Tdi Pro Coil Comparison On The Goldfields

[Jim in Idaho]

2 hours ago, snakejim said:

Jim, I have one and it's black with a white label. The label says Razorback Professional TDI Mono 5 x 10.

I need to compare it to the JIMMY TDI Dual Field Mono, that I have.

Also, maybe I could send the Razorback coil to you, so you could compare it with the one you have since mine says for TDI and yours says for Minelab?

Jim

Jim, before you go that trouble, let's wait and let the snow and ice melt around here, and let me do some testing with this coil. Then that might make an interesting comparison. There must be some electrical difference between them, or why the different labels? Unless it was done just on the ones they eventually exported to the states. Maybe initially they were included in a package deal or something on a GPX 4500, or other, and had the ML label, and then they started the TDI labels for some reason. No way to know. I'll keep you updated, in any case.

Jim 

[snakejim]

1 minute ago, Jim in Idaho said:

Jim, before you go that trouble, let's wait and let the snow and ice melt around here, and let me do some testing with this coil. Then that might make an interesting comparison. There must be some electrical difference between them, or why the different labels? Unless it was done just on the ones they eventually exported to the states. Maybe initially they were included in a package deal or something on a GPX 4500, or other, and had the ML label, and then they started the TDI labels for some reason. No way to know. I'll keep you updated, in any case.

Jim 

Jim, that sounds like a plan. Weather is still bad here also.

Best wishes!

Jim

[bobinyelm]

29 minutes ago, Jim in Idaho said:

Jim, There must be some electrical difference between them, or why the different labels? Unless it was done just on the ones they eventually exported to the states. Maybe initially they were included in a package deal or something on a GPX 4500, or other, and had the ML label, and then they started the TDI labels for some reason. No way to know. I'll keep you updated, in any case.

Jim 

On 3/19/2023 at 8:14 AM, Jim in Idaho said:

 

 

As to a difference between Razorback Coils marked "TDI" vs "ML," last week I spoke with Miner John who very graciously took a good deal of time educating me on the different coils available for he TDI.

One of the things he mentioned was that he has found that because the ML detectors put out considerably more power (more amperage to the coil), they can easily blow out coils evidently using higher gauge wire, or other components in the TDI coils. He therefore did not recommend using TDI coils on a ML detector.

On the other hand, ML coils like the Sadie work well on the TDI, but since they are designed for the higher power ML, they won't perform as well on a TDI.

Now, I did not specifically ask whether Razorback coils made for ML work as well on TDIs as do the ones specifically made for the TDI. In other words, maybe what allows the  ML coils take the additional power (Different wire of lower resistance could mean more turns to have the same coil impedance?), degrades performance in the TDI?

I am not stating a fact as far as HOW the ML coils can take more power, or whether ML coils are less effective on TDIs than TDI coils of the same make and size. Just conjecture on my part. But he DID say that MLs can blow out TDI coils. I am not sure whether if a coil blows out, it affects the detector output transistors in a ML since the pulse voltage would likely be much higher without the load of an intact coil. Again, I didn't ask him.

He did say that after taking over production of Razorback coils, and after disassembling several, he noted significant design flaws in them, and modified the ones HE produced to eliminate these flaws, so are much better. 

Though he is OUT of the coil building business for now at least (due to the forest fire that took his place), he suggested obtaining newer, improved Razorback Coils with labels including "Miner John" on them, which I guess he made along side Miner John design coils (not sure if he just stopped selling them as Razorback at some point, and continued production as Miner John, but at least SOME Razorbacks have Miner John on them, as do some improved "Jimmie " mono coils which he manufactured for Jimmy Siera for the TDI)

[Jim in Idaho]

Yes...it's been known for a long time that you can use ML coils on TDI's, but  not the other way around.

Jim

[Jim in Idaho]

I should probably test the DC resistance of this ML coil, and also the inductance, and see how those specs compare to a different mono coil made for the TDI. However, the Sadie is not made specifically, for the TDI, and it works great on them, so maybe it doesn't matter.

Jim

[bobinyelm]

2 hours ago, Jim in Idaho said:

I should probably test the DC resistance of this ML coil, and also the inductance, and see how those specs compare to a different mono coil made for the TDI. However, the Sadie is not made specifically, for the TDI, and it works great on them, so maybe it doesn't matter.

Jim

Though I have not yet received my 8X6 Sadie, from all the glowing reports, it's obviously well thought of.

Perhaps John's mention that it doesn't work as well on the TDI is more of a comment about the lesser ability of the TDI detector itself, rather than a degradation of the coil's ability when used on the TDI.

As Steve mentioned, the TDI is nowhere close to the abilities of a GPX5000. I haven't used a GPX, but I can only imagine the 6000 and 7000 are even better.

Interestingly John mentioned a quirk of the GPX6000 (I think he said) that I had heard about with at least certain PI machines. It is the tendency for them to completely ignore certain sizes or shapes of gold nuggets, finding larger, or smaller gold with no problem, but completely ignoring nuggets in the "donut hole" detection sizes. He mentioned he found this after thoroughly going over an area with the 6000 and cleaning it out, only to go over the area with the 7000 and easily turning the previously ignored nuggets up in depths easily exceeded by the 6000-it just was blind to them.

I wonder if the TDI exhibits the phenomenon with certain target sizes? I don't have enough experience with it to have a clue.  

[Jim in Idaho]

Yes...the TDI manifests the same issue, and to a greater degree.

Jim

[bobinyelm]

4 hours ago, Jim in Idaho said:

Yes...the TDI manifests the same issue, and to a greater degree.

Jim

Is it known what size/shape range it ignores? Or does it depend upon the coil used more than the machine itself?

Is it a function of the delay I wonder? It would be interesting if there were a way to "sweep" the delay, so that you could have it rapidly sweep +/-  20% above/below the selected delay setting. I've read that even the difference from 10us (the optimum for small low conductivity gold) to 13us can make a big deal in "seeing" things. Where I hunt in desert, 90% of "junk" is lead pellets or bullets, so stuff like tin foil or pop-tops wouldn't pose a bigger problem.

Obviously I am not a detector engineer-just a rhetorical curiosity.

Anyone ever detect an area at say 10us, and then again at 13 or 15us to see the differences in detecting ability in the field or a test garden I wonder?

More than 50 years ago I was an electronics engineer before changing careers, and back then it would not have been easy to accomplish that (analog and digital microcircuits were pretty new then), but today it would likely be relatively easy. If changing delay slightly would catch more targets close to the nominal ideal delay (without finding mostly junk) it would be interesting (but beyond my obsolete capabilities, unfortunately).

[bobinyelm]

19 hours ago, Jim in Idaho said:

Yes...it's been known for a long time that you can use ML coils on TDI's, but  not the other way around.

Jim

Having been well behind the times by only recently purchasing a beautifully kept TDI, I did not discover that, though I did read (recently) posts where people just said they were "interchangeable," though it didn't mention it was one-way compatible until Miner John told me when he mentioned I should buy ML coils going forward rather than TDI coils as when I upgraded to an ML it would save me money and grief.