One VLF Versus Another VLF ???

[JeffP]

OK , I 'll try to word this as well as I can .

Say you have got two different branded Detectors , both say ... 18 KHZ .
Would they be exactly the same in performance ? After all ,, they are both punching a 18KHZ signal into the ground .

All this ad hype about " our detector is the best " etc does confuse me .
What could possibly make one better ,,deeper searching , more sensitive ,, etc than the other ?

Any Tech heads out there that could shed some light on this would be greatly appreciated .

 

[crustydog]

It would depend on the type and size of the coil used i would imagine.

 

[GaryO]

Good question

 

[grubstake]

Operating frequency and coil size/type are just two of the variables that distinguish the performance of one detector make/model from another. Frequency is like the cubic capacity of a car engine, which tells you something important about a vehicle, but isn't the only determinant of a car's performance. The same goes for a VLF detector's operating frequency - just because two detector models share the same frequency, it doesn't necessarily mean that their performance will be the same.

Effective metal detection amounts to a signal vs noise problem. The better that circuit design/componentry/onboard firmware can receive and improve (amplify/filter/digitally enhance) a target signal, while minimising ground noise/circuit noise/interference, the easier it will be for an operator to distinguish that target from the background noise level. The result being more targets located/deeper searching capability/more sensitivity. ie. "better performance".

So there's a host of variables inside the box, as well as the user interface control settings and their interaction with those variables, that also contribute to the perceived performance-level of a detector, over and above the operating frequency of that detector.

 

[PhaseTech]

Grubstake pretty much nailed it, but the one potentially massive difference between detectors is effective ground balance.
A Minelab Eureka Ace operating at 19khz will still run rings around most modern manual GB gold detectors in the 17-20 kHz frequency range, in highly mineralised ground. In very mild ground (a rarity in Australia), the modern high gain circuit offerings would probably excel.

The Eureka Ace is bulky, ugly, heavy compared to modern offerings like the Gold Bug Pro, but as grubstake said, when looking for gold it's all about the Signal:Noise ratio. Can you recognize the sound of a metal object under the ground compared to all the other noises you are hearing? That's what it all comes down to.

So yes, there can be big differences in machines running on the same frequencies.

Be interesting to see what Makro's Gold Racer can bring to the table.

 

[GaryO]

Worth a read .

http://www.thomasathomas.com/Metal_detectors_work.htm

 

[Guest]

One feature on a vlf that not many machines have is a hot rock/ground reject feature which
does help with ground noise.

The XP Deus has 1 which I have not tested out as yet and the Tesoro Dingo I owned and used
had one as well. The Deus can operate at 17.8 KHZ.

"This Notch Ground feature is primarily designed for eliminating false signals caused by hot
rocks or other ground conditions".

Source: http://www.metaldetectingworld.com/xp_deus_manual_ground_balance.shtml

The Dingo with a 6x4 dd coil was lethal on tiny nuggets with crisp zap zap signals.

Tesoro also have the Diablo Umax with the same hot rock reject feature. These machines though
are highly sort and hard to find on the second hand market. Not sure why they were discontinued.

I can not remember exactly what the Tesoro's KHZ was though I think they were somewhere between
15 to 18.

There was some talk about the Diablo below in reply #5.

https://www.prospectingaustralia.com/forum/viewtopic.php?id=6677

 

[PhaseTech]

A good auto tracking will make easy meat of hot rocks. A few sweeps and they track out or the signal rapidly diminishes. Whereas a genuine target signal stays quite positive.
On a manual GB VLF you can set the ground balance slightly off so that hot rocks give a "null-boing" type response. But I can tell you, this isn't fun and wears you down.
With my old whites gm v/sat in some spots I had to re balance every 3 feet, and it just became too much work. Fast forward to the SDC2300 and finding gold is just sooo so much easier.

 

[JeffP]

Cheers for the replies fellas