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Originally posted by Geo
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- a Half-Crown is 32mm diameter, 2mm thick, and it's a silver coin.
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On behalf of Max - a Half-Crown is 32mm diameter, 2mm thick, and it's a silver coin.
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Originally posted by Qiaozhi View PostOn behalf of Max - a Half-Crown is 32mm diameter, 2mm thick, and it's a silver coin.
Hi,
all about right... but mine is not silver. From what I know my 1/2 crown of 1967 (that I often use in tests) is made of an alloy of copper/nickel.
According to
http://en.wikipedia.org/wiki/British_half_crown_coin
from 1946 the 50% silver half-crown was adbandoned for the copper/nickel alloy version. Then it was demonetised in 1970... with the decimal system introduction.
Kind regards,
MaxComment
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Hi,Originally posted by ivconic View Post
yes maybe is more than 90%... just my impression with the one I had tested (is an STmicro manifactured part).
I haven't tested 4558 (as far I remember) but LM358 and 1458 yes and both seem no good like TL082.
With TL072 I get the exact behaviour of TL082 (both from STmicro).
So till now I haven't found any better replacement for LF353 there.
Kind regards,
MaxComment
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Hi
Hi,
Max.
Nice to hear you have made this coil!
I still cant get this results?!??!!??!?!
And cant find the reason.I have sealed one in plastic case,but can reach about 25 cm.This is not good!
Can the reason be that I try with Ivconics first post for this 255 X 137 coil - TX 102 and RX 108!
Try everything changing the leads and many other things!
Also I cant find point where I dont get the signal from ferite piece!Or when I find such the detector also dont make sound and for coin!?!?
Damn still cant test I am MAD about this!
ThanksComment
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Hi,
Hi,
Ivconic well done!
You make me crazy!I still cant get my TGS working and you pick up 256 roman coins for 5-6 hours!!!NICE.
I dream to find ONE.Comment
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hi
Max,
How you null to "Nulling is (at now) around 4.5mVpp"?
What do you understand buy this?
Please explain because I am begginer and have no idea what this mean!?
Thank youComment
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Could be. The half-crown I measured was a George V from 1936. My Garrett GTAx1000 gives #9 on the display, whereas a hallmarked silver target displays #10. So it doesn't appear to be pure silver. However, a 1957 half-crown shows up as #5.5 and a 1960 as #5. These are all metal detector finds, and the 1936 coin is not discoloured, whereas the other two show signs of corrosion.Originally posted by Max View PostComment
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Originally posted by Macho View Post
Hi,
it's easy... when I test for null I connect TX leads of coil to tx pads on pcb (so to the oscillator section) then I connect the RX leads on a dummy load like this:
1 poly-capacitor (in this case it's 15nF)
1 resistor of 1Kohm
The two components are in parallel and rx leads are connected parallel to... so you have an LC resonant circuit + a dummy resistor load that avoid full resonance appear when energized... and you got same frequency as in tx side (air core transformer).
I connect it to scope probe and read values for minimum signal... moving a bit in the central area...or sliding one coil e.g. TX over RX...you can get something good for DD coil like that from e.g. 20mVpp to few mVpp... less you read is better.
I reported peak-to-peak value of my readings but you can express in other terms cause signal is sinus. I use it cause I see directly watching the amplitude of sinus on the screen... so it's easy for people having just old analog scope compare with my results.
Reached a good "null" I fix coil parts still free with some tape or other stuff... then I use epoxy to seal for real use... cause you need it very rigid and no movements inside housing.
Best regards,
MaxComment
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Hi,Originally posted by tiktak View Post
it's strange, I've done at first attempt required 2 days for getting the good results... but much more for epoxy sealing.
I've used TX=100 and RX=105 wire 30AWG(0.25 without varnish)... have you took a look at my pictures ? I've made using plywood board and nails for former... very easy.
My problems were with epoxy this time
took 1 week! Damn slow epoxy... but is really hard at the end... it's slow type for surfboards!
I think your problem is not in few turns more...but in nulling or shaping.
BTW if you have wrong preamp you cannot reach that performances... as I wrote about some posts ago. You need an LF353 or at least a TL082 to get good results... or something really close or better. Not easy task replace LF353 here.
Also you have to mount LM308 or TL082 or TL072 and avoid using the TL062 instead of LF442 of original if you have the notch equipped.
Best regards,
MaxComment
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Originally posted by tiktak View Post
It is not about detector; it is about good location mostly.....and luck of course! At the end you must have good detector for sure! No tool no result!
Comment
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Thanks to Qiaozi
and to Max .
Maybe at next week to give it a try. I want to compare it with Anker SS60 and if the locate distance is near to SS60 then i will put it to a box (anker wants big battery so it is heavy) to have it for "pinpoint" when i find something with robs (do you hear it Max )
Regards
Comment
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dear Geo
Can you give information about Anker How it is range?
Regards
Erol unallComment
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Hi Geo,Originally posted by Geo View PostThanks to Qiaozi and to Max .
Maybe at next week to give it a try. I want to compare it with Anker SS60 and if the locate distance is near to SS60 then i will put it to a box (anker wants big battery so it is heavy) to have it for "pinpoint" when i find something with robs (do you hear it Max )
Regards
if you don't need notch build directly TGSL... you'll save work, noise, and consumption that way.
So you use rods ? For pre-search ?
I mean finding an "hot" zone... I know that some people find stuff that way... but I'm really skeptic about rods usefulness... I saw a number of people play with electronic or not... so far with no real success.
Maybe is my presence that make their rods don't work ?
Anyway... TGS (or TGSL) is good not only for pinpointing... they go deep and you can find stuff with these. Disc works really good and if you are lucky with components also erratic noise is not a problem.
Actually I found the real trick is setting a right GEB on it and require some experience... but after that all the rest is really easy and results are good.
Best regards,
MaxComment
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Hi.Anker SS60 is a powerfull detector.It can detect a coin very easy at 50cm on the air, and it has a dual tone discrimination (very good). The problems are two..... 1. It has not ground balance (there is a trimer who do it but when you regulate it you change a little the disc).Originally posted by Unregistered View Post
2. When the ground is hard (with rocks) then you have some false signals fron the reflecting signal at the rocks(because the oscilator give big power). I have put a volt reg to the osc so i reg the oscilator outout.
It is not an easy project and you need a good 2 trace osciloscope to regulate it.
Regards
Comment
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Hi Max.Originally posted by Max View PostHi Geo,
if you don't need notch build directly TGSL... you'll save work, noise, and consumption that way.
So you use rods ? For pre-search ?
I mean finding an "hot" zone... I know that some people find stuff that way... but I'm really skeptic about rods usefulness... I saw a number of people play with electronic or not... so far with no real success.
Maybe is my presence that make their rods don't work ?
Anyway... TGS (or TGSL) is good not only for pinpointing... they go deep and you can find stuff with these. Disc works really good and if you are lucky with components also erratic noise is not a problem.
Actually I found the real trick is setting a right GEB on it and require some experience... but after that all the rest is really easy and results are good.
Best regards,
Max
I now learn to use robs. I have a friend who is expert at robs. One time he found a silver coin from 1.5.....2 km away, he was on a mountain. He can locate very easy small object within a area of 1x1 m or 1.5 x 1.5 m so we need a very light detector for exactly locate. He is working with robs for 25 years ago and he found a lot of coins from copper and silver but NEVER gold.
If you see him it is a Magic. You see the robs to go at one direction and you cant change it. Really if you see it you will believe. I am sceptic also but i can't give the answer......... only i see the results.
Maybe TGS to be ok for this. We have the XLT.... GTI2500...... 1270 ....... cl3 ....... ss60 and ......... and .... but i like to construct another detector (my hobby). Before 3 days i was to Athens so i found 2 metallic LM308 for TGS. Maybe next week to make it.
Regards
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