GroundScanner said:
I was going to get the 7" concentric coil, but cancelled it and got the 5x9 coil.
Both the open-frame 7" Concentric and 5X9½ DD coils are my favorites for the Impact. I enjoy the 5X9½ DD's on my FORS CoRe and FORS Relic as well and really wish I had a 7" Concentric coil option for those units, too. I am sure it was a tough decision on your part to try and single out which of the two coils to buy, and I know everyone has different opinions of what they feel works for them in their types of hunt sites.
Both sizes and types have their pros and cons, but the 7" Concentric gets the most workout on my Impact, for both Coin & Jewelry Hunting as well as in out-of-the-way Relic Hunting sites. I am sure when you get to it and add the 7" coil you'll be equally impressed with it, and pleased to own BOTH the 7" and 5X9½ DD coils.
GroundScanner said:
My soil is on the high side (8 , so thought the 7" concentric wouldn't be that great for my soil.
If you have a Ground Pause read-out of about '88' then you definitely have some terribly bad ground to deal with, especially if that is a universal or general area GB setting you need. But I usually have my GB setting on the CoRe, Relic and Impact at about '88' anyway because many places I search produce a GB setting from '81' to '86.[size=small]80[/size]' so I just tweak it up a little bit. A lot of that 'bad ground' is up around the gold mining era ghost town sites I hunt that have both high-mineralization challenges combined with a lot of rusty tin shards and other ferrous and non-ferrous debris. The 7" Concentric coil handles those sites without a problem.
Way back when, in the '70s and '80s and even into the '90s, we heard a lot of folks talk about the 'need' for a Double-D coil in higher mineralized ground and that they worked better than other coils. Well, to some degree that was correct, but some of the other coils were not a Concentric design, and detector circuitry and signal processing was also much different back then, when most detectors were analog circuitry designs. But search coils have been better engineered along that way, and we have really seen some dramatic improvements in how detectors are engineered. Today we do have some detectors and coils that can provide us with exceptional in-the-field performance, even in really ugly ground environments, using both a DD and Concentric type coil.
GroundScanner said:
I may get one and try it but not until the spring time. GS
Hopefully, between now and spring, you'll have ample opportunity to get out and use your Impact and the new 5X9½ DD coil to get to know both of them well .... and naturally have some success along the way and find some nice keepers, too. Then spring, which isn't all that far away, will let you invest in a 7" Concentric and start a new learning process.
I have every coil for the Impact and I use both of my Impacts often. Of all the search coils available, my #1 favorite and most used is the 7" Concentric and is closely followed by my #2 favorite, the 5X9½ DD.
[size=small](Let me add, also, that the smaller round 5" DD does get called into service quite often when Relic Hunting in dense iron trash and is part of my favorite Impact 'Coil Trio'.)[/size]
Best of success afield to you,
Monte