Is The Day Of A Single Frequency Detector Past ?

[Alluminati]

5 hours ago, phrunt said:

If what you're saying is correct Geotech, every single Equinox buyer in Australia is entitled to a refund on their purchase, even if they wait a few years before doing so they can get a full refund for the deceptive advertising

https://www.accc.gov.au/consumers/misleading-claims-advertising/false-or-misleading-claims

NZ has a similar law so I too could go and refund mine now.  I would imagine other countries probably do too.  It would be extremely silly of Minelab to be lying about what the Equinox is doing with it's frequencies.

I'd be annoyed Minelab deceived me, but I would be satisfied in keeping the detector as I really like it ?

 

I wouldn't call your lawyer just yet.  Square waves could be made by combining sinusoidal harmonics of the desired transmit frequency. Fourier could be used on the receiving signal too, which could be capable of receiving information not transmitted.

You can strike a bell with a hammer once a second (1Hz) and still make a multifrequncy recording. That 1Hz recording of a bell strike can in theory completely fill the band of an ideal microphone that has a response of 20Hz-20kHz. If my equipment is good enough, I could "EQ" (filter) out any information I don't want and just listen to frequencies of interest.

You could then make educated guess as to what the bell is made of by how it sounds.

A zinc penny sounds different then a copper penny when dropped on a table, electrically speaking the same thing happens, each coin has a certain frequency it wants to resonate at.

You could identify copper and zinc pennies from a audio recording by just listening to the high frequency "ring" that the copper coin has that the zinc coin lacks. Filter out all the low zinc penny information out of the recording and what you have left is just noise made from the copper coin only.  This device that will let you hear copper but ignore zinc. 

Which brings us back to the transmit side of things, the hammer. Looking at this on a scope is the same as a picture of a guy swinging a hammer. Can you look at that picture of a guy swinging a hammer at a bell and say a recording of that event doesn't have this or that frequency without even knowing what they used to record the event? Of course not.

It is interesting that the Solid State stereos that the Minelab creator used to make a few years back still go for $20,000-$30,000 USD. That says a lot because as a bit of an audio snob, I wouldn't pay more then $50 for any used Solid State amplifier used for music. Seriously, don't want it. Vacuum tubes all the way, for various reasons, which mostly center around HARMONICS.

While there are lots of audio"fools" out there, in order to sell more then a few amps like that, there must be something to it. It at least demonstrates his mastery and understanding of harmonics. Audio is an extremely tough market.

Halcro dm10 Preamplifier + Halcro dm 88 Monoblock Amplifier 

 

 

[Geotech]

El Nino, looking at the TX voltage on an MF detector is next to useless, you gotta look at the TX current to see what is going on.

[EL NINO77]

Carl, thank you for explaining ... I know you're one of the few constructors who know something about the multifrequency ..

[Steve Herschbach]

I guess when you ask if the day of single frequency has passed and it turns into a debate about the technical details of multifrequency that kind of answers the question. I had one engineer tell me he would rather saw his leg off than have to work on another single frequency detector. Boring.......

Whatever, I will let you all sort out the technical details. I am just happy I lived long enough to see this phase of the technology kicking in. The next few years will be interesting.

[Dubious]

10 hours ago, Geotech said:

And that's what I've done.

 

So you saw only two frequencies for each mode?  What method did you use for coupling the signal?  Did you take any screen shots?

I suppose two selected frequencies might do a pretty good job in each category, but disappointing (and puzzling) that Minelab would mislead so blatantly.

[Steve Herschbach]

If you read what Minelab puts out very carefully they state always that modes are choosing and processing frequencies from the ones available, but how many are used at any one time in any one mode is never explicitly stated. It is all carefully worded to let you all make assumptions and fill gaps with what you think is going on, but if you read it carefully it is not always saying what you think it is saying.

What do you all make of this statement from here (emphasis added):

“How many simultaneous frequencies?” you may ask, wondering if this is a critical parameter. Minelab has been carrying out detailed investigations into this in recent years. Just as you can color in a map with many colors, the minimum number to differentiate between adjacent countries is only 4 – a tough problem for mathematicians to prove, over many years. Similar to the map problem, it’s perhaps not the maximum number of frequencies needed to achieve an optimum result, but the minimum number that is more interesting. When it comes to frequencies in a detector, to cover all target types, how the frequencies are combined AND processed is now more important, with the latest detectors, than how many frequencies, for achieving even better results.

I am quite certain myself that if it turns out Equinox works because there is a small squirrel inside the control box that makes all the decisions it will still continue to perform for me tomorrow just like it did yesterday. Good luck to all of you trying to litigate marketing statements with engineering reality. The fact is I sure don’t know how it works... I just know it works. 

[LowTide]

My, my, my.......here we go again with the 28 frequency Bad, Bad Minelab again.  95% of a detectors performance is on the receive processing side.  I had no part in the Minelab 28 frequency design but if I did then here is how I would have gone about utilizing the possibility of transmitting and receiving the 28 frequencies.

To start a detecting session for noise cancelling I would use the receiver to sweep the 28 frequencies and record and rank the noisiest to quietest.  Then for ground cancelling I would transmit all 28 and rank them according to greatest/least amount of ground noise.  Then I would select either 2 or 3 frequencies with the low(i.e.3kHz), mid(i.e.14kHz), high(i.e.30kHz) to have a broad target response with the least amount of noise(EMI or ground).

Why only 2 or 3 frequencies?  Because more channel processing means more battery drain, and high and low conductors can be sampled accurately enough with 2 or 3 carefully chosen frequencies.

What every competitor in the world would love to get their hands on is the receive processing code.  Because that is where the money is, and the number of transmitted frequencies is basically superfluous.  But hey, if you can't produce a competitive product then beat that horse until you are squishing maggots.  Meanwhile those checks written by Equinox buyers are cashing just fine. ?

 

 

[Rick K - First Member]

Not just multi frequency (either simultaneous or sequential) but new methods of analysis of the returned signal by sampling multiple signals or time slices of signals.

The remaining problems to be solved in our hobby are reliable iron ID at depth especially in mineralized soil (or more correctly correct ID of non ferrous) and iron “see through” to detect the presence of non ferrous adjacent to or below ferrous targets.

Current multifrequency systems help with the first problem, but do little or nothing with the second.

I believe that this is significant in an era where the sites we have access to have been gone through with lots of different machines.

Traditional one frequency at a time frequency domain detectors offer literally nothing new.  They work just fine - and do what they have always done - nothing more.

[Guest Tnsharpshooter]

Well,

Evidently my squirrel inside my Nox was a running around today. Lol

Here’s one thing that stands out to me using Equinox.

Now I have done loads of head to heads comparing Equinox 800 to other detectors mostly single freakers

When Equinox detects a target and gives tone, I cannot really tell how mask or tough to detect it  is really.  With single freq detectors I can tell lots of times.

The best way for me to judge how tough the target is to detect is when I actually put certain single freqs detector models over.

So the moral of my story here.

I am KEEPING my gimmick!! 

 

[Geotech]

On 11/18/2018 at 10:50 AM, Dubious said:

So you saw only two frequencies for each mode?  What method did you use for coupling the signal?  Did you take any screen shots?

Yes. I used a magnetic field probe I designed & built. There are at least 2 threads on Geotech discussing all this, including scope pics.