Hi Tom

Have you had a chance to do a head to head comparison of the X-70 to the CZ's in your sandy soil down there? Just curious how they compare in your conditions as on low mineral fresh water beaches up here in Michigan the 70 is a deeper keeper for coins. I know conditions vary so your low mineral ground may not equal mine.

Thanks
Tom

Hi Tom,

Yes, recently I've had the opportunity to test the X-70 and was impressed with it's depth capabilities. In my test garden (yes, Florida minimum minerals).... it was less than 1" shy in capabilities on a dime,,,,, as in comparison to a CZ w/8" coil. ((( CZ takes the lead.... by just under 4" on a dime.... when CZ is 10.5" equipped ))). On a real-world hunt, I have hunted behind the X-70 with a CZ.... then had the X-70 hunt behind the CZ. Two memorable/noteworthy incidents; One was a Cu Memorial penny @7" found behind the X-70...... then later, a clad Cu dime at 9" found w/CZ behind the X-70. Thinking the hunter/operator had just simply missed these coins, I marked their location and had the X-70 try again. To my surprise, they were undetectable to the X-70. Completely silent. Went to my car and acquired a 1236-X2, Ace 250, F-75 & T-2. The 36-X2 & Ace 250 also reported absolutely nothing on these two unrecovered coins. The T-2 could easily detect the 7" penny.... but the ID was bouncing between 68 - 96. T-2 could not detect 9" clad dime at all. The F-75 could detect the 7" penny with plenty of signal strength and would ID between 66 - 83..... not considered a problem. F-75 on Cu 9" clad dime would also detect this coin...... and the ID's were consistently in the low 90's.... (still not catagorized as a problem).
I have experienced this occurance numerous times and have finally pin-pointed this ambiguity down to partial silent masking via iron oxides. Sure enough, as we dug down to the Cu penny... several blood spots (disintegrated orange/red color) were found in the soil as we approached the coin. What ever tiny iron objects there "WERE".... had disintegrated to just a orange/red oxide in the soil. Just enough to cause problems on all detectors...... some worse than others.
.... Seems to me, single freq detectors are more prone to failure w/silent masking. Now..... that being said..... The F-75 & T-2 are such completely different animals, that I dare compare them to anything else.... yet, must do so. As far as the multi-freq CZ..... I'm sure (internally/electronically) the ID'able signal was conductively high enough to always report hi-tone/coin-tone; HOWEVER,,,,, what we don't see (because there is no numerical ID readout on a CZ)... is: it TOO was reading all over the board...on the high-conductive end of the scale..... but, we the operators, could/would only witness just a simple high-tone audio report.
The T-2 & F-75 electronic design architect is notorious for "Up-Averaging" non-ferrous targets in the presence of iron & iron oxides. Not a problem, considering other single freq units would remain completely silent.

Tom

Tom, I appreciate your info and read everything I can that you've written. Since iron see thru doesn't exist, I can only assume that the 70 was sensitive enough to read the iron, but could not report a signal, therefore the coin was being silently masked. Apparently the T-2 and the 75 had a lower level of sensitivity, thereby not seeing the iron, and reporting the signal of the coin. Could lowering the sensitivity of the 70 possibly help it report the coin, and not see the iron, as apparently the T-2 and 75 didn't? I obviously know nothing about electronics, so I may be way off base. But I don't understand how the T-2 and 75 read the coin through the iron oxide, if iron see thru does not exist. Thanks for your help.

Tom

Did the X-70 user have the tracking turned on? I have seen much better performance around most types of iron with the tracking on. Case in point, an on edge dime at 6"+ near iron, properly GB'd but with tracking off signal was only good from one direction of approach. With tracking on it was nearly a walk around signal with the double beep coming in at times. Also, unless you are in an area where the sens can be cranked to at least 28 you are not getting all the depth out of an X-70. I do agree on the disintegrated iron, that masks a lot of coins I'm sure.

Up here the T2 locks on to 8" wheats with solid audio and stable ID readings. Its the nickels near iron that it won't lock on. Just like with C$ and ID Edge the ID bounces all over the place unless you get your sweep exactly right and even then it will still bounce 3-4 numbers and read high. You do know its definitely a non-ferrous target however. Anymore I look for those types of signals at my hunted out spots. Sometimes I'm just better off going with a single tone slow sweep non-ID machine for those conditions. A Tesoro Cibola with 5.75" concentric coil is killer on those types of targets. Nice smooth beeps!

Any word on a small coil for the T2?

Tom

Iron (and gold) are low conductors..... and operating Freq is more of a function of (Sensitivity) to iron. The lower the Freq, the less sensitive to iron; hence, lending a slight advantage to the appearance "Fe see-thru" abilities. Ironically, the X-70 has a (3 Khz) very low operating Freq with certain coils. ..... Another known engineering fact is that a single freq unit has the ability to handle Fe better than multi-freq units. Both types of units are still blinded (masked & silent masked) by iron,,,,, but the single freq units can ID iron with better accuracy, less falsing.... and a hair-splitting Disc setting is more ascertainable with a single freq unit.
Something worth mentioning; in reference to the CZ (and nearly all other units). When the coil is passed over a target (or multi-target co-locate scenario), the reporting circuitry will remain silent. When pique signal strength is ascertained, the detector reporting circuitry will STILL remain silent. When the electronics see the received signal strength 'start' to decay (decrease), then ....and only then, will the detector take a "best-guess" and report a target & ID. Keep in mind..... if multiple targets are under the coil at the same time, these types of detectors will wait until the largest COMPOSITE signal strength (only one) is achieved. And now...... the different animals; the T-2 & F-75. Their audio will 'fire' on ANY target,,,,, and take multiple "snap-shots" and report each one. Hence; the F-75 & T-2 will audibly sound very 'noisy'. Said differently: Let's say the dirt is Sans.... except for one single coin target at a handful of inches deep. At a normal, human sweep-rate,,,,, the F-75 & T-2 will 'fire' many many many times (dictated by micro-processor clock speed) on the coin..... and report each 'firing' individually...... BUT; what do your human ears hear/register? It just simply sounds like one continuous "beep" to you. It's not! Now..... pass your coil over many extremely close co-located targets with 75/2 and see if your brain can process at the same speed of the 75/2. You will also notice the VDI jumping radically. Do you think the VDI is incorrect!!!??? These steroiditic detectors (unfortunately) are mentally fatiguing......... not because of the detector,,,,, but due to our ears clock-speed. The CZ's are a MUCH smoother, MUCH better sounding unit..... and SO much easier to detect/hunt with. BUT, they can be quite blind (easily masked) and can close doors....... where the 75's/2's can re-open hunted-out sites.
On the X-Terra, we toy'd with ALL possible settings; "Tracking on/off", manual, auto..... Sens mostly on 29 & 30 and also much lower. Many other settings, to no avail. Familiar with this geophysics/electromagnetics phenomenon, the resultant were expected. I'd venture to say the 75 & 2's success is due to the blood spots NOT being exactly/directly over top the two individual coins..... and the clock-speed firing could "extremely rapidly" fire on BOTH the coin and blood spot in raster consecutive fashion.

Outta time!

Tom

Thanks for the response Tom. I really appreciate it. I've had many Fishers in the past (1266, 1270, CZ 3D), and beyond being fine machines, they were practically indestructible. The only reason I haven't purchased the 75 or 2 has to do with the build quality, unfortunately not Fisher like. I know First Texas has made some improvements recently, so maybe the machines are now up to par with previous Fishers. I'll have to take another look at one soon. Thanks again.

Except for the prototypes, I've had zero 'build quality' issues with the production 75's & 2's.

Tom

NASA-Tom Wrote:
-------------------------------------------------------
> And now...... the
> different animals; the T-2 & F-75. Their audio
> will 'fire' on ANY target,,,,, and take multiple
> "snap-shots" and report each one. Hence; the F-75
> & T-2 will audibly sound very 'noisy'. Said
> differently: Let's say the dirt is Sans.... except
> for one single coin target at a handful of inches
> deep. At a normal, human sweep-rate,,,,, the F-75
> & T-2 will 'fire' many many many times (dictated
> by micro-processor clock speed) on the coin.....
> and report each 'firing' individually...... BUT;
> what do your human ears hear/register? It just
> simply sounds like one continuous "beep" to you.
> It's not!

Tom,

If this is so, I have to wonder how many audible signals is actually neccessary for the operator to find/interpret co-located targets? There must be a fine line set by the engineer between the detectors processing ability and what it actually reports otherwise it would be just garbage in garbage out to our ears.

Most of the processing going on would have to be looking at the ever changing magnetic and conductive properties of the target(s) as the coil sweeps over them and making a decision on what is reported to the operator. Again, too much info would just be GIGO to our ears. Heck most people don't even use PF mode on the T2 and I admit there were a couple of heavily iron infested areas where the number of audio reports of "possible" non-ferrous targets (read mostly false iron signals) became tiring because of both the amount of these signals (audio overload) and the time it takes to check them all out. I like digging the iffies but....

I tried to find a balance between PF and 2 tone on the T2 that suited me and my sites but never really came up with one. I know its just me but I feel 2 tone is too overprocessed in the iron handling department. Something in between PF and 2 tone for those heavily iron contaminated areas would have suited a lot of us old low disc Fisher single tone machine users much better.

Tom could I get your thoughts on this please?
I did not spend much time trying different disc settings in PF mode when hunting the heavy iron and comparing the results. Disc 20 cleaned things up big time but I don't know what it did for see-thru compared to disc at 21. I do know it changed the audio somewhat on detected targets but what affect it had, if any, on co-located targets I just don't remember. Do you see a big difference between disc 21 and 20? I know you have switched mostly to the F75 but maybe you have some field notes or something on that?

Tom



Edited 1 time(s). Last edit at 12/01/2007 12:37PM by Jackpine.

It is not so much that a DE would over-engineer a detector to be audibly unintelligible; it's more a 'sensitivity function' of a gold prospecting capable unit..... coupled with a extremely fast microprocessor/clockspeed and very tight electromagnetic footprint eminating from coil. Yes, you are absolutely right; little flecks of iron will cause this particular detector set (F-75 & T-2) to sound electromagnetically unstable. I like digging "iffy's" also,,,,, but my gosh! On a recent hunt, I (as usual) was overdriving the F-75...and, in one area, it became electrically unstable (((so I thought))). Coil in the air.... and unit was stable. Coil on the ground.... and unit was mostly stable. Sweeping coil.... and EMF interference ensued. Hmmmmm....... let's dig some of these so-called "chatters". Resultant: About every 2" or 3"..... I was finding #2 lead shot from a shotgun.... at a depth of approx 1.5". I quit recovering them once I had about a dozen in my hands. ...... The small spot that I recovered these small BB's.... suddenly had no 'electrical chatter' in this one localized location of coil-sweep. Exterior of this sans spot,,,,, the electrical chatter resumed. I was 'overdriving' the F-75.... and decided to drop the Sens to a setting of '70'..... and perceived electrical chatter.... as coil was being swept.... suddenly vanished. Desensitized the detector enough to no longer detect these small targets,,,, and the unit became stable again. Masking was still taking place though. It hurts me to drop Sens to lower levels; however, I ascertain a more stable/intelligible unit and can "hunt". .... In addition to the fact that targets below these BB's are going to be "masked" anyway..... to F-75/T-2 ..... or any other detector for that matter.

T-2 Disc of "20" vs. "21". More to follow..... outta time!

Tom

Tom,
Regarding the T-2 Disc. '20' vs. '21' setting. Most would believe that there could be minimal difference in these settings..... especially considering that there is a 40-point (00 - 40) span in just the 'iron' range alone. And it would be 'questionable' as to why a design engineers brain would be wired in such a fashion in so much as to WANT to provide half of ALL the discrimination range adjustment to be concentrated in the 'iron' range.....for the entire detector..... when most folks could care less about iron. WELL..............., , Tom, you have discovered EXACTLY why this deliberate design characteristic has been implimented into the T-2. And to get back to your orig question..... YES, there is a nominal differential between a Disc setting of 20 vs. 21. In my huntable areas here in Florida, most sites are..... at best, (averaging) approx 100 years old. It's rare to find 1880's sites (or older) to hunt in Florida. ((( Aside from the fact that nearly all of the 1880's targets have sunk out of detectable range ))), the most important thing to understand is the decomposition rate of iron. In Florida, most 'within-detectable-range' iron is hardly decomposed. Hence; a Disc setting of '21' is nearly mandatory. Where ever you live.....and hunt,,, you may be in areas where the iron is 1870's era...and older. It has decomposed further.... and is less conductive. A Disc setting for greater decomposed iron happens to pinnacle at a setting of '20'...... providing even greater unmasking capabilities. Your estute attention-to-finite-detail will unmask non-ferrous targets greater then all others...... and at a maximum/peek rate allowable with current technology.

Tom

Thanks Tom!

I had mentioned this audio difference I noticed to Dave in an email and he also said that there were things done in this range (21 vs 20) that most would not see.

One question, on your first reply you said:

re: the #2 shot.. "Exterior of this sans spot,,,,, the electrical chatter resumed. I was 'overdriving' the F-75.... and decided to drop the Sens to a setting of '70'..... and perceived electrical chatter.... as coil was being swept.... suddenly vanished. Desensitized the detector enough to no longer detect these small targets,,,, and the unit became stable again"

I have to wonder, is it a true drop in gain or a change in the detectors threshold level that caused the #2 shot to not be reported at sens 70? It seems to me that should not have happened with a gain change only. #2 shot is HUGE in comparison to most nuggies found in the US. Was it in JE mode? Will all metal hit this same shot (I hope) at low sens settings???

BTW when hunting in old (100+ years) iron with the T2, foil bits at 1-2" gave solid tones and ID locks at settings around 70 (disc 21 as I recall, did not try it at 20). If the 75 is "chattering" on #2 shot at high sens and loses it at 70 then It seems to me that I do not want a F-75 for my type hunting but you do need one for the extra depth on coins in your area. Obviously totally different design philosophy between the two machines!

UK users seem to prefer the T2 and probably for this very reason!

Tom



Edited 2 time(s). Last edit at 12/03/2007 12:49PM by Jackpine.

These small BB's were near the threshold of detection capabilities in PF mode. Dropping the Sens on the F-75 & T-2 is only a minor function of detection range (primarily on coin-sized targets); rather, more so a function of volume. Threshold NOISE volume. ...... BUT, , , in my case... just enough sensitivity was reduced to lose detection abilities of these tiny targets (yes, huge nuggets). High sensitivity is CRITICAL on small & tiny targets. On the F-75, invoking the JE mode would have tremendously boosted these targets. I know this from experience; however, I did not try these particular targets in JE mode.....no need to.......,,,,, BUT, I did try all-metal mode,,, and the F-75 sounded like a machine gun. JE mode would have been even more sensitive. This #2 shot is not to be confused with #2 BUCK...... a huge difference. The #2 shot is quite a bit smaller than .177 air rifle BB's,,,,,......,,,,,, maybe nearly 1/2 the mass/size.

Yes, the T-2 will "up-average" chewing gum foil (from approx '48' VDI) up into the 70's on VDI when in iron infested areas.... AND when at fringe detection depth capabilities.

Thanks again Tom.

What I meant on the foil was that the sensitivity was around 70, not the TID reading. That was close on to proper in most instances.

Re:

"Dropping the Sens on the F-75 & T-2 is only a minor function of detection range (primarily on coin-sized targets); rather, more so a function of volume. Threshold NOISE volume. ...... BUT, , , in my case... just enough sensitivity was reduced to lose detection abilities of these tiny targets"

This is a good point. I found that reducing the sensitivity does not actually cause a loss of signal on most mid depth coins, only a reduced audio response as you noted. I never checked this in 3 tone mode. Perhaps a good thing to "build in" for the coin modes would be to increase the audio on those deeper coins only type signatures when hunting at reduced sensitivity settings. Or would reducing the threshold to a silent setting have the same affect???

Wish I had played around more with the T2 when I had it.

Tom

Yes, reducing threshold does indeed reduce depth a bit..... especially noticable on tiny targets. And yes, there is somewhat of a 'modulated audio' effect on coin-sized targets with lower Sens settings. Hi-gain Sens settings cause deep coins to sound shallow.
Tiny targets are a completely different ball-game with these hyper detectors. It certainly is nice to have the ABILITY to boost gain/Sens to unstable levels. Some areas will allow this type of hunting.... and produce 'acceptable' levels of detectable hi-gain chatter. There have been a few sites I've hunted with Sens wide open..... and absolutely zero chatter. (Not often, but there are some places). Performance is phenominal under these circumstances;.... glad it's invokable/available (overdrive abilities).

Tom

I have really enjoyed this thread, Tom and Tom.

I discovered the multiple "firing" aspect of the F-75 when I was airtesting and verifying some interference aspects. In this instance I had the machine indoors. I was testing stability at various sensitivity settings and then introducing targets, in this case a clad quarter into the field. The machine was running steady until I introduced the target then it seemed as if it was picking up interference. The magic area was at about 2"from the coil base. Even though I thought I was holding the quarter steady, It was still picking up the every so slight movement of my hand and reporting it and it sounded just like electrical interference. At first I thought I had a secondary loop effect accenting the pickup, but when you relate it to the ground in some of the tone modes, particarly the VCO modes you can actually almost hear it painting a object when you go slow and piddle. You confirmed it.

By the way, if you look at the Explorer SE manual, they actually graph out the peak signal delayed response.

Great discussion!

HH

Mike

Yes Mike, .... Very good. You have good 'tuned' ears to sense these multiple firings. Also, keep in mind (as you probably already know).... close-field targets (usually 3" or less) from the coil will give a triple-beep eminating from leading edge of coil.... to center beam (primary) of coil...... to lagging edge of coil. Passing a target close to the coil at faster rates only increases the rapid-fire succession of audio response. Try to out-run that F-75/T-2 microprocessor sometime! In the field, shallow targets audibly display this "triple-beep" effect.

Tom