20-30 Khz Detectors

[goldbrick]

There has recently been some discussion somewhere in the forums about 20-30 KHz detectors recently and their applications for prospecting. I ran across this while reading a link on a thread at NASA Tom's Forum, a quote by Dave Johnson, design engineer.

"Metal detector manufacturers generally avoid the 20-30kHz range because of electrical interference from military communications."

Here's the link to the interview-  http://www.fisherlab.com/hobby/davejohnson/davejohnsonjohngardinerinterview.htm

 

Merton

[Ivansgarage]

Thanks Goldbrick, that whole article was good reading.

 

Ivan 

[Steve Herschbach]

That explains why the White's V3i had so many EMI issues for me in Anchorage, Alaska. One of its three operating frequencies is 22.5 kHz and Anchorage has a stealth fighter squadron based there.

[AU_Solitude]

Thanks! Very interesting.

[nvchris]

One good reason to hang onto or buy used a ML XT 17,000, its 32 kHz " the sweet spot" for gold.

[Dean Stone]

I just wonder how the new up grade to the Deus will be with the 20KHz, and 30, and 40. If it gets to much interference then everyone will be going back to V3.2.  I do hope they make the VDI's better.

[Steve Herschbach]

I would assume Deus V4 will just add functions to what exists - there should be no need to go back to 3.2. You will just use the existing coils to access the existing frequency choices. And new coil to access new frequency choices.

There are a lot of 19 kHz machines and they are some of the most EMI resistant made in my experience, so I would not read too much into this. It is very dependent on an exact frequency situation existing in specific areas. Just another reason though why having frequency choices is a good thing.

[goldbrick]

I agree with Steve that you will still be able to use the existing freq's with the larger coils. I am hopeful that the 6x9 will employ all available freq's. Existing and the new ones for a total of 8 available in the elliptical coil. This will make the Deus just that much more versatile. It is one of the things I like most about the Deus is the ability to handle multiple detecting scenarios with  a few quick changes to the settings.

[Steve Herschbach]

Sadly due to the way coil harmonics work it is almost a certainty that the old frequencies will not be applied to the new Deus coil and vice versa. In theory you could apply the "off" frequencies to the coil but the mismatch would probably result in performance degradation such that there would be no point.

Ultimately not everything can be done through software only.

[goldbrick]

Aargh! My bubble of hope has been burst! LOL Thanks for your assessment Steve. I guess I will have to change coils more often if I want to employ all the frequencies.