Question for Reg.

[Frank-S]

Reg, I have a new White TDI SL.
question Minelab has come out with a new type Super-D coil.
3 coils in one. 1 TX inside coil 2 out side coils RX coils. Do you
think that coil design will work on a TDI pi.
I tryed it on my X5 VLF it did not work,it might have worked but I
did not stick with it.

 

[Reg]

Hi Frank,

Yes, the DOD coil will work fine. Also, if you flip one of the D's so it is out of phase with the other, the signals will cancel and you have a ground cancelling and noise cancelling coil. Make sure to wire the two D's in series.

I built one using a slightly different technique, where I used a large winding and formed two D's and tried it.

I posted more info on the tdi and goldmaster forum about this coil. Here is a link to that post. http://z7.invisionfree.com/whitesgoldmaster/index.php?showtopic=825

Reg

 

[Frank-S]

Thanks Reg.

 

[Frank-S]

Reg, I checked the induction on my TDI SL..
The duel field 12'' coil has a 5 pin connector.pin 5 and 4 is common
pin 2 might be ground or shield.pin 5 and 4 read .04 mh on my meter.
pin 5 will only work as + there might be a diode between pin 5 and 4.
My question on the TDI SL TX AND RX coils.I am 76 some-times a bit slow.
For a DD coil or your D 0 D coil is connector pin 5 and 4 for the TX coil and
pin 1 and 2 for RX coil or is pins 5 and 4 for RX coil,pins 1 and 2 TX coil.
Or does it make a differance

 

[Reg]

Pin 1 should connect to the RX shield. Pin 2 is the RX signal line. Pin 4 is the TX signal and pin 5 is the TX shield.

As for the coil, you should use dual coax or dual shielded wires for a DOD or a DD coil. You can use something like a S-video cable which has two shielded wires in it. It is a good idea to try to find a good quality wire with at least 26awg wire size.

Back to the coil wire going to the coil connector. Pins 1 and 5 are grounds connected to the shields of the signal wires. Do not connect them together in the coil or in the connector. PIn 2 is the RX signal wire and Pin 4 is the TX signal wire.

The SL coil could read .4mh on a basic meter. So, you can have a 300 uh to 350 uh for the TX winding. I would initially try building two separate D windings each having 200uh to 300uh inductance and connect them in series and see how that works.

Try to place the D's so they are eqaaually balanced on the TX coil.

Reg

 

[cookie58]

Hello Reg. I just purchased a TDI S/l a few months back. Still trying to learn. I originally wanted a TDI or the TDI Pro, and this S/L appeared. I thought that this was the newest thing going---newer being better, so, I purchased it. I'm still learning and I like it because there is alot to learn. I bought this metal detector for relics in East Tenn. and added it to my Minelab XS and Tesoro Tejon arsonal. Getting to the question ----- Is the S/L as good as the other TDIs? I've used the GB for what little discrimination that I can get but when I cut the nails somewhat out, I loose the minie ball. Am I doing something wrong, or is that as good as it gets. Also, the Jimmy Mono Dual field coil that came with it is not that impressive. I thought that it being smaller and elipitical, I could skirt between the nails and that hasn't happened yet. However, the 12 dual field works well. I appreciate your comments and suggestions. Thanks....

 

[Reg]

The SL is a great little detector with almost as much depth capability as the TDI. I prefer to use the SL simply because of the weight. The big reason for the depth difference is the battery voltage. Many people have tested the regular TDI against the SL and found little to no difference in depth capability.

I use the RNB battery system but just purchased a Reid 4 li ion cell setup for the SL and will be trying it soon. This should put the SL on par with the TDI depth wise as far as battery voltage goes. The Reid system can be found on ebay now.

Now, without going into details, I can say the SL is basically designed the same as the TDI including the gain, so the two models are very close in overall design except the SL is designed to use different types of batteries. The big reason for the mod was the difficulty in shipping LI Ion batteries. This is dumb because there are fewer Li Ion batteries in the TDI than in a laptop computer and they are allowed to fly.

Regardless, the SL is a great little detector.

Now, unfortunately, what you determined when trying to eliminate nails also eliminates 3 ringer bullets is true. Since such bullets are rare out here I haven't spent any time experimenting with the delay or other controls so see if I can separate the two. I just usually listen for the double blip you get with nails, but not with non ferrous items. This double blip idea works for many nails but not all and also requires you circle the buried target and listen to the signal from different directions.

Now, I have experimented with some different ideas including one that allows you to operate at perfect GB but also sense what targets are if the GB was altered. This gives both depth and the ability to tell many targets without having to adjust the GB each time. I have already experimented with a different coil design which also adds depth.

Whether any of my ideas ultimately are available is yet to be determined.

As for suggestions, well I will say, practice and experiment with the detector. It takes time to really appreciate what can be done with the TDI or SL and many people lack that patience needed. It takes months to get a real idea of what can be done.

Reg

 

[cookie58]

Thanks Reg.Your comments, as always, are very useful and informative. I intend on being patient. The Pulse Induction technology seems to be the only thing new to play with at this time. By experimenting a little, and I may have this wrong because I did'nt write anything down, I found that the time delay being set higher would cause differing caliber bullets(69 cal. vs.5 to sound and one would not. The shape would also cause this difference( round ball vs. bullet). 0n Low conductivity with a little higher time delay and a little higher Gb seems to be great on buttons but no bullets except small caliber, and if one brings the Gb lower the small pieces of iron( and small square nails) really do scream and I think you need that for the smaller calibers. If I'm understanding correctly, the Gb( discrimination) works opposite between the two conductivities. With relic hunting, I am speaking for myself only, if one could find the particular settings for both, this would be great. But with differing ground conditions, this would also maybe cause a differing setting(time delay). I don't know---too much to think about-----makes my head hurt. Also, I've seen those Reid battery packs on E-bay. I might try those if you think they would perform without causing detector problems. And as always------ Thanks------- without payment.........

 

[Frank-S]

Thanks Reg.
I never made a pi DD coil only a VLF DD coil. on the VLF coil to tune it
for max-dept i had to over lap each D coil and move one coil for null and max dept.
I am looking for a coil that will detect a coin deep( like a US nickel )We both use
a nickel to test with do you remember how deep in air test or ground you detected a
nickel with your DOD coil.
Frank.

 

[Reg]

Frank,

I didn't run an actual air test but I would guess my nickel test would approach 16" to 18".

Making a DD or a DOD coil is quite easy for a PI. You don't have to null the coil but it can help under certain conditions such as extremely bad ground.

Reg

 

[Frank-S]

Thanks Reg that sounds good,I am only using induction meter and ohm meter,when
I tuned the VLF DD coil it was by ear.What i am looking for i need 18'' up in dept.
I don't have any good wire to use, so i will see what it will do with second hand magnet wire.
and wait until you perfect your DOD coil may-be get one of your coils. What size coil did
you try. After reading your post on DOD coil,it made me think about old detector that i had
years ago.It used a o-center meter to Dis with small non-ferrous target read +, ferrous
read minus on the meter.
Frank.