My Coin Result

After posting my calculations and thoughts in my previous thread on the impressive depth with a 4000 on a 1880’s 3d coin in an advertisement for the new Coiltek Goldstaker elliptical monos, my curiosity got the better of me once again.

I remembered I had an early 3d (threepence) coin somewhere in my small collection of coins and blowed if I ended up locating 2 of them, one dated 1923 the other 1956. Also I located a 6d (sixpence) dated 1944 which just happens to be the same diameter as our Aussie 5c coin so thought I could compare these two coins for fun and see the difference in response.

The 1944 George V1 6d (sixpence) coin has a composition of 92.5%Silver, 7.5%Copper and the 1967 cupro nickel 5 cent coin I used is 75%Copper 25%Nickel.

Okay I grab the 3000 and NF18 mono and head for the scrub across the road to try my usual air testing, this time on the coins. I air tested in both Normal and Sensitive settings with the 18 mono GB’ed and resting on ground before switching to Fixed.

Sensitive / Deep gave the best results in all tests.

I swept the 3d (1923) coin above and upwards for the barest of a Dip / Rise signal response to a max air depth of 17”. I then grab the other 3d (1956) coin to verify this depth and blowed if I can only reach 15” with the same barest Dip / Rise response. That’s strange a 12% depth difference so could there be a difference of silver content between both threepences.

I then tested the 1944 sixpence for the barest of a Dip / Rise response at 18” while the 1967 5c coin hit 20” but with a reverse in response of Rise / Dip. I expected the sixpence with its high percentage of Silver content to beat the 5 cent coin but this was not the case.

Returning home and a check in my detector book as well on the internet confirmed there was indeed a percentage difference in composition of Silver between both the 3d coins. The 1923 King George V Australian 3d coin contains 92.5%Silver, 7.5%Copper and the 1926 Elizabeth11 Australian 3d coin contains 50%Silver, 40%Copper,5%Zinc,5%Nickel.

My curiosity also was to find out the Silver content of the 1880 threepence coin found with the 4000 and Coiltek Goldstaker mono so after a check on the internet I found its Silver content at 0.0419 troy ozs. A further check confirmed my 1923 threepence to also contain 0.0419 troy ozs of Silver.

Okay I now grab my calculator to confirm the percentage depth differences between my air test on my 1923 3d coin at 17” and the in-ground depth stated for the 1880 3d coin at 29.5”.

Okay the difference is 42.3% extra depth to the 4000 and CT Goldstaker 18 elliptical mono over the 3000 and NF18 round mono. I am assuming here the Goldstaker coil used was the 18.5 x12 mono?

I also expect there to be an optimum coil size for this size and type of targets.

Now the PD Nemesis will have its work cut out for it to match the performance of the GP- 4 series matched with the purpose built Goldstaker monos.

I’ll leave you to ponder....

GaryQ.

Gary I find it very hard to believe that the 4000 has 73.5% extra depth over the 3000 I would like doug and his team to do a test.
Maybe the coin was in the ground for more than a hundred years with a large halo effect it may be possible but I doubt it??
kris

Thanks Garry for the great tests.
Even allowing for a large halo footprint from the coin I do not find credible that the 4000/coil combo will give 73% more depth than the 3000. I think it is a case again of rubber rulers!
By the way the FULL schematic of the SD2000 has just been put out on the Geotech forum.So for all the DIY electroniv guru's you can now build your own SD2000 but using updated and better components or perhaps a micro controlled SD2000?
Perhaps somebody has already done this?
doug

Well members since my maths calculations needed attention I have had to revise my figures for these tests also.

I had mentioned a 73% difference which Kris and Doug found amazing in their replies when in FACT with the revised figures it is only 42% difference.

Next time I open my big mounth in print I will consult with other family members to work out any calculations. Well it is back to school for me I reckon.

Gaz.

Doug,
I'm doing a bit of a study now as to the practicality of building a SD2000 (updated) from the schematics.
I'll do some postings if I proceed.