Coil question

[robert roy]

I see there is a 3kHz coil fo9r the x-70. Why such a small frequency? What will
that one do that a 7kHz won't? Why don't we see them on OTHER machines
by other companies?
Robert R

 

[khouse]

Higher the frequency the better it will see lower conductivity with some loss of depth. So the lower the frequency the better it will see higher conductive targets and the deeper it will penetrate. So if your looking for deeper silver the 3kHz should be a little better. Just like some gold specific frequencies are around 50 kHz. This is generally speaking.

 

[rifleman]

I agree with the above. The difference between the 3 khz and the 7.5 Kkhz may not be a big one, but when you are searching right on the edge, it can make the difference between finding a coin or not. The good thing about the coils for the X-Terra 70 is that they are not all that expensive. Several good finds can easily pay for one. It's nice to take several coils with you to a new spot and if one is not getting the results you expect, another just might. No one coil or even one detector is perfect for everything.
I'm one of those people who love to experiment, so having extra coils helps keep my interest peaked. My next coil will be the 10.5" 7.5 DD, a lot of people are very happy with them. I already have the stock coil, 6" DD 18.75 and the 5 X 10 18.75 DD.


Good hunting, John K

 

[Digger]

As I have posted many times, I like the 3 kHz coil for coin shooting. As mentioned, lower frequency coils are better suited for higher conductive targets such as copper and silver. Conversely, higher frequency coils are better suited for lower conductive targets, such as gold. I won't say that the 3 kHz concentric will detect targets any deeper than the other two freqs at 9-inch concentric. But I use it for two reasons. One, it is very good at detecting old silver and copper coins. And two, it provides a more distinct audio signal on deep iron and modern trash, (than the other two freqs) when running in all metal mode.

As to why don't you see them on the other machines........ I'm sure the CEO's of those other companies are asking their design engineers the same question. HH Randy

 

[rwsnc]

[quote Digger]As I have posted many times, I like the 3 kHz coil for coin shooting. As mentioned, lower frequency coils are better suited for higher conductive targets such as copper and silver. Conversely, higher frequency coils are better suited for lower conductive targets, such as gold. I won't say that the 3 kHz concentric will detect targets any deeper than the other two freqs at 9-inch concentric. But I use it for two reasons. One, it is very good at detecting old silver and copper coins. And two, it provides a more distinct audio signal on deep iron and modern trash, (than the other two freqs) when running in all metal mode.

As to why don't you see them on the other machines........ I'm sure the CEO's of those other companies are asking their design engineers the same question. HH Randy[/quote]

OK... You're probably the right person to ask. I don't mean or want to hijack this thread but you touched on it here and I just HAVE to ask.

I hear a lot about silver and copper being "highly conductive" and gold having "lower conductivity" properties.

Aren't memory card pins coated with gold to increase conductivity and aren't the better electronic component contacts also coated in gold?

What am I missing? Can anyone explain this?

 

[BarnacleBill]

The gold on contacts is to prevent oxidation, it won't tarnish like silver & copper.

See this table:
http://www.eddy-current.com/condres.htm

Gold jewelry is alloyed with other metals.

HH
BarnacleBill

 

[rwsnc]

[quote BarnacleBill]The gold on contacts is to prevent oxidation, it won't tarnish like silver & copper.

See this table:
http://www.eddy-current.com/condres.htm

Gold jewelry is alloyed with other metals.

HH
BarnacleBill[/quote]

Thanks for the explanation about the oxidation.

Since gold nuggets are "pure". Wouldn't that be highly conductive?

I'm really feeling a little "dense". No one else seems to have a problem understanding this, except me.

 

[khouse]

I too have pondered this question. I believe more than anything that most all gold we find is small. Gold rings are not a round solid mass like a coin. Detectors are said to only see individual chain links too. So one chain link is tiny. I have not had the fortune of finding a gold coin. Nor do I own one either. But I would guess that if you had a gold coin the size of a quarter it would knock your ears out! This is just a theory. I'm sure some gold coin owners will add some solid info.

 

[robert roy]

I didn't know KHz went that high on metal detectors.
The highest I've seen is the 18.75 on the X-50 and X-70.
BTW thanks for the explanation.
RR

 

[Jackpine Savage]

Natural nuggets are far from pure. They typically range from 60% to 90% gold. Gold naturally alloys with many metals.

A pure conductive scale as posted by BB only shows one factor of conductivity. Size shape and mass are the biggest factors that apply to where a metal falls on the conductivity scale when applied to metal detecting. Alloyed gold jewelry tends to read lower than pure gold. When combined with another high conductor such as silver the resultant conductivity is lower than either metal in a pure state.. I don't know the why on that one but thats the way it works out.

Fortunately rings are relatively easy targets for a detector when laying flat. That is because of the way the eddy currents are generated in round objects.

Tom