Advice on 505 coil selection...

longcut · Aug 24, 2015

I have the stock 9 inch coil(7.5kHz) and the Coiltek 6" DD in 3hKz ..............I use the 6 inch a lot , most of my sites are old homesites in cultivated fields ........ There was a lot of CW activity here also , and most of that hunting is in cultivated fields also ...... My question is , would I benefit from adding the Minelab 10" DD in 7.5kHz to my collection

Thanks for any opinions ...........

Longhair · Aug 25, 2015

What sort of GB numbers do you normally get with the stock 9" MF? What's the level of trash that you normally encounter?
Typically, if your GB numbers are in the lowest 30% range you could easily see a depth advantage with the DD. And if trash density is sufficiently high, then a DD could be a benefit in terms of separation.
The 10.5" 7.5kHz coil is great, and I wish that it was the stock coil here in the U.S. as it is in the U.K..

longcut · Aug 25, 2015

thanks Longhair ........ I was hoping you would respond ..... GB numbers are always 8 to 12 with 10 being average.......... homesites are extremely trashy so the dd is in order , the main reason I use the 6" coil so much ............... thanks for the info ....

Mach1Pilot · Aug 27, 2015

I do think the 10.5" DD in 7.5 KHz would benefit you, as long as the sites are not too trashy. But if it's loaded the trash, you probably would be better off sticking with the 6" Digger you already own.

And I agree with Longhair (again) in wishing the 10.5" DD was the stock coil.

Longhair · Aug 28, 2015

One more thing that I would point out again, is that the MF coils will ID more honestly than either the HF or LF coils. It has to do with the target segment bin width assignments for each frequency, making HF coils more accurate on low conductors and LF coils more so on high conductors.

The bin widths for MF coils are virtually uniform across the detection range, as this illustration shows.

A target that doesn't fit within the bin will deliver an ID that is more likely to be jumpy and/or less definite.

longcut · Aug 31, 2015

I found out today that the 10.5 MF DD coil is a killer ..........I went to a local sandbar on our lake that is a weekend hangout for the pleasure boaters .... I always dig homesites and go by sound , hardly ever looking at the numbers ... Today , I watched the numbers very closely and the 505 was dead on on all targets according to my air test last yr. with the stock coil... I dug 17 holes , 11 were coins , 6 were pull tabs and 1 was some sorta metal bar about the size of a 22 long rifle hull ... All 11 coins were id as what they were and the pulltabs came up from 18 to 24 , but I dug them anyway just to see .............Some of the coins were so loud , I raised the coil off the ground thinking it was a can or ball of tinfoil ..... Turned out some of these coins were in the 10 inch range in the sand .... I sure wish this coil had come stock , I would be a lot of money ahead if it had !!!!!!!!!!!!!!!!!!! Only 17 holes cause it was hot and humid as hell and I hate sand !!!!!