Truth about MF and SF

[tragac]

What is your opinion about multi freq and single freq
In text bellow


The term "multi-frequency" and MineLabs is a bit confusing, because they actually only run on one frequency at a time (from the research I did). When you first power them on, they search for a clear frequency (one) and then operates on that. They do not process but one at a time. And minelabs loves to set back in the shadows and let this conversation roll on.

You can't choose a frequency,
The display doesn't give you anything about the other 27 frequencies,
If you want to hunt lets say gold, you cannot select the best frequency for that, its chooses the quietest one.
It doesn't even tell which one its selected.

They would have you believe that the detector is constantly scanning the ground with 28 frequencies and then based on what metal it hit it uses the best one for that metal, not so! its running a pre-selected one based on it was the one with the lest interference.


What I don't know for sure is do they have a REAL 28 frequencies to choose from, or are the 28 just harmonic frequencies and the detector actually has a much less number to run on, like 3, 5, maybe 10 Who knows, but one thing for sure Minelabs isn't going to come out and settle this, in the shadows they like all the talk, its keeps the name in the top of the post in forums all over the world.

[Funfinder]

The idea behind may be that longer waves (5kHz) penetrate the ground deeper
while shorter ones but still VLF (25kHz) is better for small stuff like nuggets.

However if Minelab uses PI with a fixed coil-size this will have no big effect.

For gold-nuggets they even could use 100kHz but of course only with a small coil (max. 15cm or 6'')


btw. a constantly transceiving of 28 frequencies would take very long for a P.I. detector and
it would especially creates distortions if after the highest fq the lowest starts again.
If it uses one frequency after another, perhaps with 500Hz steps.

And creating such many frequencies all at the same time and receiving them, too,
would be usesless and hard to realize. 3 (low, medium, high) would be already enough, anyway.


Guess the Aussie-gold-diggers have too much money otherwise Minelab couldn't
sell his 6000 bucks PI machines which may work well on clean soil but we all know
that the PI's disc always is not the best and so its no wonder when you can see in
some docu's guys who dig out every rusty nail or bottle-cap there.



A real good invention would be for all metal-detectors to have a frequency selector
from 1 to 100kHz step 3kHz so depending on the used coil-size and ground-conditions
it really would make sense if its adjustable.

Depending on the country and EM-fieldstrenght it may be allowed or restricted.

[Carl-NC]

Tragac, this has been discussed elsewhere on the forums. Minelab BBS & FBS run at 2 frequencies, 3.125kHz and 25kHz. They transmit them in rapid succession and process both frequencies all the time, so they truly are 2-frequency machines. But certainly not 17 or 28. The noise cancel feature applies a minor shift to the frequencies.

[eclipse]

Is Minelab BBS patent close to expire? It should be close probably in year ot two.

[tragac]

Thank you on answers
On the forums very often can be read opposite opinions for same topic , that produce confusion and can not have clear picture .....like mentioned text on the start of the tread

Is it advantage/disadvantage 2freq coil vs one freq in which conditions and soils....
I'm asking this because for one MD it was advertaised multi freq coil and do not know to buy existing 4 freq coil which is able to work on separate freq or wait for multi freq coil...

[Carl-NC]

Is Minelab BBS patent close to expire? It should be close probably in year ot two.

The Minelab multifrequency patent expired a couple of years ago. According to a Minelab letter, that patent did not actually cover BBS, implying that BBS was never patented.

[Carl-NC]

Is it advantage/disadvantage 2freq coil vs one freq in which conditions and soils....
I'm asking this because for one MD it was advertaised multi freq coil and do not know to buy existing 4 freq coil which is able to work on separate freq or wait for multi freq coil...

2 frequencies allow for salt rejection which makes it far better for salt water hunting. Theoretically you can do better ground tracking and target ID as well.

[tragac]

What you suggest for peat/clay soil with grass


It it true that MF
multifrequency BBS/FBS machines get better ID at depth, better discrimination, can handle ground minerals better, and so on...because of multifrequency.

[homefire]

MineLab has BS'ed the users too Often Too Many times. How Many times have you Heard about folks trying to get a 5 year old machine Fixed and told NO CAN DO? When you buy a Car your allowed the Information to Fix it your self. Emmmmmm? Not with Mine lab. Who to Hell is going to pay $10,000 for there machine.???? The Rag Heads in Africa, Australia and Southwest USA. Does any one with that kind of money really need to get sun burnt, Dehydrated, messed up by the BLM to play the Game? I found a pile of my First Gold with a $50.00 BFO from a A Rag Magazine back in the early 70's. Any one that falls for there game can pay the Price. Did You Know that a Square Wave is made up of a Infinite number of Odd Harmonics? Yes a Pulse and in PI can be looked at as a Elongated Square wave.

[BILLY]

Well then, take your 50 buck BFO and get out there and find some more gold then and stop your crying.

[crane]

Back in around 1968 I watched a guy using a commercially made BFO go over a 2.5 ounce nugget buried 2" deep and he didn't hear anything other than the same ground noise he heard everywhere else. The ground changed the frequency more than the nugget. A BFO is useless on the Oz goldfields.

[Orbit]

In most cases osciltator at certain frequencies has lower and more harmonicas and the higher power nearby covers a wide range of frequency, at one time I worked transmitter with PLL and crystal but a little discombobulated driver power 350watts it was the transmitter at 100mhz to 30km I cover complete UHF perimeter of the about 70mhz do 110mhz, if you looked at the Spectrum analyzer wiev to large coverage harmonics in all detectors be they pi or vlf .

[WM6]

Back in around 1968 I watched a guy using a commercially made BFO go over a 2.5 ounce nugget buried 2" deep and he didn't hear anything other than the same ground noise he heard everywhere else. The ground changed the frequency more than the nugget. A BFO is useless on the Oz goldfields.

According some reports, even PI technologies have hard days on some OZ gold-fields.

And there are another (almost forgotten) stories too, like this one:

[Qiaozhi]

KRinAZ has been having a lot of success in highly mineralized ground with a modified MiniPulse Plus (MPP) ->
http://www.geotech1.com/forums/showt...586#post206586

He lives in Arizona where the ground sticks to a magnet like it does in Australia. Perhaps someone in Oz could do the same modifications to their MPP, and give us some feedback on the performance, especially when compared to some of these "few thousand dollar" machines.

[crane]

Hi WM6,
I think you have been hanging around the Oz misinformation forum too much!!

Finders Pty Ltd in Dunolly was the Whites importer and distributor and they were comparing the GP Extreme with the previous Minelab SD models. The tests proved to be flawed, which resulted in Finders losing their Minelab dealership.

The only people who took notice of the tests were some of the local so-called pros who kept their SD2200s until the GP3000 was released and most of these went back to full time prospecting when they realised the GP series could hear small to medium size gold at depths that were out of reach with the SDs.

In the meantime, the blissfully ignorant tourists cleaned up with their GP Extremes.