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kHz question

Posted by 88junior 
kHz question
September 29, 2013 08:58PM
In bad mineralized soil in order to get the best depth which would be the best a lower or higher KHz? Or does the KHz matter on handling minerals in the soil and getting more depth?
Re: kHz question
September 29, 2013 10:40PM
Hi Junior.

In 'bad mineralized ground', most definently the lower kHz for depth. But there are many variations of this simple sentence.
The lower kHz of say 6 or 8 - as opposed to 15 or 20, will always detect deeper in bad ground, and the unit will run over that ground much smoother than a higher kHz.
Simply put, 20 kHz is more sensitive than 6 kHz and gets upset by smaller particles of ironstone ect. as it fingers around in the ground. 6 kHz isn't as sensitive, and even though it still slightly registers these ground changes, it will detect much deeper because it isn't swamped by noise.
If the ground gets less mineralized, then there is only a very slight difference in depth between those kHz mentioned. And we are seeing much less difference in depth between say 6 kHz and 20 kHz in the past 5 years with the advent of our 'fake' digital units than we did with the older units.
(I prefer our new 'fake' digital units btw)

Higher frequency's of 30 kHz and above still remain in a very shallow world on bad ground.
Most units we are seeing now, more so the European ones, are around 20 kHz or have 20khz in the detector range. And on mild ground when the higher gain that we see so much on the detectors nowdays can be implemented, we get what can be seen or interpreted as equal depth between them and the lower frequency's.

I've found that running the lower frequency units over bad ground, good ground too, is a much cleaner and deeper world to detect in. Only a fraction of the smallest of targets may be lost, but the deeper rewards far outweigh them.

Then of coarse it comes down the detectors themselves, and wether they are threshold based, their nuance in disc mode ect. There are so many variables with the units now that it's getting harder to place them in any one category.
Re: kHz question
September 30, 2013 12:27AM
Morgan a decade ago that would of been a cut and dry answer....

But not so anymore...

in the last decade we have seen the higher freq become the norm for more serious hunting..

Why???Its always been there just not pushed to evolve...we now have the 14 khz and higher machine's with tight DD coils pushing the depth capabilities to the depth the Lower freq's use to get to in bad dirt...

The major break through seems to be the Coils and more power being pushed to the coil...run an older technology higher freq machine say like a gold based machine around 20 khz from maybe 15 years ago and you will notice it just does not have any umph....

Run a modern Hot 19Khz machine made in the last decade and notice the performance gain's..

Jsut take a Troy Shadow X5 and watch how it perfroms and virtually EMI free to boot...thats the big plus with the newer high freq unit's they are able to handle more GAIN with less EMI...if the X5 was on 8 kHz I dont think it would be juiced up like it was..

Or say T2 on 8 Khz would not run like you know it to run....the High freq also allows for more REACTIVITY and ability to smooth out mineral's with a DD coil...

You may ask why not but a DD coil on a low freq and you can, but a higher freq drives a DD coil a bit better than a low freq also...

We are seeing the best of coils and freqs right now being combined to produce some serious horsepower detector's...

DD's help the ground penetration and the extra gain helps get back some depth...

I personlly will take a Tight DD and a higher freq now day's before I take a low freq and a concentric coil....

For the sites I hunt, thats what is required for depth and for unmasking..I hunt bad dirt and Iron sites sometimes both at the same time...

Like Oldsmobile used to say, this isn't your fathers (Olds) detector LOL!!!!

Keith



Edited 1 time(s). Last edit at 09/30/2013 03:37AM by Keith Southern.
Re: kHz question
September 30, 2013 02:00AM
Concur. For instance...... The XP GMP (or Deus) at 18-Khz is performing (paradigm shift) remarkably well ...... and with good ID...... in bad ground.
Re: kHz question
September 30, 2013 03:05AM
Hi, I see you did not ask specifically about a particular brand or model of machine new or old that would go deeper......Instead you asked this question...... "in bad mineralized soil in order to get the best depth which would be the best a lower or higher KHz?" ......My answer would be a lower khz would go deeper than a higher khz....A DD coil will handle mineralized soil better than a concentric coil and give you some more added depth ....JJ
Re: kHz question
September 30, 2013 11:54AM
Well I have a AT-Gold and love it on coins and jewelry, I recently picked up a 1270 and bought a 10-1/2" coil for it for relic hunting. My buddy uses a Vaquero and he supertunes it when hunting and he uses the 10x12 Tesoro widescan coil he has a 10" 3 ringer planted the At-Gold with 5x8 coil will hit it in all metal but not in a disc mode the 1270 will hit it in all metal but not standard mode. I haven't tried my 8.5x11" coil yet on my gold to see if it will hit the bullet in disc mode. That's why I'm asking about kHz if my AT-Gold is going to do just as good as the 1270 I might as well just use my AT-Gold then.
Re: kHz question
September 30, 2013 01:05PM
Some mighty good info by forum members but no stock answer as a lot depends on the unit in question and the mineralization you are hunting in.
Years ago the old rule of thumb low frequency for silver coins and high frequency for gold jewelry but with new technology throw that one out the window also...
Re: kHz question
September 30, 2013 03:49PM
Best depth on what? A Gold Bug 2 will hit a tiny nugget deeper than a low frequency detector, and easily at that.

The reason there are so many frequencies employed on multi-frequency detectors plus multi-frequency and PI units is there is not pat "what frequency is best" answer in detecting. It all just depends on the target and the ground/hot rocks/trash.
Re: kHz question
September 30, 2013 04:28PM
Hi,, here's Minelab's answer.....What effect does different operating frequencies have?

As a rule of thumb, the lower the frequency used by the detector, the deeper it can penetrate the ground. At low frequencies however, sensitivity to small low conductive targets is reduced. The higher the frequency, the higher the sensitivity to small targets, but will not penetrate as deeply. In general, gold detectors operate at higher frequencies (to find small nuggets), while coin and treasure detectors work at lower frequencies for deeper penetration. The exception to this is MPS type metal detectors that are sensitive and deep seeking simultaneously.......I think this answer best sums it all up.....I kinda laugh the way we take a simple question and almost turn it into a debate....LoL....JJ
Re: kHz question
September 30, 2013 06:18PM
I can recall Tom talking about not being able to outrun the 5 kHz of the Cz in his beach video with extended shaft, quickly covering ground. Just guessing the higher frequency's don't go as deep partially because of speed? Seems like it would be vice-versa, & of the dual-frequency machines do they sample both/all frequency's simultaneously? HH
Re: kHz question
October 01, 2013 01:15AM
While the electronics are probably much improved in modern detectors, I don't think the actual signal traveling out and back from the coil is going to behave differently today than it did fifty years ago.

Generally, soil attenuation increases with increasing frequency. Which means, soil resistivity increases as the op freq increases - there is greater signal loss (two-ways - to target and back).

Secondly, lower freqs produce deeper eddies in metal targets (assuming the geometry and composition are the same) - which means the eddies are influenced more by the permeability of the target interior (rather than the metal surface skin). This affords better discrimination between ferrous and non-ferrous metals when using a lower op frequency.

So, there is no free lunch. Increasing the op frequency improves the target to coil inductive coupling which enhanced the received signal but by increasing the freq the soil absorption increases. For single freq detectors most manufactures settle on a compromise between penetration and attenuation.

Generally, the multi-freq (rectangular or square waves) detector will allow better discrimination and still get good depth while handling mineralized soils better. But they cost more to build.
Re: kHz question
October 01, 2013 10:52AM
Correct.
And then enter a paradox and/or paradigm shift within current mindset.
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