WHITES DUAL FIELD COIL

[6666]

Do you understand the XL sheet content?

Hi Aziz
I dont have the XL sheet, so not sure if I will understand whats on it,
but from your experiments with the large TX coil and small RX coil
was there any ratio or size of the coils that looked good for experimenting with a dual PI coil?

[daverave]

[QUOTE=6666;180087]Hi Aziz
I dont have the XL sheet, so not sure if I will understand whats on it,
but from your experiments with the large TX coil and small RX coil
was there any ratio or size of the coils that looked good for experimenting with a dual PI coil?[/QUOTE

i experimented with a whites coil cover and wound coils the same size....i tried two different gauges of wire for the 6 inch inner coil 30 & 32 swg but the 12 inch coil was 32 swg only....i would say that i got better proformance from my single coil...im getting about 15 inches in air on an old uk penny and 12 inches on a small 9ct thin section gold ring but depth not so good on medium iron which is good for me....ive lost interest now in dual field !!!!

[Aziz]

Hi Aziz
I dont have the XL sheet, so not sure if I will understand whats on it,
but from your experiments with the large TX coil and small RX coil
was there any ratio or size of the coils that looked good for experimenting with a dual PI coil?

Yes, there was a performance ratio of the coils (a lot of variations).
Particularly you in Oz should know, that large PI coils can't be used well in the highly mineralized gold fields due to high ground response. This is, where the seperated TX (large) and RX (small) PI coil will solve the issue. And it also solves the EMI noise problem as well.
The dual field coil on the other hand will generate a higher ground response in the inner coil section, which makes the detector prone to hotrocks and minerals on the ground surface.
The seperated TX/RX coil will pick up less ground response, less EMI noise and will still detect deep and shallow small targets.
Just think of a small ground loop coil.
Aziz

[6666]

Hi Aziz

Particularly you in Oz should know, that large PI coils can't be used well in the highly mineralized gold fields due to high ground response.

I dont get much chance these days to prospect our goldfields, our ground is pretty tough, on some of our goldfields you can throw a magnet on the ground and it just clumps with magnetic material, I should make a video of that someday.

I as thinking more along the lines of the beach, to use a seperated TX/RX coil

[Aziz]

Hi Aziz


I dont get much chance these days to prospect our goldfields, our ground is pretty tough, on some of our goldfields you can throw a magnet on the ground and it just clumps with magnetic material, I should make a video of that someday.

I as thinking more along the lines of the beach, to use a seperated TX/RX coil

Yep, the seperated TX/RX coil would be very convenient for heavy mineralized gold fields. Particularly for deep and large nugget detecting.
Cheers,
Aziz

[daverave]

The cable used is Cat 6 or Cat 5.
This cable is used for data transmission, is composed of 8 conductors of 0.5 mm in diameter, in the case of Cat 6 the diameter is slightly larger, between 0.5 and 0.6 mm.
Another may use this cable between these values (0.5 or 0.6 mm) corresponding to 23 or 25 swg of acuero to the table.
The blindage we perform with Scotch tape No. 24.
In the image below is an example of a mono coil.
Jose[ATTACH]26734[/ATTACH]

im going to buy some cat6 cable..im still confused as to the winding of the coil using cat6 cable.....if i make a 12 inch coil then each turn is 1 metre long x 16T....so do i wind 16 turns of all the conductors all 4 pairs of the cat6 cable ????

[Jose]

Coil Large: 12 inches, about 30 cm, 2 laps about 2 meters.
Reel Girl 8 inches, approximately 20 cm, 2 laps, approximately 1.5 meters.
Total cat6 approximately 3.5 mtrs.
Attached photo of a coil, this cubhierta with plastic tape to give more to blindage separation.
The blindage not seen in the photo.
Jose

[Dave J.]

Yes, there was a performance ratio of the coils (a lot of variations).
Particularly you in Oz should know, that large PI coils can't be used well in the highly mineralized gold fields due to high ground response. This is, where the seperated TX (large) and RX (small) PI coil will solve the issue. And it also solves the EMI noise problem as well.
The dual field coil on the other hand will generate a higher ground response in the inner coil section, which makes the detector prone to hotrocks and minerals on the ground surface.
The seperated TX/RX coil will pick up less ground response, less EMI noise and will still detect deep and shallow small targets.
Just think of a small ground loop coil.
Aziz

Aziz is correct on this matter, as Davor figured out earlier in this thread. The "dual field" approach used on the Fisher Impulse and later by White's has its advantages in saltwater environment use, but in a gold prospecting environment its disadvantages outweigh its advantages.

--Dave J.

************************

Here's a funny piece of history.

Back when we (Fisher) introduced the Impulse, we got an inquiry from a fellow in Australia who had heard some sort of rumor that PI was the hot setup for gold prospecting in hot ground. (This was before the Minelab SD's, I'm guessing that it was Eric's machines that had given rise to this rumor.) The guy wanted us to give him a freebie for field testing, with a promise that he'd publicize the results.

Our marketing guy told him this is a beach & scuba machine, we sell gold machines and the Impulse ain't one, and we simply flat out can't recommend it for gold prospecting. (Even back then, I understood the ground balancing issues relating to PI, having fielded both VLF-style reactively balanced and "early and late timing" balanced prototypes. The Impulse incorporated neither type of ground balancing feature.)

The guy in Australia kept insisting, so our marketing guy finally caved in and sold him one for half price on the condition that he give us a report on how it did or didn't work out for him.

Of course it turned out to be worthless for that purpose, the guy bytched not only to us but badmouthed us in Australia claiming that we'd burned him.

It was a lesson well learned about human nature. A mistake like that never happened again.

[daverave]

Coil Large: 12 inches, about 30 cm, 2 laps about 2 meters.
Reel Girl 8 inches, approximately 20 cm, 2 laps, approximately 1.5 meters.
Total cat6 approximately 3.5 mtrs.
Attached photo of a coil, this cubhierta with plastic tape to give more to blindage separation.
The blindage not seen in the photo.
Jose[ATTACH]27070[/ATTACH]

thanks for the photo jose that has given me a clearer view of what the coil should be like....just 3 questions....what is the inductance and resistance of that coil cause only two laps...and can the ends be soldered directy together ???

[Jose]

Daverave
The photo shows only one of the coils, remember that they are two and are connected in series.
The two coils are constructed identically, the only difference is its diameter.
The inductance of the higher coil is 175 uH and 1.2 ohms.
The inductance of the smaller coil is 100 uH and its resistance is less than 1 ohm.
Connected in series and the coil arranged girl inside the large coil, gives an inductance of 380 uH and 2 ohm
These values are approximate, since my instruments are not accurate.
Do not understand the last question.
You can experiment with a single coil of three turns cat6, and diameter 25 cm (10 inches). You will have 8X3 .. 24 laps and an inductance between 300-350 uH with a resistance of about 1.5 ohms.
Also this type of coil is easy to make and you answer quickly, use less tin solder candidad possible so as not affect their response.
Regards
Jose

[Aziz]

Aziz is correct on this matter, as Davor figured out earlier in this thread. The "dual field" approach used on the Fisher Impulse and later by White's has its advantages in saltwater environment use, but in a gold prospecting environment its disadvantages outweigh its advantages.

--Dave J.

************************

Here's a funny piece of history.

Back when we (Fisher) introduced the Impulse, we got an inquiry from a fellow in Australia who had heard some sort of rumor that PI was the hot setup for gold prospecting in hot ground. (This was before the Minelab SD's, I'm guessing that it was Eric's machines that had given rise to this rumor.) The guy wanted us to give him a freebie for field testing, with a promise that he'd publicize the results.

Our marketing guy told him this is a beach & scuba machine, we sell gold machines and the Impulse ain't one, and we simply flat out can't recommend it for gold prospecting. (Even back then, I understood the ground balancing issues relating to PI, having fielded both VLF-style reactively balanced and "early and late timing" balanced prototypes. The Impulse incorporated neither type of ground balancing feature.)

The guy in Australia kept insisting, so our marketing guy finally caved in and sold him one for half price on the condition that he give us a report on how it did or didn't work out for him.

Of course it turned out to be worthless for that purpose, the guy bytched not only to us but badmouthed us in Australia claiming that we'd burned him.

It was a lesson well learned about human nature. A mistake like that never happened again.

Too late Dave. I've been already gone mad. *LOL*

Where is my mental doctor? Where is my good stuff medication (the colored pills)?
Doctor!!!!!! Mental Doctor pleaaaaaaaaaaaseee!!!!!!

Aziz

[daverave]

Daverave
The photo shows only one of the coils, remember that they are two and are connected in series.
The two coils are constructed identically, the only difference is its diameter.
The inductance of the higher coil is 175 uH and 1.2 ohms.
The inductance of the smaller coil is 100 uH and its resistance is less than 1 ohm.
Connected in series and the coil arranged girl inside the large coil, gives an inductance of 380 uH and 2 ohm
These values are approximate, since my instruments are not accurate.
Do not understand the last question.
You can experiment with a single coil of three turns cat6, and diameter 25 cm (10 inches). You will have 8X3 .. 24 laps and an inductance between 300-350 uH with a resistance of about 1.5 ohms.
Also this type of coil is easy to make and you answer quickly, use less tin solder candidad possible so as not affect their response.
Regards
Jose

im not sure if i want to make a dual field coil and maybe i just stick to single coil design....ive just ordered some cat6 wire pure copper and will experiment once it arraives...is the depth using this wire much better than say using ordinary copper insulated wire ???? i appreciate your help to me all you guys...im a little slow in working things out but hopefully i get there in the end !!!

[woodbob123]

Dave depth improvement comes in little steps coil, shielding, cable, amp etcetc, its all little steps which add up. once you have your MD working and optimised there are no bigsteps.

[Jose]

Do not know if Cat 6 is better than ordinary insulated wire.
A few years ago when you return to this hobby, I started with the Delta Pulse and coils did with cat5,
It worked very well and since then I use cat5 or cat6.
I will buy regular insulated wire to compare results.
Jose

[daverave]

Do not know if Cat 6 is better than ordinary insulated wire.
A few years ago when you return to this hobby, I started with the Delta Pulse and coils did with cat5,
It worked very well and since then I use cat5 or cat6.
I will buy regular insulated wire to compare results.
Jose

in your photo you show the ends of the wires joined together with heat shrink....why is that ???? ive ordered a 10 metre cat6 cable...can i just wind three 12 inch turns then solder the 8 wires together on each end of the coil ???