CZ21 Air Test

[adamBomb]

Did an air test today and here are the results - I would love to see others do the same test. Given that air tests are prone to errors I would assume there is a 1 to 2 inch (+/-) difference that can happen even with proper controls in the air test. I made sure no other metal was around, etc. My results:

Setting: Autotune, Sens 8 which is perfect no noise and my current beach setting. Ground balance set on 8 for all tests.
Penny: 9.5-10
Nickel: 9
Dime: 10-11
Quarter: 9.5
White Gold wedding band: 9

Here is how I did it. I got a plastic ruler and laid it on the ground. Then I laid the metal detector on its side and would put the targets over the ruler. At first I tried to put the ruler standing upright and use the detector normally but I wasnt very good and seeing what the ruler said so this way was much more accurate as I could clearly see where the line was. From what I have read a dime should be 10-11 inches in autotune on 10 sensitivity with an 8 inch coil. I have a 10 inch on mine so if it were on 10 sens I probably would have gotten more like 11-12+. The most interesting finding is that the nickel is the least. This is the problem with the CZ/Excals that makes me want to get a PI like the tiger shark or a more powerful ctx.

I would like to do a controlled test at the beach and have a few other machines to compare to like an excal, ctx, etc. which would make it more fun - and even compare it to other CZ21s. So if anyone is heading to new hanover/pender county NC beaches (wrightsville/surfcity/topsail), PM me.

 

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[Escape]

How meaningful are air test anyway in rating a detector for depth? Not sure.

 

[adamBomb]

How meaningful are air test anyway in rating a detector for depth? Not sure.

An air test tells part of the story. A dime sitting in the sand for a few months might be found at 15 inches whereas the air test only shows 10. Or a dime might be 5 inches from the sand and the detector wont pick it up because there is so much interference/mineralization. I think the air tests show you averages of what you might expect in the field and they are just one way (of many) to control a test to compare machine depth. A more accurate test would be to go to the beach, bury several objects, and test them with different detectors...or even better find objects in the sand already and have a machine that tell you the depth (ie ctx) and test the machines on that target. I am sure there are much more knowledgeable people on this forum that would know better than me though. I am just a newbie.

 

[SouthFLdigger]

Science, physics and many tests have shown me that air tests is the maximum your detector will detect an object in the ground under perfect soil conditions, especially so for a fresh target in the wet salty sand in the same environment. Here in South FL the mineral (magnetite, maghemite....) content is so low that max air tests numbers are exactly what the max in-ground results will be. In other words my CZ-20 will hit on a nickel set at Autotune, Sens 9, GB 5, Boost 9, 8" coil at 10-11 inches. Burying that exact nickel in moist or soaking wet sand results in the nickel being detected at no more than 10-11 inches in autotune causing a slight threshold shift. Burying that nickel any deeper say 12-14" on my backyard Miami Beach will result in nothing being heard, with either my CZ-20, or Nokta Fors Core (single freq for comparison) which works well in wet. The Halo effect is something im analyzing and leaching of the metal substrate around long burred object might make a difference or not.These test were done repeatedly many times with a clear ruler and holes carefully dug, measured for depth, while inserting the ruler and nickel through the side of the hole as to not disturb the sand matrix to simulate proper RF propagation through the sand and simulate a real life good echo.

 

[Escape]

It's pretty cool how you guys go deep into a machines capabilities through your testing.

 

[Treasure_Hunter]

I have yet to see any coins floating in the air, I prefer tests on how they test targets in the ground....

 

[Charlie P. (NY)]

My original Fisher F-75 wouldn't operate indoors because of all the EMI from lights and motors. The latest upgrade either solved that or dumbed down the sensitivity so it does function - but I don't bother with air tests. I bury coins in a "test garden" under colored plastic golf tees and have a map of them so I know what is where. Some coins under and beside nails or pulltabs. That way I can test various coils and settings in a practical environment.

Air tests are like determining the best basketball player based only on how they shoot foul shots.

 

[Phantasman]

Science, physics and many tests have shown me that air tests is the maximum your detector will detect an object in the ground under perfect soil conditions, especially so for a fresh target in the wet salty sand in the same environment. Here in South FL the mineral (magnetite, maghemite....) content is so low that max air tests numbers are exactly what the max in-ground results will be. In other words my CZ-20 will hit on a nickel set at Autotune, Sens 9, GB 5, Boost 9, 8" coil at 10-11 inches. Burying that exact nickel in moist or soaking wet sand results in the nickel being detected at no more than 10-11 inches in autotune causing a slight threshold shift. Burying that nickel any deeper say 12-14" on my backyard Miami Beach will result in nothing being heard, with either my CZ-20, or Nokta Fors Core (single freq for comparison) which works well in wet. The Halo effect is something im analyzing and leaching of the metal substrate around long burred object might make a difference or not.These test were done repeatedly many times with a clear ruler and holes carefully dug, measured for depth, while inserting the ruler and nickel through the side of the hole as to not disturb the sand matrix to simulate proper RF propagation through the sand and simulate a real life good echo.

If you go to the Fisher site, Dave J (woof) has his take on the halo effect. Basically, corrosion seeping into the soil creating a "halo ring". Iron would be a good corrosive. But Gold doesn't corrode and silver and copper barely do. I think the halo effect isn't as common as many believe. Just my nickels worth.

 

[Phantasman]

My original Fisher F-75 wouldn't operate indoors because of all the EMI from lights and motors. The latest upgrade either solved that or dumbed down the sensitivity so it does function - but I don't bother with air tests. I bury coins in a "test garden" under colored plastic golf tees and have a map of them so I know what is where. Some coins under and beside nails or pulltabs. That way I can test various coils and settings in a practical environment.

Air tests are like determining the best basketball player based only on how they shoot foul shots.

lol........

Yeah, my LRP air tests a quarter at 10". My F2 air tests a quarter at 7" (with the NEL). Yet the F2 has picked up targets the LRP "seems" to have missed. Different frequencies, different soils have a lot to do with depth. Not so in the air.

 

[Octopulse]

My CZ21 gets the best depth/sensitivity on a GB of 1.........air test only.

Tony.

 

[CASPER-2]

always found air tests to be worthless - especially with water machines
Ive gotten old gold and silver close to 2 feet down in saltwater
and have gotten CW bullets down 18 inch+ on land and iron frags even deeper
in all metal and my sensitivity cranked
I was on a couple of large relic hunts and decided to try my cz21 up against the guys with the high priced
relic machines - I hunted in all metal and was finding stuff where many of the others had hammered
and got a few faint readings and no one near me could get a good reading with a variety of machines
one guy played around and got a faint reading that kept disappearing and he told me I had a ghost
both targets turned out to be musketballs down 18+ inches
went to another area about 20 guys hit and were getting iron frags - I hit there after them and was finding
shell frags and canister shot down 2 feet +
only test I need
here is pic of 3 ringer - down about 18 inches

 

[Fletch88]

That's amazing Casper! I just don't see how it's possible but I guess you have the photographic evidence!