TURNMASTER
Active member
Should be here next Tuesday. Can't wait
Jeff
Jeff
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Ordered new coil yesterday 10.5 MF
- Thread starter TURNMASTER
- Start date
Well, the jury is in on my take of the 10.5DD coils. I had the 18.75 HF out in the field this week. It is a winner over the 7.5 MF... IN MOST CASES. Looks like in my high mineralized ground it is more sensitive to brass & lead. I still have not found anything as deep as with the MF coil thou.............
Thanks Jeff and morelic, I just got my round 10.5" HF DD about 2 days ago but have not tried it yet. Not as heavy as I thought but bigger round than I thought. Have to wait until ground thaws out. Very good read here below, Randy says the HF and MF have simular depth:
http://www.findmall.com/read.php?55,1127217
messin' with my 505, 705 and a few coils.....
Digger(Randy) wrote, "As such, it seems the "width" of the coil is a very important factor when comparing depths...As to the round 10.5 DD coils...... since the depth of detection is somewhat dependent on the width of the coil, the "wider" 10.5 round coils will be deeper than an elliptical coil of the same "length". From my observations, the large round DD coils have +/- 40% more depth than the elliptical. I've found the 10.5 DD at 18.75 kHz to be more sensitive than the 10.5 DD at 7.5 kHz. As such, I usually have to lower the sensitivity setting to operate it without falsing. But with all those things considered, both are similar in performance, depth wise."
"There is so much to consider when chosing the proper coil for a particular application. I believe lower frequencies are better suited for higher conductive targets and higher frequencies are better suited for lower conductive targets. I believe that lower frequency coils will detect larger objects at greater depths and higher frequencies are more "sensitive" to smaller targets. I believe that DD coils neutralize the effects of highly mineralized ground much better than concentric coils, making the DD coils a far better choice in those applications. And I believe that larger coils hunt deeper than smaller coils, simply due to the size and shape of the electromagnetic lines of flux being tranmitted into the ground. So when chosing a coil, one must consider the size of targets they are seeking, the mineralization of the ground they are hunting and the amount of "trash" they are likely to encounter. Remember that any of the coils are capable of finding anything metal. It is simply a matter of chosing the best tool for the job. And there are more factors than simply the conductivity of target you are searching for."
"With the 30+ inches of snow we have on the ground now, it will be a few months before I can do some actual "in the dirt" tests. As such, air tests are simply an exercise to keep my mind occupied! However, and I think I may have mentioned this once or twice before, , the 3 kHz concentric coil is a coin killer. Particularly on silver and copper coins, which is about 95% of what I dig. Nickels, gold coins and other low conductive targets...... not quite as good as the 7.5 or the 18.75. But it still hits them hard.
As I mentioned below, the higher the conductivity, the better the 3 kHz responds. I ran several hundred coins past each of these coils. On all the nickels, the few gold coins I have, a small handful of the older IH cents and for an unknown reason, a few select wheats, the 7.5 does just as well or better than the 3 kHz. And on those coins with lowest conductivity, the 18.75 does even better than either the 7.5 or the 3 kHz. But honestly, neither the 7.5 or the 18.75 are going to make me take that 3 kHz coil off when I'm coin hunting open areas. Not unless I get into a spot with half dimes and silver 3-cent pieces. That is where I am now with my airtests. I'm trying to define that point where the lower frequency's ability to be better on higher conductive targets "gives way" to the higher frequency being better on the smaller targets. Right now, my tests are inconclusive because there are many more considerations (in an actual field hunt) than what an airtest can provide. But like I said, it keeps my mind occupied! HH Randy"
Yes the HF is generally more sensitive to brass, lead, iron, and gold. But less sensitive to silver and some copper. The MF is generally more sensitive to silver and some copper and less sensitive to brass, lead, iron, and gold. BUT of course depending on the surface area size of the metal 'facing the coil'. The greater the surface area of a given metal, the higher conductivity reading, thus the higher '+ number' reading.
http://www.findmall.com/read.php?55,1127217
messin' with my 505, 705 and a few coils.....
Digger(Randy) wrote, "As such, it seems the "width" of the coil is a very important factor when comparing depths...As to the round 10.5 DD coils...... since the depth of detection is somewhat dependent on the width of the coil, the "wider" 10.5 round coils will be deeper than an elliptical coil of the same "length". From my observations, the large round DD coils have +/- 40% more depth than the elliptical. I've found the 10.5 DD at 18.75 kHz to be more sensitive than the 10.5 DD at 7.5 kHz. As such, I usually have to lower the sensitivity setting to operate it without falsing. But with all those things considered, both are similar in performance, depth wise."
"There is so much to consider when chosing the proper coil for a particular application. I believe lower frequencies are better suited for higher conductive targets and higher frequencies are better suited for lower conductive targets. I believe that lower frequency coils will detect larger objects at greater depths and higher frequencies are more "sensitive" to smaller targets. I believe that DD coils neutralize the effects of highly mineralized ground much better than concentric coils, making the DD coils a far better choice in those applications. And I believe that larger coils hunt deeper than smaller coils, simply due to the size and shape of the electromagnetic lines of flux being tranmitted into the ground. So when chosing a coil, one must consider the size of targets they are seeking, the mineralization of the ground they are hunting and the amount of "trash" they are likely to encounter. Remember that any of the coils are capable of finding anything metal. It is simply a matter of chosing the best tool for the job. And there are more factors than simply the conductivity of target you are searching for."
"With the 30+ inches of snow we have on the ground now, it will be a few months before I can do some actual "in the dirt" tests. As such, air tests are simply an exercise to keep my mind occupied! However, and I think I may have mentioned this once or twice before, , the 3 kHz concentric coil is a coin killer. Particularly on silver and copper coins, which is about 95% of what I dig. Nickels, gold coins and other low conductive targets...... not quite as good as the 7.5 or the 18.75. But it still hits them hard.
As I mentioned below, the higher the conductivity, the better the 3 kHz responds. I ran several hundred coins past each of these coils. On all the nickels, the few gold coins I have, a small handful of the older IH cents and for an unknown reason, a few select wheats, the 7.5 does just as well or better than the 3 kHz. And on those coins with lowest conductivity, the 18.75 does even better than either the 7.5 or the 3 kHz. But honestly, neither the 7.5 or the 18.75 are going to make me take that 3 kHz coil off when I'm coin hunting open areas. Not unless I get into a spot with half dimes and silver 3-cent pieces. That is where I am now with my airtests. I'm trying to define that point where the lower frequency's ability to be better on higher conductive targets "gives way" to the higher frequency being better on the smaller targets. Right now, my tests are inconclusive because there are many more considerations (in an actual field hunt) than what an airtest can provide. But like I said, it keeps my mind occupied! HH Randy"
Yes the HF is generally more sensitive to brass, lead, iron, and gold. But less sensitive to silver and some copper. The MF is generally more sensitive to silver and some copper and less sensitive to brass, lead, iron, and gold. BUT of course depending on the surface area size of the metal 'facing the coil'. The greater the surface area of a given metal, the higher conductivity reading, thus the higher '+ number' reading.
You know, I couldn't use one of the HF DD coils on the couple of sites I'm working right now. Simple reason is that they are CW picket posts that in modern times have been used for skeet shooting and small game hunting. A HF coil picks up the small bird shot easier and will drive you nuts. Its one of the reasons I like the swappable coils on the X-terra, makes it easier to adapt to conditions.
TURNMASTER
Active member
I don't know that I will get any more coils as this will make 4. The stocker, 6" and 5 x 10 HF DDs and the soon to be here 10.5 MF DD. I believe this should round out this package well.
The possibility of getting a 10.5 HF would be there if I were to find an area of success with prospecting.
Jeff
The possibility of getting a 10.5 HF would be there if I were to find an area of success with prospecting.
Jeff
Mark in S.E. IA
New member
If your ground is a lil on the hot side and in places with a lot of iron I'm sure that your going to like that coil. I do, It's the only coil I use.