Read a question about true multi-frequency on the Finds V3 forum and was wondering if anyone has the answer...Thanks in advance.

[www.findmall.com]

I'll jump in here as Tom has answered this question for me before as well as reminded me on a couple of occasions! I have a V3i and E-Trac btw.

The Minelab's and Fisher CZ line are true multi frequency technology (not sure if that is all the models). The frequencies are combined. In that a gain is made as far as in mineralized soil penetration, but sensitivity to see into iron might be the drawback. Not sure if that is why E-Tracs have trouble with iron falsing and CZ's aren't known to be very good in iron. The E-Trac seems to do pretty well in iron though, but Tom has said before, I believe the F75LTD and such, are much better. (Though on coins I don't know if that is always true.)

The V3i never combines it's frequencies, they are kept separate. It merely searches for the best response (under "best data") or the two best frequency response (when running "correlate" - which is great in iron or mineralized soil.) So, Tom said this is not a "true multi frequency platform" as the frequencies remain separate.

Hope that was helpful, sure someone like Tom can add more,
Albert

[www.findmall.com]
CZ, Sovereign, Explorer, Etrac, DFX, and V3 are all multifrequency. All of them transmit a digital waveform; the easiest is the CZ which uses a simple 5kHz square wave and derives a weaker 15kHz 3rd harmonic from it, so it's a 2F detector. The DFX is also a 2F detector but uses a complex digital waveform to equalize the TX signal strengths. The V3 is similar to the DFX but is a 3F detector. All these -- CZ, DFX, and V3 -- utilize full-wave demods typical in so-called "frequency-domain" detectors.

The Sovereign also transmits a digital waveform but it alternates between a single 3.125kHz square wave and 8 cycles of 25kHz. Therefore, despite all the marketing claims to the contrary, it is a 2F detector. Unlike the CZ/DFX/V3 detectors, the Sov utilizes sampling methods more akin to how PI detectors work, so some people like to think of it as a "time-domain" detector. Regardless of the details of the signal processing, it has a high frequency channel, a low frequency channel, and then a third "low/high" channel which is still sampled from the low frequency signal.

The Explorer uses the exact same TX waveform as the Sovereign, so even though I've never dug into its operation the TX waveform clearly says it's a 2F detector; the "28 frequencies" is marketing bunk. I suspect the ETrac is the same.

All these detectors continuously transmit and receive and process 2 or 3 frequencies, so they are all multi-frequency. There are some detectors which can transmit/receive/process multiple frequencies but are not "multi-frequency." The Xterras and the Eureka come to mind; they can switch between radically different frequencies, but can't run them simultaneously.

- Carl

I replied with the following and to understand my statement you perhaps have to read the thread:


I'm confused. Yes, they are all mult-frequencies in the sense that they are transmitting more than one frequency but I thought the difference was that the E-Trac, Explorer and CZ's were combining the 2 or 3 frequencies they transmit and the V3i was keeping them separate? I think like Larry said, this is a question of terminology. How could the V3i be combining frequencies if there is "best data" and "correlate" options. It seems to me right there that the frequencies are not combined. And, I'm not saying there is anything wrong with that, just trying to define the terminology and function in a little easier to understand English.

Rob - Do you really always have to be so hard in your words? "Bogus" implies shammy, almost intentionally deceitful or the like. My intention is nothing like that. You are making it seem like there is an ulterior motive from me (or whomever you were directing the bogus comment against) with your comments, use of bold, underlining, etc. So, when you say "I'm not starting a war again", well, it sort of looks like you are.

Sincerely,
Albert

Looks like what I said above was off base (I think).

Anyway, Tom, Carl from White's said the following so it does appear like the V3i does indeed combine it's frequencies. What led you to believe otherwise?

Begin quote -

Albert,

All the MF detectors I mentioned have common design features:

1) a transmit signal that combines 2 or 3 frequencies
2) a received signal that has also has combined frequency information
3) the received signal is then separated into individual frequency "channels"
4) each channel has demods that converts the individual frequency to a baseband signal
5) the resulting baseband signals are analyzed in some manner to produce the target response

What makes a detector multi-frequency is the ability to simultaneously operate with 2 or more frequencies, and all those models do that. They all separate the composite received signal into individual frequency channels, and they all re-combine the individual channel information to produce target information. The DFX and V3 differ from the other models in that you can select how the frequency info is combined (Best Data or Correlate), and the V3 further lets you see the individual frequency responses.

- Carl

-End Quote

A mulit frequency detector is defined as one that Simultaneously or in a Automated Sequence, transmit, receives and processes
more than one . From Whites V3 owners guide

The words Automated Sequence and Simultaneously might be the sticking point here as thy are not the same. , .

.

Let me start with this:

What is the specific difference(s) between the operating platform of the CZ vs V3i ??

Analog and digital

CZ machines combine the 5KHz demod signal and the 15 kHz demod signal in a 'factory set' way (I think the 'Salt' setting changes this, but most adjustment is fixed internally). The Whites machines look at the demod signals independantly, and thus have more options, in terms of - responding individually to each freq; responding to the 'best' one at any given time; responding to various combinations, such as using the lowest freq as the 'main' operating freq, and using the other 1 (or 2 ) to help counteract ground mineralisation.
It would also seem (based on the previous posts) that the Whites machines transmit a stronger level of the higher two frequencies. Thus the detected signals at those frequencies should be less affected by circuit-noise / EMI, etc, and so provide a more useable signal.

Tom - This was getting interesting, can you go on? (Please ;-)


Also, in my E-Trac & V3i video you said it looks like an iron mineralization issue. Was there anything in the V3i's response that made you think so?
I now do wonder (again) about the V3i being true multi frequency as you put it after the head to head results.

Thanks,
Albert

Albert,

Although it was hard for me to concentrate/see in the video....if the coil was being swept over the exact top-dead-center of the target each time....... but assuming it was......... the jumping VDI on the V3....... especially into the negative numbers....... leaves high suspicion of dirt mineralization for the cause/effect. And for (say the 8" coin)..... these targets were fairly shallow for the V3's true depth capabilities...... and its ability to VDI 'lock on' to these fairly shallow targets. In my Florida inert dirt..... the V3 will lock on to targets with a accurate VDI.... to 10" fairly easily. Yes.... the numbers do jump..... but in a much smaller bandwidth/window.

Thanks Tom. I am always learning.

So, and not to start a war, but if the V3i was true multi frequency ( combining them) then the mineralization wouldn't have been such a problem? I am confused by Carl at Whites comments about it being a true multi frquency now. Something must be different?

Thanks,
Albert

I think there's a little more going on inside the Minelab...... as they are a complex waveform analyzation process....... allowing it to see, measure and compensate for ground mineralization a bit differently than any other platform.

Even if both are multifrequency the way they work is very different, as Tom says.

Very different in a visible way too if You test with objects from both ends of the conductive scale.

Try not only with a silver coin or large conductive finds, also try with a small gold pendant or an earknob.

Thanks for the replies.

frnifo - Yeah, the V3i is very sensitive on small items, fine gold and such. I imagine the frequency sett of the E-Trac are all low relative to the V3i's 3 frequencies. I'm just a coin hunter but thought the 3 frequency V3i would do well in my soil on deeper coins.

Tom - I wonder about this "complex waveform analyzation process"process of the E-Trac. There are 11 "channels" and I think they are fixed, but this analyzation process is at the ground matrix level then and not a part of the "noise cancel" process? Anyone else have an idea here? Perhaps this should be put in the E-Trac thread....

Thanks,
Albert

Yes, there is a large difference between operating freq(s) .....vs...... noise-cancel channel selection. Usually...... noise-cancel channel selection are very minute' changes in freq that merely seek to find a less-noisy condition ..... whilst remaining VERY close to the units operating frequency(s). If/when a major performance gain is ascertained by the lowest noise channel.............. it is NOT because there has been a major operating freq change.............. rather........... a channel selection that allows for deep/tiny signals to be 'seen'/detected; subsequently reported.

The Explorer platform 'might' be an exception to the rule...... and 'might' be selecting a different 'group' of operating frequencies ........ if the channel selection process does not meet a minimum 'clear' acceptable level; however, I somewhat doubt this.

As far as 'ground matrix level'........ (noise from the ground due to varying mineral levels)................... I believe the only way the Explorer (or any detector) would be able to perform this is.... if the coil was being 'pumped' or swept on the ground whilst 'noise-cancel' function is being performed. And this is never the case. The coil must be stationary.

earthmansurfer Wrote:
-------------------------------------------------------
> So, and not to start a war, but if the V3i was true multi frequency ( combining them) then the mineralization wouldn't have been such a problem?
> I am confused by Carl at Whites comments about it being a true multi frquency now. Something must be different?

Hi Albert,

All these detectors are true MF designs. They all have remarkably similar receiver hardware designs, in that they all split the received signal into individual frequency channels. That is, ALL of them do the analog processing on the individual frequencies, NOT a combination of them. This is very easy to determine with an oscope.

It is also an easy way to determine that the so-called 17-frequency BBS is really only 2 frequencies, and no more. They are roughly 3.125kHz and 25kHz. I haven't bothered to probe an FBS design but the identical transmit waveform dictates that it is also a 2-frequency design. The noise channels are minor perturbations of the transmit waveform, and not the selection of wholly different frequencies. That is, the channels might result in 3.15/25.2, 3.175/25.4, 3.2/25.6, etc (I don't recall the exact numbers)... the frequencies don't change much, and maintain an 8:1 ratio. DFX and V3 do the same thing with "frequency offset."

With all these designs the baseband signals from the individual frequency channels are sampled by an ADC and fed to a microprocessor. It is certain that they all process the BB signals in some algorithmic way that combines information from the individual channels to effect GB and to identify targets. It is pretty certain the 3 manufacturers all do it differently, resulting in pros & cons amongst the 3 approaches. But they are all unquestionably multifrequency.

- Carl

Carl.

Cudos for coming foreward and settle a 11 year old riddle.

I have always been advocating that the BBS and FBS are 2 frequency designs but biased towards the lower frequency and therby being way much hotter on higher conductive finds and larger masses of metal then lower conductive finds and smaller masses of metal.

The BBS Sovereigns seem to better on lower conductive finds then an Explorer though and opposite when we talk higher conductors. The E-trac seem to be au pair with Explorer on high conductive finds but a bit better on lower conductive finds.

Can the frequencies have changed within the 2 freq waveform from design to design since we know coils work even if they are not fully tuned to the operating frequencies.

Another riddle i would like to have solved is the " automatic " ground cancel in the same detectors. I think all of them have fixed ground balance to deal with higher minerals and use heavy filtering and salt range subtractions to go with it.

There must be a reason there is no all metal mode connected to the dual freq and no change in treshold when you try to feel the minerals. And BTW... very weak pinpoint in the dual modes too.

have a nice evening.

frnifo

Don't stop now. Keep it going.

Not sure I am understanding exactly what you are saying,Thanks....

> Can the frequencies have changed within the 2 freq waveform from design to design since we know coils
> work even if they are not fully tuned to the operating frequencies.

I've measured the TX waveforms on the Sov XS, Explorer XS, and Etrac. They were all identical. However, there is no reason why the RX processing couldn't be changed to alter sensitivities.

> Another riddle i would like to have solved is the " automatic " ground cancel in the same detectors.
> I think all of them have fixed ground balance to deal with higher minerals and use heavy filtering
> and salt range subtractions to go with it.

I've only looked in detail at the Sov and I don't have my notes handy, but there is a separate ground channel besides the channels for the 2 frequencies. As I recall, it is taken entirely from the low (3.125kHz) frequency. BBS is done quite differently than traditional VLF, in that it doesn't utilize normal I/Q baseband demodulation. Std VLF I/Q demodulation is phase-rotated to achieve a null in the reactive signal, resulting in GB. Without knowing how the software works, I can only speculate, and without my notes I don't even care to do that.

> There must be a reason there is no all metal mode connected to the dual freq and no change in
> treshold when you try to feel the minerals. And BTW... very weak pinpoint in the dual modes too.

Not sure about this, so I'll have to take another look.

- Carl

Carl...... thankyou for your sharing and IP intelligence. Broad perspective is gained.