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jasong

Not All Ferrite Rings Are Equal

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I was going to post this in one of the X Coil threads, but it might be of interest to everyone.

I bought a replacement ferrite ring since I left my ML ferrite in Arizona. It's one of the Doc's ferrites with the white backside (off Ebay), I did not realize they were not ML ferrites when I bought it. The OEM Minelab ferrites have a black backside.

It would not balance on the X Coils at all and actually sounded like a screaming target (I didn't try the Z14) so I reported that to the coil manufacturer. He responded that the white backed aftermarket rings are not the same as the ML rings. So, as I normally do, I checked for myself, bought an authentic ML ring, and he was right.

They are the same size, but the Doc's ring is 10 grams heavier (something I noticed immediately but did not have a ML ring to compare to until recently). It is also more magnetic. The Doc's ring is also conductive whereas the ML ring is non-conductive - the Doc's ring was reading about 38 ohms from side to side whereas the ML ring read infinity. And after I sanded the backs to get a fresh surface to check resistances on I noticed the ML ring looks dull and black as a ferrite should, but the Doc's ring looks shiny and metallic, like iron.

So, clearly there are differences between the two rings. Thought people might like to know even if you are just using the stock coil, as I'm not sure how this affects the ground balance, but someone could be running suboptimally using this ring.

rings.jpg.10314455f4ba04f4b5fb081173b4b742.jpg

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I guess it's like ferrite chokes, the composition determines the frequencies they can filter out so differences in composition must also change the ferrite ground balance I guess.  It would be wise to stick to genuine with this sort of thing.

It's easy to buy a $1 ferrite spray paint it and sell it for $10 or whatever, there is a few aftermarket ones of them on auction sites 🙂

Were you able to balance out the ferrite better on the genuine one?

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I haven't tried to balance on the ML one yet, but I will when I get some free time again to get away from town. 

The fact that the aftermarket ferrite is conductive is the concerning part to me. Because if a person tries to balance it in manual they will be changing both X and G and leaving it set wrong. At least that's the way I understand it. That, and the X itself may be not matching the X in the ML ferrite either. 

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From the Minelab Knowledge Base Article at https://www.minelab.com/__files/f/254884/KBA_26-1 GPZ 7000 Tips for Better Ground Balance.pdf

"A ‘dust iron’ toroid suitable for the HF frequency band (e.g.1–30MHz with an initial permeability of between 6 and 10) has been carefully selected. It is recommended to use this specific Minelab accessory, only. Alternate ferrites may significantly degrade ground balance quality."

Note the words "recommended" and "may". Not trying to knock Doc but I would only use the Minelab ferrite personally.

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7 hours ago, jasong said:

So, clearly there are differences between the two rings. Thought people might like to know even if you are just using the stock coil, as I'm not sure how this affects the ground balance, but someone could be running suboptimally using this ring.

Jason - I was just curious if the Xcoil did ok balancing on the new ML ferrite ring you just got?  Mine has worked in probably 3 out of 4 locations. 

oops - I just saw Simon beat me to the question.

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This is a pretty significant bit of information. It will be helpful to hear if anyone has a problem GB'ing with the replacement ring, or if the GB is correct when using it.

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I always  follow the manufacturer’s instructions...

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