Aussie 3 pence test

[Rob (IL)]

OK Peter I buried the 90% 3 pence coin in my yard. What's funny is I found a 1800's 3 pence myself this year.

I buried it at 8" and picked this coin as it was the smallest of the two coins. I was running my Hi Pro program and just left it the same as it was when I was hunting this last week. The basic gains were RX12, AM75, and Disc90. I used the 10x12 SEF and Whites D2 and both coils hit the coin just fine in both directions. I used 5 band and 5 high as well as the two 7.5 filters and all worked. I liked the 5 band best. I also got a better hit with a +1 G/B offset.

I got good hits with both correlate and best data. I was running the AM at 75 for deeper pinpointing and but AM has no affect on the Disc hunting mode. I like to run my SAT at 10. I ran RD at 85 to 104 and still all good hits. RD would depend on the trash in the area. 104 would be too long in trash.

I lifted the coil and it looks like I got a diggable signal between 9 and 9.5 inchs.

OK, ask your questions and I will try to see what happens. If it hits the small coin, it will hit the bigger coin.

[attachment 267672 greatday.jpg]

 

[burlbark]

Hmmm...... I would like to jump in here and say the 950 is a poor coil choice for mineralized soil?

Earnestly awaiting on Peter..... Sorry Rob, I had to get my fix for the day, posting that is.

 

[Rob (IL)]

Peter could you start by doing a ground probe and listing the readings. Then I will go from there. Don't forget to zero. Lets see how much and what type of minerals are down under.

I don't have a 9.5 concentric coil as I use the DD coils in my ground. I sold it because I don't get to the beach.

I also have to remember you have a VX3 not a V3I. If an option only works for the V3I we won't talk about it.

 

[Count Pierre]

Rob, you've definitely thrown me with the 8" depth. I'll try your settings & see if it makes any difference.

My settings were:

VX3
coin & Jewellery
RX 6
AM 55
Disc 75
Freq 3F Normal - correlate......(only option)
Filter 5hz
SAT 20

FISHER F2

Turn on & GO!

Pete

 

[Count Pierre]

Rob, these are the Ground probe Figures.

2.5kHz 177

7.5kHz 175

22.5kHz 172


Pete

 

[Rob (IL)]

You are talking about the strength readings correct? You are holding the coil in the air, tabbing down to to zero, pressing enter to zero. Then lowering the coil over clean ground.

 

[Count Pierre]

I followed the instructions in the manual.............I'll re do it tomorrow, a bit away from the first try.

 

[Rob (IL)]

These are the numbers we want. Yours must have been the phase angles. Telling us your (type of ground). A ferrite bead will come in very close to 180 degrees (-95 VDI). Most ground that we see is 178 degrees (-94 VDI) to 165 degrees. It's just easier to just check the VDI. Now how strong is it? The numbers will go up with RX so let me know where RX was set during the test.

So VDI= type of ground Strength = how mineralized is the ground

[attachment 267723 ScreenHunter_43Jun.0802.30.jpg]

 

[Rob (IL)]

OK, I planted the 3 pence in my front yard because I didn't want to leave it buried in a park and could easily go back to it. I checked my VDI (ground probe) and it was -91 (approx 175 to 172 phase angle). That tells me my yard soil is less ferrous in nature than the ground I usually hunt which is -95 to -93.

Now at RX 12 my strength readings were approximately 1.5% which indicates my yard is low in mineralization. I could have cranked the V3I up to RX 15 in this ground. Now we need to see what you get. If yours is bad maybe I can find some bad stuff to test.

 

[Rob (IL)]

Until you get back, Australian time difference, I checked the F2 it operates single frequency ar 5.9 Khz and fixed G/B. So you could try single frequency 7.5 and run the Rx up until you get about 30% signal, stay below 40%. Start Disc at 85 and work up if it isn't noisy. Then adjust the filters for best operation. Try +1 G/B. Try the same for 2.5 kHz single frequency.

You will need to swing slow with the 5khz and faster with the 12.5 filter.

The single frequency will get you away from correlate.

 

[Count Pierre]

Thanks, Rob. I like that last suggestion.

That sounds as if it might work, because I tried out an X-Terra 705 with the 7.5kHz concentric coil, & it also picked up the coin with no trouble.

I did the Ground Probe again, These are the results

PHASE
VDI -93
2.5kHz. +177.5
7.5kHz +176.8
22.5kHz +175.9

STRENGTH
2.5kHz 4.5%
7.5kHz 4.5%
22.5kHz 4.6%

RX GAIN 6

Hope this helps.

Pete

 

[Rob (IL)]

OK, your soil seems to be pretty good and about the same as mine. It is well under 10% I was expecting a lot worst.

A signal strength of the ground as follows 0 to 10% weak, 10% to 20% Moderate and 20% and up to be strong. The lower the mineralization, the slower one should sweep - which may mean a lower filter should be selected. As you run up RX the ground probe readings will go higher see if they stay 10% or lower.

When you are running up the RX use the sensitivity zoom to see signal%, stay below 40%.

Oh course the 10D2 coil handles the minerals better and is a more sensitive coil.

I tried my CZ6a with its 8" concentric coil and it hit the 3 pence just fine. It didn't hit the coin as well if I lifted the coil above the ground. It runs 5 and 15 kHz.

See if you can get your gains higher. Monitor the signal% and ground strength at the higher numbers.

 

[Count Pierre]

Rob, it looks as if you have hit on the solution.

I left all my settings as they are, & changed to 7.5kHz frequency only

Picked up the coin at 4" with no trouble, VDI 48/51 with a diggable signal on the Spectra Graph.

Somehow the three frequency/correlate must upset or confuse the small silvers signal.

However, that doesn't matter....my confidence in the VX3 has been restored!

Thank you, Rob. Your help has been certainly been appreciated. .

Pete

 

[Rob (IL)]

Now by increasing the Disc and RX you should be able to see it deeper than 4". Try the Disc at 85 see, how that works and then see if increasing RX helps.

 

[Rob (IL)]

I'll wait and see if increasing your gains help you get increased depth before closing this post. Again try setting the Disc to 85 and then lets see if you can get the RX to maybe 9. Remember to check the sensitivity probe to keep the signal% to a good level when raising the RX. Disc 85 is pretty standard as the default for most of the programs. Be careful you might get a real deep 3 pence reading.

 

[Rob (IL)]

Peter, are you still there?

 

[Count Pierre]

I am now, Rob.

 

[Rob (IL)]

Where you able to increase your gains? At least move Disc up to 85.

 

[Count Pierre]

Yes. Moved the RX to 10, & the disc to 85.....all good.

A mate & I are heading for a paddock this weekend, so I will be able to give the VX3 a good workout on 7.5kHz, & play with the adjustments.

 

[Rob (IL)]

Real Depth
Use the Rx gain to accommodate interference and then utilize the Disc Sensitivity to optimize depth. For real depth, the important setting is the Discrimination. These settings are what make the detector more sensitive to deeper and smaller targets. If background noise is too loud, you will never hear the deeper and smaller targets. Again, you cannot run the AC beyond where it is stable either. Too much Sensitivity will also cause noise and obscure targets and destroy the benefits of a higher level of Sensitivity. I found that in moderate soil the 5HZ Band gave much better depth. I just run the RX up till I get interference then I back off. Then I try to adjust my AC or Disc Sensitivity up till I get interference and back off. The Disc Sensitivity is where you get the depth. The RX Gain is really how loud the signal gets, not the sensitivity to the target. You need it high enough to hear a good signal but not so high as to hear ground interference or outside electrical interference.

When the RX gain is set too high, you will get false readings when the coil is swept over the ground. If discrimination sensitivity is set too high, you will notice erratic behavior when the detector's coil is held at waist level.