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Offline darkkitten2000Topic starter
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Miner4 eeTH
« on: May 05, 2010, 10:56:12 am »
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Well, here it si.....

i must say this is the best BFO i have ever seen and quite frankly, it performs better as i have expected. The ground effect is still there, but it's hardly noticed and does not pose a problem. Both oscilators are quite stabil in short term (it could be compared by Cornelius's descriminating BFO), thermic drift is severe, but once (in a couple of minutes) the detector is in "thermic equilibrium" the drifting is slow an requires turning of the "fine control" knob every 1/2 minutes or so, it enables quite comfotrable searching. The audiable frequency produced by mixing the base frequency of search oscilator gives loud but quite short audiable window, difficult to maintain balanced, it is the 1st harmonic which is not so loud (but loud enought) that is really useful. It is the sensitivity (mixing circuit) that differenciate this BFO from all others. The frequency change caused by the target is so abrupt it can easy be destinguished from drift(s), the detector reports 1 EUR cent (16mm coin) at 10cm and large targets up to 40cm measured in air. It finds very small pices of metal, and it's perfect for small shallow targets. The detector does not perform good in wet grass (static dischards could be heard in spite of Faraday's shielding).

regards,
d.

...and the .pdf from Geotech......

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Offline xavier
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« Reply #1 on: May 05, 2010, 02:51:16 pm »
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Hi Darkkitten

Nice to here from you with such an interesting report well done to you. You must have quite a nice collection of detectors by now .

Regards Xavier

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So many questions so little time

Offline darkkitten2000Topic starter
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« Reply #2 on: May 05, 2010, 02:58:09 pm »
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hi,
i stockpiled 6 of them, but only using few.....i missed one on the low end.

regards,
d.


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Offline xavier
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« Reply #3 on: May 05, 2010, 03:02:59 pm »
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So I guess that you now have VLF,PI and BFO

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« Reply #4 on: May 05, 2010, 03:06:35 pm »
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Any kids in vicinity?  Smiley

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« Reply #5 on: May 05, 2010, 03:11:04 pm »
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Not at this time of the year all are at school I live in a holiday village about 80km from the town so we get invaded mostly in December but now it's very quite

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« Reply #6 on: May 05, 2010, 03:39:29 pm »
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No xavier,

i have 3 BFOs and i hope i will be using only the ETI561 as a shallow skimmer for a recently lost items, and i have 3 PIs, but i am only using the Miner4 as a casual hobby detector (with small coil-down to 1.5m only) since it features a discriminator and few more things and my best PI,the DBP2010 for deep dedicated targets. Funny,but i sold the only VLF i have ever built (and i have built and sold over 100 detectors, mostly fairly simple and chip PIs - down to 1-1.5m). I have never contemplated to build a good VLF since the material would cost the same as for a fair PI and probably more as commercial VLF (i.e. Garret's ace). I have only bought one machine, a military BFO out of curiosity, but i gave it to kids. Now i have two BFOs and one PI spare (to change hands).

regards,
d.
And yeah, i am still looking in schematics for a magnetometer and conductometer with data loger, the two i am still missing.

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« Reply #7 on: May 06, 2010, 02:41:39 am »
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BFO I have build a number of them and the only one that I will ever recommend to anyone is the design that I got from Cornelius all the others thus far have been a total deception VLF now that's been a one year project and still going the reason behind the one year is that when I started I did not know what was a transistor well I knew what it looked like but did not have a clue as to it's functionality so you can say that the VLF has been my teacher and if I may say so it has been a very strict teacher and then there is the PI I tend to think that the PI is the simpler one to build for one you don't have the same problems with the coils it gives a lot of power resulting in a good ground penetration and getting a good ground penetration from a VLF is to my opinion much more difficult I don't know how you feel about that?

Regards Xavier   

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Offline darkkitten2000Topic starter
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« Reply #8 on: May 06, 2010, 03:16:27 am »
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Yes, the Cornelius's discriminating BFO is such a nice circuit, i have made one and it performes well, definetly worth building, but ETI561 exhibits somewhat better sensitivity.

I never had problems with coils, just have to be strict and cordial with it. I do not belive an VLF could outperform an PI depth wise, but if you are after discrimination it is definetly the way to go. PIs could be very sophisticated, specially if you'd like an discriminating one (or very deep one). Simple VLF such as the buccanner doesn't really perform any better than ETI561 BFO (or Cornelius's design), even thought they will go deeper, but the problem is they should be keept balanced in a narrow window, which in praxis, due to ground effect, costs quite some depth. So a 3 coil system with authomatic ground effect compensation is a must, that is a more sophisticated design which would cost at least EUR 100, since the Garret ACE 150 costs EUR 140, it just doesn't pay to build one, but is shure could be fun.

regards,
d.

P.S. i have made an ETI561 due to quite "hot" conversation over a crystal controlled refference oscilator in here, just out of curiosity, but now, i must say this circuit is quite comparable with Cornelius's design. The mixing circuit is similar, but eti's gives a bit more sensitivity, so the solid phisical outfit (such as shilding, litle or no floating wires....) is what really counts here.

d.


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« Reply #9 on: May 06, 2010, 06:28:42 am »
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Thanks for the info DK also at what frequency dose the ETI561 run at?

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