Vallon VMH3CS Mine Detector

[kingswood]

There is a possibility that it is a static discharge. I have experienced this in Australia with another detector when you get a long hot dry spell, particularly if it is windy. A static charge builds up on the plastic of the search head, which when discharged by touching vegetation, gives a sharp audio pulse. Any coil shield will not stop this, as it is 'grounded' only to an electronic reference and not to a true ground. Try it again when you get a damp, cool, and rainy day.

Eric.

Yes I will try that...Added bonus of the Vallon is been able to use it in the rain
In regards sweep speed, did you find with the bigger coil you made that you had to have a faster or slower sweep??
I am not sure now if I was sweeping to fast or to slow with the 30cm coil!! I started with the same speed I use with the standard head and it made all sorts of false signals!....I then slowed right down and the alarms mostly stopped....what I didnt try was speeding up! Looking at the report I posted earlier, they said the Vallon UXO needs to be faster than 900mm a second....I was probably doing less than half that speed Oh well, more playing with it!!
EDIT: I looked at the promo video on the Vallon website and they were sweeping the 30cm coil twice as fast as I was...will have to try that

[Ferric Toes]

The grass is wild grass that grows on our gold tenement....I sure know that if the coil hits a bit of this, it false alarms....both the coils do it, but worse today with the 30cm Makes a signal noise as if you have just hit a rock or branch. Its not "regular" grass, more like this stuff: [ATTACH]39243[/ATTACH]
(The stuff in the middle, not the big bushes )

There is a possibility that it is a static discharge. I have experienced this in Australia with another detector when you get a long hot dry spell, particularly if it is windy. A static charge builds up on the plastic of the search head, which when discharged by touching vegetation, gives a sharp audio pulse. Any coil shield will not stop this, as it is 'grounded' only to an electronic reference and not to a true ground. Try it again when you get a damp, cool, and rainy day.

Eric.

[kingswood]

Interesting about your grasses, here in Victoria at a place called stringy-bark creek if you touch the ferns there they send my VLF machines nuts, have not tried a PI, its a gold bearing creek, the whole area is a goldfield but more concentrated along the creeks, panned a few nice specks from the creeks, lots of small gem stones to, I dont know but could the ferns be sucking up some of the mineralisation ? , running the vlf machines on the bare ground around the mullock heaps is no problem , but get near to touching the ferns and its no go, very puzzling.

Given that they have found gold in the leaves of Australian trees, I think your thing about sucking up excess and likely concentrating the minerals may be right on the money

[6666]

Interesting about your grasses, here in Victoria at a place called stringy-bark creek if you touch the ferns there they send my VLF machines nuts, have not tried a PI, its a gold bearing creek, the whole area is a goldfield but more concentrated along the creeks, panned a few nice specks from the creeks, lots of small gem stones to, I dont know but could the ferns be sucking up some of the mineralisation ? , running the vlf machines on the bare ground around the mullock heaps is no problem , but get near to touching the ferns and its no go, very puzzling.

[kingswood]

I am surprised that rubbing on grass would set it off as I know that Vallon coils are shielded with Scotch 24 mesh. I have not encountered problems with wet grass, seaweed, wet beach, or dipping the coil in and out of the sea. That is the standard coil of course.

Eric.

The grass is wild grass that grows on our gold tenement....I sure know that if the coil hits a bit of this, it false alarms....both the coils do it, but worse today with the 30cm Makes a signal noise as if you have just hit a rock or branch. Its not "regular" grass, more like this stuff:
(The stuff in the middle, not the big bushes )

[Ferric Toes]

.grass rubbing the bottom of the coil set it off on numerous occasions. I also found that if I raised the coil, it sounded off. In regards swing speed, if I swung the coil to fast, I got false alarms...Literally was standing still and sweeping from side to side, then moving a step forward. I will have to practise more with it!....May well work better in an area after I have raked off the grass, rocks and twigs!

I am surprised that rubbing on grass would set it off as I know that Vallon coils are shielded with Scotch 24 mesh. I have not encountered problems with wet grass, seaweed, wet beach, or dipping the coil in and out of the sea. That is the standard coil of course.

Eric.

[kingswood]

BTW I always video my test results with the camera down at a level that I get the result so I can review the depth later for accuracy.

Yep...that was what I was planning the wife to do....Next time

[garyq]

I will try the measuring stick next time Also will try burying the coins to a known depth.
I was looking at youtube videos of "air tests" and a lot of them have the MD laying on a flat surface...I can try that if it helps

For my air testing Ive done it two ways either with the target resting on the ground and coil swung above OR coil resting on the ground and target swung above.
Although I do feel when I swing the coil above I produce a more accurate swing speed and signal response as the edge of the coil is swung close to my measure stick.
I also perform a Ground Balance at the test spot before an air test however this could effect the result depending how mineralised that particular spot is.
Therefore I expect my procedure is not a true air test in the true sense of the word.

As Eric said in posts #80 & #81 when air testing a US nickel coin with his Vallon it appeared to have lost 2 inches of depth after he Ground Balanced over a 0.5lb (0.227kg) lump of Australian ironstone.

BTW I always video my test results with the camera down at a level that I get the result so I can review the depth later for accuracy.

Also as another addition to my previous post in regards to that 23 gram nugget I have achieved only 1 inch of extra air depth using a much larger 101 gram nugget.

[kingswood]

Also thanks for your effort kingswood.

Your 30cm coil result on the 5c coin is impressive especially as you say with the Vallon screeching at 18"-20".
Would be good if possible to confirm that depth by using a measure stick of some sort pressed into the ground and coil swung beside it and above the coin resting on the ground.

In regards to your question on what size gold nugget would the 5c coin relate too then from my tests a 5c coin produced a similar result to a 3/4 oz (23 gram) nugget.
However I have found gold nuggets of a similar weight can differ with one another in their depth response.
Therefore it is difficult to say a certain size nugget will be detected at a certain depth.

I will try the measuring stick next time Also will try burying the coins to a known depth.
I was looking at youtube videos of "air tests" and a lot of them have the MD laying on a flat surface...I can try that if it helps

[garyq]

Apologies for the crappy video!...Hopefully will get the wife to record a better one with the iphone soon
What is the TC on the 5 cent??....What size gold nugget would the 5 cent TC relate to?? (If there is a simple answer!)
(Up until a couple of months ago, I didnt even know what a TC was !!)

Also thanks for your effort kingswood.

Your 30cm coil result on the 5c coin is impressive especially as you say with the Vallon screeching at 18"-20".
Would be good if possible to confirm that depth by using a measure stick of some sort pressed into the ground and coil swung beside it and above the coin resting on the ground.

In regards to your question on what size gold nugget would the 5c coin relate too then from my tests a 5c coin produced a similar result to a 3/4 oz (23 gram) nugget.
However I have found gold nuggets of a similar weight can differ with one another in their depth response.
Therefore it is difficult to say a certain size nugget will be detected at a certain depth.

[kingswood]

Thanks for the report, reason for 5c and 2$ is the 5c has a short time constant and the $2 is a long TC, you may have to drop the sens down with big coil, interesting though.

Apologies for the crappy video!...Hopefully will get the wife to record a better one with the iphone soon
What is the TC on the 5 cent??....What size gold nugget would the 5 cent TC relate to?? (If there is a simple answer!)
(Up until a couple of months ago, I didnt even know what a TC was !!)

[6666]

Thanks for the report, reason for 5c and 2$ is the 5c has a short time constant and the $2 is a long TC, you may have to drop the sens down with big coil, interesting though.

[kingswood]

I did some further reading....Perhaps I was actually sweeping the coil to slowly and this was causing the false alarms!....
Found this:

[kingswood]

Out on my own as the wife was home with the sick kids !...hence, apologies in advance for the crappy video, as she has the iphone and I dont ha ha
So Australian 5 cent piece just dropped on the ground is easily detected at about a foot with the standard coil (mineralized mode, sensitivity on 12). The 30cm coil with the same settings screeches at about 18-20 inches. Not the most accurate testing in the world though! And sorry about the thumb https://www.youtube.com/watch?v=kpIS...&feature=share
Didnt try with a 2 dollar coil as I seriously could not find one anywhere in the house or car ha ha....Will have to withdraw some cash to buy something to get some change
Now I did use the 30cm coil for a while this morning....took longer to GB than the standard coil and I had a lot of false alarms....grass rubbing the bottom of the coil set it off on numerous occasions. I also found that if I raised the coil, it sounded off. In regards swing speed, if I swung the coil to fast, I got false alarms...Literally was standing still and sweeping from side to side, then moving a step forward. I will have to practise more with it!....May well work better in an area after I have raked off the grass, rocks and twigs! I did drop the 1.8g nugget down in front off it and it signalled loudly....didnt bury it today as I was struggling (Frustrated!!) with the large coil!...once I have sort of "mastered" how to use it, I will try a few burials

[kingswood]

Hopefully kingswood can find time to test, even an air test result, using both coins for any difference between his stock Vallon coil and his newly acquired 30cm coil.

Yep Will get that done tomorrow as I am heading out detecting in the morning....