I have a question for you Digger.

[NH Bob]

With my first XT70 I used the 10" round 7.5 kHz coil exclusively. I am waiting for the same to be replenished as I've ordered one.
My question, You say you have used the 3 kHz coil and like it. Can you give me a reason why I would be happier with the 3 kHz over the 10" DD in 7.5 ? I am open to try anything on the XT to better my deep coin finds. I really only want to buy one more coil. So its a toss up.

 

[Digger]

First of all, I don't know that you would be happier with the 9-inch, 3 kHz concentric, compared to the 10.5-inch, 7.5 kHz DD. All I know is that I prefer the 3 kHz concentric for where I hunt and what I hunt for. For my moderately mineralized soil, I don't need the attributes of a DD coil. The 9-inch concentric hunts deeper here than the 10.5 DD. The 9-inch is much lighter weight and better balanced than the 10.5-inch DD. And the 3 kHz allows me to have better audio separation of ferrous targets while hunting in the all metal mode. Granted, I have to be more aware of overlapping the coil. But we all should, if we want to maximize depth of detection and ground coverage.

The ferrous targets are simply discriminated better at lower frequencies. On the same token, higher conductive targets (silver and copper) are more readily detected. I won't say the 3 kHz hunts any deeper than my 9-inch concentric at 7.5 kHz. But I can sure tell a difference in the audio tones of ferrous targets. Your results may vary, depending on your soil conditions and the sites you hunt. JMHO HH Randy

 

[B.T]

That makes a ton of sense. I have noticed in some mineralised grounds here in oz that "sometimes" the 18.75khz DD can at times not make up its mind on a target, regardless of ID Stabiliser. I dug up an old bigbanger cartridge the other day (45/70?) and I was getting conflicting readouts, good target, bad target, each sweep. Even prospecting mode was doing the same on Iron mask setting of just 1. The ground had large bands of mineralised country rock as bedrock which was only 6 inches deep which was the cause of the confusion.
I reckon what you say Digger about the freqs would probably have seen a more stable Id as the 18.75 was just reactive enough on the bands of rock to give a slight but discernable signal.
The lower freq , now that you have popped that thought process into the old mind, would more than likely have totally ignored them and not have been affected.
Makes me want to get a low freq like the 3khz you use, maybe in DD though, and go back over areas like that which Ive done good at!
Food for thought indeed. Good post.

 

[Digger]

Minelab doesn't currently offer a DD coil in the 3 kHz frequency. Just the 9-inch concentric. Hopefully, the ferrous rejection capabilities of the 3 khz coils "catches on" and they become more popular. I think that is what it will take for Minelab to consider expanding the 3 kHz coil options. Especially considering it only works on one model of X-Terra, the X-70. JMHO. HH Randy

 

[NH Bob]

n/t

 

[paddywhack]

Hi DIGGER I have the 3 khz coil which Ive never used, how does it perform on ploughed,and how doesit perform on ploughed and rolled,whats your verdict on using the 3khz on airey soil,will it pick up small objects at depth in the conditions that I have mentioned,look forward to your reply,goodluck with the detecting,many thanks.

 

[Digger]

As I've mentioned before, I like the 3 kHz coil. Most of my coin shooting is done at sites that were picnic grounds, chautauquas and fair grounds 100 - 150 years ago. Today, they look like any other corn field or soy bean field around here. To be honest, it was a lot more "productive" 10 or 15 years ago when the farmers were still plowing the ground every fall. Since the introduction of minimum tilling, and the rising prices of fuel, the fields never get plowed and seldom get tilled at all. Every few years, during a crop rotation, they may chisel or disc the stalks. But usually, it is one crop planted after another, with chemicals doing the job that tilling use to do.

But, to answer your question..... I use the 3 kHz coil almost all the time in farm fields. I hunt in 4-tone all metal and ignore the low tones of iron. To me, the 3 kHz coil does a better job of identifying those deep pieces of iron, and assigning the low tone. Better than the 7.5 kHz and much better than the 18.75 kHz. I don't see any appreciable difference in the depth of detection between the 3 kHz and the 7.5 kHz. But both seem to be deeper for me than the 18.75.

The 3 kHz coil should be more receptive to silver and copper, than the higher frequencies. Although an 1838 Seated Liberty dime is the oldest and smallest coin I have found with the X-Terra, I know that there is a half dime or silver 3-cent piece just waiting out there for me! And, hopefully, it will be in better condition!!! But, I have no doubt that the 3 kHz coil would find smaller silver! HH Randy