New Deus HF round coil question - large targets

[matisam]

Hi all!
I have been detecting in Israel as an archaeologist for a few years now. I get invited to interesting digs and usually find lots of interesting finds. Originally a Garett user I have quickly became a Minelab E-Trac and then CTX 3030 and now I also operate an XP Deus which I am still learning.
Yesterday I received the new HF round 9 inch coil and took it out to a short hunt today. All in all very happy. Found some 15 Roman and Byzantine bronze coins in relatively mineralised ground. After going home I ran some air tests (all frequencies but seems to be "worse" at higher ones) and was surprised to notice the coil seems to easily pick up small gold and silver targets but "struggles" a bit with large silver coins at medium distance (5-6 inches). It does pick them up but much less clearly than the CTX would and probably less clearly than the Deus 11 inch standard coil. I am aware of trade offs... but does this make sense to you? Do I run the risk of missing a silver hoard at medium/shallow depth? This off course could only be the learning curve and a few tweaks will help, but I would appreciate to hear your view on this.
I mainly work GM power program, but it seems to be the same with most programs I quickly tested (maybe number 5 was slightly better).
Any thoughts appreciated!
All the best - HH Mati

 

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[austin_luker]

I don't have a HF coil but would think that your observations are semi correct since the HF coils are for small targets not large targets but I'm very curious about others chime in.

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[toasted]

The new HF coils should have no problems with high conductors using the 15khz frequency. The higher frequencies are for small gold and other low conductors

 

[vferrari]

The HF coil runs from 14 to 59 khz. At 14 khz it operates like a typical VLF detector on high conductor targets and should hit plenty hard on large silver. As you signficantly increase frequency, it will hit harder on small mid-conductor targets like small gold, but its depth performance will suffer significantly for large conductors, which is basically just straight forward physics (the higher frequency signals tend to get scattered and attenuated greater than the lower frequencies), so lower frequencies tends to get you more depth but won't hit as well on small, low-to-mid conductive targets or edge on coins. It's a standard trade off and could explain why you are not getting as good depth performance on large silver as the lower frequency 11" coil which can operate a 4, 8, and 12 khz which are all below the minimum operating frequency of the 9" HF coil. I would expect the HF coil to hit slightly better on large, high conductive targets at 14 khz than if you were operating the 11" at its max frequency of 18 khz. In summary, what you are describing is exactly what I would expect from the HF coil. The CTX is a multifrequency machine (transmits at multiple frequencies at the same time) so it behaves differently than the Deus. Hope that helps.

 

[matisam]

The HF coil runs from 14 to 59 khz. At 14 khz it operates like a typical VLF detector on high conductor targets and should hit plenty hard on large silver. As you signficantly increase frequency, it will hit harder on small mid-conductor targets like small gold, but its depth performance will suffer significantly for large conductors, which is basically just straight forward physics (the higher frequency signals tend to get scattered and attenuated greater than the lower frequencies), so lower frequencies tends to get you more depth but won't hit as well on small, low-to-mid conductive targets or edge on coins. It's a standard trade off and could explain why you are not getting as good depth performance on large silver as the lower frequency 11" coil which can operate a 4, 8, and 12 khz which are all below the minimum operating frequency of the 9" HF coil. I would expect the HF coil to hit slightly better on large, high conductive targets at 14 khz than if you were operating the 11" at its max frequency of 18 khz. In summary, what you are describing is exactly what I would expect from the HF coil. The CTX is a multifrequency machine (transmits at multiple frequencies at the same time) so it behaves differently than the Deus. Hope that helps.

Very helpful answer, thanks! It mostly confirms my initial impression. I did not like the depth on big silver at 14 kHz either with the new coil, but will test it again in the field over the next few days (it was less than a smaller gold target by a few inches). I guess I will have to adjust and make the necessary changes in order to cover all target types and get the most out of the machine. I can add that the CTX/E-Trac were good on all types of targets and helped me find sub 0.15 gram coins and also deep hoards. Admittedly, they have other problems (weight, price, complexity, relatively slow recovery compared to XP etc.) but the VDI system is more accurate in terms of target identification, as it uses the FE 1-35/CO 1-50 system rather than a 1-100 scale. I would be horrified to find multiple small targets and miss a significant hoard. I mainly work relatively clean sites, but occasionally (as goes with the territory) I have a lot of cartridges and other "militaria" which come up as good targets, but were more easily distinguishable with the FE-CO system. I am excited to learn the XP and hope to use it as my main machine, I just hope it will treat me as nice as the Minelab did. Thanks for the quick replies - it's good to find knowledgeable users. I will probably keep asking questions in the near future...
Thanks again,
Mati

 

[Welgund]

With the new high frequency coils from what I read you should be able to shift the 15k down to the 14k range also which would help on high conductors. Just make sure your silencer is -1 and your reactivity is no higher than 2 to 2.5 if the area is not to trashy for good depth performance.

 

[Railo]

Sry to ask my question in your thread, but how would the new HF coil compare to the standard 11'' coil in modern trashy areas. I would like to try the smaller 9 '' coil in very trashy areas for even better separation but I don't see any use of buying the standard 9'' coil anymore when the HF coil is out.
Wouldn't higher frequencies be even more sensitive to small foil and aluminium than 18khz, so in modern thrash it would be best to use the 14khz with the HF coil ?

Currently i've been using 18khz with the 11'' coil in parks/beaches, but would be tempting to try the smaller coil if it could separate even more, maybe in quiet areas the higher frequencies could identify objects that aren't lying flat better, and could be used ?
So my question is would you rather use the 9 HF coil or 11'' (standard) in parks/beaches, or is the difference noticable ?
Also what about the upcoming elliptical ?

 

[Eu_citzen]

Really depends on what you are searching for. If you are searching for small gold items and similar, perhaps it makes sense.
However the Deus is sensitive a plenty as is, IMO.

In fact, sensitivity to small items may just make it even worse, since there already is plenty of trash around.
The detector might just "see" more trash, making it harder to pick out the good stuff. (if that makes sense)
"More isn't always better".

Although a small coil is a good idea on those areas, I'm not sure the High freq will be of any aid to you.

 

[Railo]

Really depends on what you are searching for. If you are searching for small gold items and similar, perhaps it makes sense.
However the Deus is sensitive a plenty as is, IMO.

In fact, sensitivity to small items may just make it even worse, since there already is plenty of trash around.
The detector might just "see" more trash, making it harder to pick out the good stuff. (if that makes sense)
"More isn't always better".

Although a small coil is a good idea on those areas, I'm not sure the High freq will be of any aid to you.

That is my thought also.
I just have mixed feelings about buying the standard 9'' instead of the HF coil if i'm going to use both with 12-18khz, the HF just adds more options from there. Of course I would use the HF coil outside parks/beaches too, just wondering how it would manage those areas.
Secondly I dont know how much better the smaller coil is with target separation, the 11'' coil is already good.

 

[Eu_citzen]

That is my thought also.
I just have mixed feelings about buying the standard 9'' instead of the HF coil if i'm going to use both with 12-18khz, the HF just adds more options from there. Of course I would use the HF coil outside parks/beaches too, just wondering how it would manage those areas.
Secondly I dont know how much better the smaller coil is with target separation, the 11'' coil is already good.

Perhaps it adds more options, but are those options going to be useful to you? I mean, they will excel at nugget hunting.
But perhaps not so much at the average use of a beach hunter or coin shooter. But I never tried one, my notes are just general theory.
Let's hope someone with experience will jump in.

In fact, I still only got the 9" coil. Hoping for a used 11" some day.