Question for Monte please

[billm]

Hello,
I look for coins here in Australia and the high value coins ($1 and $2 dollar) are high on the conductivity scale about the same as brass. My question is if 6.5kz(XLT)is better for higher conductors and 14.7kz(MXT) better for low, would the XLT be a better choice for me when I,m chasing them or is the actual differance betweem them in terms of depth and sensitivity to high conductors small.

Thank you
Billm

 

[Jeff Foster]

I know this question wasn't directed to me, but here's some info that may be helpful.

Briefly, I don't think you'll see much difference. Ultimately, side by side testing is needed.

Here's the data on which I'm basing this opinion:

In general, higher conductivity targets are favored by lower frequencies and lower conductivity targets favor higher frequencies. But, there are other factors. From a practical standpoint, this can be restated as: higher VDI targets are favored by lower frequencies and lower VDI targets are favored by higher frequencies.

The distinction being made here is that silver for example, while it is very conductive, responds to detector frequencies very differently based on target size. Large U.S. silver dollars (VDI +92) are favored by lower frequencies, but smaller, thinner silver pieces (VDI numbers in the 50s, say) respond better to higher frequencies. Target conductivity influences VDI numbers, but from a detector performance standpoint, the frequency performance resolves to a function of target VDI number.

There's another torturous detail that influences performance. The ground-balance system is designed to eliminate sensitivity to the ground-based mineralization. It does this by eliminating sensitivity to targets that have the same VDI number as the ground. The VDI scale is like a wheel, with the +94 end of the scale back-to-back with the -95 end. Because of this, when the ground-balance is set to ground whose mineralization is chiefly magnetic (near -95) some of the ground-balance canceling effects wrap around to the +95 end of the scale and reduce high-VDI target sensitivity.

Operating frequency comes into play here too. Lower operating frequencies skew the target IDs toward lower VDI numbers (versus the standard 6.6kHz scale) and higher operating frequencies tend to crowd target's VDI numbers up towards +95. Because lower frequencies skew target ID's away from the +95 end, the ground-balance "wrap-around" has less effect on them. Conversely higher frequencies, because they crowd the target ID's higher towards +95, are more effected by the ground-balance wrap-around.

So, again, based on my experience and testing, my guess is there will not be much difference between the two machines unless these coins register higher than mid +80s or into the +90s and the ground is near -95 VDI (MXT GND 84). Here the XLT may have an edge.

Enjoy.

 

[billm]

Jeff,
I have an MXT and wondering if I was missing out because of the frequency and higher target conductivity. The VDI for the $1 and $2 coins are around 69 to 74. It's not uncommon for the ground to be mid to high 70s.
From what you said in your post, my coins VDI are well below 95 VDI so it sounds I would have not much to gain by an XLT other than it's extra discrimation features etc.

Thanks for the reply
billm

 

[Monte]

billm,

A long day of work so I am just getting to your post. I read through Jeff's response and then your reply to him, so I'll touch on all those topics as well, adding my personal views about observed/experienced in-the-field performance.


I look for coins here in Australia and the high value coins ($1 and $2 dollar) are high on the conductivity scale about the same as brass. My question is if 6.5kz(XLT)is better for higher conductors and 14.7kz(MXT) better for low, would the XLT be a better choice for me when I,m chasing them or is the actual differance betweem them in terms of depth and sensitivity to high conductors small.... I have always held that there is "Book Theory" and there are Demonstrated Truths.

According to "Book Theory", and generally proven in an 'in-air' test (aka "bench test") with a stationery detector and no actual 'ground signal' involved to hamper the "perfect scenario" performance, ... Yes, a lower-frequency model might show a little better depth of detection and audible responsiveness to the higher-conductive targets, while a higher-frequency model might show enhanced performance to the lower-conductive targets.

But here are some things to keep in mind, and if I may let me use actual in-field results to support my views.

 

[billm]

Monte,
What can I say to a reply as detailed and considered as this, other than thank you very much.
I do have several coils for the MXT. 9.5, 10 by 6 , 6 by 4 and the bigfoot. When I,m going for the $1 and $2 at sports ovals I'll use the bigfoot first for covering the area. This finds the hotspots and then drop to 10 by 6 and finally to the 6 by 4 near the tuckshops where the trash is worst but finds can be good.
It sounds like a 5.3 should be on my "to get" list. I love my MXT especally its balance with the bigfoot and 10 by 6 coil, it's fast sweep speed,quick recovery and good VDI.
I think I'll be staying with the MXT after reading the response from you and Jeff.
Thanks again
billm