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Benchmarking The 5x10 DD Coil


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The Fisher 5x10 DD coil hasn’t been my most favorite coil because, in my mind, it always seemed to be lacking something.  I have suddenly found myself owning several different higher frequency detectors, each equipped with a 5x10 or 6x10 DD coil.  As a result I have decided to spend some time bench marking this particular coil size.   Is the Fisher 5x10 DD coil really lacking something or is its performance in line with other brands similar size and type coils.

Since my 5x10 DD coil came with my Fisher F19, I have elected to stay with higher frequency detectors for my bench marking.  Nothing lower than 15 kHz.   This allowed me to use comparable detectors and coils; the F19 with 5x10 DD, the Lobo SuperTraq with 5x10 DD, the DFX with 6x10 Eclipse.

The targets consist of a modern nickel, a clad dime, a very thin (the band is perhaps 5/32” wide by maybe a 1/16" thick), 18K white gold ring that a penny will fit perfectly inside, and two halves of a fired .177 lead pellet.  I cut the pellet in two, separating it into the solid head, and the hollow tail. 

All detectors were tested in Disc mode:

The F19 operates at 19 kHz and fitted with the stock 5x10 DD coil.   The settings were Disc at 40, no notch, Volume at default, Sensitivity maxed out at 100.   At this setting there is an ongoing threshold like response at fringe depth that can be heard in air tests for a couple of more inches than what I recorded.  I do not consider this to be a true audio response and I ignored this response.  The responses I used to measure with were what I considered a real audio response.  In other words, it approximated a beep type response rather than a threshold like response.  

The Lobo Supertraq operates somewhere above 18 kHz and fitted with the stock 5x10 coil.  There are apparently two versions out with slightly different operating frequencies above 18 kHz.  I do not know which one mine is but I am assuming it is 18.75 kHz.   Settings were Disc at 2 to reject iron, Normal Soil setting, and Sensitivity at 10.  I did not go into the Max Boost Range.   Threshold settings play no role in Disc mode.   The Lobo ST has a great audio response at fringe depth. As you review the results, keep in mind that the Lobo ST still had the availability of the Max Boost sensitivity settings available for use.  Note that the dime response is a little bogus as I have the preset ground balance in Disc mode set negative  but it still shows coil performance similarities.

The DFX was tested in the 15 kHz single frequency Prospecting mode with the 6x10 Eclipse with Silent Search turned on to remove the threshold response.  Pre-Amp Gain at 3, AC Sensitivity at 64, tone Id turned on and iron discriminated out.  As with the Lobo, there is additional sensitivity available for use.   The AC settings were rather tame but I wanted a rock solid response. 

The results of the bench marking told me that the 5x10 DD coils tested share the same basic performance and that my Fisher 5x10 DD is operating as it should be.  This has increased my trust and understanding of the coil.  Or should I say I feel more comfortable using the coil now.

I'll add the GoldStrike 5x10 DD coil results to the mix tomorrow.

HH
Mike

5x10 slide.jpg

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Thank you Mike, great post and read. I love to see direct comparison tests on similar machines. It would be fun to have a detector Rodeo where we could get any and all makes and models together and have a hands on comparison.  Soil conditions would come into play but nothing substitutes for hands-on.

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Thanks Mike - I have the equivalent of the coil on every detector I have so maybe I can correlate with your results and add a few.

Once you get your head around the idea that they all are within an inch of each other it really does illustrate just how hard it is to get any real edge with any of them once you put them on the ground.

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