulled out all the stops on my CZ7a to get maximum "depth." That is, ground balance was set at "10," audio boost was set at "10," and sensitivity at "10."
"All-metal" Autotune; nothing notched ---
Quarter: 18"
Dime: 15"
Nickel: 16"
Penny (copper): 16"
Penny (zinc): 16"
These readings are about 2" deeper than the Tejon.
Autotune with Iron and Pulltabs notched out ---
Here the CZ7a was set to accept only Nickels, Zinc Pennies, and High Coins...
Quarter: 18.0"
Dime: 15.0"
Nickel: 16.0"
Penny (copper): 16.0"
Penny (zinc): 16.0"
These values are identical to the all-metal, nothing notched mode so nothing is lost by accept/reject settings.
High coin plus Nickel setting with ID ---
This final test had everything notched except the Nickel and High Coin. This is the "finest" level of discrimination and gives an idea of what you will be digging.
Control settings are the same as before and distances were measured only if IDs were correct.
Quarter: 12"
Dime: 10.5"
Nickel: 10.5"
Penny (copper): 11.0"
Penny (zinc): 11.0"
Let me hasten to add that in the field these distances don't always hold up. That is, in the real world, I begin to lose confidence in the ID accuracy beyond about 8" with my CZ7a...indicators can bounce around, iron can sometimes ID as a coin, etc. So, in my case, useable ID depth is about 8"-10".
So comparing the two detectors, it appears that the CZ is about 2"-3" deeper in detecting the presence of a signal caused by a coin (all-metal mode), can tell you that it is probably a coin 5"-6" deeper than the Tejon (main discrim/coin notch accept), but has virtually no advantage in definitely telling you that you have a high coin (alt discrim/ID notch)...both ID accurately in the 8"-10" range.
I'll be testing extensively in the field so the preceding are likely to change but I thought I'd pass on the results on my initial non-field testing.
HH...Thomas

 

[Anonymous]

If you have a CZ that can air test at those numbers, I'd keep it ! I've never seen one do that.
John

 

[Anonymous]

A fully counterclockwise setting on the Tej

 

[Anonymous]

I did recently have my CZ tuned up by Fisher, requesting maximum depth but the air test results aren't that unusual.
Back when they were still publishing air tests, the November, 1991 issue of W&E Treasures (p. 53)published air tests of the CZ-6 (progenitor of the CZ7a) and got the following results:
Quarter: 10"
Dime: 9"
Nickel: 10"
Penny: 10.25"
Half: 12"
These were accurately IDed in the ID mode and at 80% sensitivity. (The author also didn't mention where he had the ground balance set which make a difference in air tests of the CZ of up to 2".)
They also mentioned retrieving a quarter-sized pill box in the field in the ID mode at a depth of 14".
Again, my CZ might be a little hotter but not unusually so...and yes, I'm keeping it <img src="/metal/html/wink.gif" border=0 width=15 height=15 alt="">

 

[Anonymous]

I'm sure I'll see differences when properly ground balanced in the field...although there's not a huge difference with my CZ in my low-mineral soil.

 

[Anonymous]

in all fairness, an impractical and errant setting, just as it would be to adjust any GB model to a full clockwise setting. While some models will not be impacted, others will see a very noticable change in performance from what might be expected if they were just <EM>a little</EM> negative or positive.
Don't get me wrong regarding "air tests." I have long felt that the DO have a practical place in some initial comparison work. It is just that I think settings should be as close to 'functional' as possible.
<EM>Monte

 

[Anonymous]

on the detectors I've owned. Fully counterclockwise/negative just represents the lowest amount of phase shift that the control can provide.
As I understand it from studying a couple of schematics and from observing the behavior of the detectors I own, the ground balance control shifts the phase of (usually the transmitting coil) to offset or "zero out" any phase shifts introduced by the minerals in a given soil so that an optimal phase relationship exists between the transmitting and receiving coils. Maximum depth is only achieved when this relationship is established and is seen by the phase demodulator/comparator.
Because all soils, even those with the lowest mineralization, introduce some phase shift that needs to be cancelled and because detectors are not designed to operate in the "zero phase shift" medium of air, the GB controls I have experience with have a phase shift range that does not extend down to zero or "off."
Since you are, therefore, unable to "ground balance" air, the phase shift "correction" provided by the GB control in reality becomes a phase shift "error" that results in a less than optimal phase relationship between the transmitting and receiving coils with a resultant loss of depth/distance. This phase shift error is least in the fully CCW or negative setting.
An obvious implication of this is that, in theory, air tests should underestimate the ultimate depth capabilities of a properly ground balanced detector in the field, something that I have observed with my detectors and have read that others have observed and one of the reasons, I believe, that ground balancing in air is sometimes dismissed as being an inaccurate indicator of performance in the field (especially when depth performance is confounded by other variables such as sensitivity and discrimination settings).
I'm still pretty new to this hobby and I'm just trying to learn the inner workings and vagaries of the detector but, as outlined in the original post, I, at my present level of knowledge, believe that air test data can be instructive if the detectors under test are configured for optimal performance and with careful regard to potentially confounding control settings.
HH...Thomas

 

[Anonymous]

with anything in the way of technical lingo! While I am sure the basic truths to what you expressed might generally apply, I will simply state that detectors, even within a single manufacturer's own product line, can vary greatly as to how certain controls can function and inter-relate.
In your case the "air test" data, to which I did comment can have merit, was performed with a Tesoro Tej

 

[Anonymous]

with what you are saying. And I realize that not all detectors are designed the same. I've run the air tests on the detectors I own (Tejon, Bandito, CZ7a, and BHID) and they all perform in air tests as described. That's not to say that all detectors will do the same. The point is that if you are doing an air test to compare detectors, you should determine beforehand their optimal settings for maximal performance...in my case, so far, that setting for GB has been CCW. And the comparison was between two detectors that perform as stated, the Tejon and CZ7a.
And yes, I've run the air tests at the extremes (and center setting) of my detectors and the depth difference between "most negative" and "most positive" is at most 2" in air (CZ7a with a quarter); most measurements yield a difference of about an inch.
As far as the differences between air testing results and real world results go, I also agree. In my very low mineralization soil, I can occasionally get readings that exceed my air test numbers, but not always. It totally depends on the type of soil I am in. I can imagine situations where real world results don't even approach air test "depths" (all other things being equal).
In the real world, there is a cacophony of phase shifts in a given volume of soil(from constituents with different conductivities, angles of incidence/reflection, multiple reflections, etc.) and the GB control can only provide a single phase shift, perhaps to deal with the predominant one or maybe an overall average phase shift (I don't know). In this situation, I would expect a noticeable reduction in performance compared to air test results.
So yes, the ideal comparison would involve side-by-side tests in a variety of conditions with a variety of settings but that paradigm isn't always readily attainable, thus, enter the air test.
And finally, I viewed your initial response as being only mildly critical but no offense was taken (exclamation points always convey a deeply held position though <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=""> ). I was simply providing the answers to questions that I had earlier asked on several forums that had not been answered. Although the absolute depths reported undoubtedly would differ in the field, the general trend of differences in depth as a function of discrim control settings, relative depth of the Tejon vs. the CZ, etc., I believe, would hold true, and those were the things that were of interest to me and thought might be of interest to others.
HH...Thomas

 

[Anonymous]

I forgot to address in your post. That regarding the fact that most GB adjustments occur in the "middle" portion of the GB control range.
The wavelength of, for example, an RF signal of 10 kHz is around 19 miles! It would take one heck of a ground mineralization situation to result in a significant shift in phase! The needed phase adjustment, therefore, in a detector would need to be of very limited range to cover the extremes of mineralization likely to be encountered, I would think, and it would be logical for the engineers to place the center of that range at the middle of the control.
On my CZ, 95% of the time my GB is set at around "6," ("5" being the "preset") and the most extreme I've had to go has been about "4.5" (heavy humus) and "~8," the latter being in leached beach sand on a playground.
Anyway, enough of this. I just wanted to address another point that you had made.
HH...Thomas

 

[Anonymous]

Most areas don't have extreme mineralization. However, for those that do, it's important to have the controls necessary to eliminate as much as possible the ground effect.
There are areas in the US where most detectors can't hit a dime buried 3" down. We in Florida are blessed with our sandy and low mineralization.
If the phase change produced by a target is less than that produced by the ground matrix, the target won't be detected. I hope I added to the confusion.. <img src="/metal/html/wink.gif" border=0 width=15 height=15 alt="">
John

 

[Anonymous]

an available anywhere material to use as a <span style="background-color:#ffff00;">standard</span> for testing and to replace "air testing" <img src="/metal/html/wink.gif" border=0 width=15 height=15 alt=""> . A material that would put a load on the machine and require ground balancing. Just another one of my two corroded zincs worth <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt="">.....................

 

[Anonymous]

John,
When I was playing around with the X5 on a Lake Michigan beach using a nickel as a test target I found that the GB setting was not critical for max depth. Buried at about 10" there was little if any difference between preset GB, manual GB 1/4 to 1/2 turn positive or 1/4 to 1/2 turn negative in target response on the nickel.
Have you ever noticed that in your ground?
Tom

 

[Anonymous]

a standard by which to set the GB controls so that everything is nice and proper so far and this unit being compared to that unit. You still wouldn't have dealt with all the ground problems, only that of having a similar medium to GB to.
As I stated in Thomas' post replies, and have thru the years, an Air Test comparison has its good points. You can hear the audio and get an idea what the audio responses might be (how targets sound; see if there is any audio saturation; check the modulation, etc.), and get a <EM>rough</EM> idea of depth potential in favorable conditions.
You still wouldn't be dealing with the ground medium and the detector's abilities to handle the ground signal unless you had a large amount of comparison medium and were able to sweep the coil over the medium and a buried target. Waving a target and not presenting any ground into the mix is also not a true demonstration of performance. You have to consider EMF distortion and distruption caused by ground or other matter.
<EM>Monte

 

[Anonymous]

....in the form of a ferrite sample such as a pot core. This is what most detector manufacturers use to adjust internally pre-set ground balance points to handle the widest range of ground conditions without the need of manual ground balancing. But you will still be "off" on the ground balancing point in some cases, depending on the ground matrix you are hunting in. But as far as air-testing is concerned, using a ferrite sample will give you a "basis point" in setting the ground balance point on different machines to make them as equally adjusted as possible for such testing. And as others have found, having such a standard to determine your GB point between different machines can be important in getting a true evaluation between different makes or models. Using a ferrite standard for ground balancing, and then using standard target items for determining target response and range is about as "fair" as air testing gets, and like Monte says, will give you a basic understanding of signal response and "potential" under ideal ground conditions with most any machine.

 

[Anonymous]

Yes. Most places down here seem to be totally devoid of minerals. Just GB the best you can or use Fixed and start hunting !
John

 

[Anonymous]

both of your ideas and input <img src="/metal/html/smile.gif" border=0 width=15 height=15 alt=""> , however I had envisioned a consistent material that was fairly thin (about 1" thick) and perhaps 1' to 2' wide by 3' to 4' long. You could use layers of this material and put targets in between the layers. The coil could be ground balanced to it and used in a normal manner except you may have to elevate the whole mess off the ground so the detector "sees" just the material and not include the ground underneath (I'm not sure that would be a problem). A few more corroded zincs worth....................

 

[Anonymous]

explain, or try to, why that still wouldn't work.
<img src="/metal/html/frown.gif" border=0 width=15 height=15 alt="">

 

[Anonymous]

[No message]

 

[Anonymous]

....is that you would need something considerably larger than the size(s) indicated so that the detector could get a solid "average" of the material you are using to duplicate the ground conditions. If doing a test on a small area, your machine will be "compensating" at it approaches and leaves the "material", no matter which angle it was approached from..... right to left, front to rear, or straight on. There would just be no way to duplicate true ground conditions with such a small (or even thin) sample of such a material. It would be something similar to "duplicating" ground conditions by using only a small bowl of dirt. There would just not be enough volume or area to do a proper test.