FBS Facts

[Mark-VA]

Is the Minelab FBS machines actually transmitting 28 frequencies or not?
I read on another forum that it was just advertising bunk.
Some say it only transmits a set of three frequences and then some sort of harmonics.
With all the techies here someone most likely knows the truth.

[Skippy]

I'm sure it has been discussed on here before, but there's also several discussions on Dankowski's forum: http://www.dankowskidetectors.com/discussions/index.php
It's two frequencies used in a clever way to get 'more than two' frequencies worth of info out of them.

[Mark-VA]

Been there for several years now, just thought someone here might know the actual facts.

[Skippy]

Were there any specific 'Actual Facts' you were looking for? I would think these two threads would answer most of your questions:http://www.dankowskidetectors.com/di...ad.php?2,23116 and http://www.dankowskidetectors.com/di...ad.php?2,24272 Among the posters on those threads is Carl who runs this Forum. There's also little point in fully reverse-engineering the machines, anything clever is likely to be covered by patents so you can't copy it anyway, and the clever stuff is mostly in software, which is expensive to reverse-engineer.

[Carl-NC]

The actual facts are what I posted on Tom's forum. BBS is a 2-frequency method. That's all, no more. The 17-f claim is pure marketing spin.

FBS uses the exact same TX waveform, so it is highly unlikely it is anything but a 2-f method as well. I have not analyzed the receiver to verify.

BTW, it is interesting that ML seems to have dialed back the marketing spin with the CTX-3030... I've seen none of the "28 frequencies" nonsense. They only claim "Multiple frequencies: 1.5 - 100kHz" which would be true for a 2-f machine using 3.125k and 25k.

[Mark-VA]

I've been very reluctant in mentioning what you said.
I switched from the Fisher LTD to the Explorer SE then three years ago I switched to the Etrac.
The machine seems to do okay, but I can honestly say my hunting buddy has been using the V3i with the 12 x 10 SEF coil and can usually see any target I can. Now we know the V3i is a true 3 frequency machine and would explain why this machine does so well.
I've been very interesting is switching to the V3i.

[Carl-NC]

While I have openly complained about Minelab's marketing BS surrounding BBS and FBS (which, I admit, is very effective marketing BS*) even before I ever thought of joining White's, I haven't complained about their performance. Truth is, Explorer/Etrac have an edge on deep silver over V3. However, the relatively low TX power at 25kHz results in much less sensitivity to small gold for FBS vs V3. So there are trade-offs.

- Carl

[mikebg]

Can anyone explain how many samples should be made in time domain to calculate frequency response for 17 or 28 frequencies?
http://www.dspguide.com/pdfbook.htm
http://www.google.com/patents/US4506225

[moodz]

... sample at twice the rate of the highest frequency. ( ie if highest is 50 Khz ... sample rate = 100 Khz ).

[mikebg]

... sample at twice the rate of the highest frequency. ( ie if highest is 50 Khz ... sample rate = 100 Khz ).

Moodz, my question is not for sample rate, but for number of samples in a period of TX current. I will try to explain the question with a drawing showing the received signal of PI machine as step-down response in time domain. We need information for responses at a number of frequencies (for example 17 or 28, below are shown 5).

Let assume I wish a PI metal detector to collect data for calculation response of a single frequency (operation as VLF) machine. My RX should calculate target response at frequency f1. I take a sample of step-down response at delay t1. This corresponds to maximal operating frequency f1 in frequency domain. When I increase delay, the frequency f1 decreases. However this is not enough for calculation of single frequency response. Stability of calculation needs additional samples for reference. That means, when I wish to use a PI detector as single frequency mashine, I should take minimum two samples to calculate stabile results.

When I wish my PI to operate as a sine induction mashine with 5 frequencies, no need of additional samples because one sample is reference for the other and the calculation will be stabile.

[Aziz]

*LOL*

Only 28 frequencies?
That's not enough.

I'm using 18 times more... *LOL*

Aziz

[Mark-VA]

Carl, have you ever compared the Fisher 75 or LTD with the V3i?