Find's Treasure Forums

Welcome to Find's Treasure Forums, Guests!

You are viewing this forums as a guest which limits you to read only status.

Only registered members may post stories, questions, classifieds, reply to other posts, contact other members using built in messaging and use many other features found on these forums.

Why not register and join us today? It's free! (We don't share your email addresses with anyone.) We keep email addresses of our users to protect them and others from bad people posting things they shouldn't.

Click here to register!



Need Support Help?

Cannot log in?, click here to have new password emailed to you

Goldquest and a DD coil

A

Anonymous

Guest
Hi All,
First I would like to say I don't really have a Goldquest but do have a modified Beachscan set to the same delay as the GQ and equipped with the new autotune feature so the results should be about the same. I guess I should say my Beachscan is more like a GQ clone.
Anyway, I built and installed a DD coil on my GQ clone and it worked fantastic. A couple of things came out of the experiment that I thought people should know.
First, the DD does an excellent job of eliminating the ground signal if the coil is properly built. My experimenting at home and use at Gold Basin indicated the ground signal can be minimized to the point that it is almost non-existent over a wide range of conditions. As such, just a DD coil may be better than ground balance (GB) in many places simply because GB has a tendency to introduce noise while the DD seems to actually reduce noise when compared to a mono with no GB.
I am sure there will be places where just the DD will not completely eliminate the ground response, but where I live and at Gold Basin, it sure did a fantastic job.
I found the DD to give a slightly weaker signal to really small gold, but because of the fact there is less noise and the target response is more distinct, I can actually detect smaller nuggets better and deeper. I could tell the signal level difference because I have built a VCO type audio so any target will both change in volume and frequency. There was a slightly less tone change on the DD to my small test nuggets, yet I could hear them farther from the coil. I attributed this to the reduction in noise level.
What really surprised me was the fact that my 11" DD would detect a nickel at a greater range than my home made 9" by 13" mono. I gained an inch or so. How does between 16" and 17" air test sound? It sure looked and sounded good to me. (I have just built an 8" by 11" DD which did drop me back down to between 13" and 14" on a nickel.)
My limited testing of in ground targets indicate I get about the same depth as the air testing which also impressed me. This was done in extremely mineralized ground, but was not a red clay environment. So far, I have not had a chance to test in under red clay conditions but hope to do so in the near future.
Now for the down sides and there are a few. The DD does not do quite as well on small meteorites like those found in Gold Basin as the mono coil does. I suspect this is because the meteorite signal is more like a ground change than a metal target. It does extremely well on medium and larger meteorites. That is what I found this last trip was one nice meteorite, plus the usual quantity of trash.
One thing I also noticed with the DD coil is the use of the delay to test for iron is not as accurate. For some reason, at least on my detector, I don't get the usual easy separation of targets by turning the delay up. I am not sure why this is the case and I am looking into it.
Now, the big down side. This is a do it yourself project since there are no readily available coils. The detector does require some minor modifications which really should only be done by someone who has worked on pc boards. One should also realize this mod is not sanctioned or approved by Eric or Mr. Bill so it will most likely void the warranty. More important, any problems one might encounter shouldn't be directed them since both are too busy with other projects to try to coach someone though possible mistakes.
Setting up a DD coil isn't really difficult but the best results can only be done with a scope. Of course, proper shielding is required for best results also.
So, if you are a "do it yourselfer" like me and you like to experiment, then this is a great project to improve a really good detector, especially for nugget hunting.
Finally, how does the GQ equipped with a DD coil stack up against the big boys on the block. Well, it isn't a giant killer, but it can easily bruise their ego, especially on small nugget response.
Reg
 
Good post Reg. Certainly something to think about for the future. 16 - 17in on a nickel with the 11in DD sounds a hard one to beat! Even for the big boys <IMG SRC="/forums/images/wink.gif" BORDER=0 ALT=";)">
Eric.
 
Reg,
Way to go!!! **** Wow **** you seem to have done a fantastic job. Its great to hear that your work is paying off so well. 16" - 17" on ANY 11" coil is going to be pretty hard to beat.
 
Hi Dave,
I realize the numbers seem farfetched but they are legit. So, I probably should explain my measurements and a little about the conditions.
A nickel was placed on the ground and the coil was passed over the nickel raising the coil each time a good repeatable signal was heard. The distance was measured with a yardstick and verified with a tape measure.
Now, I do have to say this test was done on a weekend, no wind, and the noise level was extremely low. In fact, it seemed almost non-existent.
I switched to the mono coil and the noise level increased significantly. As such, the mono didn't show any improvement even though the xmit coil was larger. In fact, it didn't do as well as the DD. The main reason as best as I can tell was the increased noise level which seemed to be internally generated. However, as Eric pointed out to me, there is a difference in size of the coils, so maybe the larger mono coil was actually a better antenna.
On other days, when the noise level is higher the measurements have reduced to more typical levels of 13" to 15" for the DD also. A signal can be heard above those levels but it really cannot be distinguished from the random noise pulses.
I am considering adding a switch that would allow me to switch a DD coil from a DD operation to a mono operation. This mod would would allow me to compare noise levels better as well as make the coil/detector combination more versatile. I am just not sure how much of a negative impact, noise wise, the switch would make. I guess I should try it and see but I would hate to introduce more noise. The detector was so quiet when I was using it in AZ that it was scary. I would hate to change that.
Reg
 
Reg,
My testing here tells me the distances that you are getting are true. I am getting about an inch less than you are but this gap may well close as I make a few mods. It sounds to me that you have done a really excellent job. Congratulations for sticking with it and making it fly! I too hope to be posting some results very soon. All the best, Dave. * * *
 
HI Dave,
You may be at a disadvantage if you are near a lot of places generating noise.
I am not sure what all is shut off at various periods of time near my house, but I can find times when the noise level is extremely low. Generally, this is on the weekends. At these times I can duplicate my original findings.
Also, when I was down in AZ and out in the field and away from most everything electrical, I experienced the same quiet operation. I could distinguish the slightest target signals. That really spoiled me.
I also checked the noise level increase with the detector equipped with a mono coil. Boy, what a difference. I quickly went back to the DD.
Reg
 
Hola Reg, please tell me the diameter off the receive coil off your DD of 11 inch (transmit ) .it is hard to beleive your detection range but possible ,with my detector i am two inch below with a simple coil of 11inch.thank you Alexis
 
Hi Alex,
The coil diameter is about 8.5", maybe just a little more. Actually, the xmit is just a little larger than the receive. I just adjusted my simple winding form to squeeze as large of a diameter as I could into the coil housing and still work, so it isn't exactly 8.5".
If you read my posts below, you will notice that specified the procedure used when I got the results I did. Now, I will say the signal I got from the nickel at the maximum range was very low but distinguishable and repeatable. Also, the external noise level was extremely low at the time of the testing.
One more thing, the winding design doesn't look quite like a standard DD also. The receive coil is more like a D with more of a straight side in the overlap area and the xmit has more of a bow so the xmit extends farther into the receive zone. It is a little strange, but it seemed to work better.
I had to modify a coil housing I had to build it since I didn't have a ready made housing at the time that would work.
Reg
 
be interested in this coil if any were to be made for sale. Sounds like a nice improvement. Depth and smoothness/quietness at the same time. Maybe not so smooth and quiet in my(Ct.) area but I think it could be worth trying. John in Ct.
 
John,
At the present time, this is not on the drawing boards. <IMG SRC="/forums/images/frown.gif" BORDER=0 ALT=":(">
As Reg. explained, this is a doit your self project. It is not a plug in coil change. Circuity changes need to be made to the detector.
Bill
 
Top