Since today, AMDTT will publish a selection of its articles not only in Italian but in English language too! We want to reach our foreign readers and friends and we hope you’ll enjoy our efforts…
Detech SEF 12”x10” V-Nulled Edition for White’s Spectra V3/V3i/VX3
Written by Mauro “Mauroki”
Edit & Tech Notes by Leonardo “Bodhi3”
Translation by Massimo “Gladiatore”
(c) 2012 – Advanced Metal Detecting Technical Team
Well….I wanted to make a Christmas gift to myself….
The opinions in the international forum and the various reviews were disagreeing and furthermore I did not want a “white-coloured” Detech SEF (Symmetric Electromagnetic Field) V-NULLED which could bring me into the same problems I had with my old SEF on my Spectra V3i (Leonardo ”Bodhi3” Techninal note: the previous versions, suitable for White’s DFX, MXT and M6 did not allow to get best effiency on Spectra due to the “nulling” which is not optimized for the 3 frequencies the Spectra is supposed to work. It was possible to use the old SEF with a single frequency 2,5 Khz, 7,5 Khz or in multi-frequency but decreasing the sensibility quite considerably. The use of 22,5 Khz frequency gives really big stability problems and basically could not be used).
I have taken a look at Detech website and I’ve discovered they still don’t have the V-nulled coil in their catalogue yet. Then I decided to contact the Bulgarian manufacturer and supplier who posted a sale information (very nice and reliable person) who assures me that the coil is really a V-NULLED one and should then be perfectly suitable and optimized for Spectra. I was getting more and more excited ! I then decided to send the purchase order ……
After 4 days the parcel arrives with no problems. The SEF coil is packed in its usual box bearing the Detech logos. As soon as I opened the box, I’ve seen its white colour and I didn’t get so crazy about that. The white colour makes it appearing larger than it is. (Bodhi3’s Tech note: the white coloured coils has got the advantage to not absorb ultra-violet rays as much as black coloured ones and subsequently it gives a lower temperature to the coil. This allows to reduce internal coils’ induction balance drifts due to temperature increases related to direct sunlight giving a better stability to the metal detector). I have to say it is really well manufactured. The coil cover, available both in black or white colour is fine and fit perfectly to the coil bottom but can be easily removed when necessary for washing or substitution. Considering I have been using the coil for more than two months and not always in a “gentle” way, I can say it is really sturdy and tough !!
Some technical features:
– Detech SEF 12”x10”: Butterfly “00”. (Double 0) type coil
– Total weight, including cable and coil cover,580 g(White’s D2 is 525 g. )
– The cable has got the same length as White’s D2 coil
– Metal connector (not die-casting) .
– Overall dimensions: 12”x10” inches – 25 x31 cm.(White’s D2 diameter is10”inches -25,5 cm.)
Once fitted on Spectra, after using to the stock D2 coil since I’ve bought the detector, I did not actually realised that the SEF is slightly heavier than the D2 as the DETECH coil is really well balanced thanks to the central connection point to the lower shaft.
I didn’t resist too much and started to make some air test suggested by White’s (Bodhi3 Tech Note: Three Frequency or 22.5 KHz Monofrequency Operating, Rx-Gain: 15, Discrimination Sens: 90 and TXBoostON) to check if the coil is really optimised and stable and I’ve had positive results:EUREKA!!! – IT WORKS !!
I immediately went in my garden and buried a 200 Lire Italian 1977 old coin, a very common “Bronzital” coin made of copper (92%), aluminum (6%) and nickel (2%). Sensations were really good. I’ve immediately noticed an excellent stability and a capacity to extreme settings. It can handleTX-boostONvery well even for extended time. .The target pinpointing is really accurate. After 2-month of continous use Iìve never got a “Ghost Signal” and all the targets are perfectly localized and pinpointed.
(Bodhi3 Tech Note: a ghost signal is a wrong target positioning, which with DD or 00 type coils are very often localized in different ground positions, some centimeters away from the real position. This is due to the special geometric coil shape which tends to give wrong positioning for targets which are not perfectly parallel to the ground)
Let’s go ahead with further tests !!!
I’ve decided to do my tests using the same setting I have been using for a while with my stock D2 coil on land hunting, and to keep it unchanged, just switching the 3 frequencies operating mode. I was so being able to compare both coils having the same reference values for Sensitivity and Gain. I’ve set the basic Sens value (Discrimination Sensitivity) to 90 and Rx Gain to 10. This is what I’ve set in most of my programs that I use every time I go hunting. In the used configuration, I have done a program RESTORE at every change of coil, in order to “clear” possible internal software errors due to too many program changes submitted to the metal detector.
1st test – Depth test :
I have buried the 200 Lire coin deep in the ground, cutting a square piece of soil I’ve later used as a lid. After checking that soil surrounding and inside the hole was clean as well as the dug soil, I have buried the coin to a depth that V3i, fitted with the D2 coil, could not reveal. I had then mounted the SEF coil doing the ground balance. The coin has been signalled with a “dancing” VDI, but with a repeatable and solid sound that I normally would surely dig. I have repeated the test with the 3 frequencies on, getting the same results (obviously with different target depths). As all V3i expert users know, the best depth performances, for a coin-sized object and with a normal soil condition, is given by the 22,5 KHz single frequency. Using the SEF coil, the difference is even more evident and is far stronger by having TX-Boost set to ON.
2nd Test: Separation/Reactivity
I’ve covered the ground with a mulching cover and put the coin on it, covering the same with those big nails you can see in the picture. I’ve started to sweep and noticed there is a better separation and reactivity. The coin is much easily detected compared to the standard stock coil.
3rd Test: Firebricks!
I never did this test with mineralized bricks before, because this is not the a common conditions during my huntings, but when I was performing other tests, I’ve seed some old fireclay oven panels, 30×30 cm and about4 cmthick . Since it’s a very requested test from my friends, I’ve said to myself: “OK…why not ?? Here we go!”. In the first test I’ve just used one panel and, sweeping the coil over it, as prevised the threshold went silent. The quantity of mineralization was obviously high enough to be discriminated .
Sincerely I did not think Spectra was able to detect the coin, even under just one single brick, but it detected the 200 Lire coin under with no hesitations, with a clean VDI 50! Then I said to myself: “Let’s try… Let’s add another brick”. Here we had the biggest the differences with the stock D2… With the D2 coil you know there is an object just cancelled by the brick which shut-off the threshold In some cases, it happens that coin gives some values out of the set discrimination, between VDI -95 and VDI-30, making the V3i able to sound it with a spit-and-sputter tone but looking at the SPECTRAGRAPH, you would normally not dig it . With SEF coil, this is another music ! VDI is far higher with a value that reaches +1- +5, alittle bit “dancing” and not perfecly clear, but surely repeatable and to be digged ! As suggested by Leonardo “Bodhi3” I have tried to put the coin in between the 2 firebricks like in a sandwich. Even in this case it has been very clearly detected by both the coils, but in a more accurate way from the SEF (with a higher VDI and a more solid sound). The firebricks test has been done by balancing the V3i on the ground and even over a brick. I had to say that the coin detected under 2 bricks, is better detected if the balancing is done on a brick rather than on the soil.
The dealer that have sold me the SEF, very serious and friendly, even after the sale, has replied to all my questions. He was even ready to immediately replace the coil whenever I would have encountered any troubles with it. I have to say he has been really patient with me because, being caught by the SEF “fever”, I did not understand some troubles which were generated by a wrong V3i setting. A negative point? The cable looks of a poorer quality compared to the one supplied with the stock coil, even if it is better than all cables fitted to the previous SEF I’ve got. The connector weldings are not the best ones, but I appreciate the possibility to open it in order to make some possible repairs if any. I have waited for over 2 months before togive my opinion on this coil; I wanted to test it in real field tests and not only “tea table” testings. Now I can say with no doubts this is ABSOLUTELY a coil to purchase. It is an excellent replacement of the very good D2 stock coil, that could give your Spectra that extra-performance that sometimes can really make the difference.
AMDTT Senior Member – Land & Sea Expert
PS. Should you need to ask quetions on this test and on others too, feel free to do it on our website “ASK THE EXPERT!”
For more informations on the DETECH coils: